# Presentation: 763300

## Future Opportunities In Exo-Planet Research:Transits and Light Curves From Space

- C. Beichman
- Michelson Science Center
- Caltech/JPL

*With Contributions from John Krist, Tom Greene, Marcia Rieke*

- “Transit Experiments are the worst form of exoplanet measurements.
- Except for all the others which are so much worse.”
- ---With apologies to Winston Churchill

## Subtracting Two Big Numbers Is Easier in Space

- Straightforward technology
-  Compared with angular  planet-star separation  (TPF-C, TPF-I/Darwin)
- Sensitivity and stability
*Stable* PSF (No seeing)
*Stable* environment, esp. non-LEO
- Low, *stable* sky background
- Continuous, broad  coverage
- Sensitive IR operation
-  Continuous, long- term coverage
-  Orbital, spacecraft, TAC constraints

- Ultra-precision photometry is hard anywhere!
- Moon-, earthshine, etc
- Cosmic rays,  other rad effects
- Limited Telemetry Postage stamps, not images
- Long, expensive development

**What’s Next for Transit and Light Curve Science?**
- Surveys for broader range of spectral types & closer stars
- Follow-up observations for detailed characterization

## Surveys with Large Space Telescopes

- HST, Spitzer, JWST have *great* sensitivity but *small* fields.
**Explore distant, peculiar regions**
- HST survey of 1.8x105 bulge stars down to 26 mag (Sahu et al 2006)
- 16 viable candidates (out of 165)
- Hard to follow-up but 45% estimated to be planets based on light curves.
- 2 with RV limits consistent with 4-9 MJup
- NIRCam capable of comparable surveys, e.g. star formation regions
***Limited utility compared with small telescopes with large FOV***
*** ******Who wants 20 mag transit candidates?***
***HST, Spitzer, JWST best suited for follow-up than surveys***

## Prospects for Future Transit Science

|  | Sur-vey | Primary
Transit
Curve | Secondary Transit
Curve | Full Orbital Light Curve | Primary Transit
Spectroscopy | Secondary
Transit
Spectroscopy |
| --- | --- | --- | --- | --- | --- | --- |
| Spitzer Cold |  | IRAC | IRAC/MIPS | IRAC/MIPS | IRS | IRS |
| HST (+SM4) |  | STIS? |  |  | NICMOS, COS |  |
| MOST |  | Limits to albedos for few stars |  |  |  |  |
| EPOCH |  |  |  |  |  |  |
| Upcoming Missions |  |  |  |  |  |  |
| Kepler |  |  | Albedo for ~1000 giants |  |  |  |
| JWST |  |  |  |  |  |  |
| Missions Under Consideration |  |  |  |  |  |  |
| Spitzer Warm |  |  |  |  |  |  |
| PLATO |  |  | Albedo for giants |  |  |  |
| TESS (All Sky) | Vis |  |  |  |  |  |
| ASTrO (All Sky) | IR |  |  |  |  |  |
| Tracer |  |  |  |  |  |  |
| Other Characterization Missions: GAIA & SIM, then (sometime) TPI-C,TPF-I/Darwin |  |  |  |  |  |  |

## Why Wide Angle Surveys?

- Validation (RV) and characterization need LOTS OF PHOTONS.
- Rare alignments (~1%)  hosts  distant:  D~15 pc
- pc (=7.5 mag) for       100 sq. deg. (Kepler)
- 250 pc (=6.1 mag) for       550 sq. deg. (PLATO)
- 75   pc (=3.4 mag) for 20,000 sq. deg. (Ground, ASTrO, Tess)
- Many small cameras to monitor 105-106 brightest, closest stars
- Variants: Near-IR for  M stars, space for small planets (1/5× radius)

| Transit Survey Missions (Ongoing, Planned, Possible) |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
| 
Survey Property | 
Ground
Based | 1st Generation |  | 2nd Generation  |  |  |
|  |  | CoRoT | Kepler | PLATO | TESS | ASTrO |
|  (sq. deg.) | 102~104 | 54  | 100 | 550 | 40,000 | >26,000 |
|  | Vis | Vis | Vis | Vis | Vis | near-IR |
| # Stars | 103-105 | 105 | 105 | 105 | 2.5106 | 2106 |
| Brightness (mag) | 6-15 | 11-15 | 10-14 | 8-14 | 4-13.5 | 4-13.5 (J) |
| Precision (ppm)  | 2,000 | 50  | 25,1h, V=11 | 25, 1h, V=11  | 77,1hr
I=9  | 50-100,
1hr, J=9 |

## PLATO --- Extended Area Survey

- ESA Cosmic Vision Mission presently approved for Phase A assessment
- 28 (sci.)+2 (tracker) telescopes (0.01 m2)
- 550 sq. deg. (x2) with *4k×4k* 12.5” pixels
- Continuous monitoring with <5-7% gaps
- 25 ppm/hour for V~11 mag
*SNR>37,000 for 75,000 dwarfs V< 12 mag*
*SNR> 12,500 for 500,000 dwarfs V< 14 mag*
- Roughly 4x as many stars as Kepler to same SNR, but 1~2 mag brighter
- Transit and light curve science as well as asteroseismology of host star

## TESS ---Visible All-Sky Survey

***SMEX mission now in Phase A !!!***
- Talk to follow
- Good luck!

## All Sky Transit Observer (ASTrO) Near IR All Sky Survey

- Discovery/Probe Class
- 24x0.1 m cameras
- 96 2kx2k HgCdTe arrays
- 0.6-1.6 m
- L2 orbit for stability
- Improved SNR for K,M stars in NIR vs. Vis
- Trade SNR (x2), #planets (x3) vs. cost
- Monitor >60% (100%) of sky ~ 2×106 stars
- Continuous dadence: for 60d-365d

- IR/VIS SNR Ratio
- Vis: 0.4-0.95 m
- IR: 0.65-1.65 m

## ASTrO Science Yield

- Planet yield d<100-150 pc: 300 Rocky; 2000, Gas/Icy

## Follow-up Opportunities:Why Bright Stars Are Important!

## Follow-up with JWST

|  | Validate | Primary Light Curve | Secondary Light Curve | 1-2.4 m Spectra | 2.4-5 m spectra | 5-20 m spectra |
| --- | --- | --- | --- | --- | --- | --- |
| NIRCAM |  |  |  |  |  |  |
| NIRSPEC |  |  |  |  |  |  |
| MIRI |  |  |  |  |  |  |

*See JWST White paper s by Clampin et al (2007), Seager (2008)*

## NIRCam Opportunities

- Validate transits with high angular resolution imaging
- Use stable PSF (coronagraph?) to look 20 mag eclipsing binary next to 10-15 mag Kepler/CoRoT sources
- Primary and secondary transit or Hot Jupiter light curves with high precision using defocused images (1-2.4 m) and *slitless *grisms (2.4-5.0 m).
- Short and long-lam data obtained simultaneously
- Spectroscopy at R~ 500-2,000 at 2.5-5.0 m where exoplanets have important spectral features.
- NIRCam may be preferable, or at least highly competitive, with NIRSPEC for many transit observations
- Immunity to initial pointing and subsequent drifts
- High photon efficiency and stability due to *no slit losses*
- Simultaneous long and short lam observations
- Monitor pointing and some drifts using other arm of NIRCam

## NIRCAM F212N w. Weak Lenses

## Long- GRISM Spectroscopy

- Grism for JWST segment capture  provides R=2,000 spectra
- Spectra improve saturation limit and reduce flat field error
- No slit losses  immune to pointing drifts
- Average over few 103 pixels for precision mapping
- Average over few 102 pixels for R~50-100 spectra

- High S/N R=500 spectra of a Jupiter around M2-3V star
- Secondary transits of Hot Earths around M5V stars

## Distance

-  Matters

## What is Brightest Star  Can NIRCam Observe

- F212N + 12 lens yields 1 ×105 elec (~full well) in 0.25 sec (160x160 pixels) in brightest pixel for **K=1 mag star**. For precision light curve (SNR=34 on Earth transit in 6.5 hr)
- Grism (R=1500) yields  1×105 elec (~full well) in 0.16s (1024x16 pixels with 10 pixel spot) for **[4.6] = 3 mag star **(G2V star at ~7 pc)

## MIRI Observations of Transits---Greene, Rieke

- MIRI images with filters for temperature determination
- Disperse w. slitless prism for R~100 spectra (5 – 14 m)
- Hot Jupiters (spectra) & Hot Super-Earths (photometry)
- Warm (HZ) Super-earths around M stars (no spectra)

## More Mission Concepts:5 minutes of fame! 

- EPOXI
- TRACER
- BEST
- THESIS
- TESS
- ASTRO
- PLATO
- MOST
- Warm Spitzer
- Hubble
- JWST

## EPOCh Transit Observations

-  Deep Impact’s 30-cm telescope  in 350-950 nm band
- De-focused image & heliocentric orbit  for high precision
-  Observations Jan-Aug, 2008
- Giant planet transiting systems
-  Reflected light (secondary transit)
-  Search for rings and moons
- Search for transits of terrestrial 	planets - now observing GJ436
*Timing search* for planets

*Courtesy Deming:*
*Note EPOCh posters 91, 92*
*& Christiansen talk!*

## Tracer ---Transit Characterization Explorer

* *SMEX mission not selected this round
*Characterize Atmospheric Properties*
- Physical conditions, chemistry, dynamics and cloud properties
* **Determine Physical Structure*
- Precision light curves for robust radii, detection of rings and/or satellites
*Detect Unseen Planets*
- Terrestrial planets in transit or by via perturbations of transit timings

***TRACER uses a 0.6 meter telescope with R~ 50 two channel spectrograph (0.8-1.7 ************m)***

**Tracer **---Transit Characterization Explorer

## The Balloon-borne Exoplanet Spectroscopy Telescope (BEST)

*Using molecules as probes of conditions, composition, and chemistry*
- Great Observatory class exoplanet science
- 70 cm telescope
- 2 - 5 μm
- R~500 spectroscopy
- Fills the spectroscopy gap
- Prebiotic and carbon
-      chemistry
- H20, CH4, CO, CO2, NH4 ...

- Mark Swain, Gautam Vasisht, Pin Chen, Drake Deming & Phillip Ward

## THESIS: the Terrestrial and Habitable-zone Exoplanet Spectroscopy Infrared Spacecraft

*using molecules as probes of conditions,  composition, and chemistry*
- A purpose built, dedicated exoplanet mission
- No new technology
- Simple & optimized for stability
- ~1.5 m telescope
- 2 - 15 μm
- R~500 spectroscopy
- Detailed FPA characterization
- High-precision pointing
- Optimized for detection of molecules
- 105:1 dynamic range possible on bright targets
- Long-term calibrated stability
- Non-transiting exoplanet spectroscopy
- Day & night characterization of M dwarf HZ planets
- Full orbit spectroscopic light curve
- Long-term weather monitoring
- High-precision transit timing

- Swain, Vasisht, Akeson, Deming, Grillmair & Burrows

## Transit Science Summary and Recommendations

## Transit Science Summary

- Era of (giant, hot) planet characterization is here using transits, light curves + RV
- Mass, radius, albedo, density, atmospheric composition and temperature structure
- Push to smaller, cooler planets
- M stars with survey of 104 -105  stars (Earths in HZ!)
- All sky survey to find targets around bright stars
- Recommendations for future transit observations
- Warm Spitzer for photometric follow-up
- Long duration Kepler/CoRoT missions + follow-up
- Tess (All Sky Survey)
- High priority for JWST follow-up  at all wavelengths
- Dedicated probe scale missions for spectroscopic characterization