WASHINGTON — The European Space Agency is ending efforts to restore operations of the Sentinel-1B radar imaging satellite that malfunctioned more than six months ago and will instead expedite the launch of a replacement.
ESA said in an August 3 statement that the agency and the European Commission, partners in the Copernicus series of Earth observation satellites, had given up trying to restore the Synthetic Aperture Radar payload. (SAR) on Sentinel-1B and ended the spacecraft’s mission. more than six years after its launch. This payload malfunctioned in December 2021 and ESA has been working since then to try to recover it.
A summary of the SAR payload failure investigation concluded that two 28-volt power regulators for the SAR payload had malfunctioned. One is needed to run the payload. Efforts to restore them have failed except for one case in April when the main regulator turned on for 4.4 seconds before turning off again. This provided “valuable observations for identifying possible failure modes,” the abstract says.
The report concluded that the most likely reason for the failure of the power regulators was “a potential ceramic capacitor leak” found in the two regulators that had to be replaced during manufacture and testing of the payload. The replacement was soldered in a way that may have damaged it.
“The conclusion reached by the Anomaly Review Board is that it is impossible to recover the 28V regulated bus from the satellite’s C-band Synthetic Aperture Radar Aperture Power Unit, which is needed to power the radar electronics,” Simonetta Cheli, director of the Earth observation program at ESA, said in the statement announcing the end of the Sentinel-1B mission.
There had been rumors in recent days that the ESA and the European Commission had abandoned their efforts to recover Sentinel-1B. the last public update on recovery efforts was in April. An ESA spokesperson said Aug. 2 that the agency was still “gathering additional information” and coordinating with the commission about the mission.
Sentinel-1B worked in tandem with Sentinel-1A, launched in 2014, to provide SAR imagery for a variety of Earth science applications. Sentinel-1A remains operational but has the same potential flaw in its payload power system. The ESA investigation noted that Sentinel-1A’s payload power system has not experienced any issues since launch, and since the Sentinel-1B anomaly, its performance is being closely monitored.
“The permanent unavailability of the Sentinel-1B satellite represents a significant loss for the European Union’s space program and the European Commission is committed to mitigating its impact,” said Paraskevi Papantoniou, Acting Director for Space at the Directorate General for Defence, Industry and Space of the European Commission. , said in the statement.
In the short term, ESA and the European Commission are buying SAR data from other satellites. This includes the Canadian Radarsat-2 and Radarsat Constellation mission, the German TerraSAR-X, the Italian COSMO-SkyMed and the Spanish PAZ.
A new satellite, Sentinel-1C, is almost ready for launch. ESA announced in April a contract with Arianespace for the Vega-C launch of Sentinel-1C. At the time, the launch was scheduled for sometime in the first half of 2023.
“Our goal is to accelerate the launch of Sentinel-1C,” Cheli said in the statement. “Now, thanks to the successful maiden flight of the Vega-C rocket on July 13, we, together with Arianespace, are targeting launch in the second quarter of 2023.” There was, however, talk at the beginning of the year of advancing the launch of Sentinel-1C by the end of this year.
Despite the failure of its SAR payload, the Sentinel-1B spacecraft itself remains operational. “We have Sentinel-1B under control,” Alistair O’Connell, Sentinel-1 spacecraft operations manager, said in a statement. “We perform regular spacecraft health monitoring and routine orbit check maneuvers.”
ESA will deorbit Sentinel-1B after the launch of Sentinel-1C. O’Connell said the spacecraft will comply with orbital debris mitigation guidelines which require the spacecraft to be de-orbited within 25 years of the end of its mission. “In practice, the length of re-entry should be much shorter,” he said.