National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
SIM-Lite Update
M. Shao JPL
© 2008 California Institute of Technology. Government sponsorship acknowledged.
M. Shao
Jan 2009 - 1
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
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
M. Shao
Jan 2009 - 2
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
SIM and SIM-”Lite”
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
~130
~60
6800 KG
4300 KG
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
A
B
BCD schedule
77 mon
58 mon
BCD cost to go
1470 M
940 M
400M
170 M
# Stars surveyed 1Mearth-HZ
Mass (with reserve)
Number of Interferometers
Payload Risk Class
Mission Ops 5yrs
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.
Note: Centaur
upper stage
used in both
vehicles.
-Inside fairing.
-ETSO orbit
SIM
PlanetQuest
551
M. Shao
521
SIM“Lite”
Jan 2009 - 3
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
From Technology to Flight Component Engineering
• Much of the SIM hardware for flight already exists in engineering model
and brassboard form.
Metrology
Source
External
Metrology
Launcher
Astrometric Beam Combiner
(Drawings released)
Fast Steering
Mirror
Instrument
Siderostat
ball screw
Double Corner
Cube
Spacecraft
&
Instrument
Electronics
Internal Metrology
Launcher
M. Shao
Jan 2009 - 4
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
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
M. Shao
Jan 2009 - 5
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
Ultra Deep Search for Earth Clones
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
TPF-C
(8 m)
M2
K2G2 F2
Planets ~Tidally Locked
M. Shao
Jan 2009 - 6
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
Double Blind Test, Astrometric Detection
of Earths in Multiplanet Systems
48 Planetary systems
95 planets & ~300 Asteroids
48 detectable planets (<5yr,
SNR>5.8)
Threshold 1Me @ 1AU
Two key metrics
Confidence of detection
Completeness
M. Shao
Jan 2009 - 7
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
•
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
Self luminous
Jupiters
Jupiters
Discover
(Mass)
(Orbit)
Simplified Diagram
Where we are.
Where are we going.
Neptunes
Hot Sup-Earth
Spectra
Terrestrial
In HZ
M. Shao
Jan 2009 - 8
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
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 - 9
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
•
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
Contrast vs planet-star separation over an orbital period
-9
10
To Observatory
-10
contrast
10
-11
10
-12
10
-2
10
-1
10
angular separation arsec
0
10
M. Shao
Jan 2009 - 10
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
•
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
-
•
Discovering Earths, (False Alarms)
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.
Pale blue dot, Neptune an ice giant
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.
To Observatory
M. Shao
Jan 2009 - 11
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
Imaging: Planet Status Uncertain
Without Masses and Ages
• 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
Three Planets Imaged Around
HR 8799 masses of 5-13 MJUP
SIM Lite Science Review
M. Shao
Jan 200912
- 12
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
SIM Will Help Establish How
Planetary Systems Form & Evolve
• Astrometry can find gas giants
within 1-5 AU of parent stars
Disk Lifetime << 100 Myr
– 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
Age Distribution of SIMYSO Sample
60
mag. Signal>=22uas. Mass>=.20,<=2
D=140 pc  <200 pc <12.5 25<D<50
pc
>0 pc <12.5 mag. Signal>=6uas. Mass>=0.2,<=2
40
20
0
5.8
6.2
6.6
7.0
Age (Myr)
7.4
7.8
8.2
Log Age (Myr)
SIM Lite Science Review
M. Shao
Jan 200913
- 13
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
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 mas for DV=0.05
mag variability at 140 pc) will
not prevent detection of gas
giants
SIM Lite Science Review
M. Shao
Jan 200914
- 14
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
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 - 15
National Aeronautics and Space
Administration
Jet Propulsion Laboratory
California Institute of Technology
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.
M. Shao
Jan 2009 - 16