National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of...

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 1

SIM-Lite Update

M. Shao JPL

© 2008 California Institute of Technology. Government sponsorship acknowledged.



Outline

• SIM-Lite Instrument Update- 6m baseline, 50cm, ~900M cost

• Technology Update- Systematic errors and floor

• SIM-Lite terrestrial planet discovery capability

• Double blind multiple planet study summary

• The changing landscape of exoplanet science and the role of SIM-Lite



SIM and SIM-”Lite”

SIM

PlanetQuestSIM- “Lite”

Note: Centaurupper stageused in bothvehicles. -Inside fairing.-ETSO orbit

551 521

Parameter SIM-PQ SIM-LITE

Wide Angle (global) accuracy 2.4 uas 3.6 uas

Narrow Angle Accuracy 0.7 uas 1.0 uas

Mag limit 20 mag 20 mag

# Stars surveyed 1Mearth-HZ ~130 ~60

Mass (with reserve) 6800 KG 4300 KG

Number of Interferometers 3 2

Science Baseline 9m 6m

Guide-1 Baseline 7.2m 4.2m

Guide-2 7.2m 0.3mTscope

Launch Vehicle Atlas V 551 521

Payload Risk Class A B

BCD schedule 77 mon 58 mon

BCD cost to go 1470 M 940 M

Mission Ops 5yrs 400M 170 M

Smaller size also meant end to end performance test of flight hardware could be done in thermo-vac chamber at JPL, instead of S/C contractor.



From Technology to Flight Component Engineering

• Much of the SIM hardware for flight already exists in engineering model and brassboard form.

Spacecraft& Instrument Electronics

Instrument

ExternalMetrologyLauncher

Internal MetrologyLauncher

Metrology Source

Double CornerCube

Siderostat ball screw

Astrometric Beam Combiner(Drawings released)Fast Steering

Mirror



Instrumental Systematic Errors

• Thermal drift affects all measurements

• For narrow angle observations, we “chop” between target and reference stars every 90 sec.

• When this observation procedure was tested in the MAM testbed we showed that thermal drift noise became “white” after chopping.

• The remaining question, is the thermal drift in the MAM testbed, representative of the thermal stability we will see on SIM in orbit?- Detailed (>104 node) thermal

model of SIM shows current design ~5 times more stable on orbit than testbed is in Lab.

1pm/6m = ~0.04uas



Ultra Deep Search for Earth Clones

HIP 1475

HIP 56997

HIP 67275

GAIA (70 µas)

RV @ 1 m/s TPF-C (8 m)

M2 K2G2 F2

Planets ~Tidally Locked

Concentrate a lot of observing time 40% on a small number ~60 for SIM-Lite) over a 5 year mission.

To achieve sensitivity to 1 Mearth @ (1 AU) scaled to the luminosity of the star



Double Blind Test, Astrometric Detection of Earths in Multiplanet Systems

48 Planetary systems95 planets & ~300 Asteroids48 detectable planets (<5yr, SNR>5.8)Threshold 1Me @ 1AU

Two key metrics Confidence of detection Completeness



The Current Era of Exoplanet Science(Where does SIM-Lite fit in?)

• Where are we now?

- >350+ exoplanets have been found, Mostly RV (4.5 Mearth, in few day orbits)

- Kepler is in norbit , coupled with JWST, get spectra of Jovians (100’s)

- All sky transit missions have been proposed

- Technology for an astrometric mission is complete

- Considerable technology progress for direct imaging from space.

- Extreme AO coronagraphs on 8~10m telescopes to come on-line in 2010/2011. Spectra of self luminous jupiters soon. Perhaps spectra of planets in reflected light with TMT, ELT

Jupiters

NeptunesHot Sup-Earth

TerrestrialIn HZ

Discover(Mass)(Orbit)

Spectra

Self luminousJupiters

Simplified Diagram

Where we are.Where are we going.



Where is the next frontier, where does SIM-lit fit?

• The next Major (Space) advance in exoplanet research is the discovery of Terrestrial planets in the habitable zone.- SIM plays a pivotal and unique role

• After discovery, spectroscopic characterization Earth-clones with large space coronagraphs/interferometers to look for biosignatures.


M. Shao Jan 2009 - 10

10-2

10-1

100

10-12

10-11

10-10

10-9

cont

rast

angular separation arsec

Contrast vs planet-star separation over an orbital period

Discovering Earths, Why SIM is Unique

• The most important parameter, of a planet is its mass. We know a planet is a terrestrial planet IF and ONLY IF we know its mass.

- We can’t tell the mass of a planet from its color, and brightness.

• Neptune is 4X the diameter of Earth. A Neptune @ 4 AU has the same apparent magnitude as Earth @ 1 AU.

• The apparent brightness of a planet depends on the orbital phase angle.

Pale blue dot, Neptune an ice giant

To Observatory


M. Shao Jan 2009 - 11

Discovering Earths, (False Alarms)

• With a single image (and spectra)- We’ve imaged the first Earthlike planet in the

habitable zone, but this planet doesn’t have Oxygen and it has a lot of Methane

• OR with Astrometry- We’ve measured the spectra of a 15 Mearth ice

giant planet at 4AU, it has a lot of methane in its atmosphere and no oxygen.

• The discovery of a habitable planet around a nearby star will be a major scientific discovery.

- If the probability of a false alarm is in the 10‘s of percent, this does NOT constitute a major discovery

- The claim of finding a planet in the habitable zone can be made with a Measured orbit, (Not a guess)

- The claim of finding a terrestrial planet can be made with a Measured mass, not a guess of the mass.

Pale blue dot, Neptune an ice giant

To Observatory


M. Shao Jan 2009 - 12

Three Planets Imaged Around HR 8799 masses of 5-13 MJUP

• Ages, Models, Masses uncertain– Assumed Age: 60 Myr 5-13 MJUP

– Age Range: 30 Myr-1.2 Gyr 40 MJUP

– Are these Planets or Brown Dwarfs?• Orbits unstable? SIM determines masses directly SIM will calibrate mass, luminosity, age relationships which make imaging studies so uncertain

Imaging: Planet Status Uncertain Without Masses and Ages

12SIM Lite Science Review


M. Shao Jan 2009 - 13

SIM Will Help Establish How Planetary Systems Form & Evolve

• Astrometry can find gas giants within 1-5 AU of parent stars

– Mass measurements critical to evolutionary models

– What fraction of young stars have gas-giant planets?

– Do gas-giant planets form at the “water-condensation” line?

• AO imaging will find distant planets (>10 AU), but cannot determine mass, find inner planets

• Variability, spectral jitter, & rotation >>100 m/s preclude planet detection via RV, transit

0

20

40

60

5.8 6.2 6.6 7.0 7.4 7.8 8.2

Age (Myr)

Age Distribution of SIMYSO Sample

<200 pc <12.5 mag. Signal>=22uas. Mass>=.20,<=2

>0 pc <12.5 mag. Signal>=6uas. Mass>=0.2,<=2

Log Age (Myr)

D=140 pc 25<D<50 pc

Disk Lifetime << 100 Myr



M. Shao Jan 2009 - 14

SIM Probes the Broad Planet Mass Range Around Young Stars

• SIM surveys critical mass and age range

– Gas giants around youngest stars (1-10 Myr at 140 pc)– Gas and icy giants around closest stars (>10 Myr at <50 pc)– Large rocky planets around nearby, young, low mass stars

• GAIA can find only Jupiters around the closest young stars (d<50 pc, ages >10 Myr)• Star spots (<2 as for V=0.05 mag variability at 140 pc) will not prevent detection of gas giants



M. Shao Jan 2009 - 15

Astrometry and RV Detection of ExoEarths

• Given “Perfect” instruments, the ultimate limitation to both RV and Astrometric detection of exoplanets is astrophysical noise from the target star.- Star spots on the Sun produce 10~12X higher bias to RV than

Astrometry (for planets in a ~1 yr orbit).

• A 10-3 area spot on the sun produces- ~1m/s RV bias (Earth-Sun 0.09m/s signature)

- ~0.25 uas Astrometric bias (0.3uas signature)

• Whatever the astrophysical limitations ultimate turn out to be there is a ~12x advantage for astrometry (for 1 yr orbits).- Planets with shorter periods favor RV, planets with longer periods

favor astrometry.

• Spot “noise” is correlated on time scale of ~1week. Two measurements < 1 week apart will see the same bias due to spots. (Accu;racy improves as sqrt(#weeks) 1 m/s to 0.015m/s takes ~4000 weeks ~80 yrs


M. Shao Jan 2009 - 16

Summary

• SIM-”lite” is much reduce cost version of SIM that still retains the potential to detect Earth Clones around ~ 60 of the nearest stars. (1.3~1.5B)- It’s possible that we would get better science searching 160 stars for 2

Mearth planets, but the capability exists to get to 1 Mearth @ 1AU.

- Find addresses for the nearest potentially habitable planets

- SIM-Lite also has a strong astrophysics program, (Dark Matter, stellar physics, compact objects)

• The technology for SIM is ready. Flight designs and models exist for many flight picometer level precise components.

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