The Atmospheric Neutral Density Experiment

The Atmospheric Neutral Density Experiment (ANDE) is a mission proposed by the Naval Research Laboratory to monitor the thermospheric neutral density at an altitude of 400km. The primary mission objective is to provide total neutral density along the orbit for improved orbit determination of resident space objects. The mission also serves as a test platform for a new space to ground optical communications system. The measurements also provide a critical validation point for the upcoming Special Sensor Ultraviolet Limb Imagers (SSULI) to be launched on each of the five Defense Meteorological Satellite Program (DMSP) spacecraft in block 5D3 starting in 2002. In addition ANDE provides two calibration objects for use in the Air Force High Accuracy Satellite Drag Model (HASDM) initiative to help maintain and improve accuracy of the space object catalog. The mission consists of two spherical spacecraft fitted with retro-reflectors for satellite laser ranging (SLR). One spacecraft is completely passive, the other carries three active instruments; a miniature Wind And Temperature Spectrometer (WATS) to measure atmospheric composition, cross-track winds and neutral temperature; a tri-axial Miniature Electro-Static Accelerometer (MESA); and a Thermal Monitoring System (TMS) to monitor the temperature of the sphere. The active satellite will be fitted with modulating retro-reflectors (MRRs), The spacecraft telemetry will be transmitted to the ground by modulating and reflecting the SLR laser interrogation beam.