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July 9, 2014. Destination: PASPPreprint typeset using LATEX style emulateapj v. 11/10/09

INSTRUMENTS ON LARGE OPTICAL TELESCOPES – A CASE STUDY

S. R. KulkarniCaltech Optical Observatories 249-17

California Institute of Technology, Pasadena, CA 91108(Dated: July 9, 2014)

July 9, 2014. Destination: PASP

ABSTRACT

In the distant past, telescopes were known, first and foremost, for the size of the aperture. However,the astronomical output of a telescope is determined by both the size of the aperture as well asthe capabilities of the attached instrument. Advances in technology (not merely those related toastronomical detectors) are now enabling astronomers to build extremely powerful instruments to theextent that instruments have now achieved comparable importance to the aperture of the telescope.Unfortunately, the cost of successive generations of instruments has risen far above inflation. As such,observatories are confronted with additional expenses comparable to the running costs. Here, giventhe vast sums of money now being expended on optical telescopes and their instrumentation, I arguethat astronomers must undertake “cost-benefit” analysis and not merely rely on their “gut” instinctsfor future planning. I use the scientific output of the W. M. Keck Observatory as a laboratory foranalysis of instrumentation and associated costs. I find, in the absence of upgrades, that the time toreach peak paper production is six years and that the useful lifetime of instruments is a decade. Wellthought out and timely upgrades can double the useful lifetime and thus are highly cost effective. Iinvestigate how well are instrument builders rewarded (via citations by users of their instruments) andfind acknowledgement ranging from almost 100% to as low as 60%. Next, given the increasing costof operating optical telescopes new partnerships are sought by existing observatories. This naturallyraises the issue of “What is the cost of a single night of telescope time”. I provide a rational basis tocompute this quantity. Finally, I make some remarks about the cost effectiveness of small diametertelescopes and separately review the major changes brought forth by the arrival of “mega” instruments.Subject headings: instruments: efficiency

1. MOTIVATION

Historically, ground-based optical telescopes have beenthe primary experimental method by which astronomersinvestigated the heavens. The serendipitous discoveryof cosmic radio emission and later cosmic X-ray sourcesled to a flood gate of exploration in other electromagneticbands. Today it is routine for an active astronomer to callupon data from radio (dekameter to the sub-millimeter),thermal infra-red (IR), near infra-red (NIR), space ultra-violet (UV) and high energy (X-ray, γ-ray) bands to drawconclusions about celestial objects.

Space-based astronomy offers exquisite performance inseveral ways. For certain bands (e.g. UV, X-ray, THzand others) we have no choice but to go space. For otherbands (e.g. mid IR) ground-based observations sufferfrom high background noise. Next, atmospheric turbu-lence degrades the wave-front leading to poor image qual-ity and a corresponding decrease in precision and accu-racy of photometry and astrometry. This has motivatedmissions such as the Hubble Space Telescope and Gaia.Space also offers a very stable platform to make certaintypes of ultra-fine measurements (e.g. extra-solar planettransits and astero-seismology, CMB observations).

Separately, there is now substantial investment offunds in non-electromagnetic astronomical facilities (neu-trino, gravitational waves, cosmic rays – primarily pur-sued by physicists). These very large investments are atestimony to the fecundity of astronomy.

Despite investments in flagship space-based missionsand flagship non-electromagnetic facilities the fact re-

mains that ground-based optical and NIR (hereafterOIR) telescopes continues to play a leading role in theoverall development of astronomy. The sky is rela-tively quiet (especially in the optical). The opticalband is moderately rich with spectral lines which providenot only elemental abundances but also velocities (andthence the distance, masses and temperatures). Further-more, we now have the ability to build larger telescopesat lower costs (when normalized by collecting area). Asa result the global astronomical community now enjoysa dozen large aperture (8-m and 10-m) telescopes.

A telescope is clearly only as useful as the backendinstruments. The costs of instruments were minor forthe first generation of modern telescopes (e.g. the Lick36-inch refractor or the Mt. Wilson 60-inch). Imagingwas provided by a simple camera with a photographicplate. The imaging was, at best, seeing limited and thusthe optics were simple (the plates could also be curved, ifneed be, thus further simplifying the optics). The focuswas on single object spectroscopy and this simplified thedesign of the spectrographs. In both cases, the observerundertook the guiding.

Given that the cost of the telescope construction is al-ready a sunk cost and given that number of usable nightsis fixed it makes sense to invest as much money as one canafford to build instruments which yield the largest possi-ble amount of useful data. Fortunately, advances in tech-nology have made it possible to build instruments whichreturn more data thanks to larger field-of-view (FOV),mosaics of detectors filling the FOV, massively multi-

2 S. R. Kulkarni

plexed spectrographs and so on. In short instrumentswith large reach.

Instruments with large reach have fundamentallychanged the landscape of optical telescopes. While in thepast (say about three decades ago) one talked of the aper-ture of telescopes today astronomers talk of the capabil-ities of the instruments just as much as (and sometimeeven more than) the apertures of telescopes. While theper pixel cost of the newer instrument is lower than thatof early generation instruments the fact remains that thecosts of the newer instruments routinely run $10M andup. Separately, Adaptive Optics (AO) has now come ofage and can offer finer imaging and better astrometry.The methodology of laser guide stars (LGS) makes itpossible to access targets over a reasonable fraction ofthe sky. However, AO facilities are quite expensive.

Next, the usable lifetime of instruments (lacking up-grades) is 10 years and the peak lifetime can be as smallas five years. Consider an Observatory desiring a mini-mum set of powerful “workhorse” instruments along tra-ditional lines (low spectral resolution and high spectralresolution optical spectroscopy, NIR spectroscopy, opti-cal imaging, NIR imaging). Given this set of five instru-ments and the limited lifetime of the instruments theObservatory will find itself developing a workhorse in-strument every few years.

Given this situation Observatory directors have to bal-ance the investment in instruments and AO with tra-ditional needs for infra-structure improvement, develop-ment of pipelines, archives and so on. Such decisions re-quire doing some sort of “cost-benefit” analysis. Next, alarge investment in an instrument that benefits one par-ticular area of astronomy results in “opportunity cost”penalties for other areas of astronomy. As a result as-tronomers in those other areas would necessarily be ask-ing the question “Was the investment in your area ofastronomy worth the cost to my area of astronomy?”.

Concepts such as “cost-benefit” analysis and “oppor-tunity costs”, while perhaps not commonly discussed inacademia (and even considered as anathema by some ofmy colleagues), are central to ordinary life (businesses).Ongoing business concerns base their decisions on futureinvestments using data in hand accompanied by a viewof where the best opportunities for growth lie (“marketsurvey”) but consistent with their “core competence”.It is my view that optical astronomy is no longer “smallscience” and as such optical astronomers must undertakecost-benefit analysis and come to grips with opportunitycost.

One could argue that, since astronomical research isfar removed from ordinary life, the very concept of cost-benefit analysis is meaningless. I do not agree with thissentiment for two reasons. First, when tens of millions ofdollars are being spent then funding agencies necessar-ily demand a greater level of scrutiny and justification.Next, to me it is a self-evident truth that research is sim-ply another human activity and as such subject to thesame set of issues as in ordinary life.

Here, I use the scientific output of the W. M. Keck Ob-servatory (WMKO) as a laboratory for the “business” oflarge OIR telescope observatories. I analyze the impactand productivity of the instruments of this 20-year oldObservatory. Even if one reluctantly agrees to undertakea cost-benefit analysis there still remains the issue of how

one can define “benefit”. I face this vexing issue head onin §2.

The rest of the paper is organized as follows. I pro-vide a brief history of WMKO (§3). In §4 I summarizethe principal instruments that were or continue to beemployed at the Observatory followed by the AdaptiveOptics Facilities (§5). The primary input for this reportare the papers which have resulted from data based onthe Keck Observatory. In §6 I summarize the method-ologies used and metrics employed in this paper. Theanalysis and basic inferences can be found in §7 and §8.The increased cost of operating large optical facilities ismotivating the operators of Observatories to seek part-nerships (and inversely late entrants seek partnership onexisting telescopes). In §9 I argue that the cost of a nightof telescope time should bear a relation to the produc-tivity of the Observatory. I end the paper by visiting thedismal state of the economics of small telescopes (§10)and the economics of “mega” instruments (§11).

2. MEASURING PROGRESS

The cost of an astronomical instrument or facility iseasy to define. For telescopes and instruments it is thecost to design, fabricate and commission the instrument(“capital cost”). For facilities one must also include therunning costs (“operation or ops” cost per night or peryear). The benefits are much harder to quantify andsome may even argue that benefits cannot even be agreedto by a group of astronomers (with disparate interests).

However, the situation is not entirely hopeless. Thereexists a rich literature of astronomers defining and mea-suring progress and confronting the analysis with widelyheld views and opinions. A good review of astronomical“bibilometrica” (or “scientometrica”) is provided by Abt(2005). I found myself entirely in full agreement with theopening paragraph by the author :“Astronomers insistupon seeing quantitative evidence in scientific papers orthey will not believe the results claimed. However, whendiscussing policies or making decisions about funding,instrumentation, promotions, etc., they depend mostlyupon impressions, feelings and intuition. But measuresof productivity, success and importance can be quanti-tative, and quantitative measures should replace impres-sions.”

In this paper I will be using two metrics to mea-sure progress. Most research consists of making gradualprogress. An active area of astronomy (almost by def-inition) will have a large flux of papers and necessarilythis flux will be associated with a large flux of citations.In most cases the increased activity results in progressbeing made. It is thus reasonable to use the citation fluxas a measure of routine progress.

Next, Abt (ibid) demonstrates that the top cited pa-pers are almost always agreed to be landmark papersby eminent astronomers and inversely those consideredto be landmark papers are also heavily cited. Abt ar-rives at this conclusion by using the Centennial Issue1

of the Astrophysical Journal as the input sample andcleverly builds the control sample (papers which, in theAstrophysical Journal, precede highly cited papers). Asa simple check I culled my top 10 cited papers and com-

1 http://www.amazon.com/American-Astronomical-Society-Centennial-Astrophysical/dp/0226001857

Instrumentation on Large Optical Telescopes 3

pared this list to my own view of my top papers. I foundan excellent concordance between the two lists. Thus, asa second measure of progress, I will be using the collec-tion of the most cited papers.

Returning to the subject of “bibliometrica” I refer thereader to a series papers by V. Trimble and associates andby H. Abt (e.g. Trimble, Zaich & Bosler 2005; Trimble &Zaich 2006; Trimble & Ceja 2008; Abt 2012). These au-thors use citation rates and investigate the productivityand impact of telescopes of various apertures, of differentvintages and undertaken a comparative study of facilitiessorted by wavelength and so on.

Before proceeding further I would like to acknowledgethat the statistics of citation are, in part, dependent onfashion and certainly influenced by the number of peo-ple who work in a given field. In astronomy, currently,most sub-fields related to cosmology are popular and in-creasingly the same is true of extra-solar planets. Pepe &Kurtz (2012) define a new index “Total Research Impact”or tori which takes into account of (1) field-dependentcitation rates (popular versus less popular fields), (2) thenumber of co-authors (papers with many co-authors arelikely to be cited more often than single author papers)and (3) shot noise (some papers become very popularfor reasons that are not clear after the fact, cf. GangnamStyle2). Here, I will stick to the two measures, both basedon citations, but add the caution that, for all the rea-sons cited by Pepe & Kurtz (ibid), it is not appropriateto compare the citation returns from, say, ground-basedoptical facilities to say those resulting from ground-basedradio facilities or space-based facilities. Indeed, one couldreasonably speculate that in (large) part the apparentproductivity of space-based missions is due to the munif-icent financial support received by astronomers for theanalysis of data.

3. THE W. M. KECK OBSERVATORY: A BRIEF HISTORY

The history of optical/IR astronomy has been, for along time, driven by ever increasing apertures. Largercollecting areas allow for spectroscopy of faint objects–an almost unique contribution of ground-based opticalastronomy. However, over time astronomers recognizedthe importance of “delivered image quality” (which re-quires both excellent site seeing and also fine telescopeoptics) The Canada-France-Hawaii (CFH) 3.6-m tele-scope (commissioned in 1979), located atop Mauna Kea,demonstrated the value of siting a modern large tele-scope at a site with superb seeing. It was only naturalthat Mauna Kea was chosen as the site for the next largetelescope coming from California – the Keck 10-m tele-scope(s).

3.1. The Era of Large Optical Telescopes

Breaking the tradition of monolithic primary mirrorthe large aperture of the Keck telescope was realized by36 hexagonal segments. This approach was pioneered byJerry Nelson and Terry Mast of the Lawrence BerkeleyLaboratory (LBL), University of California at Berkeley(UCB). The Keck project began with a grant, in 1985, of$70M from the W. M. Keck Foundation to California In-stitute of Technology (Caltech) towards the constructionof the first Keck telescope. The University of California

2 http://en.wikipedia.org/wiki/Gangnam Style

(UC) and Caltech formed a non-profit entity, the Califor-nia Association for Research in Astronomy (CARA) andjointly led the Keck project. As a part of this agreementUC signed up to pay for operations of the Observatoryfor the first 25 years. Following ground-breaking in 1986first light on Keck I (with all segments) was obtainedon 14 April 1992. Routine observations began in early1994. The run-out cost through first light for Keck I was$94.3M. The first light instruments were NIRC, LRISand HIRES.

In 1992, the Keck Foundation donated a secondtranche, to the tune of $74.5M, to Caltech for the con-struction of the Keck II telescope. The construction wascompleted in early 1996 and routine observations beganin October of 1996. The runout cost3 for Keck II was$77.8M. Following first light on Keck II NASA joined theKeck Observatory as a partner with an infusion of $44Min capital (CHECK) and agreeing to pay 1/6th of the op-erating costs (and receiving about 1/6th of the observingtime, in return). The University of Hawaii receives 10%of Keck I and 15% of Keck II time.

The capital cost for the two Keck telescopes is $172M(or $187.6M, if post-construction commissioning costsare included). Usually the average of these two num-bers is often quoted in the media4. This low cost is atestament to both the ingenuity of the designers of thetelescope as well as vivid demonstration of the segmentedarchitecture in breaking the cost scaling law for mono-lithic telescopes (Stepp, Daggert & Gillett 2003).

The Keck telescopes had a major impact (Crabtree2008; Kim 2011)5 because not only the telescopes repre-sented a huge jump in collecting area (relative to the ear-lier generation of large telescopes with useable effectivediameters of about 5-m) but were also able to producesuperb images limited only by the exquisite seeing atMauna Kea. The first generation of instruments were notonly powerful but also were available for observations ator close to first light. The next group of large telescopes,the 8.2-m ESO VLT telescopes (Paranal, Chile), the Sub-aru 8.2-m telescope (atop Mauna Kea), the 6.5-m Magel-lan telescopes (at Las Campanas, Chile) and the Gemini8.2-m telescopes (Cerron Pachon, Chile and Mauna Kea)came into operation starting 1999 (and later).

A different approach was taken by astronomers at theUniversity of Texas and the Pennsylvania State Univer-sity: the realization of large aperture but with a fixedspherical primary (cf. Arecibo). The Hobby-Eberly tele-scope (HET; McDonald Observatory, Texas) was thefirst such telescope. It used fixed segmented hexago-nal segments for the primary. The telescope was nom-inally commissioned in 1996 but keeping the segmentsphased was problematic. Fixes were designed (Boothet al. 2003) and implemented by 2004 (Booth et al.2004). The lessons learnt were applied to the SouthAfrican Large Telescope (Sutherland, South Africa; com-

3 All the cost numbers reported here, including the extendedcommissioning costs, were obtained by the author from J. Smith,the Project Manager for the Keck Telescopes.

4 http://www.nytimes.com/1996/05/09/us/world-s-biggest-telescope-has-finally-met-its-match-a-twin.htmlNew York Times, May 9, 1996. Money left over from the construc-tion of Keck II, including interest earned, were applied towardsthe development and construction of the first AO system (§5).

5 Crabtree issues a yearly update to his 2008 paper.

4 S. R. Kulkarni

TABLE 1Facility Instruments at the W. M. Keck Observatory

Instrument Upgrade(s) Period Refs Cost$M

NIRC - 1989-1994 [1a,1b] 1.9LRIS X 1988-1994 [2a] 4.3

. LRIS-Blue 1995-2000 [2b,2c] 4.3

. LRIS-ADC 2003-2007 [2d] 0.9

. LRIS-Red 2007-2010 [2e] 1.6HIRES X 1988-1994 [3] 4.2

. HIRES-3-CCD 2002-2004 - 1.5ESI - 1996-2000 [4a,4b] 4.0

NIRC2 - 1994-2000 - 6.0NIRSPEC - 1994-2000 [6] 4.4DEIMOS - 1993-2002 [7] 11.0

OSIRIS - 2000-2005 [8a,8b] 5.6MOSFIRE - 2005-2012 [9] 17.2

Note. — From left to right.: the name of the instrument, theperiod of construction, the run-out cost (marked to first light orthereabout; in “then” dollars) and code(s) which maps to theofficial instrument bibliographic reference. The mapping is asfollows: [1a] Matthews & Soifer (1994a). [1b] Matthews & Soifer(1994b). [2a] Oke et al. (1995). [2b] McCarthy et al. (1998).[2c] Steidel et al. (2004). [2d] Phillips et al. (2008). [2e] Rockosiet al. (2010). [3] Vogt et al. (1994). [4a] Sheinis et al. (2002).[4b] Sheinis et al. (2000). [6] McLean et al. (1998). [7] Faber etal. (2003). [8a] Larkin et al. (2006). [8b]Larkin et al. (2006).[9] McLean et al. (2012).

missioned 2005). Both these telescopes achieve largeapertures (effective aperture size of about 9-m) at lowcost (but with observations limited to small hour anglesand also, relative to conventional telescopes, a limitedfield-of-view).

4. THE INSTRUMENTS

There are (or have been) ten “facility” (major) instru-ments at the Keck Observatory. The facility mid-IR in-strument, the Long-Wavelength Spectrometer (Campbell& Jones 2004) which was on the Keck I telescope for atotal of 363 nights is not included in the above Table norin the analysis below. In Table 1 I list nine remainingfacility instruments. A summary of the nine instrumentsnow follow.

4.1. Near-Infrared Camera (NIRC)

NIRC was the first instrument to be commissioned atthe W. M. Keck Observatory. The instrument was lo-cated in the forward Cassegrain module of the Keck Itelescope. The Long Wavelength Spectrometer (LWS)was also housed in this module. Both instruments arefed by a gold-coated f/25 chopping secondary mirror.

The preliminary study for NIRC began in 1987 in re-sponse to a call for first light instruments for the Keck Itelescope. First light was obtained in March of 1993 onthe Keck I telescope (Matthews & Soifer 1994a, 1994b).Construction for NIRC was initiated in 1989 and com-pleted by the end of year of 1992. The principal investiga-tors of the project were Keith Matthews and B. ThomasSoifer of Caltech.

The primary detector for NIRC was a 2562 pixel InSbdetector (and fabricated by Santa Barbara Research Cor-poration). Thanks to a careful design NIRC achievedlow background which allowed for sensitive imaging andgrism (low resolution) spectroscopy in the wavelengthrange of 1–5µm. In 1995, an image expander option

was added and this allowed for high resolution imagingvia speckle imaging6 (Matthews et al. 1996). The samemode was used later on for aperture masking experiments(Tuthill et al. 2000). The instrument was decommis-sioned following the run of 30 January 2010. NIRC cannow be found in the lobby area of the WMKO head quar-ters in Waimea (Kamuela), Hawaii.

4.2. Low Resolution Imaging Spectrometer (LRIS)

As with NIRC the study for LRIS began in 1987. LRISwith one arm optimized for blue bands and the other forred bands was designed to be a workhorse low resolu-tion optical spectrograph. LRIS, as implied by its name,also had an imaging mode. Unlike the previous genera-tion of slit spectrographs LRIS was designed to routinelyundertake multi-object spectroscopy.

Construction of LRIS was completed in 1992 and in-stalled at the Cassegrain focus of the Keck I telescope.First science light was achieved in the summer of 1993(see Oke et al. 1995). Owing to financial reasons onlythe red arm was populated for first light. The PrincipalInvestigators were J. Beverly Oke and Judith G. Cohen.Following first light some repairs were undertaken be-tween 1994 and 1996.

The blue arm of LRIS was populated as a part of the“LRIS-Blue” (LRIS-B) upgrade project. This projectwas led by James K. McCarthy and Charles C. Steidel,both at Caltech, and lasted from 1995 through 2000. Theaddition of the blue channel thus doubled the data (withthe existing channel providing the red spectrum or redimage). In 2002 the original Tektronix (SITe) 2K×2K24-micron pitch pixel detector was replaced by a blue-optimized CCD mosaic of two EEV 2K×4K CCDs witha 15µm pitch. The new CCD mosaic not only offered abetter match to the spectral resolution but also increasedthe nominal spectral coverage by 25%. The primary ref-erences for the LRIS-B project are McCarthy et al. 1998(the design) and Steidel et al. 2004 (the performance).

The availability of red sensitive CCDs (deep-depletionCCDs) made it attractive to replace the original Tek-tronix chip by a mosaic of two 2K×4K fully depleted,high resistivity CCDs for the red arm. In addition, theelectronics were upgraded and a new focus mechanisminstalled. This project was led by Constance M. Rockosiof UCSC. The initial CCD was found to be unreliableand a replacement was installed by end of year of 2010.The official reference for this upgrade is Rockosi et al.(2010).

The “Atmospheric Dispersion Corrector” (ADC)project was headed by Joseph S. Miller and A. “Drew”Phillips, both from UCSC (Phillips et al. 2008). Theproject was initiated in 2003 and the ADC was commis-sioned in 2007. The ADC increases the flexibility of themulti-object spectrograph mode (the slit mask can be de-signed without paying much attention to parallactic an-gle) and also, as the author can attest, contributes to in-creased target throughput for single object spectroscopy.

4.3. High Resolution Spectrograph (HIRES)

As with the previous two instruments HIRES was se-lected following a call for first-light instruments for the

6 this mode was listed as “NIRCs” in the scheduling logs.


Keck I telescope (although the conceptual idea and earlydesign started in 1983). The project was led by Steven S.Vogt of UCSC. It took five years (1988–1993) to designand build the instrument. HIRES is mounted on one ofthe Nasmyth ports of the Keck I telescope. First lightwas achieved on July 16, 1993. Further details on theinstrument can be found in Vogt et al. (1994). Since theinstrument is mounted at the Nasmyth focus the sky im-age rotates, with respect to the detector, with the move-ment of the telescope and thereby limited the integra-tion time. The “de-rotator” project was led by David R.Tytler (during the period 1997–1999).

HIRES was originally built for high resolution spec-troscopy of stars and quasar absorption line studies. Theoptical design is versatile to accommodate operation inthe entire band 0.3–1.2µm. Over time it has been exten-sively used for extra-solar planet searches via precisionradial velocity (RV) studies. To this end an insertableIodine cell and an exposure meter were added.

In 2004 Vogt led a project to replace the original en-gineering grade 2K×2K Tektronix CCD with a mosaicof three science grade CCDs. The smaller pixel scale(15µm) of the new detectors was better suited to theHIRES camera. Furthermore, the three CCDs are eachoptimized for the wavebands of the dispersed spectrum(more precisely, two are blue sensitive and one is red sen-sitive). The upgrade contributed to both an increase inthe spectral coverage by a factor of three and also im-proved the precision in RV from 3 m s−1 to 1 m s−1 (But-ler et al. 2006). To my knowledge there is no officialreference which summarizes the technical details of theupgrade.

HIRES is noteworthy for two reasons. First, early on,a pipeline to reduce the data was available (MAKEE)– a novelty (at least for the California community) inthose days. The pipeline allowed for rapid exploitationof HIRES data. This became particularly important fol-lowing the upgrade of HIRES. Second, starting 2004 thedata from HIRES were archived on behalf of NASA bythe Infra-red Processing & Analysis Center (IPAC) – an-other first for the Observatory. The data, following theexpiration of a default proprietary period (which is, bydefault, 18 months; in a few cases some astronomers haveobtained exclusive rights lasting a decade), is now avail-able to the global astronomical community. The data aremade available via the Keck Observatory Archive (KOA)portal7. The success of the HIRES archive project ledNASA to fund a phased approach of ingesting data fromother Keck instruments.

4.4. Echellette Spectrograph & Imager (ESI)

ESI is a medium-resolution spectrograph with imagingcapability (Sheinis et al. 2000). The instrument has anechellete grating and two prisms for cross-dispersion. Inthe low dispersion mode (50 to 300 km s−1) the disper-sion is provided by prisms. This mode has high through-put but owing to the large number of sky lines (in thered region of the spectrum) this mode is only popularwith astronomers interested in the study of blue objects.In the echellete mode the two prisms cross-disperse thebeam diffracted by the echellete grating. The spectralresolution is moderate, about 50 km s−1 over the entire

7 http://www2.keck.hawaii.edu/koa/public/koa.php

range 0.39–1µm. The moderate spectral resolution iswell suited to kinematics, abundance studies of faintstars (especially giant stars in the Local Group) and faintgalaxies and absorption line studies of quasars.

The project was led by J. Miller of UCSC. The instru-ment was officially commissioned towards the end of 1999(Sheinis et al. 2002). In early 2010 an Integral Field Unit(IFU) capability was commissioned.

4.5. Near-Infrared Echelle Spectrograph (NIRSPEC)

NIRSPEC is a cross-dispersed echelle spectrographthat operates in the 0.95–5µm band. The instrument hastwo spectral modes: high spectral resolution mode withresolution of about 25,000 and a low spectral resolutionmode with a resolution of 2,000. NIRSPEC is mountedon one of the two Nasmyth ports of the Keck II telescope.It can be used in a stand-alone mode (seeing-limited) orbehind the Keck II AO system which is mounted on theother Nasmyth port (§5). This latter mode is referredas “NIRSPAO”. The NIRSPEC project was led by IanS. McLean of the University of California at Los Angeles(UCLA). The primary reference paper for the instrumen-tation is McLean et al. (1998).

The NIRSPEC project ran from October 1994 throughSeptember 1999. First light was achieved on April 23,1999. A refurbishment of some gears and motors wasalso performed in 2000. In the same year the NIRSPAOmode was implemented. This necessitated fore optics forzooming the input image and a corresponding smallerpupil stop in the filter wheel.

NIRSPEC has two NIR cameras: a slit-viewing camera(SCAM) operating in the 1–2.5µm band and a camerafor the spectroscopic channel and served by an Alladin1024×1024 pixel detector. Some astronomers have madeextensive use of SCAM for purely imaging projects.

4.6. Deep Imaging Multi-Object Spectrograph(DEIMOS)

DEIMOS is a multi-object optical spectrograph opti-mized for studying large scale structure of the Universe(via spectroscopy of galaxies). It is mounted at one ofthe Nasmyth focus of the Keck II telescope. The spec-trograph employs an array of eight red-sensitive CCDs.Sufficient spectral resolution in the red band allows forminimization of bright terrestrial OH lines. The effectiveslit length on the sky is 17 arc minutes (a second barrel,if built, will double the slit length). The key feature ofDEIMOS was the wide-angle camera, which offers botha long slit length and a wide spectral coverage. Theproject was led by Sandra M. Faber of UCSC and theofficial reference is Faber et al. (2003). The project ranfrom 1993 to 2002. First light was achieved in Spring of2002. DEIMOS was unique at the time it was built andis only matched by IMACS which was commissioned onMagellan in 2004.

4.7. Near Infra-Red Camera 2 (NIRC2)

The Near Infra-Red Camera 2 (NIRC2) was designedto be the primary imager for the Observatory’s Adap-tive Optics system (both Laser Guide Star and NaturalGuide Star; §5). The instrument is located behind theAO bench at the other Nasmyth focus of the Keck IItelescope. Three pixel scales allow for diffraction lim-ited imagery in each of J, K and L bands. The detector

6 S. R. Kulkarni

is 1024×1024 pixel InSb Aladdin-3 array and capable ofY through L and M band operations. The filter wheelaccommodates a large number of filters over the spec-tral range 0.93–5.3µm. Two prisms allow for low andmedium-resolution slit spectroscopy. A choice of pupilmasks and coronagraphic stops allow for low backgroundand high contrast imaging and spectroscopy.

The principal investigators were K. Matthews and B.T. Soifer. The instrument is sited at the Nasmyth focusof the Keck II telescope. With the view of undertak-ing decade-long astrometry careful attention was paid tokeep the instrument very stable.

Construction for NIRC2 began in 1994 and concludedin 2000. First light was achieved in the summer of 2001.Unfortunately there is no publication describing the in-strument. Since there is no paper detailing the designand performance of the instrument the reader is directedto the instrument homepage8 for further details.

4.8. OH-Suppressing Infrared Imaging Spectrograph(OSIRIS)

OSIRIS is a NIR integral field spectrograph designedto take advantage of diffraction limited images madepossible by the Observatory’s Adaptive Optics system(§5). The principal investigator of the project was JamesLarkin (UCLA) and the co-Principal Investigator was A.Krabbe (UCB). A lenslet array feeds a rectangular patch(1000 spaxels) of the sky into a moderate spectral reso-lution (R ∼ 3800) spectrograph which can operate fromthe z band through K band. The 1000-spaxel format issuitable for imaging compact objects (0.3 arc seconds to3 arc seconds in the short axis). With the advent of a sec-ond LSG system on Keck I (see §5) OSIRIS was movedto Keck I in late 2012.

The design study for OSIRIS was undertaken in 1999.First light was achieved during 2005. The primary refer-ence for OSIRIS is supposed to be Larkin et al. (2006a).However, I have also included the reference Larkin et al.(2006b) since it appears to have garnered more citationsthan the officially favored instrument reference.

Shortly after OSIRIS was commissioned it becameclear that the throughput of the instrument was lowerthan expected. It was traced to a grating which was notmanufactured to specifications. In 2013 a new gratingwas installed and OSIRIS has now achieved the sensitiv-ity that was expected from the initial design.

4.9. Multi-Object Spectrograph for Infra-RedExploration (MOSFIRE)

MOSFIRE, a multi-object near-IR (0.97–2.1µm) spec-trograph and imager, is the latest instrument to the sta-ble of facility instruments (McLean et al. 2012). Theinstrument is notable for an “on-the-fly” configurableslit mask. The user can obtain moderate resolution(λ/δλ ≈ 3600) slit spectra of 46 objects spread over a6 × 6 square arc-minute field-of-view. Cryogenic cool-ing of the slit mask, a low-noise 2K×2K Hawaii-2RGdetector and the large collecting area of the Keck tele-scope makes MOSFIRE perhaps the most sensitive multi-object spectrograph at the present time. The instrumentis mounted at the Cassegrain focus of the Keck I tele-scope. The principal investigators are I. S. McLean of

8 http://www2.keck.hawaii.edu/inst/nirc2/

UCLA and C. C. Steidel of Caltech. The project beganin 2005 and first light was achieved in Spring of 2012.9

There were some teething troubles and routine opera-tions began in 2013.

5. ADAPTIVE OPTICS

The ability to exquisitely align the 36 segments limitedonly by the roughness of the segment surfaces (40 nm to80 nm) allow the Keck telescopes to take full advantageof the superb seeing of Mauna Kea (Chanan et al. 1998;Chanan, Ohara & Troy 2000). Provided the seeing co-operates the Keck telescope can produce images in thevisible and with 0.4 arc-second full width at half max-imum (Wizinowich et al. 1994a). This exquisite per-formance when combined with the large diameter, D, ofthe Keck telescope makes adaptive optics (AO) a naturalstrength10 of the Observatory. As a result, planning11 forAO began immediately after commissioning of the firstKeck telescope (Wizinowich et al. 1994b).

In early 1999 a natural guide star (NGS) AO systemwas commissioned on the Keck II telescope (being lo-cated at the left Nasmyth focus; Wizinowich et al. 2000).Routine observations began in Fall of 1999. The systemwas based on a 349-actuator Xinetics deformable mirrorand a 64×64 fast-readout CCD. The initial detector wasan engineering camera (“KCAM”). In early 2001 NIR-SPEC was used behind the AO system and later NIRC2became available for use as well. Two years later an iden-tical NGS AO system for Keck I, located also on the leftNasmyth station, was commissioned (see Wizinowich etal. 2003).

The AO roadmap included a Laser Guide Star (LGS)assisted AO. The laser guide star can be used to infermost of the wave front distortion but not the phase gra-dients (which lead to tip-tilt errors). A natural guide staris still needed for this purpose but it can be much fainter(approaching V=19) as compared to a purely NGS AOsystem (V=14). A 13-watt Sodium laser supplied bythe Lawrence Livermore Laboratory was installed at theKeck II telescope and LGS observations began in 2004(van Dam et al. 2006; Wizinowich et al. 2006). In2007 a major improvement was undertaken for both theKeck I and Keck II AO systems. The wave-front sen-sor and wave-front electronics was upgraded. As a resultthe quality of correction (Strehl ratio for bright stars)increased from 0.58 to 0.71 and the limiting magnitudefor NGS AO also improved (V< 14); see Johansson et al.(2008).

There are two major improvements that are in progressfor the Keck II LGS system. The Keck II laser islaunched using a telescope mounted to the side of theKeck II telescope. As a result there is a perspectiveelongation of the Laser Guide Star as seen by the AOwave-front sensor, due to the thickness of the sodiumlayer. The elongation naturally reduces the quality ofcorrections. This reduction can be reduced by having the

9 The first attempt for a multi-slit IR spectrograph was KIR-MOS. Following the preliminary design phase (2002–2005) the es-timated cost of the rather ambitious instrument was deemed to betoo high to warrant construction. However, much of the develop-ment undertaken for KIRMOS was of use to MOSFIRE.

10 The gains for AO grow as Dn where n = 2 to 4, dependingon what quantity is being measured.

11 see footnote 4.


TABLE 2Adaptive Optics at the W. M. Keck

Observatory

System Tel Year Cost ($M)

NGS II 1999 4.0LGS II 2004 7.5

WF-Upgrade II 2007 2.2Center-Launch II 2014 2.6

TOPTICA-Laser II 2015 4.0NGS I 2002 3.0

LMCT-Laser I 2011 3.1LGS-Infrastructure I 2012 5.5

NIR-Tip-Tilt I 2014 3.1

Note. — From left to right: The name of thesystem or sub-system followed by the telescopenumber on which it is located, the year of com-missioning and the cost for the project.

launch telescope behind the secondary mirror and thusaligned to the axis of the telescope. Current status ofCenter-Launch project.

Next, the current dye laser will be replaced with a 20 WRaman fiber amplified laser fabricated by a consortiumof TOPTICA and MPBC (Friedenauer et al. 2012). Thenew laser (hereafter “TOPTICA”) is expected to have atleast ten times the coupling efficiency to the sodium layerthanks to its continuous wavelength and the use of someof the laser power to re-pump the sodium atoms.

The Keck I AO LGS system began shared risk obser-vations in summer of 2012 (Chin et al. 2012). Thereare two differences between the Keck I and Keck II LGSsystems. First, the Keck I laser system is a high power(20 W) solid-state CW laser supplied by the LockheedMartin Coherent Technology group (Sawruk et al. 2010)and launched by a telescope mounted behind the sec-ondary cage. Hereafter, we will refer to this as the LMCTlaser. NSF funded the acquisition of the laser. The in-stallation was funded by WMKO (and listed in Table as“LGS Infrastructure” in Table 2). Finally, going into thefuture, an infra-red tip-tilt sensor based on a Hawaii-2RGdetector was developed (listed as NIR tip-tilt in Table 2).Tip-tilt sensing will be done on the AO-corrected core ofthe NGS image of the tip-tilt star. Dichroics will be usedto send the Ks-band or H-band light, over a 100 arcsecsquare field, to the sensor. When using Ks-band light thesky fraction over which the 1-D rms tip-tilt error is lessthan 20 mas will be increased from 45% to 75%. ThisNIR tip-tilt sub-system was installed in early 2014 andis expected to be come operational later in the year.

Clearly, the Keck I LGS system is an improvement, inseveral respects, over the venerable Keck II LGS system.The reader is referred to Table 2 for a comprehensivesummary as well as the timetable of both the AO sys-tems. The OSIRIS instrument has now been moved fromKeck II to Keck I in order to take advantage of this newLGS facility. Since many long term astrometry projectsinvolve NIRC2 there are no plans of moving NIRC2 fromKeck II.

6. DATA, METHODOLOGY & METRICS

6.1. Primary Data

The primary data for the analysis is the bibliography12

of refereed papers maintained by the librarian (PeggiKamisato) of the W. M. Keck Observatory. For everypaper Kamisato lists the following attributes: Authors(limited to first six authors), Title of the paper, Jour-nal name, Volume, First page, Year of publication, In-strument(s) used and the bibcode.13 The assignmentof the instruments were made by P. Kamisato based onher scanning the literature and reading of the papers. Atotal of N = 3628 papers were published by the end of2012 and the score by March 2014 stood at 3988.

At the time I began my research (April 2012) the database was expected to be complete going forward of 1996.P. Kamisato and I did a search of the literature andadded papers for 1994 and 1995. Next, about 150 pa-pers lacked instrument entry. For about half the papersKamisato did not have easy access (primarily commer-cial publications for which the WM Keck Observatorydid not carry a subscription) and those for which an in-strument assignment was not clear (see below). I readthese papers and made the instrument assignments. Fora fraction of the cases the assignment was difficult tomake because the authors do not provide sufficient de-tails other than thanking the W. M. Keck Observatory.Through patient reading in most cases I could discernthe instrument used.

Finally there remained a group of papers that still re-mained problematic from the point of view of assigningan instrument. In some cases it is clear that there wereno new data that the authors were reporting and werereferring to published data. Another sub-set of the pa-pers were primarily modeling papers and made minoruse of existing data to validate their modeling. A thirdsub-set of papers were primarily concerned with deepimages of regions of sky (with an eye towards large scalestructure and galaxy formation). Such papers combinedata from several observatories (e.g. Hubble, Chandra,Spitzer, VLA, Keck and so on) and several instrumentswithin the same observatory. In all these cases the Keckdata has already been published and inferences drawn.Altogether about FIFTY (CHECK) papers fell in one ofthese three categories. These papers have not beenassigned to any instrument(s).

For the analysis here I have considered all Keck papersfrom 1993 through the end of 2012. Citations to Keck pa-pers beyond 2012 are not included in the analysis (otherthan in Figure 11 and indirectly in Table 7).

6.2. Usage of Nights

Starting from the commissioning14 of Keck I in 1993through semester 2012B15, using the “Query” tool16 pro-vided by WMKO, I found a total of 7143 nights wereavailable on Keck I. The Query tool shows that betweencommissioning17 of the Keck II telescope through the end

12 http://www2.keck.hawaii.edu/library/keck papers.html13 A unique identifier to each paper by the SAO-NASA As-

trophysics Data System (and usually simply called as ADS). Seehttp://adsabs.harvard.edu

14 The first run appears to have taken place on 1-October-1994.15 A year, as is the tradition in many observatories, is divided

into two semesters. The “A” semester starts 1 February and the“B” semester starts 1 August.

16 http://www2.keck.hawaii.edu/schedule/schQuery.php17 The first run appears to have taken place on 1-October-1996.

8 S. R. Kulkarni

of 2012B a total of 6148 nights were available on Keck II.The same tool allowed me to find the number of nightsallocated to each of these facility instruments.

Sometimes the scheduling logs list, for the same night,NIRC and LWS. Both these instruments were sited atthe forward Cassegrain focus of the Keck I telescope.The designation “NIRC-LWS” meant that the primaryinstrument for the night was LWS where the designation“NIRC/LWS” meant that the two instruments sharedthe night (R. Campbell, WMKO, pers. comm.). Thetotal number of NIRC and NIRC+LWS nights is 1094.Of this, 984 nights are solely ascribed to NIRC. I splitthe remaining balance of 110 evenly between NIRC andLWS, leaving NIRC a total of 1049 nights.

Next, there are some nights which are shared betweenengineering and observing. In such cases, two instru-ments are listed for the same night. The most commonexample involves the Phasing Camera System (PCS)which is a workhorse for engineering tests. The PCS islocated at one of the four bent Cassegrain ports in eachtelescope. Following the engineering test(s), the tele-scope is, almost always, returned for astronomical use.In this case the Keck database (at the above URL) showsPCS and a facility instrument (say LRIS). For such casesI have not attempted to assign fractional nights. Insteada full night is allocated to LRIS (in this example) anda full night to PCS. For this and similar reasons (seebelow) the sum of nights assigned to each instrument isslightly largely than the number of total nights formallyallocated to the instrument. The allocations of nights byinstrument is summarized in Table 3.

For completeness, I discuss the Keck Interferome-ter. Originally it was envisaged to include a collectionof smaller telescopes (“outriggers” or “side-Kecks”) foryear-around precision astrometry and occasional Keck I–Keck II interferometry (visibility and nulling) to char-acterize the distribution of zodiacal dust in a sampleof nearby Sun-like stars. This ambitious project wasfunded by NASA. The first phase of the project wasthe development of the standard visibility mode (“V2”;commissioned in 2001) followed by the “Nuller” mode.Phase referencing methodology (first demonstrated atthe Palomar Testbed Interferometer) was successfully un-dertaken with the Keck I–Keck II interferometer (the“ASTRA” project). The Keck Interferometer project of-ficially ended in 2012A. A total of 508 nights were allo-cated to this project (which in reality meant only half asmany nights since both telescopes are needed to run theinterferometer).

To complete the census of the allocated nights I notethat guest or PI instruments – MAPS, STEPS, MIRLINand OSCIR – obtained a total of about four months.Finally, about 5% of the nights appears to have beenused for engineering, commissioning new instrumentsand other purposes.

6.3. Methodology

I wrote a series of MATLAB programs to analyzeKamisato’s database. Each Keck paper is assigned astructure. The attributes of each paper in Kamisato’sdatabase are assigned to the structure. For each bibcodeI wrote a program that queried the ADS (see footnote 13)database and obtained information of papers citing agiven Keck paper. The data thus obtained was condensed

TABLE 3Allocation of Nights (1993–2012)

# Instr. Tel Period Nights Open

2 NIRC I 1994–2010 1049 0.513 LRIS I 1994– 3197 0.694 HIRES I 1994– 2631 0.785 ESI II 2000– 620 0.766 NIRC2 II 2000– 1136 0.387 NIRSPEC II 2002– 1622 0.608 DEIMOS II 2001– 980 0.729 OSIRIS I 2005– 583 0.63

Note. — Number of nights on Keck-I: 7143. Numberof nights on Keck-II: 6148. Fraction used by above instru-ments: 88.9. # is an internal index. The years over whichthe instrument was (and continues to be) used is given by“Period’. We make no distinction between NIRSPEC orNIRSPAO, LRIS-R or LRIS-B or LRIS-ADC or LRIS, NIRCor NIRCs and HIRES, HIRESr or HIRESb.The last columnis the typical open-shutter fraction.

to yield ck(tk, t), the number of citations in year t to Keckpaper with index k (whose year of publication is tk). Thisvector was added as an element to the structure.

The analyses worked off the structures. All the anal-yses programs use these structures as the inputs, filterthem on instruments and directly produce all the Tables(in LaTeX format), the Appendix (also in LaTeX format)and all the Figures displayed in this paper.

6.4. Aggregate Metrics

I define the productivity of an instrument as the num-ber of nights taken to produce a paper (by a given in-strument). This is computed by taking the ratio of to-tal number of papers ascribed to that instrument to thenumber of nights assigned to the same instrument (seeTable 3). The impact of the instrument is defined bythe number of citations garnered per night of telescopetime assigned to that instrument. Additional measuresof impact are the H-index18, the mean and median of thenumber of citations.

6.5. Flux Curves

Here I discuss functions of metrics which capture thetemporal evolution of the productivity and impact of theObservatory.

1. The annual flux of refereed publications, P(t). Thiscurve is obtained by binning the list by the year ofpublication. This is a widely used metric.

2. The sum of citations from publication to presentyear (t) of the kth paper and for a list of papers(k = 1, 2, ..) is, respectively,

Ck(t) =∑t>tk

ck(tk, t)

C(t) =∑k

∑t>tk

ck(tk, t). (1)

Focusing on a single paper, colloquially, Ck(t) isreferred to as the “number of citations” and oftensimplified to “citations” of that paper. However,

18 http://en.wikipedia.org/wiki/H-index


Ck(t) changes with time (for young papers Ck usu-ally increasing with t; for older papers it remainsconstant with t; when a subject is revived, citationsto an old and dormant paper flourish again). As aresult Ck(t) does not lend itself to a clean interpre-tation. I therefore will not be using C(t) as metric(other than a brief mention in Table 7).

3. The citation flux curve, C(t) measures the num-ber of new citations generated by a given list ofKeck papers in a given year (t). The easiest wayto understand this curve is to view ck(tk, t) as aresponse function (launched at t = tk) of the kthpaper. In order to compute the citation flux curvein year t one needs to sum the response functionof all the relevant Keck papers prior to that year.Mathematically, the citation flux curve is given by

C(t) =∑k

ck(tk, t). (2)

In §7 I present the paper and citation flux curves for theprincipal instruments of the Keck Observatory.

I make some observations about two “light curves”:P(t) and C(t). On general grounds we expect P(t) torise slowly and then reach a plateau as users become fa-miliar with the instrument and data reduction tools ma-ture. Once the “low hanging fruit” projects are finishedP (t) will likely decline (unless a major discovery opensup new avenues of investigation). Additionally, the de-cline will be precipitated by the arrival of more powerfulinstruments (in the same area) at other observatories.

Next, a typical C(t) light curve rises slowly, enjoys aplateau for nearly a decade and then gradually declineIn order to interpret the citation light curve it is worthnoting that there is a lag between the publication of apaper and the accrual of citations. Next, an importantpaper is also durable which means that it keeps gettingcited for many years. As a result, we can make threegeneral observations.

I. The higher the value of the peak (plateau) flux thehigher is the impact of the instrument.

II. The larger the duration of the plateau (the widthof C(t)) the higher is the impact of that instrument.

III. A decreasing C(t) almost always signifies that theinstrument should be retired. Indeed, given the sixto ten year timescale for development and fabri-cation of instruments, one could say that seriousplanning for the next instrument should alreadystart beginning when C(t) starts plateauing.

7. ANALYSIS & RESULTS

The productivity and impact of the instruments of theKeck Observatory (as defined in §6.3) are summarized inTable 4 and Table 5, respectively. The light curves of theinstruments is summarized in Figure 1. The light curveof each instrument can be found in in §7.1–§7.5.

As noted in §2 the singular or exceptional impact of aninstrument (or an author, for that matter) is measuredby the highest cited papers. Initially I thought listingthe top five papers (for each instrument) would be ad-equate. However, I realized that a few papers claimed

TABLE 4Productivity of Instruments

Inst. NP NC n−1P nC

NIRC 234 13926 4.5 13.3LRIS 1245 116374 2.6 36.4

HIRES 945 60005 2.8 22.8ESI 248 19306 2.5 31.1

NIRC2 273 10467 4.2 9.2NIRSPEC 386 20653 4.2 12.7DEIMOS 440 28665 2.2 29.2

OSIRIS 58 1951 10.1 3.3

Note. — Columns (from left to right): NP

is the total number of papers NC is the sumof citations. n−1

P is the inverse of the numberof papers per night. nC is the number ofcitations per night.

TABLE 5Impact of Instruments

Inst. H M NC/NP

NIRC 63 33 60LRIS 144 40 93

HIRES 125 40 63ESI 72 38 78

NIRC2 50 23 38NIRSPEC 69 26 54DEIMOS 88 35 65

OSIRIS 28 26 34

Note. — H is the h-index, M isthe median and NC/NP is the meannumber of citations per paper.

the top spots for several instruments. The most heavilycited papers from LRIS, DEIMOS and ESI are all of fouroptical instruments are all related to the same topic – theuse of supernovae for cosmography. Looking at the toppapers cited by other Observatories I realized that thesame topic – supernova Ia cosmography – is also claimedto be the top contribution by several observatories. Thusin order to assess the unique contribution of Keck I ex-panded the list to ten papers (Table 6). The titles ofthese papers can be found in the Appendix (§A). Thereader is urged to look at this list of papers to appreci-ate the singular (and distinct) returns from each of theseinstruments.

7.1. NIRC

The light curves of NIRC (Figure 2) are worthy of fur-ther study because NIRC did not undergo an upgradeand since the commissioning of NIRC there has been asteady growth in the size of NIR detectors. As a con-sequence of the latter NIRC has been subject to strongexternal forces. Thus in some ways NIRC provides anideal “test” instrument for the purpose of this paper.

The NIRC paper production reached a peak six yearsafter commissioning and this was followed by a lineardecline. In contrast, the citation light curve reached aplateau nearly ten years after commissioning and is nowslowly declining. The lag between paper production andgarnering of citations is not unexpected. We now havean empirical measure of this lag, about three years. Forfuture discussion I note that the width of plateau of C(t)

10 S. R. Kulkarni

TABLE 6Most Cited Papers

Inst. Tops

NIRC 579 507 483 460 430 408 402 368 301 258LRIS 7820 7693 2666 1700 1621 1352 1340 1302 1159 1148

HIRES 640 623 565 515 498 386 359 339 338 329ESI 682 676 626 608 562 490 483 394 359 357

NIRC2 576 509 434 357 308 200 195 172 159 158NIRSPEC 2666 608 562 507 301 293 272 257 207 195DEIMOS 1700 1031 682 505 425 406 404 306 297 284

OSIRIS 154 99 93 88 84 83 77 73 72 64

Note. — The number of citations of the top 10 papers arising fromeach Keck facility instrument

1990 1995 2000 2005 201010

0

101

102

103

104

105

C(t)

NIRCLRISHIRESESINIRC2NIRSPECDEIMOSOSIRIS

Fig. 1.— The citation flux curve for every facility instrument (marked) of the W. M. Keck Observatory.

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

10

20

30

NIRC

P(t)

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

500

1000

1500

C(t)

Year

Fig. 2.— publications, P(t). (Bottom) The annual flux ofcitations of papers, C(t). See §6 for definition of these threequantities.

is in excess of a decade.

7.2. ESI, NIRSPEC, DEIMOS

None of these instruments have undergone any (or sig-nificant) upgrades. The paper curve of ESI mimics thatof NIRC (except shifted in time). The impact of ESIremains quite high though (see Table 5).

NIRSPEC, like NIRC, had peaked in paper productionabout seven years after commissioning. However, it re-cently seems to be undergoing a renaissance with a hint

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

10

20

30

40

ESI

P(t)

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

500

1000

1500

2000

C(t)

Year

Fig. 3.— The light curves for ESI.

of a second peak beyond 2012. Consistent with this hintthe citation light curve of NIRSPEC shows a continuedgrowth. This resurgence is surprising given that singleobject NIR spectrographs built at other Observatoriesand of later vintage employ more sensitive NIR detec-tors and have thus better performance than NIRSPEC(e.g. CRIRES on VLT). I venture to guess that targetsprovided by the WISE mission (which lasted most ofCY2010) are responsible for the continued demand forNIRSPEC. In a similar manner I venture to suggest thatthe Gaia mission will lead to a resurgence in the use ofESI.


1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

20

40

60

NIRSPECP(t)

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

1000

2000

3000

C(t)

Year

Fig. 4.— The light curves for NIRSPEC.

DEIMOS continues to enjoy a strong growth in paperproduction for nearly a decade, despite no upgrades. Thecitation light curve could be argued to be accelerating.Both indicators are consistent with an apparently near-infinite demand by astronomers for highly multiplexed(spectroscopic) instruments.

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

20

40

60

80

DEIMOS

P(t)

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

2000

4000

6000

C(t)

Year

Fig. 5.— The light curves for DEIMOS.

7.3. LRIS and HIRES

LRIS and HIRES are remarkable instruments. Thesetwo first light instruments show no flagging in produc-tivity. Clearly, this continued fecundity is due to thetimely and powerful upgrades (which LRIS received in2000, 2007 and 2010; see §4.2). The productivity in-crease due to upgrades is clearly delineated in the lightcurve of HIRES (Figure 7). In the first phase the rateof papers rises gradually and reaches a plateau by 2000which is maintained for another five years. Then we geta gradual rise starting the year 2006 which appears tobe unabated by 2012. It is not unreasonable to conclude

that the 2004 upgrade (§4.3) has directly contributed tothe increase in productivity of HIRES.

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

50

100

LRIS

P(t)

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

5000

10000

15000

C(t)

Year

Fig. 6.— The light curves for LRIS.

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

50

100

HIRES

P(t)

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

2000

4000

6000

8000

C(t)

Year

Fig. 7.— The light curves for HIRES.

7.4. NIRC2 and OSIRIS

The paper production of NIRC2, even 10 years aftercommissioning, is still rising as is the citation light curve(Figure 8). Since NIRC2 is only used behind the AOsystem the fate of NIRC2 is firmly tied to improvementsin the AO system. From Table 2 we note there has beensignificant investment in improving AO (on both Keck Iand Keck II) for the past decade. The continued rise ofP(t) and C(t) thus is reasonable.

OSIRIS is both a young instrument and also sufferedfrom a throughput problem (which appears to be solvedas we go to press). Given its effective youth I have electednot to display the light curve.

7.5. Adaptive Optics

12 S. R. Kulkarni

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

20

40

60

NIRC2P(t)

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

1000

2000

3000

C(t)

Year

Fig. 8.— The light curves for NIRC2.

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

20

40

60

80Adaptive Optics

1994 1996 1998 2000 2002 2004 2006 2008 2010 20120

1000

2000

3000

4000

Year

C(t)

Fig. 9.— The light curves of papers arising from AO method-ology.

The number of AO papers (which means both NGSand LGS) is 429 and the total number of citations cur-rently stands at 15,632. As can be seen from Table 4NIRC2 and OSIRIS contribute 332 publications (withthe remaining due to Keck interferometry and the earlyuse of AO which used KCAM). The citation flux curve isshown in Figure 9. AO methodology is now generatingabout 10% of the total citation returns. The H-index ofAO publications is 62 and the median of the number ofcitations is 22.

8. INFERENCES

8.1. The Observatory Light Curve

The citation light curve for all the instruments puttogether can is displayed in Figure 10. The number ofpapers published in a given year and C(t) are displayedin Table 7 Here C(t) is the number of citations accumu-lated by papers published in year t (see Equation 1). Asbriefly discussed in §6.5 this metric and the related met-ric of “[total number of] citations” have an additional

TABLE 7Papers & Citations:All Instruments

Year Papers C(t)

1994 11 7321995 36 39091996 53 91131997 68 76181998 109 201071999 127 193262000 168 149452001 176 147392002 194 129542003 212 198022004 214 163932005 232 162792006 277 181702007 313 186442008 262 150972009 269 114972010 289 116722011 298 97532012 320 6613

Note. — Columnsfrom left to right: year,the total number of paperspublished in the year andthe number of citations ac-crued by the papers pub-lished in that year. Asnoted in §6.5 and Equa-tion 1 the value of C(t)depends on the time atwhich the sum is evalu-ated. The exercise was un-dertaken circa March 2014.

dependence on the epoch at which the metrics are mea-sured.

From Table 7 I note that C(t) is approximately con-stant between 1998 through 2007 and with a value of say20,000. It is reasonable to use this interval since it takesabout 5 years for paper production to peak and there isa lag of about 5 years between the publication and max-imum citations. Thus, in steady state we would expectthat C(t) would also be around 20,000. The current valueof 30,000. So we can expect that C(t) to decrease in a fewyears and asymptote to 20,000 (unless of course the usersof WMKO become more productive than in the past).

8.2. The High Impact of Optical Instruments

As can be gathered from Tables 4 & 5 and Figure 1optical instruments are both productive and also have alarger impact relative to NIR instruments as well as AO-assisted observations. There are two strengths that op-tical instruments enjoy relative to NIR: (i) natural back-ground that is orders of magnitude smaller in the opticalrelative to NIR and (ii) detectors that are nearly per-fect in their response (with virtually no dark current).NIR and/or AO win only when the natural conditionsfavor them: objects suffering from extinction (the posterchild here is observations of the stars in the center of ourGalaxy) or when the diagnostics are uniquely in the NIRband (e.g. cool objects, asteroid spectroscopy). Nothingon the present horizon suggests a change in this situationover the coming decade.

8.3. The Longevity of Instruments


1990 1995 2000 2005 20100

1

2

3

4x 10

4

C(t)

All Instruments

Fig. 10.— The citation flux curve of all the instruments, taken together, of the W. M. Keck Observatory.

From an inspection of the paper generation curves Iconclude that instruments which have not undergone sig-nificant upgrades achieve a peak between five to eightyears after commissioning (e.g. NIRC, ESI and NIR-SPEC). Some care should be exercised in interpreting thelight curves of NIRC2 and OSIRIS since the full powerof these instruments arises from the performance of theLGS AO system. As a result the impact of the instru-ments will track improvements in the LGS AO system(which is undergoing considerable improvements sincecommissioning in 2004; see Table 2).

For the sake of argument we will accept the time topeak as six years. Accepting this figure we ask the ques-tion: what sets this timescale? There are two possiblereasons. First, users exhaust “low hanging fruit” projectsthat can be undertaken with the instrument. Second, theinstrument does not remain competitive – that is, otherobservatories start deploying more advanced instrumentswith larger reach or better better detectors and so on. Iargue that the decline in productivity of NIRC is becauseof increasing obsolescence. The 256×256 InSb detector ofNIRC was state-of-the-art in 1993 but the standard NIRimager these days is 2K×2K pixel detectors (with bet-ter quantum efficiency, lower read noise and lower darkcurrent).

Thus, in the absence of planned upgrades and recog-nizing that it takes about five years to design and de-velop even a modest instrument for large telescopes, oneshould start working on the next instrument almost assoon as the first generation instrument is delivered andcommissioned!

8.4. The Importance of Upgrades

The first light instruments are NIRC, LRIS andHIRES. NIRC shows the expected classic behavior:peaking, as measured by paper production, about sixyears after first light and then gradually declining. Incontrast, LRIS achieved a plateau six years later and ismaintaining the plateau. A simple explanation for thiscontinued productivity are the upgrades: Blue-channel(2000), ADC (2007) and Red-channel (2010). LikewiseHIRES shows a rise to a plateau in the year 2000 and thenundergoes another rise starting the year 2004. HIREScontinues to show a sustained increase in both produc-tivity and impact. I attribute this to the 3-CCD upgradethat was undertaken in 2004.

NIR detectors are on a virtuous trajectory: the formats

TABLE 8Citations to Instrument Papers (until 2012)

Instrument Papers (Np) Citations (Nc) Q(%)

NIRC 234 219 −6LRIS 1245 1436 15

HIRES 945 708 −25ESI 248 206 −17

NIRC2 273 - -NIRSPEC 386 347 −10DEIMOS 440 270 −39

OSIRIS 58 61 5AO 429 306 −29

Note. — Name of the instrument, number of refereedpapers (Np) arising from the instrument and the numberof citations to the fundamental paper(s) which describesthe instrument (Nc). Q is defined by Equation 3. For eachinstrument, the fundamental references are listed in vari-ous subsections of §4. In order these are NIRC (Matthews& Soifer 1994a-b); LRIS (Oke et al. 1995; McCarthyet al. 1998; Steidel et al. 2004; Rockosi et al. 2010);HIRES (Vogt et al. 1994); ESI (Sheinis et al. 2000, 2002);NIRSPEC (McLean et al. 1998); DEIMOS (Faber et al.2003); OSIRIS (Larkin et al. 2006a-b) and the AO system(NGS & LGS; Wizinowich et al. 2000, 2006; van Dam etal. 2006). There is no entry for Nc for NIRC2 since thebuilders did not publish a paper describing the instrument.

are doubling every few years and the performance (darkcurrent, read noise, wide wavelength response). As aresult upgrading NIRSPEC or adding an NIR channel toDEIMOS is clearly advantageous. Such an upgrade will,as with HIRES and LRIS, likely perk up the light curves.

ESI appears to now be gently declining in paper pro-duction. However, with the imminent launch of Gaia wecan expect all sorts of very interesting stellar astronomytargets. Recent developments now allow for CCDs withalmost perfect QE from 1µm to the UV cutoff. An optionis to employ an EMCCD so that high speed spectroscopycan be undertaken.

8.5. Are Builders Well Recognized?

Astronomy, particularly OIR astronomy, is perceivedto have a culture that does not reward astronomers withinstrumentation skills. Astronomers certainly appreciatethe value of sophisticated instruments but rewards, es-pecially those which are concrete (faculty appointments),are primarily recognized by papers which are fundamen-tally astronomical in content. Some areas of astronomy– radio astronomy (particularly research related to Cos-

14 S. R. Kulkarni

mic Background Radiation, development of new facili-ties, pulsar research) – have a long tradition of reward-ing astronomers with primary talent in instrumentation.Perhaps the difference lies in the fact that in the early his-tory of optical astronomy (and extending through the eraof large telescopes in California) the instruments were rel-atively simple and great value was (in effect) attributedto the astronomers who were able to secure time andmake discoveries. However, over the past several decadesthe complexity of OIR astronomy instrumentation hasdramatically increased and some of the instruments arenow poised to cost as much as 5-m telescopes (§11).

In Table 8, I present, for each Keck facility instru-ment as well as the AO system (NGS, LGS) the numberof published papers (Np) that can be ascribed to thatinstrument. As noted in the section on the Keck instru-ments (§4) some instruments have multiple references tothe performance of the instrument (usually reporting asignificant upgrade). I have summed up the citationsfrom these papers (the papers are listed in the captionto Table 8) and present the total number of citations(Nc) for each instrument in Table 8).

Along with Np and Nc I present

Q =Nc

Np− 1 (3)

expressed as a (rounded) percentage. Q < 0 is the per-centage of astronomers who use a Keck instrument with-out acknowledge the instrument team which made theirobservations possible. The users of NIRC, LRIS andOSIRIS and perhaps NIRSPEC can be argued (withinPoisson noise) of being grateful to the builders of the in-struments. However, users of HIRES, ESI, DEIMOS andthe AO system(s) appear to be quite lax of acknowledg-ing the instrumentation teams which made their observa-tions possible. In case of LRIS we curiously have Q > 0.The explanation is that some of the observational papersrefer to the original LRIS paper (Oke et al. 1995) as wellas one or more upgrades (McCarthy et al. 1998; Steidelet al. 2004; Rockosi et al. 2010). Clearly, LRIS usersare the most sincere in showing the appreciation to theinstrument builders.

8.6. Advice to Instrument Builders

I have some (common-sense) advice for future instru-mentation builders. First, it is essential that you write upthe instrument paper as soon as possible after the instru-ment is successfully commissioned. Users are likely toread the commissioning paper to better understand thenew instrument. Next, it is not useful to publish the in-strument papers in journals which are not routinely readby astronomers. In particular, SPIE proceedings requireone’s institutional membership to SPIE. Many institu-tions appear not to carry SPIE subscriptions. In any caseSPIE papers are not refereed and are widely regardedby astronomers (including me) as “work in progress” re-ports. In contrast, society journals such as PASP andothers are easily accessible to all astronomers. Multi-ple papers on the same instrument dilute the impact (bydecreasing the H-index of the instrument, for instance).Finally, a major upgrade must have its own instrumentpaper. All these steps will ensure that the hard work onpart of the instrument team is formally and fully recog-

nized.

9. THE COST & VALUE OF A NIGHT OF TELESCOPETIME

Unlike radio astronomy (rather specifically, wavebandsfrom dekameter through decimeter) very few (if any) op-tical observatories have an “open sky” policy. In opti-cal astronomy it has long been the tradition that accessis primarily restricted to astronomers from institutionswhich funded the construction of the telescope. Oncean observatory is successful it is not unusual to find as-tronomers elsewhere push their institutions to obtain ac-cess to such telescopes. Nor is it unusual for observatoriesto seek new partners (either as a buy-in or limited timelease) to fund new initiatives at their observatories.

Recognizing this situation and also acknowledging in-adequate public investment in optical astronomy (at leastrelative to private investment), in the United States,the National Science Foundation (NSF) commissioned astudy. The resulting “McCray report” led to the estab-lishment of the Telescope System Instrumentation Pro-gram (TISP). This program aimed to increase telescopeaccess to the US community by funding existing privateobservatories. The funding was either for building newinstruments or for compensating the running costs. Thisinitiative directly raises the question of “How to value anight of telescope access?”.

The TSIP formula19 for computing the value of a nightis to sum three contributions: the cost of the telescopelinearly amortized over twenty years, the cost of instru-mentation amortized over ten years and the current an-nual operating cost. For the first two items “then year”dollars. For the third item (ops cost) current year dol-lars are used. For a telescope older than twenty yearsthe recommendation is to set the value of the telescopeto the “current estimated cost to build a telescope of sim-ilar characteristics reduced by a factor equal to inflationover the last ten years” and then to linearly amortize thisestimate over the next twenty years.

The light curve of NIRC provides some justification forthe TSIP 10-year amortization rule. However, the lightcurves of instruments which received upgrades would fa-vor a longer period for amortization.

In my opinion the TSIP methodology, whilst appro-priate in a typical commercial setting (e.g. used cars),is not appropriate for telescopes. The primary functionof a telescope is to collect light and project into a smallimage. This ability of the telescope decays very slowlywith age. I quote an example that I know very well– the Hale 5-m telescope (first commissioned in 1949).Thanks to refurbishments and a better ability to modelthe mechanical structure the primary mirror of the Haletelescope is in better shape today than it ever did sincefirst light. The pointing has been steadily improved andis now as good as a modern telescope. In my opinion andexperience the primary danger to the basic functioningof an older telescope is light pollution and incompetenceon the part of management.

Next, the final output of an Observatory is the scien-tific results and here – and this is the theme of the paper –the instruments matter tremendously. As noted right atthe start of this paper (§1) the output of the observatory

19 http://ast.noao.edu/system/tsip/


1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 20140

1

2

3x 10

4

Year

C(t)

1993-20132003-20132008-2013

Fig. 11.— (Top) The citation flux curve for all instruments but with papers restricted to those published between year ”y”and 2013. Here y=1993 (the year in which Keck I saw first light), y=2003 and y = 2008. (Bottom) A graphical summary ofC(t) (see Table 7).

is the product of the light-gathering power of the tele-scope and the “reach” of the instrument. Even modest-size telescopes with powerful instruments can dominatecertain fields and return great results, e.g. 2DF on the3.9-m AAT and MegaPrime on the 3.6-m CFHT.

With all modesty I suggest that the cost of a singlenight should be determined by the annual citation flux.This suggestion is is a market-based approach and willthus favor observatories which maintain their telescopes(so nights are not lost due to telescope failures), under-take periodic infra-structure improvements (so that thefraction of productive usage remains high), build up asuite of powerful instruments (optimized for dark andbright time, for excellent and moderate seeing) and un-dertake upgrades of instruments as detectors improveand so on.

From Figure 10 I note that the current yearly cita-tion flux is about 30,000 citations. Using the parametersof the last known TSIP grant (in which each night wasvalued at about $100K)20 the value per Keck citation isapparently 2.3K$.

A critic may argue that the benefits of the impressivecitation curve (Figure 1) accrue to early users (investors).Certainly there is some truth to this criticism. First,there is a lag of about 5–10 years between publicationand the accrual of substantial citations. Second, there isno question that the Keck telescopes, by being the first10-m telescopes to go on air, helped the early users un-dertake “low hanging” projects with associated substan-tial citation returns. In order to answer these criticismsI plot the citation flux curve papers published 5 and 10years ago (Figure 11). The citation flux of these papersin 2012 is 15,000 per year and 22,000 per year. Theserates can be divided into the TSIP cost for a night toobtain a citation cost for new comers.

10. CHALLENGES FACED BY SMALL OBSERVATORIES

So far the discussion has been about the W. M. KeckObservatory which is one of the largest routinely func-tioning optical telescope. In this section I address issuesrelated to smaller telescopes. Some studies have shown

20 I assume that the effective number of nights is 365× 2 minusthe number of nights due to engineering and commissioning. Thisis about 680 nights.

that smaller telescopes contribute mightily to new dis-coveries as well as routine progress of our subject (Abt2012; Trimble, Zaich & Bosler 2005). In this vein I notethat while the Hale 5-m telescope of the Palomar Ob-servatory is famous for the discovery of quasars the 48-inch Oschin telescope has been a veritable discovery ma-chine including the rewriting of our view of the Solarsystem via the discovery of dwarf planets (Brown, Tru-jillo & Rabinowitz 2005). The first clear detection of abrown dwarf was done with the 60-inch Palomar tele-scope (Nakajima et al. 1995). In the same spirit I drawthe reader’s attention to the storied and varied achieve-ments of the Kitt Peak 84-inch telescope (Abt 2009).Next, the Sloan Digital Sky Survey (SDSS)21 is wellknown for being a most productive facility even thoughthe telescope aperture is a mere 2.5-m across. Continuingwith this theme, a recent article (Savaglio & Grothkopf2013) finds that the Swift X-ray Observatory is as pro-ductive as the two flagship missions X-ray: Chandra X-ray Observatory (NASA) and the XMM-Newton mission(ESA).

Despite this combination of anecdotal and quantita-tive analyses the fact remains that moderate and smallaperture telescope observatories find themselves practi-cally under a siege – not merely financial but also onewhere their very value is begin questioned. Many ofthese can reprogrammed to be discovery machines (e.g.Palomar Transient Factory)22 or discovery-aiding ma-chines (e.g. SMARTS)23. However, such re-programmingrequires moderate injection of capital – which is not avail-able given that most of the federal funding is devoted toflagship (large) projects.

A significant clue to this puzzle is that there are veryfew citations to the papers listed above. Thus the logi-cal conclusion is that the astronomical community (as awhole) appear not to find the analysis presented in suchpapers (as above) to be compelling enough to take upto arms and bring about real changes in the distributionof astronomical funding. Below I suggest two steps thatmay help the small observatories in bringing to light theircontributions.

21 http://www.sdss.org/22 http://www.ptf.caltech.edu/iptf23 http://www.astro.yale.edu/smarts/

16 S. R. Kulkarni

10.1. Conquer the Bibliometric Divide (Branding)

Large observatories which are funded by national gov-ernments or via international treaties (e.g. ESO, NRAO)and plushly funded space missions (e.g. Hubble SpaceTelescope) have long recognized the importance of mea-suring and advertising the impact of their facilities totheir sponsoring agencies and to the public. These insti-tutions have employ librarians and other personnel whocomb through the astronomical literature on a regularbasis and produce on an annual basis an analysis of theoutput of their Observatories. These reports are mailedto funding agencies and in turn help the funding agenciesto justify future allocations.

Smaller observatories have to keep up with the currentparadigm and likewise build up their “brand”. The firststep is to advertise their achievements but it would behard to beat the powerful EPO departments of large ob-servatories. The most influential step would be to presenta thorough comparative analysis of the returns from theirObservatories, normalized by, say, the total investment.To this end it is critical to build a high-fidelity biblio-metric data base for the small observatories. I appre-ciate that smaller observatories lack financial resourcesand lack the manpower to develop and maintain the bib-liography of their facilities. It is my opinion that this“bibilometrica divide” has resulted in the exaggerationof the contributions of well funded large facilities rela-tive to those of leaner facilities (such as Palomar, LasCampanas, McDonald, Lick and others).

Smaller facilities should recognize that promoting thelegitimate achievements of their facility is simply the costof doing business (in the same vein as setting aside fundsfor paying utility bills). Accomazzi et al. (2012) havescoped the software and labor involved in setting up asuch a facility.

10.2. Archives & Pipelines

It is now well demonstrated that a high qualityarchive24 enables additional exploitation of the data col-lected from the Observatories. For instance, in 2011,the 4-telescope Very Large Telescope (VLT) facility ofthe European Southern Observatory (ESO) reported 550refereed publications that were based on new data. Anadditional 100 papers arose from archival data analysis25

Thus, apparently, archival analysis can boost the produc-tivity of a ground-based facility by about 20%.

Very few small observatories have usable data archives.Unfortunately, a properly designed and a highly func-tional archive is expensive. Perhaps, there is a smallbusiness opportunity here. For instance restaurants anddoctors’ offices do not develop their own software. Asoftware enterprise develops a product and other enti-ties then customize the basic software for each office orrestaurant. Perhaps NASA and NSF could provide ven-ture capital for such a noble endeavor.

In the near term observatories should take responsi-bility for the curation of the raw data and the reduced

24 A good archive is not merely a collection of FITS files but onewith an intelligent query interface and the ability to provide fullycalibrated data and higher level products. In the absence of suchproducts, the archives are essentially write-only storage of data.

25 ESO Annual Report 2011, p. 30. The report can be found athttp://www.eso.org/public/products/annualreports/.

data26. At the very least the design of new instru-ments must include the availability and future main-tenance of pipeline(s) for that instrument. Expand onthis theme.

11. THE EVOLVING LANDSCAPE OF INSTRUMENTATION

The landscape of ground-based optical/NIR astronomyis undergoing rapid changes for two reasons. The firstdriver is the increasing capability (and cost) of instru-mentation and is the primary subject of the paper. Thesecond is the proliferation of the synoptic surveys. Inthis section, keeping with the spirit of the paper, I makean attempt to understand the impact of both the costsand the astronomical returns from these developments.

The desire for instruments with great reach (see §1)began with “massively multiplexed” spectrographs andmosaiced detectors behind large imaging cameras. Earlyexamples include the 2dF spectrograph on the 3.9-mAustralian Astronomical Observatory (AAO; Colless etal. 2001); the Suprime-Cam on the Subaru 8.2-m tele-scope (Miyazaki et al. 2002) and MegaCam on theCanada-France-Hawaii (CFH) on the 3.6-m CFH tele-scope (Boulade et al. 2003). These, in turn, have madeit almost mandatory for all large observatories to beequipped with multiplexed spectrographs (e.g. DEIMOS,MOSFIRE on Keck; IMACS on Magellan; VMOS onVLT and so on). However, these highly capable instru-ments also cost a lot more than previous generation in-struments. For instance, as can be gathered from Ta-ble 1, MOSFIRE costs five times that of NIRC (when or-dinary inflation and growth in GPD has been accounted;see Figure 12).27

1990 1995 2000 2005 2010 20150.5

1

1.5

2

2.5

3

Nominal GDPCPI−UReal GDP

Fig. 12.— GDP and inflation indices from 1990–2012. Ineach case the index is obtained by dividing the value in anyyear by that in 1990. The inflation corrected GDP index isalso shown (and noted as “Real GDP”).

The second driver arises from synoptic surveys. SDSS(starting circa 2000) undertook the first large-area digitalsky survey in five optical bands and covering a quarter ofthe sky. SDSS inspired other surveys (e.g. VLA/FIRST).Full sky surveys such as 2MASS, VLA/NVSS, GALEXand WISE made SDSS even more useful. We are nowsolidly in the era of imaging surveys. In the North,

26 If only to resupply the data when the PI has a disk crash etc.27 Data from http://www.measuringworth.com


PanSTARSS has just concluded a 5-band all-sky surveyand SkyMapper is midway on a similar mission for theSouthern Sky.

The sophistication and maturity of optical synopticimaging can be measured by the increasing number ofspecialized surveys. The growing legions of amateur as-tronomers with sophisticated CCD detectors contributemightily to the discovery of nearby supernovae. CatalinaSky Survey and PS-2 are entirely devoted to the study ofNear-Earth Asteroids. The on-going Palomar TransientFactory and the imminent Zwicky Transient Factory28

have a singular goal of studying optical transients. TheCFH Legacy Survey was tuned for Ia cosmology. TheDark Energy Camera and the HyperSuprimeCam weremotivated by a single goal: probing Dark Energy throughseveral techniques. Incidentally, NIR and radio synop-tic capabilities are growing slowly and are likely to havecomparable maturity only by the end of the decade.

The ramifications (economic and astronomical) ofthese two driving force are discussed in the next two sub-sections.

11.1. Mega Instruments

The dramatic increase in the cost of “workhorse” in-struments notwithstanding we are now witnessing an en-tirely new “arms race” for optical telescopes – “mega”instruments. I define a mega instrument as that whichcosts (i) either $30M (FY2012) or more or (ii) has a costcomparable to the cost of the telescope on which it ismounted. So far, these mega instruments come in twoflavors: those with large reach and those which are de-signed to answer specific but important questions.

Related to the first category are facilities built aroundhighly multiplexed spectrographs: the Sloan Digital SkySurvey (SDSS) and the Large Area Multi-Object FibreSpectrograph (LAMOST)29. In case of SDSS the back-end was, at the time, a very large imager and (and ar-guably more importantly) a 320-channel fiber spectro-graph feeding two arms of a low resolution spectrograph.The backend for LAMOST is an impressive 4000-channeldual beam spectrograph and this is fed by a wide FOV4-m Schmidt camera (which also happens to be the largeSchmidt telescope in the world).

HERMES has 390-fibers feeding four spectrographicarms on the 3.9-m AAT telescope30. HETDEX consistsof 150 IFU spectrographs on the Hobby-Eberly 9.2-mtelescope (HET)31. WEAVE is a 1000-channel spectro-graph on the 4.2-m William Herschel telescope32. Theplanned MS-DESI is a 5000-channel spectrograph on the4-m Mayall telescope33. The planned Prime Focus Spec-trograph (SuMIRE)34 on the Subaru 8.2-m telescopehas 2400 fibers feeding a 3-arm spectrograph. Then wehave large field-of-view (FOV) cameras: the Dark EnergyCamera (3 square degrees) on the Blanco 4-m telescopeand the Hyper-Suprime Camera (HSC)35 (1.7 square de-

28 http://www.ptf.caltech.edu/ztf29 http://www.lamost.org/public/?locale=en30 http://www.aao.gov.au/HERMES/31 http://hetdex.org/hetdex/32 http://www.ing.iac.es/weave/about.html33 http://desi.lbl.gov/34 http://sumire.ipmu.jp/en/265235 http://www.naoj.org/Projects/HSC/

grees) on the Subaru 8.2-m telescope. These are majorundertakings with costs36 that place them squarely inthe mega-instrument category.

In the second category, the instruments appeared to berooted in Adaptive Optics. The Gemini Planet Imager(GPI)37 on the Gemini South 8-m telescope is a high-contrast AO imager for high dynamic range (extra-solarplanets) studies. SPHERE38 is also a “planet finder” buton the VLT 8-m telescope. The run-out cost of GPI andSphere are estimated to be $30M and $50M, respectively.The Gemini Multi-Conjugate Adaptive Optics System(GeMS)39 aims to deliver a very well corrected beamover one arc-minute field-of-view. The run-out cost ofGeMS is TBD.

There are both rewards and risks in building mega in-struments. A well chosen mega instrument can have alarge impact on the scientific fortunes of an Observa-tory. For instance, Subaru (SuprimeCam and now HSC)and CHFT (MegaPrime) are very well known for theirprowess in wide field imaging. In a similar vein there arehigh hopes that the results from GPI and SPHERE willstrongly irradiate their parent Observatories and makethem proud.

The risk in building a mega instrument is that the re-turn may turn out to be less abundant than the earlyaspirations or that costs and delays become unbearable(and in some cases may even sink the Observatory).Clearly, one assumes that the management of observato-ries will undertake a decision to proceed only after carefulanalysis of all such issues.

There are two interesting consequences resulting frommega instruments. Say, for argument’s sake, that a pro-posed mega instrument costs $50M. We will accept 10years as a reasonable peak lifetime. Say, over this pe-riod, 1,000 nights are allocated to the mega instrument.In fixed dollars, the instrument depreciates at the rateof $50K per night of usage. The per night amortizationis comparable to the basic operating cost of the currentgeneration of large telescopes. Thus mega-instrumentsresult in almost doubling of the true operating cost. Theopportunity costs of a mega instrument are very high.

The first consequence I had in mind is the loss of nightsfor users of the telescope who are not interested in theastronomical returns offered by the mega instrument inquestion. Specifically, let me consider the case of theSubaru HSC instrument. Given the total cost of theinstrument (including telescopic modifications) it is rea-sonable to expect that HSC will be used for most of thedark time over the next five years. Thus users of Sub-aru who are interested in dark time optical observationswill have to seek observing time elsewhere. Inversely, as-tronomers outside the Subaru family would be salivatingat the prospect of using HSC. Thus, it is most likely thatthe era of mega-instruments will result in significant timeswaps between major observatories.

The second consequence is that the cost of astronomi-cal observatories will be higher than the traditional ruleof thumb: an annual ops cost of 5% of the capital cost. As

36 including the cost of modifying the primary support system,the camera optics, the data taking system and pipelines

37 http://planetimager.org/38 https://www.eso.org/sci/facilities/develop/instruments/sphere.html39 http://www.gemini.edu/sciops/instruments/gems/

18 S. R. Kulkarni

noted above the cost of mega instruments, when spreadover the usable lifetime, can be comparable to the basicannual ops cost. Furthermore, mega instruments pro-duce either large amounts of data (e.g. HSC, LAMOST)or unique data (e.g. GPI, SPHERE). In either case, therewill be great value for a robust archive. Taken togetherambitious observatories should be planning for operatingcosts close to 10% of the initial telescope capital cost.

11.2. The Telescope System in the Synoptic Era

In my opinion SDSS became highly successful for tworeasons: (1) it was the first major digital sky survey inthe optical band and (2) its powerful highly-multiplexedspectrograph allowed astronomers to undertake spec-troscopy of large samples (see introduction to §11.1). Forsimilar reasons Gaia with its precision photometry, spec-trophotometry and unparalleled astrometry of nearly 109

objects is poised to revolutionize stellar and Galactic as-tronomy.

In contrast to the above two surveys other synopticsurveys do not have a built-in follow up capability. Theoutput of the current imaging surreys is already strain-ing the existing follow up resources. Thus I conclude thatmost massively multiplexed spectrographic projects willhave a bright future – especially those which can providevalue to several sub-fields of astronomical research. Inaddition, there will be a need for facilities which hostmassively multiplexed spectrographs and whose usagewill be determined by proposal pressure (c.f. ngCFHTand SSST).40 For reasons discussed above the costs ofthese proposed (and urgently needed) facilities will notbe small.

Given the large data returns from the on-going synop-tic surveys and Gaia there will be an increased demandfor undertaking detailed studies of interesting objects,carry out precision measurements of carefully culled sam-ples of objects and follow-up observations of transientsources. There will be a great need for linking the syn-optic facilities with the follow-up facilities. With lit-tle doubt I would expect such telescopes to be robotic.Those Observatories which will undertake vertical inte-gration (linking discovery machines to follow up lightcurves and especially follow up spectroscopy) will benefitfrom this new golden age of transients. By re-purposingexisting telescopes such vertical integration can be un-dertaken at low cost (but not zero cost). Money spentfor such vertical integration will result in highly cost-effective returns.

At the risk of repeating the obvious the large data rates

of current synoptic surveys will force astronomers to de-velop new techniques optimized for large target through-put. In particular for transient object astronomy onecan envisage – ultra-low resolution spectral classification(REF) and the use of energy resolved detectors for flex-ible single object spectroscopy (ultra-low- to moderate-resolution).

The large rates of candidates (targets) call for algo-rithmic decision making and certainly robotic telescopes(cf. Las Cumbres Global Observatory Telescope41). Wemay even see the rise of inexpensive 3-m class telescopesdesigned explicitly for follow up (cf. Kyoto segmentedtelescope). Just as (some) astronomers of the past learntelectronics, just as many of the first generation radio as-tronomers came from electrical engineering backgrounds,astronomers of the future will be experts in computerscience. The landscape of optical astronomy 10 yearsfrom now will be very different from the landscape thatmy generation of astronomers grew up. My generationshould prepare for a brave new world.

I am grateful to the Peggi Kamisato (WMKO Li-brarian) for providing the Keck bibliography in a ma-chine readable format, to Barbara Schaefer (WMKOScheduler) for patiently clarifying my queries and to Dr.Marten van Kerkwijk (U. Toronto) for help with pro-gramming to query ADS. I would like thank the sci-entists who led the projects for providing estimates ofcost and other details of their projects: K. Matthews(NIRC, NIRC2), J. Cohen (LRIS, LRIS-B), R. Camp-bell (LWS), I. McLean (NIRSPEC), X. Prochaska (ESI),M. Bolte (ESI, ADC), S. Faber (DEIMOS), J. Larkin(OSIRIS), P. Wizinowich (AO), S. Adkins (MOSFIRE),S. Vogt (HIRES), C. Rockosi (LRIS-R) and G. Chanan(Phasing and quality of images). I would like to thankH. Lewis, V. Trimble and P. Wizinowich for a wide vari-ety of discussions. I am grateful to R. Goodrich for hiscareful reading and constructive criticism of the paper.

I am grateful to Wendy Freedman of the Carnegie Ob-servatories for hosting me during a mini-sabbatical. Theserene surroundings combined with the graceful settingsthat are steeped in astronomical history minimized thepain of tedious investigations and program writing asso-ciated with the early phase of the paper writing.

As usual, I very much appreciate the excellent workundertaken by librarians at various centers and Univer-sities who maintain the ADS data base. The ADS, atremendous global effort at this point, is now a cornerstone of astronomical research world wide. In particular,without ADS this paper would not have been possible.

REFERENCES

08 1.Abt, H. A. 2005, in Communicating Astronomy, ed. T. J.

Mahoney, 2.Abt, H. A. 2009, in American Astronomical Society Meeting

Abstracts #213, volume 41 of Bulletin of the AmericanAstronomical Society, #200.08.

Abt, H. A. 2012, AJ, 144, 91.

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41 http://www.lcogt.net

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APPENDIX

A. TOP PAPERS

A.1. NIRC

1. The Rest-Frame Optical Spectra of Lyman Break Galaxies: Star Formation, Extinction, Abundances, and Kine-matics (2001), ApJ 554, 981–1000 [2001ApJ...554..981P 582]

2. Submillimetre-wavelength detection of dusty star-forming galaxies at high redshift (1998), Natur 394, 248–251[1998Natur.394..248B 509]

20 S. R. Kulkarni

3. A Survey of z > 5.7 Quasars in the Sloan Digital Sky Survey. II. Discovery of Three Additional Quasars atz > 6 (2003), AJ 125, 1649–1659 [2003AJ....125.1649F 485]

4. Stellar Orbits around the Galactic Center Black Hole (2005), ApJ 620, 744–757 [2005ApJ...620..744G 463]

5. The Rest-Frame Optical Properties of z ∼ 3 Galaxies (2001), ApJ 562, 95–123 [2001ApJ...562...95S 429]

6. High Proper-Motion Stars in the Vicinity of Sagittarius A*: Evidence for a Supermassive Black Hole at theCenter of Our Galaxy (1998), ApJ 509, 678–686 [1998ApJ...509..678G 411]

7. The unusual afterglow of the γ-ray burst of 26 March 1998 as evidence for a supernova connection (1999), Natur401, 453–456 [1999Natur.401..453B 403]

8. Multiwavelength Observations of Dusty Star Formation at Low and High Redshift (2000), ApJ 544, 218–241[2000ApJ...544..218A 369]

9. The Stellar, Gas, and Dynamical Masses of Star-forming Galaxies at z ∼ 2 (2006), ApJ 646, 107–132[2006ApJ...646..107E 309]

10. The Spectra of T Dwarfs. I. Near-Infrared Data and Spectral Classification (2002), ApJ 564, 421–451[2002ApJ...564..421B 261]

A.2. LRIS

1. Measurements of Ω and Λ from 42 High-Redshift Supernovae (1999), ApJ 517, 565–586 [1999ApJ...517..565P7904]

2. Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant (1998), AJ116, 1009–1038 [1998AJ....116.1009R 7778]

3. Type Ia Supernova Discoveries at z > 1 from the Hubble Space Telescope: Evidence for Past Deceleration andConstraints on Dark Energy Evolution (2004), ApJ 607, 665–687 [2004ApJ...607..665R 2681]

4. The Supernova Legacy Survey: measurement of ΩM , ΩΛ and w from the first year data set (2006), A&A 447,31–48 [2006A&A...447...31A 1708]

5. High-redshift galaxies in the Hubble Deep Field: colour selection and star formation history to z ∼ 4 (1996),MNRAS 283, 1388–1404 [1996MNRAS.283.1388M 1629]

6. Discovery of a supernova explosion at half the age of the universe (1998), Natur 391, 51– [1998Natur.391...51P1357]

7. Lyman-Break Galaxies at z & 4 and the Evolution of the Ultraviolet Luminosity Density at High Redshift (1999),ApJ 519, 1–17 [1999ApJ...519....1S 1348]

8. Cosmological Results from High-z Supernovae (2003), ApJ 594, 1–24 [2003ApJ...594....1T 1308]

9. The Keck Low-Resolution Imaging Spectrometer (1995), PASP 107, 375– [1995PASP..107..375O 1170]

10. Spectroscopic Confirmation of a Population of Normal Star-forming Galaxies at Redshifts z > 3 (1996), ApJ462, L17– [1996ApJ...462L..17S 1152]

A.3. HIRES

1. The Planet-Metallicity Correlation (2005), ApJ 622, 1102–1117 [2005ApJ...622.1102F 653]

2. Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT PlanetSearch Programs (2005), ApJS 159, 141–166 [2005ApJS..159..141V 627]

3. A Transiting “51 Peg-like” Planet (2000), ApJ 529, L41–L44 [2000ApJ...529L..41H 569]

4. Attaining Doppler Precision of 3 M s-1 (1996), PASP 108, 500– [1996PASP..108..500B 522]

5. Catalog of Nearby Exoplanets (2006), ApJ 646, 505–522 [2006ApJ...646..505B 506]

6. The Deuterium Abundance toward Q1937-1009 (1998), ApJ 499, 699–712 [1998ApJ...499..699B 386]

7. Galaxies and Intergalactic Matter at Redshift z ∼ 3: Overview (2003), ApJ 584, 45–75 [2003ApJ...584...45A360]

8. Further evidence for a variable fine-structure constant from Keck/HIRES QSO absorption spectra (2003), MNRAS345, 609–638 [2003MNRAS.345..609M 344]


9. The Cosmological Baryon Density from the Deuterium-to-Hydrogen Ratio in QSO Absorption Systems: D/Htoward Q1243+3047 (2003), ApJS 149, 1–28 [2003ApJS..149....1K 338]

10. The Opacity of the Lyα Forest and Implications for Ωb and the Ionizing Background (1997), ApJ 489, 7–20[1997ApJ...489....7R 330]

A.4. ESI

1. Observational Constraints on the Nature of Dark Energy: First Cosmological Results from the ESSENCE Super-nova Survey (2007), ApJ 666, 694–715 [2007ApJ...666..694W 687]

2. Spectra and Hubble Space Telescope Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2Compilation (2010), ApJ 716, 712–738 [2010ApJ...716..712A 685]

3. Evidence for Reionization at z ∼ 6: Detection of a Gunn-Peterson Trough in a z = 6.28 Quasar (2001), AJ122, 2850–2857 [2001AJ....122.2850B 633]

4. The Farthest Known Supernova: Support for an Accelerating Universe and a Glimpse of the Epoch of Deceleration(2001), ApJ 560, 49–71 [2001ApJ...560...49R 610]

5. A Survey of z > 5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the SpatialDensity of Luminous Quasars at z ∼ 6 (2001), AJ 122, 2833–2849 [2001AJ....122.2833F 568]

6. Constraining the Evolution of the Ionizing Background and the Epoch of Reionization with z ∼ 6 Quasars. II. ASample of 19 Quasars (2006), AJ 132, 117–136 [2006AJ....132..117F 502]

7. A Survey of z > 5.7 Quasars in the Sloan Digital Sky Survey. II. Discovery of Three Additional Quasars atz > 6 (2003), AJ 125, 1649–1659 [2003AJ....125.1649F 485]

8. The Observed Offset Distribution of Gamma-Ray Bursts from Their Host Galaxies: A Robust Clue to the Natureof the Progenitors (2002), AJ 123, 1111–1148 [2002AJ....123.1111B 394]

9. Galaxies and Intergalactic Matter at Redshift z ∼ 3: Overview (2003), ApJ 584, 45–75 [2003ApJ...584...45A360]

10. A median redshift of 2.4 for galaxies bright at submillimetre wavelengths (2003), Natur 422, 695–698[2003Natur.422..695C 358]

A.5. NIRC2

1. Direct Imaging of Multiple Planets Orbiting the Star HR 8799 (2008), Sci 322, 1348– [2008Sci...322.1348M 593]

2. Measuring Distance and Properties of the Milky Way’s Central Supermassive Black Hole with Stellar Orbits(2008), ApJ 689, 1044–1062 [2008ApJ...689.1044G 522]

3. Optical Images of an Exosolar Planet 25 Light-Years from Earth (2008), Sci 322, 1345– [2008Sci...322.1345K446]

4. The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy’s Central Black Hole: AParadox of Youth (2003), ApJ 586, L127–L131 [2003ApJ...586L.127G 357]

5. Confirmation of the Remarkable Compactness of Massive Quiescent Galaxies at z ∼ 2.3: Early-Type GalaxiesDid not Form in a Simple Monolithic Collapse (2008), ApJ 677, L5–L8 [2008ApJ...677L...5V 318]

6. Images of a fourth planet orbiting HR 8799 (2010), Natur 468, 1080–1083 [2010Natur.468.1080M 212]

7. A Close Look at Star Formation around Active Galactic Nuclei (2007), ApJ 671, 1388–1412[2007ApJ...671.1388D 198]

8. Variable Infrared Emission from the Supermassive Black Hole at the Center of the Milky Way (2004), ApJ 601,L159–L162 [2004ApJ...601L.159G 176]

9. Discovery of a Jupiter/Saturn Analog with Gravitational Microlensing (2008), Sci 319, 927– [2008Sci...319..927G161]

10. On the Progenitor of SN 2005gl and the Nature of Type IIn Supernovae (2007), ApJ 656, 372–381[2007ApJ...656..372G 160]

22 S. R. Kulkarni

A.6. NIRSPEC

1. Type Ia Supernova Discoveries at z > 1 from the Hubble Space Telescope: Evidence for Past Deceleration andConstraints on Dark Energy Evolution (2004), ApJ 607, 665–687 [2004ApJ...607..665R 2681]

2. The Farthest Known Supernova: Support for an Accelerating Universe and a Glimpse of the Epoch of Deceleration(2001), ApJ 560, 49–71 [2001ApJ...560...49R 610]

3. A Survey of z > 5.8 Quasars in the Sloan Digital Sky Survey. I. Discovery of Three New Quasars and the SpatialDensity of Luminous Quasars at z ∼ 6 (2001), AJ 122, 2833–2849 [2001AJ....122.2833F 568]

4. The Mass-Metallicity Relation at z & 2 (2006), ApJ 644, 813–828 [2006ApJ...644..813E 520]

5. The Stellar, Gas, and Dynamical Masses of Star-forming Galaxies at z ∼ 2 (2006), ApJ 646, 107–132[2006ApJ...646..107E 309]

6. Toward Spectral Classification of L and T Dwarfs: Infrared and Optical Spectroscopy and Analysis (2002), ApJ564, 466–481 [2002ApJ...564..466G 294]

7. The Structure and Kinematics of the Circumgalactic Medium from Far-ultraviolet Spectra of z = 2–3 Galaxies(2010), ApJ 717, 289–322 [2010ApJ...717..289S 279]

8. Multiwavelength Constraints on the Cosmic Star Formation History from Spectroscopy: the Rest-Frame Ul-traviolet, Hα, and Infrared Luminosity Functions at Redshifts 1.9 < z < 3.4 (2008), ApJS 175, 48–85[2008ApJS..175...48R 258]

9. Hα Observations of a Large Sample of Galaxies at z ∼ 2: Implications for Star Formation in High-RedshiftGalaxies (2006), ApJ 647, 128–139 [2006ApJ...647..128E 208]

10. A Close Look at Star Formation around Active Galactic Nuclei (2007), ApJ 671, 1388–1412[2007ApJ...671.1388D 198]

A.7. DEIMOS

1. The Supernova Legacy Survey: measurement of ΩM , ΩΛ and w from the first year data set (2006), A&A 447,31–48 [2006A&A...447...31A 1708]

2. New Hubble Space Telescope Discoveries of Type Ia Supernovae at z ≥ 1: Narrowing Constraints on the EarlyBehavior of Dark Energy (2007), ApJ 659, 98–121 [2007ApJ...659...98R 1035]

3. Observational Constraints on the Nature of Dark Energy: First Cosmological Results from the ESSENCE Super-nova Survey (2007), ApJ 666, 694–715 [2007ApJ...666..694W 687]

4. Star Formation in AEGIS Field Galaxies since z = 1.1: The Dominance of Gradually Declining Star Formation,and the Main Sequence of Star-forming Galaxies (2007), ApJ 660, L43–L46 [2007ApJ...660L..43N 526]

5. Cosmos Photometric Redshifts with 30-Bands for 2-deg2 (2009), ApJ 690, 1236–1249 [2009ApJ...690.1236I 445]

6. The Mass Assembly History of Field Galaxies: Detection of an Evolving Mass Limit for Star-Forming Galaxies(2006), ApJ 651, 120–141 [2006ApJ...651..120B 412]

7. The Kinematics of the Ultra-faint Milky Way Satellites: Solving the Missing Satellite Problem (2007), ApJ 670,313–331 [2007ApJ...670..313S 413]

8. Metallicities of 0.3 < z < 1.0 Galaxies in the GOODS-North Field (2004), ApJ 617, 240–261[2004ApJ...617..240K 311]

9. The All-Wavelength Extended Groth Strip International Survey (AEGIS) Data Sets (2007), ApJ 660, L1–L6[2007ApJ...660L...1D 302]

10. Galaxy Stellar Mass Assembly Between 0.2 < z < 2 from the S-COSMOS Survey (2010), ApJ 709, 644–663[2010ApJ...709..644I 297]


A.8. OSIRIS

1. The Kiloparsec-scale Kinematics of High-redshift Star-forming Galaxies (2009), ApJ 697, 2057–2082[2009ApJ...697.2057L 157]

2. Two ten-billion-solar-mass black holes at the centres of giant elliptical galaxies (2011), Natur 480, 215–218[2011Natur.480..215M 100]

3. The Lick AGN Monitoring Project: The M BH-σ∗ Relation for Reverberation-mapped Active Galaxies (2010),ApJ 716, 269–280 [2010ApJ...716..269W 94]

4. Integral Field Spectroscopy of High-Redshift Star-forming Galaxies with Laser-guided Adaptive Optics: Evidencefor Dispersion-dominated Kinematics (2007), ApJ 669, 929–946 [2007ApJ...669..929L 88]

5. Dynamics of Galactic Disks and Mergers at z ∼ 1.6: Spatially Resolved Spectroscopy with Keck Laser Guide StarAdaptive Optics (2009), ApJ 699, 421–440 [2009ApJ...699..421W 86]

6. The formation and assembly of a typical star-forming galaxy at redshift z ∼ 3 (2008), Natur 455, 775–777[2008Natur.455..775S 83]

7. Near-infrared Spectroscopy of the Extrasolar Planet HR 8799 b (2010), ApJ 723, 850–868 [2010ApJ...723..850B78]

8. High Angular Resolution Integral-Field Spectroscopy of the Galaxy’s Nuclear Cluster: A Missing Stellar Cusp?(2009), ApJ 703, 1323–1337 [2009ApJ...703.1323D 75]

9. Clouds and Chemistry in the Atmosphere of Extrasolar Planet HR8799b (2011), ApJ 733, 65–[2011ApJ...733...65B 79]

10. Resolved spectroscopy of gravitationally lensed galaxies: recovering coherent velocity fields in subluminous z ∼2–3 galaxies (2010), MNRAS 404, 1247–1262 [2010MNRAS.404.1247J 68]

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