Measured spacecraft dynamic effects on atmospheric science instruments

In September 1991, NASA launched the Upper Atmosphere Research Satellite (UARS). In addition to its atmospheric science mission, spacecraft dynamic effects on science measurements were analyzed. The investigation included two in-flight experiments to determine how each onboard instrument, subsystem, and environmental disturbance contributed to the spacecraft dynamic response and how these disturbances affected science measurements. Three case studies are presented that show the impact of spacecraft dynamic response on science measurements. The case studies have demonstrated that the influence of spacecraft dynamic response needs to be examined in most remote-sensing spacecraft that have attitude jitter levels commensurate to instrument pointing requirements. In the first case, correlation of independent atmospheric meridional wind measurements taken by two instruments with the spacecraft dynamic response demonstrated that excessive vibration (exceeding instrument pointing requirements) resulted in wind measurement disagreement. In the second case, solar array disturbances produced a spacecraft response signature on radiometer measurements. The signature explicitly demonstrated that if an instrument has sufficient spatial and temporal resolution, spacecraft dynamic response could impact measurements. In the final case, correlation of an instruments fine Sun-sensor data and CO₂ measurements demonstrated the effect of temporal and spatial sampling resolution and active pointing control on science measurements. The Sun sensor had a frequency modulated characteristic, due to spacecraft vibration and the periodic scanning of another instrument, which was not present on the CO₂ measurements