WASHINGTON — A NASA astrophysics mission remains on schedule to launch in April after teams went “above and beyond” to fix a problem with one component of the spacecraft that could also affect two other missions.
Speaking at a Nov. 8 meeting of the Committee on Astronomy and Astrophysics of the National Academies’ Space Studies Board, NASA astrophysics division director Mark Clampin said the SPHEREx mission had resolved problems with reaction wheels on the spacecraft used for attitude control.
“We identified a number of issues” with the reaction wheels, he said, “several of which were essentially conditions in their operation that we could not countenance on an operating mission.”
He didn’t elaborate on the problems but said they required sending the reaction wheels back to their manufacturer, a German company called AstroFein. That company made hardware and software changes to the wheels and returned them to be reinstalled on the SPHEREx spacecraft.
The mission is doing what he described as “extended testing of the wheels” by running them for several hundred hours to confirm the wheels are operating as intended. “The folks involved really went above and beyond to make this happen and make sure we stay on our launch date,” he said, adding that the mission remained within its cost cap.
The cost of the reaction wheel work was covered by project reserves held by NASA Headquarters, he said at a Nov. 7 meeting of the agency’s Astrophysics Advisory Committee (APAC) where he also discussed SPHEREx. “We’re within reserves,” he stated there, maintaining the overall cost cap.
Berlin-based AstroFein offers a range of reaction wheels and related components for spacecraft, as well as engineering and manufacturing services. The company did not respond to questions about the SPHEREx reaction wheels.
Clampin said at the National Academies meeting that he believed that two other missions were affected by the same reaction wheel issue, NASA’s Carruthers Geocorona Observatory and NOAA’s Space Weather Follow On L-1. Both those spacecraft are scheduled to launch in the spring of 2025 on a SpaceX Falcon 9 with NASA’s Interstellar Mapping and Acceleration Probe.
SPHEREx will separately launch in April 2025 on a Falcon 9 from Vandenberg Space Force Base, with a NASA heliophysics mission, Polarimeter to Unify the Corona and Heliosphere (PUNCH), flying as a secondary payload. Clampin said the next major milestone for SPHEREx is an operations readiness review in early December.
NASA selected SPHEREx, or Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer, in 2019 as a medium-class Explorer, or MIDEX, mission, with a cost cap of $242 million. The mission was originally scheduled to launch in 2023 but was delayed in large part by issues associated with the pandemic. NASA selected SpaceX to launch SPHEREx in 2021.
SPHEREx will map the sky in at near-infrared wavelengths. The spacecraft’s distinct appearance features a set of concentric cones intended to shield the optics and instrument to allow them to cool to temperatures required for their near-infrared observations.
Clampin added at the APAC meeting that the mission separately resolved a “detector artifact issue” with the instrument on the spacecraft. That also does not affect the mission’s schedule or cost cap.
