Separation in space: the backstory

This superb footage was acquired by cameras on the Soyuz Fregat upper stage that released Sentinel-1 into orbit on 3 April 2014. It shows the Sentinel-1 satellite separating from the Fregat to start its life in orbit around Earth.

But do you know how it got to Earth?

The recorded video data were downloaded from Fregat via ESA’s 15m ground tracking station in Perth, Australia, just prior to Fregat’s deorbit burn. The team from ESOC and Perth station worked over many weeks to prepare for the single pass that Fregat would make (see ESA ground tracking network supports Soyuz VS07 today).

In fact, between the time that Fregat’s cameras recorded Sentinel-1A separation at 21:25:55 over St Hubert (near Montreal), Canada (just before 21:27:15 GMT, when Sentinel started transmitting from space), to acquisition of signal (AOS) by the Estrack team at Perth station, at 21:58:51, there was only about 31 minutes to anticipate the data download (of course, the team were ready long before that).

And then, the downlink had to happen perfectly correctly the first time, because Fegat wasn’t coming back for a second pass (it made its deorbit burn just after the pass over Perth).

“The Sentinel-1A separation took place over Canada. However, the camera system dumped all the data over Perth for exactly 12min:52sec with a bitrate of 5 Mbps,” said ESA Estrack engineer Robert Launer, who was at Perth.

“We stored the data locally, then transferred it right after the pass ended to Arianespace. Moreover, the camera data downloading took place in parallel to receiving the launcher telemetry.”

Robert says that to prepare for the one-chance-is-all-you-get event, Estrack teams conducted detailed radio compatibility tests (to ensure communication between the Fregat and the Estrack station would work), station performance tests and mission readiness tests.

All of which proved that the teams and station were ready, indeed, for show time.

The 2.3 tonne satellite lifted off on a Soyuz rocket from Europe’s Spaceport in Kourou, French Guiana at 21:02 GMT (23:02 CEST). The first stage separated 118 sec later, followed by the fairing (209 sec), stage 2 (287 sec) and the upper assembly (526 sec). After a 617 sec burn, the Fregat upper stage delivered Sentinel into a Sun-synchronous orbit at 693 km altitude.

 

Comments are closed.