Comparison of OARE ground and in-flight bias calibrations

Abstract

A comparison is made between in-flight and ground baed bias calibrations for the Orbital Acceleration Research Experiment (OARE) instrument. Performance requirements for the OARE sensor, calibration system, and data handling system are given. Bias is modeled as a function of several variables, including time from the launch event, sensor range, temperature, sensor axis, time, and external noise. Time variations of bias are evident in the X axis primarily, due to dielectric charging of the ceramic insulator material which surrounds the cylindrical axis electrodes. Variations of bias with range are due to the pick-off null offset of the sensor and the reference voltage range scaling. Biastemperature coefficients for the MESA are -0.036 microgi°C for the X axis, +0.027 micro-gi°C for the Y axis, and 4.019 micro-g/OC for the Z axis in their most sensitive ranges. Ground calibration results from before and after the mission are compared with flight results. Ground calibrated parameters are not indicative of flight calibrated parameters. It is shown that periodic in-flight calibration is critical for ultra-sensitive accelerometers such as the electrostatic suspension sensor used on OARE