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.

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 2

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 3

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.

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 4

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 5

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 6

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 7

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 8

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.

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

M. Shao Jan 2009 - 9

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.

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

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

13SIM Lite Science Review

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

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

14SIM Lite Science Review

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

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

National Aeronautics and Space AdministrationJet Propulsion LaboratoryCalifornia Institute of Technology

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.