Thursday, December 17, 2009

Close encounters of the FalconSAT kind

by Jack Anthony, U.S. Air Force Academy Space Systems Research Center

U.S. AIR FORCE ACADEMY, Colo. (AFNS) -- Satellites from the U.S. Air Force Academy and the Department of Energy intentionally passed within five kilometers of each other in orbit Dec. 13, with one satellite's sensors trained upon the other.

The two satellites are the Academy's cadet-built FalconSAT-3 satellite and the Cibola experimental satellite operated by the energy department's Los Alamos National Laboratory, N.M.

Cibola's sensors were trained on FalconSAT-3 to help the FalconSAT team investigate a spacecraft altitude determination and control problem, said Col. Marty France, the head of the Academy's Astronautics Department. The anomaly has hindered FalconSAT-3's array of Defense Department on-orbit space experiments.

In the past, not much thought was given to this occasional flyby. This time the Cibola visit would be a potential benefit to the FalconSAT-3 team. Cibola could use its star camera sensors to observe FalconSAT-3, possibly shedding light onto the nature of FalconSAT-3's wobble and contributing to corrective actions for FalconSAT-3.

"The key to success was making sure Cibola knew where FalconSAT-3 was and then imaging the satellite when the sun was in the right position relative to the two spacecraft," said Cadet 1st Class Ben Shoptaugh, the FalconSAT-3 Ops team lead.

Los Alamos officials developed a complicated series of attitude maneuvers to support the encounter. The partnership between Los Alamos and the Academy began March 8, 2007, when FalconSAT-3, Cibola and three other research DOD Space Test Program-sponsored satellites were launched from an Air Force Atlas V rocket from Cape Canaveral Air Force Station, Fla.

Since achieving orbit, FalconSAT-3 and Cibola have followed similar orbits and pass close to each other every 225 to 250 days, remaining in close proximity for about two days during each pass.

Dr. Diane Roussel-Dupre, the Cibola program manager and mission operations lead, and Cindy Little, the spacecraft command programmer, spearheaded the cooperative assistance. They and the Cibola operations team quickly planned the two-day encounter wherein both spacecraft would briefly share the same orbital neighborhood. 2nd Lt. Joe Robinson, a student at the Massachusetts Institute of Technology, has also helped with the investigation.

In just two days, the Cibola and FalconSAT teams shared information and agreed that the joint effort was a go. The cadet team configured FalconSAT-3's systems and physics sensors to collect additional information during the flyby. Cadet Shoptaugh and his crew sent commands Dec. 12 to prepare FalconSAT-3 for the Cibola visit and reported the cadet satellite was ready.

Next, the Cibola team went into action, executing nearly 36 hours of high-tempo operations as the DOE satellite reoriented and aimed its sensors during the weekend. They aimed at FalconSAT-3 26 times to capture information that could help the cadets resolve the problem.

The Los Alamos- and Academy-based teams will continue their partnership when the FalconSAT-3 cadets return in early January, collaborating with detailed data processing and analysis. The data will give cadets a better shot at fixing FalconSAT-3's wobble and fully resuming the Academy's space science exploration endeavors.