AN OVERVIEW OF THE ANDE RISK REDUCTION FLIGHT

The Atmospheric Neutral Density Experiment (ANDE) Risk Reduction flight 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 test the deployment mechanism from the Shuttle for the ANDE flight in late 2005. Scientific objectives of the ANDE risk reduction flight include; monitor total neutral density along the orbit for improved orbit determination of resident space objects, monitor the spin rate and orientation of the spacecraft, provide a test object for polarimetry studies using the HI-CLASS system. The mission consists of two spherical spacecraft fitted with retro-reflectors for satellite laser ranging (SLR). Each spacecraft contains a small light-weight payload designed to determine the spin rate and orientation of the spacecraft from on-orbit measurements and from ground based observations. A unique design requirement of one satellite is to telemeter the data to the ground without external protrusions from the spherical spacecraft (i.e. an antenna). This satellite will carry a communications system developed by the USNA that uses two aluminum hemispheres as the ends of a dipole antenna, at amateur radio frequencies.. This system will act as a backup communications platform in the full ANDE mission, planned for 2005. The techniques for determining spin rate and orientation of the satellite include: an orthogonal array of photovoltaic cells, an orthogonal array of laser diodes (to be observed by the HICLASS sensors at the Air Force Maui Space Surveillance Site), and variations in the light reflected by the ANDE sphere, which will have a specific pattern of different surface finishes. This paper presents a mission overview and emphasis will be placed on the design, optical layout, performance, ground station, and science capabilities of the mission.