1 Direct Observation of Exo-planets Enabled by Return to the Moon Webster Cash University of Colorado November 30, 2006

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3 How Can We Make Use of Return to the Moon?  Future of Astrophysics is in Large Structures and Formations  Will use Exo-planet Studies with Occulters as Example

4 A Core Principle of Science  Fastest route to the science wins  Fastest is almost always the Cheapest  If we can’t save money using RTM, we should not even consider it.  i.e. Nobody would ever again observe from the ground if it weren’t vastly cheaper.

5 What is the Financial Advantage of RTM?  What can manned or robotic presence do to lower costs?  What can “Luna Firma” do to lower cost?

6 How Do We Save Money Using Surface?  General Infrastructure –Power, Communications, Maintenance  Astronomy Infrastructure –Low Cost Instruments –Permanent Telescope Mounts  Large Stable Platform –Long Baseline Interferometry –Vacuum Beamline

7 Exo-Planets  Exo-planets are the planets that circle stars other than our Sun.  There are probably 10,000 exo-planets within 10pc (30 light years) of the Earth. Indirect means have now found over 200.  If we can observe them directly, we will have a new field of astronomy every bit as rich as extragalactic.

8 Occulter Diagram  Telescope big enough to collect enough light from planet  Occulter big enough to block star –Want low transmission on axis and high transmission off axis  Telescope far enough back to have a properly small IWA  No outer working angle: View entire system at once NWD Starshade JWST Target Star Planet

9 Fly the Telescope into the Shadow

10 Dropping It In

11 Occulters  Several previous programs have looked at occulters –First look by Spitzer (1962)  Used simple geometric shapes –Achieved only suppression across a broad spectral band  With transmissive shades –Achieved only suppression despite scatter problem BOSS Starkman (TRW ca 2000)

12 The Apodization Function for and This Function Extinguishes Poisson’s Spot to High Precision

13 Off Axis Performance  The off axis performance shows a rapid rise to unit transmission for the radii greater than the inner edge of the habitable zone

14 Suppression of Edge Diffraction Can Be Understood Using Fresnel Zones and Geometry  The occulter is a true binary optic –Transmission is unity or nil  Edge diffraction from solid disk is suppressed by cancellation –The power in the even zones cancels the power in the odd zones  Need enough zones to give good deep cancellation Sets the length of the petals –Petal shape is exponential  b is scale of petal shape  n is an index of petal shape  a is the diameter of the central circle a b

15  The Residual Intensity in the Shadow is  By Babinet’s Principle where E A is field over Aperture  So We Must Show  F is distance to starshade, s is radius of hole, k is 2  /  To one part in Doing the Math(Cash, Nature 2006)

16 Contrast Ratio  Preceding integral shows the contrast ratio is – –n is an integer parameter, typically n=6  To keep R small a~b –this is the reason the occulter has that symmetric look

17 Scale Model Lab Demo

18 Data from Heliostat by Doug Leviton Shadow Map Bottom at 1x10 -7 Image of Backlit Starshade

19 Starshade Tolerances  Position  LateralSeveral Meters  DistanceMany Kilometers  Angle  RotationalNone  Pitch/YawMany Degrees  Shape  Truncation1mm  Scale10%  Blob3cm 2 or greater  Holes  Single Hole3cm 2  Pinholes3cm 2 total

20 Simulated Solar System (Using NIRCam of JWST)

21 Discoverer Science Simulations Jupiter Saturn Exo-Zodiacal Starshade Shadow Earth Mars Jupiter Saturn

22 NWD Sensitivity Semi-Major Axis (AU) Planet Mass (M E ) pc 4pc 10pc Habitable Zone

23 The First Image of Solar System Jupiter Saturn Uranus Neptune Zodiacal Light Galaxies 10 arcseconds

24 Spectroscopy  R > 100 spectroscopy will distinguish terrestrial atmospheres from Jovian with modeling O2O2 H2OH2O CH 4 NH 3 S. Seager

25 Photometry Calculated Photometry of Cloudless Earth as it Rotates It Should Be Possible to Detect Oceans and Continents!

26 What Will RTM Provide Up To This Point?  Refueling  Fly starshade back from L2 to rendezvous  Hugely extend life of instrument  Thousands of targets instead of just hundreds  Repair  Patch micrometeor holes  Replace/Upgrade Electronics & Instruments  Telescope on Lunar Surface?  Difficult to hold starshade in position  No Financial Advantage  Probably Not…

27 Earth Viewed at Improving Resolution 100 km 300 km3000 km1000 km TRUE PLANET IMAGING

28 Solar System Survey at 300km Resolution

29 New Worlds Imager Concept 1500km starshades collector craft combiner 50,000km 1500km

30 Hypertelescope Problem  How Many Apertures Needed?  One per pixel (no!)  Cost control of multiple craft  Formation Flying to Tolerance  Labeyrie has worked on this  Amazing telescope even without starshades

31 Sims Established that information is present in the fringes and detectable. How do we invert into images? Is this enough?

32 Lunar Option  Planet Imaging is exciting enough to justify the expense level  Appropriate Level of Challenge for 20+ years from now Surface of Moon 1m Collectors Delay Lines, Beam Combiner, Detector Starshades in Orbit 4m Telescope 1m Collimator

33 Tradeoff ProCon InfrastructureMoon Rotates Moon StableBench100km class delay lines Predictable Bench Refuel Starshades

34 Can We Avoid Long Delay Lines? Should We Look at Hybrids? Surface of Moon Relay Delay Lines, Beam Combiner, Detector Starshades in Orbit 4m Telescope 1m Collimator Takes out First Order Effects Farther Away, Lower OPD

35 Return to Moon  Engineering presence in deep space via humans and robots will greatly extend the lifetime and range of New Worlds  Should we place some telescopes on surface? – Perhaps tiny telescopes make sense – Can we image planets and black holes from surface?  Stability, predictability and Infrastructure are Positives  Rotation of Moon is a huge negative

36  This is a new box. We have to think outside the old box.  The old solutions and ways of thinking should be suspect.  Perhaps, with enough work, we can find new solutions to the problem that will tilt the answer toward the surface.  Have we given this enough thought? – NO!