MEASURED SPACECRAFT DYNAMIC EFFECTS ON ATMOSPHERIC SCIENCE INSTRUMENTS

In September 1991, NASA launched the Upper Atmosphere Research Satelli te (UARS). In addition to its atmospheric science mission, spacecraft dynamic effects on science measurements mere analyzed. The investigati on included two in-flight experiments to determine how each onboard in strument, subsystem, and environmental disturbance contributed to the spacecraft dynamic response and how these disturbances affected scienc e measurements. Three case studies are presented that show the impact of spacecraft dynamic response on science measurements. The case studi es have demonstrated that the influence of spacecraft dynamic response needs to be examined in most remote sensing spacecraft that have atti tude jitter levels commensurate to instrument pointing requirements. I n the first case, correlation of independent atmospheric meridional wi nd measurements taken by two instruments with the spacecraft dynamic r esponse demonstrated that excessive vibration (exceeding instrument po inting requirements) resulted in wind measurement disagreement. In the second case, solar array disturbances produced a spacecraft response signature on radiometer measurements. The signature explicitly demonst rated that if an instrument has sufficient spatial and temporal resolu tion, spacecraft dynamic response could impact measurements. In the fi nal case, correlation of an instruments fine sun-sensor data and CO2 m easurements demonstrated the effect of temporal and spatial, sampling resolution and active pointing control on science measurements. The su n sensor had a frequency modulated characteristic, due to spacecraft v ibration and the periodic scanning of another instrument, which was no t present on the CO2 measurements.