Data Set Overview : The Sub-Kilometer Asteroid Diameter Survey (SKADS) (Gladman et al. 2009) acquired good-quality orbital and absolute magnitude (H) determinations for 1087 small main-belt asteroids in order to study the orbital and size distribution beyond H : 15, down to sub-kilometer sizes (H > 18). This data set contains the astrometry, photometry, and orbits of the 1087 asteroids detected by SKADS which have one-week time baselines or more.  The detected asteroids range from H(R) : 12 - 22 and provide a set of objects down to sizes below 1 kilometer in diameter. We find an on-sky surface density of 210 asteroids per square degree in the ecliptic with opposition magnitudes brighter than m(R) : 23, with the cumulative number of asteroids increasing by a factor of 10^0.27/mag from m(R) : 18 down to the m(R) ~ 23.5 limit of our survey. In terms of absolute H magnitudes, we find that beyond H : 15 the belt exhibits a constant power-law slope with the number increasing proportional to 10^0.30H from H ~ 15-18, after which incompleteness begins in the survey.  Observations :  Six nights were allocated for the SKADS program at the 3.8-m Mayall telescope at Kitt Peak National Observatory: March 21, 22, and 23 UT 2001 at the beginning of the dark run, and March 29, 30, and 31 UT at the end of the dark run. An asteroid detected in at least one night in both blocks would thus have an observed arc length of between 6 and 10 days if multiple observations could be successfully linked. The KPNO mosaic CCD camera gives a 36x36 arcminute field of view on the Mayall. We created a grid of contiguous sky coverage along the ecliptic plane that was within a few degrees of the opposition point on the first night, covering 8.4 square degrees of sky (which accounts for gaps between the mosaic's CCDs). The fields were translated 13.5 and 5.4 arcmin to the west and north (respectively) per day to keep as many main-belt asteroids as possible in the imaged region. These translation rates were determined using the average rates of known main-belt asteroids within a few degrees of the initial pointings.  Filter choice was governed by a balance between obtaining maximum magnitude depth (discovering as many objects as possible) and the desire to acquire some color information on the asteroids. Obtaining V-R colors allows us to estimate (even if only on a probabilistic basis) the taxonomic type of each detected asteroid. On photometric nights we thus acquired triplets of 120-sec images for object detection in R-band with an inter-exposure spacing of roughly 15 minutes.  Immediately before or after one of these three R-band exposures on any given night, we acquired a 120-sec V-band exposure; the temporal proximity minimizes any possible light curve variations in the color measurement.  Photometric and Astrometric Calibration :  On each night, Landolt standard fields were acquired at multiple airmasses. Using this data, the standard 1 ADU/sec zeropoint and the airmass correction term in both V and R were measured. When conditions were taken in photometric conditions, aperture correction photometry was used to produce R-band and V-band magnitudes (corrected to airmass:1.0) for each asteroid image, with photometric uncertainties provided by DAOPHOT.  When the wide 'VR' filter was used in either above-median seeing or non-photometric conditions, a transformation from VR instrumental magnitudes to R-band magnitudes was estimated; the provided R-band measures thus have a unmeasured colour-dependent term and may be in non-photometric conditions. Such measurements are flagged by having no uncertainty given for the R-band magnitude estimate and these photometric data are just 'sanity checks', with expected errors on the level of 0.3-0.5 mags, and should not be used to draw scientific conclusions.  The astrometric reference frame is based on the USNO-A2.0 catalog (J2000.0).  Object Identification :  Individual detections are identified by an internal identifier of the form pXXXYYN where XXX is the pointing number, YY is the chip number (1-8) of the Mosaic Camera, and N is a character in the range (1-9, a-h) indicating the specific detection within an image. The first digit of the pointing number XXX indicates the night (1-6), and the pointing centers are listed by pointing number in the file pointings.tab.  Detections linked (identified with a single orbit) across at least three nights and over both blocks of the run are assigned an object identifier which is the detection identifier of the first detection, but with the prefix changed to s: sXXXYYN.  Astrometry for all detections were submitted to the Minor Planet Center and either identified with known asteroids or assigned provisional designations. The cross-identification between internal SKADS designations and MPC asteroid numbers and provisional designations is given in the file mpcids.tab.  Data :  The SKADS data set includes the following directory structure and files:  Data directory:  * mpcids.tab - The cross-identification between internal SKADS designations and MPC asteroid numbers and provisional designations. * pointings.tab - Mosiac camera pointing centers on each of the six nights.  Subdirectory 'astrometry': * multinightobs.tab - The master astrometry list of all SKADS asteroids with 3 or more nights linked. * twonightobs.tab, onenightobs.tab - Lists of astrometric observations that are unlinked or linked on only two nights of observation. * night1obs.tab-night6obs.tab - Full astrometric information for all detections on each of the six nights.  Subirectory 'photometry': * skadsphot1.tab-skadsphot6.tab - Photometric measurements of the detections on each of the six nights.  Subdirectory 'orbits': * skadsorb.tab - Master list of skads orbits for asteroids with 3 or more nights linked. * twonight.tab - Summary of orbits for two-night links that were not identified in the other block (likely due to faintness or leaving the field in the time between the two blocks).  References :  For full details about the SKADS program and results, see Gladman et al. (2009).  Gladman, B.J., D.R. Davis, C. Neese, R. Jedicke, G. Williams, J.J. Kavelaars, J.-M. Petit, H. Scholl, M. Holman, B. Warrington, G. Esquerdo, and P. Tricarico, On the asteroid belt's orbital and size distribution, Icarus, 202, 104-118, 2009.

Confidence Level Overview : Judged by known asteroids in the field the typical uncertainties in the SKADS orbital elements (a/e/i) are less than 0.03AU/0.03/0.5deg. The distances to the objects are sufficiently well known that photometric uncertainties (of 0.3 magnitudes or better) dominate the error budget of their derived H-magnitudes. See Gladman et al. (2009) for a detailed discussion of the uncertainties.  Considerable effort was expended to understand differences between our results and other published works, particularly as to the effect of the detection efficiency, measured or assumed, on the resulting absolute magnitude distribution. The results from this investigation, as well as a discussion of the is described in detail in Section 9.1 of Gladman et al. (2009).  In general, the uncertainties reported in this paper represent the authors best efforts to accurately describe the quality of both the data and the derived products, e.g. orbits and absolute magnitude distributions.