Beyond TAOS: Future Blind Field Surveys Charles Alcock University of Pennsylvania With major contributions from The TAOS Science Team & Ball Aerospace Charles Alcock University of Pennsylvania With major contributions from The TAOS Science Team & Ball Aerospace

Plan of the talk: The scientific need for an occultation survey that is more capable than TAOS Description of occultations by TNO’s –What TAOS will do –What TAOS will not be able to do Beyond TAOS: –An expanded ground-based array –A space-based survey

The Scientific Needs (beyond TAOS): Census of TNO’s with size < 1 km to study the collisionally eroded regime Better estimates of sizes Shape determination Distance estimates are critical! Ultimate goal should be to survey the entire Solar System – out to the Oort Cloud!

R = 5 km = 845 nm r = 50 AU The basics of TNO occultations (again!):

The basics of TNO occultations r 2R λ

A “representative”sequence of occultations by “spherical TNO’s” (1 FSU = ( r/2) 1/2 )

Stellar colors, magnitude, temperatures, and radii (A. N. Cox, “Allen’s Astrophysical Quantities”, 2000.)

Next Generation TAOS: an expanded ground-based array Larger telescopes for more stars at greater S/N (1 meter class with field of view > 1.5 o ) More telescopes (~10) spread out over several kilometers to sample the diffraction patterns –Distance estimates become possible –Sample smaller objects

Multiple telescopes are useful Help to control false positives (critical in TAOS) A spatially expanded array can sample the shadow pattern (shape & distance information) –Spacing ~1 km North-South –Spacing >10 km East-West (may need to move telescopes seasonally) –Real estate problem (Atacama plateau?)!

Site selection not straightforward: Dark sky, good seeing for photometric precision Accommodate array kilometers across Possible need to move telescopes seasonally –Western US –Northern Chile

Need to operate faster than 5 Hz: Use “frame-buffer” CCDs –Increase sampling rate (~10 Hz) –Eliminate streaking characteristic of zipper mode –Scalable to large focal planes May upgrade TAOS using this architecture (TAOS II)

Beyond TAOS: a space-based system similar to Kepler S/N > 10 on ~150,000 stars at 30 Hz Potential to survey down to ~100 meters Reliable statistical estimates of distances Crude shape estimates Thousands of events Oort Cloud …?

“Straw man” design based upon Kepler Kepler will follow 160,000 stars in one field to search for planetary transits Aperture 95 cm Schmidt design gives wide field of view (8 o ) Photometric samples taken every 2.5 seconds –Co-added into 15 minute bins to give very high precision photometry

“Straw man” design based upon Kepler Occultation mission similar, but: –Add small angle prism to corrector lens to give modest spectral dispersion –Sample frequently (nominally 30 Hz) –Lower S/N ~ 10 is acceptable –Extremely high data rate –Multiple pointings along and near the invariable plane

Add small angle prism to corrector lens to give modest spectral dispersion

The focal plane and data path are very challenging: million imaging pixels Each star spectrally dispersed over 5-10 pixels Sample at ~30 Hz Need substantial pre-processing on board

Summary: Substantial growth potential beyond TAOS for ground-based occultation work Space-based occultation survey needed to address all the key questions: –Size spectrum in collision-eroded regime –Nature and distribution of objects beyond the Kuiper Belt