Atmospheric Neutral Density Experiment The Atmospheric Neutral Density Experiment ( ANDE ) is an experiment using two spherical satellites to measure the effects of atmospheric drag on spacecraft . ANDE is part of the Space Test Program of the United States Department of Defense , and was deployed in September 2006 from the Space Shuttle " Discovery " . Satellites . The two spacecraft used for the ANDE mission are the Mock ANDE Active ( MAA ) sphere and the Fence Calibration ( FCAL ) sphere . These microsatellites , developed by the Naval Research Laboratory , will measure drag through the use of precision orbit determination . Ground based lasers will be used to track the orbits of the sphere to with a couple centimeters of accuracy . Perturbations caused by density gradients and winds will be backed out from these measurements . The two ANDE satellites are nearly perfect spheres ; this was done to make the drag on the satellites independent of their orientation , and because the drag coefficient , optical cross - sections , and radar cross sections of spheres are well understood . Each spherical micro satellite was constructed using the novel technique of centrifugal casting . This manufacturing technique was advantageous due to its low cost and its ability to achieve the high tolerances necessary to make the sphere as round and smooth as possible . The ANDE MAA sphere is made from a proprietary alloy of AL 6061 that is castable , while the FCAL sphere is made from brass . The ANDE FCAL sphere has the distinction of being the only micro satellite to have its structure composed primarily of brass . The differences in materials and hence density and mass of the spheres will cause them to separate from each other along track over time . This separation will be measured and compared to predicted models of where the satellite should be based on computed models of the space environment . Uses . Beside their use in the in - situ determination of upper atmospheric density these satellites also function as technology demonstrators and as amateur radio digipeaters . Each satellite can be accessed via HAM radio using the APRS protocol . Part of the technology demonstration was the integration of a command and telemetry system that would not require the use of normal antennas that would destroy the spherical shape of the micro satellites . The MAA sphere communicates by electrically isolating its two hemispheres with an insulating center disk . The FCAL sphere actually does deploy four whip antennas but each antenna is only a few thousandths of an inch in diameter . Power is provided to these microsatellites using lithium inorganic primary cells – another technology demonstrator . The MAA also has photovoltaic cells made from copper indium gallium selenide ( CIGS ) deposited on a stainless steel substrate which is used for coarse sun sensing and is another technology demonstrator . The FCAL sphere uses standard photodiodes . ANDE was deployed from the Space Shuttle Discovery on December 21 , 2006 near the end of the STS - 116 servicing mission . The ANDE - FCAL satellite deployed and is functioning , however the ANDE - MAA failed to deploy at the same time as the FCAL sphere after it became stuck in its launch canister . The deployment of these spheres was another technology demonstrator for the newly developed Canister for All Payload Ejections ( CAPE ) system . One of the difficulties encountered and solved with this technology was the ability to restrain and deploy microsatellites that did not have any type of standard attachment points . The ANDE MAA did finally deploy on December 22 , 2006 and has been observed by NORAD as well as by radio contacts .