Could a leaky capacitor be at fault on ESA's Sentinel-1B?

Prepare your 'turn it off and on' jokes as engineers get ready to flip the heaters


Attempts to recover ESA's stricken Sentinel-1B satellite are continuing and one of the failure scenarios engineers are considering will be familiar to some of us: possible leakage of a ceramic capacitor.

The satellite, launched in 2016 aboard a Russian Soyuz rocket from the Arianespace facility at Kourou in French Guiana, remains under control. However, power problems have rendered its C-band Synthetic Aperture Radar (C-SAR) instrument pretty much useless, thus defeating the point of the spacecraft.

Sister spacecraft, Sentinel-1A, has continued to collect data despite recently having to dodge some debris.

While a leaky capacitor is all too familiar to engineers repairing faulty electronics on the ground, dealing with one in orbit is altogether trickier. This particular capacitor is part of the main and redundant regulators of the 28V bus that supplies power to the SAR electronics. Earthbound boffins reckon the failure mode is possible, but remain open to other possible causes for the anomaly.

The good news is that there have been signs of life during the repeated attempts to switch it back on. On one attempt to fire up the prime regulator, engineers noted that it remained on for 4.4 seconds before being autonomously switched off.

This was the first time this had happened since recovery attempts began at the start of the year – and has given engineers hope that perhaps the issue is one of degradation rather than a permanent fault.

The next step is going to be turning the heaters of the power supply on and off in order to vary the temperature. "This could influence the behavior of the regulators," said a hopeful ESA before parroting the line that it was still too early to write off the hardware as permanently failed.

Spacecraft steerer Thomas Ormston said "we've got a busy few days heating things up and cooling them down" as engineers continued the recovery effort.

A comparison was also drawn to ESA's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) spacecraft, which suffered a failure in 2010 when data stopped being downlinked. Science resumed when the temperature of the floor hosting the computers was raised by 7°C.

While the Sentinel-1B issue is quite different, Ormston remarked: "There is a bit of deja vu going on..." as engineers got busy with the heaters.

The conclusions of the anomaly review board are expected in May. A third satellite in the Sentinel-1 series, Sentinel-1C, is set to launch next April... onboard a Vega-C this time, rather than a Soyuz. ®

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