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[en] We conducted a search for occultations of bright stars by Kuiper Belt Objects (KBOs) to estimate the density of subkilometer KBOs in the sky. We report here the first results of this occultation survey of the outer solar system conducted in 2007 June and 2008 June/July at the MMT Observatory using Megacam, the large MMT optical imager. We used Megacam in a novel shutterless continuous-readout mode to achieve high-precision photometry at 200 Hz, which with point-spread function convolution results in an effective sampling of ∼30 Hz. We present an analysis of 220 star hours of data at a signal-to-noise ratio of 25 or greater, taken from images of fields within 3 deg. of the ecliptic plane. The survey efficiency is greater than 10% for occultations by KBOs of diameter d ≥ 0.7 km, and we report no detections in our data set. We set a new 95% confidence level upper limit for the surface density Σ N(d) of KBOs larger than 1 km: Σ N(d ≥ 1 km) ≤ 2.0 x 108 deg-2, and for KBOs larger than 0.7 km Σ N(d ≥ 0.7 km) ≤ 4.8 x 108 deg-2.
[en] We present a pre-survey study of using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) high sampling rate video mode guide star images to search for trans-Neptunian objects (TNOs). Guide stars are primarily used by Pan-STARRS to compensate for image motion and hence improve the point-spread function. With suitable selection of the guide stars within the Pan-STARRS 7 deg2 field of view, the light curves of these guide stars can also be used to search for occultations by TNOs. The best target stars for this purpose are stars with high signal-to-noise ratio (S/N) and small angular size. In order to do this, we compiled a catalog using the S/N calculated from stars with mV < 13 mag in the Tycho2 catalog, then cross matched these stars with the Two Micron All Sky Survey catalog, and estimated their angular sizes from (V - K) color. We also outlined a new detection method based on matched filter that is optimized to search for diffraction patterns in the light curves due to occultation by sub-kilometer TNOs. A detection threshold is set to compromise between real detections and false positives. Depending on the theoretical size distribution model used, we expect to find up to a hundred events during the three-year lifetime of the Pan-STARRS-1 project. The high sampling (30 Hz) of the project facilitates detections of small objects (as small as 400 m), which are numerous according to power-law size distribution, and thus allows us to verify various models and further constrain our understanding of the structure in the outer reach of the solar system. We have tested the detection algorithm and the pipeline on a set of engineering data (taken at 10 Hz instead of 30 Hz). No events were found within the engineering data, which is consistent with the small size of the data set and the theoretical models. Meanwhile, with a total of ∼22 star-hours video mode data (|β| < 100), we are able to set an upper limit of N(>0.5 km) ∼ 2.47 x 1010 deg-2 at 95% confidence limit.