ESA's Sentinel-1A satellite narrowly dodges debris

Who left that bit of rocket there? It's getting a bit crowded in orbit

There was a sigh of relief from ESA controllers over the weekend as the Copernicus Sentinel-1A satellite successfully dodged a decades-old rocket fragment.

The debris' closing speed was over 50,000 km/h (∼31,068 mph) and it was expected to come close enough that controllers opted to perform a pair of thruster burns in order to lift the satellite 100 meters (∼328ft) above the predicted point of closest approach.

One of the engineers responsible for flying the spacecraft, Thomas Ormston, summed things up with the inevitable meme.

#MissionControl for #Sentinel1 right now... (all in a day's work 😏😜) https://t.co/BIFk60FsPe pic.twitter.com/gK8t9toXiX

— Thomas Ormston (@ThomasOrmston) April 1, 2022

Quite.

Controllers had time to plan the maneuver, however, the incident is a reminder of the increasing clutter lurking in orbit around the Earth. ESA described the object as "a 30-year-old fragment", which astronomer Jonathan McDowell identified as being a bit of an old Zenit rocket stage. ESA later confirmed this was indeed the case.

Sentinel-1A, a radar imaging satellite launched in 2014, has run into debris before. One of the solar arrays was smacked with a millimeter-size particle in 2016, resulting in a small drop in power and a sudden change in the orientation and orbit of the satellite. Such small fragments cannot be tracked. However, a lump of rocket stage most assuredly can be.

Unfortunately, the second of the two Sentinel-1 satellites, imaginatively named Sentinel-1B, remains out of action following a problem with the power bus supplying the Synthetic-aperture radar (SAR) instrument. While the spacecraft remains under control, users of the information collected by it were warned to "assume a long-term unavailability of data provision."

"It is however too early to consider a permanent unavailability of Sentinel-1B," said ESA.

Both Sentinel-1A and 1B were launched on Soyuz rockets from Arianespace's Kourou launch site. The next in the series, Sentinel-1C, was planned for launch in 2023 – although given the situation regarding European vehicles flying on Russian rockets, launching on time, let alone bringing things forward, seems unlikely.

Which leaves Sentinel-1A, which has already comfortably exceeded its seven-year mission life.

"With every manoeuver, something – fuel, time, science data – is lost," said the ESA operations team.

And as the clutter increases above the Earth, and current events demonstrate the criticality of orbital infrastructure, "Avoiding collisions alone is not a long-term solution." ®