1. Exoplanets and the NRO Telescopes
Webster Cash
University of Colorado
NEW Telescope Meeting
Princeton, NJ
September 6, 2012

2. The Importance of Exoplanets
The citizens of this country pay the bills.
They don’t want science, so much as exploration.
They want us to map the local systems so we know where to land a starship
They want us to find life in the galaxy
They don’t want to wait 20 years.
Science and Exploration is a race. No medal for second place.
We must move quickly or, as Geoff Marcy famously put it:
“The future home of mankind will be named in Chinese”

3. What should a NEW Exoplanet mission be?
Any new mission with a coronagraph is going to cost well over a $billion
For this pricetag, we simply cannot afford marginal results
For this class of mission we must go after the “Earth Problem”
But the pricetag also ensures it will take over a decade to build once it started. Launch no earlier than 2027
We should worry now about the shelf life of the science. (No repeat of SIM)
Other approaches continue to be amazing, because they don’t have to wait for funding.

4. We need to perform spectroscopy on m=30 objects
The exoplanet problem
Earth is in there
The Basic Problems:
Stars are very bright and their glare makes it difficult to see fainter objects near them.
We need to perform spectroscopy on m=30 objects
25 Aug 2008

5. Starshade prevents starlight from entering the telescope
The telescope is shaded from the star by the starshade
Aside from a vanishingly small residual signal, the starlight does not enter the telescope
Starshade
But 100% of the planet light reaches the telescope

6. The New Worlds Observer 60m starshade, 4m telescope

7. Target Stars: Exo-zodiacal Light
4m Case
Local zodi
From P. Oakley
1.5m
2.4m 4m
10m

8. Planet Finding with Starshades Five Random Systems from Raymond Database
JWST
The higher resolution of ATLAST brings weak signals out of the noise
ATLAST

9. Alternate Starshade Missions
Cash, W., T. Glassman, A. Lo, and R. Soummer,
“Alternative starshade missions”
Proc. SPIE 7731, 77312J 10pp (2010)

10. Missions to Compare ATLAST 10m Telescope, 100m Starshade
NWO 4m Telescope, 50m Starshade
JWST 6.6m IR Telescope, 50m Shade
ACCESS 1.5m Telescope, 50m Shade
DEMO 0.5m Telescope, 12m Shade

11. The Map for Comparison The Solar System viewed
Mars
Saturn
Jupiter
Venus
Mercury
1 Zodi
Earth
The Solar System viewed
At 30 degrees from edge on at a distance of 10pc.
Assume up to one day for image and two weeks for spectrum.

12. ATLAST 10m Telescope, No Zodi
8000Å
4000Å

13. ATLAST 10m Telescope, 1 Zodi
4000Å
8000Å

14. ATLAST 10m Telescope, 106sec
No Zodi
One Zodi

15. NWO 4m Telescope, No Zodi
4000Å
8000Å

16. NWO
4000Å
8000Å

17. NWO
No Zodi
One Zodi

18. JWST 6.6m Telescope, 50m Starshade
Mars!
6500Å
1.7

19. JWST
6500Å
1.7

20. JWST
No Zodi
One Zodi

21. ACCESS 1.5m Telescope, No Zodi
4000Å
8000Å

22. ACCESS 1.5m telescope, 1 Zodi
4000Å
8000Å

23. ACCESS Spectra, 106sec
No Zodi
One Zodi

24. DEMO 0.5m Telescope, 12m Starshade
Measures Zodi
And Outer Planets
One Zodi
A few spectra of outer
Planets.
No Zodi

25. Summary Telescope Starshade Detect Spectra Detailed Cost $
Diameter m Diameter m Earth pc Earth pc Study
ATLAST >5Billion
NWO ~3Billion
JWST Million
ACCESS Billion
DEMO Million

26. Where to Look for ExoEarths? The Turnbull Diagram
FUV Spectroscopy of YSOs, Protoplanetary Disks, & Extrasolar Planets
April 25, 2008
Where to Look for ExoEarths? The Turnbull Diagram
NEW + Starshade
NEW + IC
The very first question to be asked is where shall we look for Earth-like planets? It’s worth stepping back and re-examining the stars in the solar neighborhood. There are 2350 Hipparcos stars within 30 pc (including ~200 within 10 pc, ~1000 within 20 pc). Of those, about 2100 have precise distances and magnitudes.
These stars are shown in this plot. The x-axis is the angular size of the habitable zone around each star. The y-axis is the brightness of an Earth-like planet in the habitable zone of the star relative to the stellar brightness. Each possible planet is plotted as a line going from the inner edge of the habitable zone to the outer edge.
The colors correspond to the spectral types of the central stars. Red is for M stars, orange for K stars, yellow for G stars, blue for F stars, cyan for A/B stars, and purple for giant stars. An Earth-twin around a Sun-like star at 10 pc is shown by the black circle. Please ignore the thin dashed vertical lines; they’re left over from an old version of this plot. 
For NWO with a 4 meter aperture, the inner working angles are 40 milliarcseconds in the blue and 65 milliarcsec in the red. There is no outer working angle. We are aiming for a contrast of 10^-11 at the inner working angles. In this case, there are about 110 stars whose entire habitable zone can be imaged and 280 stars with at least half of their habitable zone available.
This large potential target set makes uncertainties in the fraction of stars with Earth-like planets in their habitable zones less critical. If Eta_Earth is low, say 0.1, there are still tens of possible targets. If Eta_Earth is high, there could actually be a statistically significant sample of ExoEarths and we’ll all be ecstatic.
[ Inner HZ Location = aIHZ = 0.7 AU × Sqrt( L_star / L_sun )
Outer HZ Location = aOHZ =1.5 AU × Sqrt( L_star / L_sun ) ]
10-8 J
10-10
Local Zodi – 2.4m E
25 Aug 2008 26

27. PlanetRise / Zodiac What one of the NRO missions could look like
SUNRISE
Solar Balloon
Capability comparable to NEW with internal coronagraph
Just fewer targets.
Could address many of the questions we have during this decade
Cost: under $50M
(Thanks to S. Chakrabarti)

28. Suborbital Starshades Starting Now Potentially Reach 0.6” at 10-10
0.5m Starshade
1-100km
Hours on Target
20cm Telescope
Saturday, November 24, 2018

29. Situation
NRO Telescopes can be used as wide field imagers without pushing on Technology. Seems like a great idea to me.
The value to cost ratio of using one of the mirrors for exoplanets is not so clear. Needs further study.
But there’s a problem:
There is no program for exoplanet instrumentalists to propose to:
Too expensive for R&A (APRA)
Too risky for even a small Explorer
The community still desperately needs a flight demonstration program.

30. FY08 Astrophysics Edifice
Understanding (Priceless)
Theory and Lab Astro ($16M)
Data Analysis ($71M)
Technology Flight Proven Here
Operations ($343M)
Mission Fabrication and Launch ($1017M)
Directed Development ($75M)
Missions Selected Here
Basic Development ($39M)
Congress and Taxpayers

31. A Better Balance Congress and Taxpayers Understanding (Priceless)
Theory and Lab Astro ($35M)
Data Analysis ($120M)
Operations ($200M)
Facility Fabrication and Launch ($650M)
Facility Development ($150M)
Orbital Experimentation ($150m)
Missions Selected Here
Basic/Suborbital Experimentation ($200M)
Technology Flight Proven Here
Congress and Taxpayers