AAS 205th Meeting, 9-13 January 2005
Session 108 LSST
Poster, Wednesday, January 12, 2005, 9:20am-6:30pm, Exhibit Hall

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[108.21] LSST Solar System Survey Cadence and Sky Coverage Requirements

A. W. Harris (Space Science Institute), E. L. G. Bowell (Lowell Observatory)

Solar system goals with LSST include cataloging small Potentially Hazardous Asteroids (PHAs), surveying the main belt asteroid population to extraordinarily small size (where radiation pressure effects may play a dominant role in sculpting orbital distributions and spin states), discovering comets far from the sun where their nuclear properties can be discerned without coma, and surveying the Centaur and Kuiper Belt populations. The present planned observing strategy is to ``visit" each field (8 sq. deg. net non-overlapped) with two successive exposures of ~ 12 sec, reaching to at least V magnitude 24. An intra-night revisit time of not less than ~20 minutes will distinguish stationary transients from even very distant (~ 70 AU) solar system bodies. The nightly cadence should be two, or possibly 3, revisits spaced by about half an hour. In order to link observations and determine orbits, each sky area must be re-visited on two, or better 3, nights during a month, spaced by about 5 days. Formally, two visits on two nights (2/2) is sufficient for orbit determination, but 2/3, 3/2, or 3/3 cadences would yield detection threshold improvements nearly enough to offset the additional time taken, provide redundancy for missed detections, and result in better orbit determination. We therefore recommend the 2/3 cadence, or even 3/3 if possible. We have explored the efficiency of the PHA survey with less than all-sky coverage. It appears that covering a band of the ecliptic ±10\arcdeg in latitude and ±120\arcdeg in longitude from the opposition point, less a swath ±20\arcdeg in galactic latitude through the ecliptic plane, is sufficient to achieve nearly ``all-sky" efficiency of surveying, requiring only ~ 4,000 sq. deg. per month. However, much of this area must be imaged at air mass >1.5, unsuitable for some of the other scientific goals of LSST. It appears that a survey in r band only of < 2000 sq. deg. per month that must be reached at higher air mass, combined with coverage in g, r, and i filters done as a part of the astrophysical surveying, can meet the goals of the solar system survey.

The author(s) of this abstract have provided an email address for comments about the abstract: harrisaw@colorado.edu

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