multiple spacecraft observatories for 2020 and beyond: breaking a tradition of four centuries...
TRANSCRIPT
Multiple Spacecraft Observatories for 2020 and Beyond: Breaking a Tradition of Four Centuries
Webster Cash
University of Colorado
Telescope
Multiple Telescopes
Large Space Telescopes
• ATLAST 8-16m Visible light
• Gen-X 1000x area, 10x res (vs Chandra)
• SAFIR 100x Spitzer area
These represent the largest affordable telescopes.They are being proposed right now.
Multiple Space Telescopes
• Stable - not rotating like Earth surface
• No Gravity – Large Lightweight Structures
• Large Diameters -- formation flying
• Very Long Baselines – formation flying
• Reduces pointing problem -- formation flying
Natural Evolution, because space has major advantages
Thin Lens Behavior
As a thin lens wobbles, the image in space does not movePosition on the detector changes only because the detector moves
Formation Flying
If detector is on a separate craft, then a wobble in the lens has no effect on the image.
But motion of detector relative to Line of Sight (red) does!
Much easier than stabilizing array.
Let’s Look at Some Multiple Craft Observatories
Constellation-X
Grouping of similar craft to increase area.Can only be of use in a low noise application like x-ray astronomy.
New Worlds Observer
External OcculterLarge Distance but Loose Formation
MAXIM
Dilute aperture telescope
TPF-I
Dilute aperture (nulling) telescope
LISA
Complete break with telescope traditionBut gee! It’s gravity waves. What do you expect?
Trend in Multiples• Gang together
– Save some money
• Dilute aperture telescopes– Driven by resolution– Formation fly to optical tolerances– They’re gonna be expensive!
• Special Applications– LISA for gravity waves– New Worlds for contrast enhancement
New Worlds Observer
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 JWSTTarget Star
Planet
Big Sheet of Specially Shaped Plastic can suppress diffraction
Performance
(with circularly symmetric apodization)A 50m diameter occulter at 50,000km will reveal Earths at 10pc
a=b=12.5mn=6F=50,000km
Shadow of 16 Petal Mask
Linear Log
Simulated Solar System
Image of Solar System with 4m Telescope
JupiterSaturn
Uranus
Neptune
Zodiacal Light
Galaxies
10 arcseconds
Spectroscopy• R > 100 spectroscopy will distinguish terrestrial
atmospheres from Jovian with modeling
O2
H2O
CH4
NH3
Photometry
Calculated Photometry ofCloudless Earth as itRotates
It Should Be Possible to Detect Oceans and Continents!
1.5m Telescope
2.4m Telescope
4m Telescope
10m Telescope
1.5m Telescope
2.4m Telescope
4m Telescope
Conclusion
Multiple Spacecraft Observatories are inevitable
They uniquely enable fundamental new science.
They are being developed now. 2020 Observatories
Simpler applications likely to go first while the astronomy community completes its large telescope imperative.