The New Horizons (NH) spacecraft is on its way to study the Pluto system during a flyby. After the Pluto encounter, it is planned that the spacecraft will be retargeted to one or more yet-to-be-discovered Kuiper Belt Objects (KBOs) to learn about small KBOs and the Kuiper Belt debris body population. We are actively carrying out dedicated ground-based observations in 2011 and 2012 using large class telescopes to discover a KBO target that will be within the trajectory cone of NH. Unfortunately, the NH trajectory's line of site is within the galactic plane (Sagittarius) making stellar confusion a major problem in detecting and tracking KBOs in this region. HST’s sensitivity, resolution and PSF stability are a significant advantage in these confusion-limited starfields. We are requesting TOO orbits for up to 3 KBOs (2 orbits per KBO) to be triggered in the event that a candidate object is found in the NH trajectory. Objects must be recovered at multiple epochs to determine if their orbits will continue to place the object within the NH trajectory in the future. The observations we propose will also determine if the candidate is binary (~30% probability per candidate) and make a preliminary color determination. We obtain 2-455 second exposures in the F606W filter using a manual dither pattern and 2-640 second exposures in the F814W filter to obtain a color measurement (0.1 magnitude uncertainty) on the NH KBO candidate. All the TOO orbits are planned to take the same set of exposures, the only difference is the actual target. This project imposes no orientation constraints and uses ordinary blind target acquisition. We tracking the object under FGS control, target motion rates are very slow, at most a few arcsec per hour. 12 false 0.0 0.0 false false false false SUPPORTED SOLAR SYSTEM ASTEROID NewHorizons-Candidate1 TYPE=ASTEROID,A=45.92576064,E=0.13552798,I=1.87353,O=209.21519,W=136.94517,M=304.23985,EQUINOX=J2000,EPOCH=19-APR-2011:00:00:00,EpochTimeScale=UTC EARTH SOLAR SYSTEM ASTEROID NewHorizons-Candidate2 TYPE=ASTEROID,A=43.99788026,E=0.03856975,I=2.60734,O=231.49086,W=90.10902,M=317.85132,EQUINOX=J2000,EPOCH=19-APR-2011:00:00:00,EpochTimeScale=UTC EARTH SOLAR SYSTEM ASTEROID NewHorizons-Candidate3 TYPE=ASTEROID,A=43.15228839,E=0.03596879,I=2.39422,O=154.69962,W=211.72576,M=274.18700,EQUINOX=J2000,EPOCH=19-APR-2011:00:00:00,EpochTimeScale=UTC EARTH false -1 -1 false -1 -1 false -1 -1 false -1 -1 false -1 -1 false -1 -1