Update on High Resolution Searches for KBO Binaries using New Horizons LORRI

The New Horizons (NH) spacecraft has been traversing the Kuiper belt for the past four years, enabling observations of known Kuiper belt objects (KBOs) at unique geometries, including at large phase angles not possible from the inner solar system and at ranges that provide higher spatial resolution than available from Earth, or Earth-orbiting, facilities. New Horizons carries a large aperture (20.8 cm) visible light imaging system, the LOng Range Reconnaissance Imager (LORRI), whose resolution (IFOV=1,4 arcsec for 1x1 and 4x4 modes, respectively) permits searches for binaries at finer spatial scales than available from the Hubble Space Telescope (HST). We have already observed 13 KBOs (1 Plutino, 1 Hot Classical, 1 Scattered Disk, and 10 Cold Classicals) that passed within 1 AU of the NH spacecraft, and two more KBOs are scheduled for observations in early September 2019. We are actively searching for additional candidates using ground-based telescopes. Five of the observed KBOs passed within 0.2 AU of the NH spacecraft, including two with ranges of ~0.11 AU (82 km/pix for 1x1 mode). LORRI's photometric sensitivity for these satellite searches (V~16.3 in 1x1 mode after co-adding ~125 0.5s exposures; V~21 in 4x4 mode after co-adding ~50 30s exposures, and even deeper after implementing 64s exposures in fall 2019) is comparable to, or exceeds, that available from HST. Five of the six highest resolution (1x1 mode) NH KBO satellite searches were performed during the latter half of 2018, and some of those data are scheduled for downlink in Oct-Nov 2019. Here we report on the binary search limits achieved for the 1x1 data that were downlinked by the end of Nov 2019.