In-flight performance of the HASI servo accelerometer and implications for results at Titan

The Huygens Atmospheric Structure Instrument (HASI) includes a high sensitivity servo accelerometer to sense deceleration in the direction of the probe trajectory as it enters Titan's atmosphere in January 2005, These data will be used to determine the atmospheric density profile in the upper reaches of the atmosphere where it is least well constrained. Results are presented of the performance of this subsystem during the in-flight checkouts performed to date. In particular, the noise performance is assessed. This is especially important as it limits the resolution, and therefore performance, of the sensor at the very top of Titan's atmosphere. Implications for the results expected at Titan are presented.