Effective Mirror Diameter 6.5 mField of view 9.6 sq degExposure (‘Visit’) Time 2x15 s /visitSurvey length 10 yearsData rate ~15 TB/nightSky coverage ~18,000 sq degSite Cerro PachonFilters ugrizyTypical seeing 0.7”Photometric accuracy 10 mmagAstrometric accuracy 50 masAstrometric precision 10 mas

Solar System Science with LSST

Inventorying the Solar System is one of the four key science drivers for the Large Synoptic Survey Telescope (LSST). Over its 10 year lifetime, LSST will survey over 20,000 square degrees with a rapid observational cadence, to typical limiting magnitudes of r~24.5. Near the ecliptic, LSST will detect approximately 4000 moving objects per visit (two 15s back-to-back exposures) with its 9.6 square degree field of view. Automated software will link these individual detections into orbits; these orbits, as well as precisely calibrated astrometry (~50mas) and photometry (~0.01-0.02 mag) in multiple bandpasses will be available as LSST data products. The result will be multi-color catalogs of hundreds of thousands of NEOs and Jupiter Trojans, millions of asteroids, tens of thousands of TNOs, as well as thousands of other objects such as comets and irregular satellites of the major planets.

The LSST catalogs will provide an order of magnitude or more increase in sample sizes over those currently existing for small body populations throughout the Solar System, generating new insights into Solar System evolution. Precision multi-color photometry will allow determination of lightcurves and colors for a significant fraction of the objects detected, providing constraints on the physical parameters of small bodies. Some examples of science enabled with this rich data set: A large sample of TNOs with highly accurate orbits (and well-understood sample characteristics) will allow much tighter constraints on planetary migration models. Large samples of comets (especially comets with perihelia beyond a few AU) will provide new constraints on the structure and mass of the Oort Cloud. Using sparse lightcurve inversion, spin state and shape models could be derived for thousands of main belt asteroids. A ten-fold (or greater) increase in asteroid family members, particularly at smaller sizes, and including their color information, will provide unprecedented study of collisional and dynamical processes. A sample of hundreds of "active" asteroids will provide ground truth for theoretical models of impact physics.

R. Lynne Jones1, Zeljko Ivezic1, Mike Brown2, Renu Malhotra3, Andrew C. Becker1, Yan Fernandez4, Jon Myers3, Mike Solontoi5, & Alex H. Parker6

1University of Washington, 2Caltech, 3University of Arizona, 4University of Central Florida, 5Lynchberg College, 6Southwest Research Institute

The Large Synoptic Survey Telescope (LSST)LSST will repeatedly image the night sky, creating a rich dataset to address the four major science drivers:• understanding dark energy and dark matter• mapping the Milky Way and Local Volume• exploring the transient and variable sky• cataloging small bodies in the Solar SystemAs a survey project, LSST will process, precisely calibrate, and create catalogs – including catalogs of moving objects – from all images. Both the images and the catalogs will be publicly available.

Solar System CatalogsMoving object catalogs will be produced by linking detections coming from individual images after subtracting a deep template image. These ‘difference image detections’ are in large part the same as the sources released as LSST’s “Alert” stream. The current minimum detections required for linking are: 2 detections per night within a 90 minute window, over 3 separate nights within a 15 night window. After fitting an orbit to the linked detections, the orbit and all detections which were linked to that object are available in the moving object catalog database.

u g r i z y

Visits 70 100 230 230 200 200

Depth 23.9 25.0 24.7 24.0 23.3 22.1

Left: LSST’s 9.6 square degree field of view.

Above: LSST’s M1/M3 is in the final stages of polishing and acceptance testing.

Above: LSST’s M2 is being prepared for polishing.

Right: Simulated LSST survey from the Operations Simulator (OpSim). These plots show the total number of visits in each filter in this example survey.

LSST’s large field of view is due to the fast focal ratio (f/1.2) and very large (3.2 gigapixel) camera. A readout of 2s, coupled with a fast slew/settle time of 5s, ensures a high duty cycle.

Size Distributions and Collisional FamiliesThe figure to the right shows the proper orbital parameters of Main Belt Asteroids, color-coded according to ugriz colors measured by SDSS (Parker et al, 2008, Icarus). Note how the asteroid families become visible as clumps in proper elements and colors, even when viewing the entire population (as in the top panels). Families can be separated from the background population (as in the middle and bottom panels, respectively). Without separating collisional families from the general background population, it is difficult to apply the measured size distributions as constraints on accretion or collision models. The properties of the families also provide unique insight into collision physics, the historical collision rate, injection rates into the NEO and comet populations, interior structure of the asteroids, the interpretation of small body colors, space weathering, and many other outstanding questions in the study of the solar system.By providing precise colors as well as highly accurate orbits for 10-100 times the currently known population of small solar system bodies, LSST will enable a more detailed characterization of known families and discovery of new families, including amongst the Trojan asteroids of Jupiter, the irregular satellites of the outer planets, and TNOs.

Rare Objects and Population LinksLSST will be very good at discovering rare types of objects or events, such as retrograde TNOs (like 2008 KV42 - Gladman et al, 2009, AJ) or other objects on extraordinary orbits (such as Sedna - Brown et al, 2004, AJ), comets outbursting for the first time, or collisions between ordinary asteroids. An example of an asteroid collision serendipitiously discovered by LINEAR is shown to right. P/2010 A2 was first thought to be perhaps a main belt comet undergoing an outburst; followup observations indicate that it is more likely to be the result of an collision (Snodgrass et al, 2010, Nature; Jewitt et al, 2010, Nature). LSST will discover hundreds of such "active" asteroids.LSST will also significantly improve our samples of all currently known populations, including ‘crossover’ populations like the Main Belt Comets. It is already known that Main belt asteroids migrate into the NEO population and Oort Cloud objects transfer slowly into Centaur orbits due to gravitational perturbations, but the details of these links are difficult to study with the current limited populations. What other linkages will become apparent with these increased sample sizes, where each object comes complete with accurate orbits and well-measured colors?

Left: Diagram of LSST camera.Right: Prototype sensors and raft assembly.

Rght: Simulated photometric observations, reduced to unit distances to Earth and Sun, for an MBA. Above: Estimated shape obtained through sparse lightcurve inversion for the MBA.

Shape, Spin and Rotation PeriodsUsing “sparse light curve inversion” techniques, we expect to derive models of global shape, spin axis direction, and rotation period for about 104 to 105 main-belt and near-Earth asteroids from LSST photometry, which means that we will be able to map a substantial part of the asteroid population. Roughly speaking, once we have at least ~100 sparse brightness measurements of an asteroid over ~5 years, calibrated with a photometric accuracy of ~5% or better, a coarse shape model can be derived. The sparse data inversion gives correct results for both fast (0.2-2 h) and slow (>24 h) rotators (Durech et al. 2007, IAUS).For TNOs, the viewing/illumination geometry changes very slowly and the full solution of the inverse problem is not possible. However, accurate sparse photometry can be used for period determination. Moreover LSST sparse photometry can be also used for detecting (but not modeling) 'non-standard' cases like binary and tumbling asteroids. A fully synchronous binary system behaves like a single body from the photometric point of view. Its binary nature can be revealed by the rectangular pole-on silhouette and/or large planar areas of the convex model. In some cases - when mutual events are deep enough - asynchronous binaries can be detected from sparse photometry. Interesting objects can be then targeted for follow-up observations.

Pop. Expected # detected

# w/ >100 detections

NEO 100,000 1,400MBA 5.5 M 1.6 MTrojan 280,000 80,000TNO 40,000 11,000

Simulations indicate that LSST could detect substantial numbers of small bodies in the Solar System – see above and left. LSST’s faint individual image limiting magnitude provides significant sensitivity to small objects – see right.

LSST Timeline