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Atmospheric Neutral Density Experiment (ANDE) consists of two microsatellites launched from the Shuttle payload bay will measure the density and composition of the low Earth orbit (LEO) atmosphere while being tracked from the ground. The data will be used to better predict the movement of objects in orbit.

The ANDE risk reduction FCal satellite is a 45 cm sphere with a mass of 75 kg. Its name is derived from its intended use as a calibration target for the radar fence, a space surveillance system recently transitioned from the Naval Network and Space Operations Command to the Air Force 20th Space Control Squadron. The size requirement of FCal satellite was determined by the resonant frequency of the Navy radar fence. The two hemispheres are fabricated by spin-casting brass, followed by machine finishing. The exterior of each hemisphere is nickel coated for durability in the harsh space environment. The equator consists of an anodized aluminum deck that incorporates an antennae deployment system, and mounting locations for the FCal payload. A cubesat ballast mass is included for center of gravity symmetry.

The FCal satellite will have the same geometry as the MAA satellite for its for the retro reflector array. It will also contain temperature sensors and sun sensor modules distributed similarly. The FCal satellite is different from the other ANDE satellites in size, mass, finish, and payload. The size and mass differences will cause the satellites to separate over time into lead-trail orbit as the atmospheric drag causes a greater retardation of the larger and less massive MAA sphere. Consequently, the greater mass of the FCal sphere will enable it to have a longer lifetime before reentry, two years as compared to one year. By having two co-planar satellites, scientists can gain a better understanding of the geographic and temporal variations of the local atmospheric density at these altitudes. Attaining the necessary mass of the FCal satellite was one of the main challenges of designing this particular satellite.

The FCal satellite contains another microsat as a payload: a cubesat, a cube-shaped microsatellite that stores its experiments like shelves in a cabinet. The cubesat is a four-inch pico-satellite originally designed as an educational platform. It is a fully functional satellite with solar power (not used in FCal), battery power, a computer, and a communications subsystem. It can accommodate small payloads in the internally available space. The cubesat in Fcal was developed by Ivan Galysh, a member of the StenSat group working in the Space Applications Branch of NRL's Naval Center for Space Technology.

When the FCal is deployed, the processor boots and initializes all the satellite components. It then waits one minute and deploys the antennas one at a time. There is a one-second delay between the deployment of each antenna. Once deployed, the satellite starts monitoring all the sensors and internal parameters and transmits the telemetry once every two minutes. The satellite can accept commands during this period. The telemetry transmission interval can be set and the receiver audio can be routed to the transmitter to turn the satellite into a transponder. Telemetry data includes voltage and temperature from each of the six phototransistors, battery and power data, and internal temperature data. The purpose of the telemetry is to determine the spin rate and orientation of the FCal spacecraft.

The arrangement of the MAA and FCal satellites in a lead-trail orbit provides an exceptional set of targets to study drag modeling and its effect on satellite drag. This mission will demonstrate the effectiveness of flying low-cost calibration targets to support DoD and NASA requirements for precision orbit determination and collision avoidance. In addition, data from this mission will be used to improve the scientific understanding of the interaction between a spacecraft and its environment.

Alternate Names

  • Atmospheric Neutral Density Fence Calibration Satellite
  • 29667
  • ANDEFCal

Facts in Brief

Launch Date: 2006-12-10
Launch Vehicle: Shuttle
Launch Site: Cape Canaveral, United States
Mass: 75 kg

Funding Agencies

  • United States Naval Academy (United States)
  • United States Air Force Academy (United States)
  • US Air Force Research Laboratory (United States)
  • US Naval Research Laboratory (United States)


  • Communications
  • Technology Applications
  • Earth Science

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office

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