Atlas 5 SBIRS GEO-6 launch
Two secondary payloads, including a NASA space science cubesat, lost a rideshare launch opportunity on the SBIRS GEO-6 launch because they could not meet guidelines for deorbiting after the end of their missions. Credit: ULA

LOGAN, Utah — A NASA cubesat was removed from a recent rideshare launch opportunity on a U.S. Space Force mission because the spacecraft could not meet guidelines for deorbiting at the end of its life.

The GTOSat mission, developed by NASA’s Goddard Space Flight Center, was manifested to fly as a secondary payload on the Atlas 5 launch of the SBIRS GEO-6 missile-warning satellite. The SBIRS satellite was successfully launched Aug. 4.

However, GTOSat and a second, unidentified rideshare payload were not included on the launch. Space Force officials said in a prelaunch briefing that the satellites were not compliant with orbital debris mitigation guidelines but did not elaborate.

In an Aug. 8 presentation about GTOSat at the Small Satellite Conference, John Lucas of NASA’s Katherine Johnson Independent Verification and Validation Facility said the issue was with the requirement that satellites deorbit no more than 25 years after the end of their mission.

“We had worked on a number of deorbit analysis issues, trying to meet the 25-year rule,” he said. That was particularly challenging for GTOSat, a 6U cubesat that would be placed in a geostationary transfer orbit to study the dynamics of the Earth’s outer radiation belt.

Meeting the 25-year timeline, he said, was highly sensitive to when the spacecraft launched because of the complex orbital dynamics. A final slip in the launch of SBIRS GEO-6 “pushed us above the limit.”

Lucas said GTOSat and the other payload sought waivers to the 25-year deorbit rule, and went so far as to make the last-minute addition of a retroreflector to the spacecraft to aid in the tracking of the satellite. Ultimately, though, the spacecraft could not get waivers and were removed from the launch.

The mission is now working with NASA’s Conjunction Assessment Risk Analysis program, becoming what Lucas called a “pathfinder” for dealing with debris analysis issues. The spacecraft itself is being returned to Goddard, where it will be put into long-term storage “while we look for a new ride” with the support of NASA’s Cubesat Launch Initiative.

The 25-year rule has become controversial in part because some believe leaving defunct satellites in orbit for that long is unwise. Some space sustainability advocates have pushed for shortening that timeframe, perhaps to as little as five years.

A recent White House report could prompt action on that issue. The Office of Science and Technology Policy (OSTP) issued in July a National Orbital Debris Implementation Plan, which outlined activities to address issues in orbital debris mitigation and remediation.

One element of that plan calls for a short-term study to be led by NASA “to better understand the impact of changing deorbit requirements” for the U.S. government, including “the potential benefits and cost in reducing the deorbit timelines.” The report, though, did not specify by how much deorbit timelines should be shortened.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...