Session
Technical Session III: Advanced Technologies I
Abstract
The communication subsystem of NASA’s Lunar Atmospheric and Dust Environment Explorer (LADEE) makes use of the Space Micro µSTDN, a digitally intensive S-Band transponder. The effects of received radio frequency power, downlink data rate and temperature on transponder’s ranging accuracy were investigated. The LADEE flight ranging data is corrected using calibration data taken during thermal vacuum testing of the flight transponder. The root mean square single standard deviation accuracy of the LADEE transponder ranging after calibration for temperature and uplink power is 5.2 ns, which corresponds to a single shot range accuracy of just 78 cm. Since both uplink power and temperature are measured inside the transponder, such post measurement calibration is valid over the entire qualification temperature range (-30 ºC to 65 ºC) and over four orders of magnitude of radio frequency uplink power (-120 dBm - -80 dBm). The root mean square variability of the flight data after calibration is found to be just 2.2 ns.
Digitally Intensive Precision Ranging Subsystem of the Lunar Atmospheric and DustEnvironment Explorer’s Transponder
The communication subsystem of NASA’s Lunar Atmospheric and Dust Environment Explorer (LADEE) makes use of the Space Micro µSTDN, a digitally intensive S-Band transponder. The effects of received radio frequency power, downlink data rate and temperature on transponder’s ranging accuracy were investigated. The LADEE flight ranging data is corrected using calibration data taken during thermal vacuum testing of the flight transponder. The root mean square single standard deviation accuracy of the LADEE transponder ranging after calibration for temperature and uplink power is 5.2 ns, which corresponds to a single shot range accuracy of just 78 cm. Since both uplink power and temperature are measured inside the transponder, such post measurement calibration is valid over the entire qualification temperature range (-30 ºC to 65 ºC) and over four orders of magnitude of radio frequency uplink power (-120 dBm - -80 dBm). The root mean square variability of the flight data after calibration is found to be just 2.2 ns.
