One might think
One might think that after being able to bring the launch date forward from 15 to 3 April (since when do launch dates come forward?), that after successfully achieving the shortest launch campaign in ESA’s history, after having executed the pre-launch simulations in the shortest time ever, after a flawless launch, after a perfect (although incredibly complex) deployment sequence of the solar arrays and radar antenna,  after managing to publish the video of the satellite separation in record time (when have we had such a beautiful view before?), after publishing the first ever ‘selfie’ of an ESA Earth observation satellite …… after all of this you might think that you would have time to relax, just a little. One might think. But, in the Sentinel-1 project, the point at which you can relax— as Ramón puts it – “a point of accumulation’ of hope, a point in the space-time that you can glimpse but never reach”.

Luisella and Pier-Paolo on shift. (ESA)

Luisella and Pier-Paolo on shift. (ESA)

The alert
At the end of the first day after the launch (4 April): all deployments have been executed during the night and completed early in the morning at the beginning of the first ‘day shift’. As the first day shift nears its end, a serious alert is received: there is a danger of a collision with a NASA satellite called ACRIMSAT, which has run out of fuel and can no longer be manoeuvred. Not much information at the beginning, we are waiting for more information, but a collision avoidance manoeuvre may be needed.  ‘Are you kidding? A collision avoidance manoeuvre during LEOP? This has never been done before, this has not been simulated!’

The satellite has not yet reached its ‘normal pointing mode’, we cannot manoeuvre it before this is reached. There is no alternative. After a brief team consultation Juan, the ‘day shift’ Deputy Flight Operation Director,  decides to start preparing the satellite in case a manoeuvre is needed, and to be executed by his colleagues on the night shift.

The safest hands
The night shift starts at 21:00 on 4 April. Hand-over between Juan and Pier-Paolo’s teams. More precise information comes in: the risk of collision is significant, there are two possible occurrences, at 09:43  and at 11:21 on the following morning. Distance: 20 m! This is serious. No Hollywood fiction, this is Gravity  for real!

It is decided to manoeuvre Sentinel-1A. Its orbit altitude needs to be changed to escape the chaser. Decision taken: this manoeuvre is the first one of the mission, before the subsystems could be commissioned, we go for the lowest risk – which is a weird expression to use in this case.

Luisella, the Sentinel-1A Project Representative at ESOC, insists that the manoeuvre is executed in the earliest possible pass. The satellite needs to reach nominal pointing mode for the manoeuvre to be executed. A command ends up triggering the redundant heaters: a trivial error in the command database configuration, a bit of tension. Pier Paolo knows how to let the tension evaporate, “Well, we have even already commissioned the redundant chain and the recovery procedure: they both works fine!”

Patiently, Ian, who Pier Paolo secretly calls ‘his bodyguard’, takes the satellite into nominal pointing mode. He earns even more recognition tonight: ‘after your mother, his are the safest hands you would leave yourself in as a child’.

The manoeuvre
We are ready for the manoeuvre that takes 39 seconds. The sequence of commands was uplinked during pass 37 in Alaska/Svalbard/Kiruna/ at 04:33 UTC for execution at 05:14 UTC, outside visibility. The atmosphere was tense and the Main Control Room was filled with suspense. Eyes were looking up at the big screens on the wall, waiting for a sign. As the satellite approached Troll ground station on the next pass and the telemetry started to scroll down in the twilight of the control room, the team hold their breath…and yes, the satellite was in Orbit Control Mode and the GPS on-board shows a change in the orbit status … Yes! the manoeuvre has been successful!

For the first time that night, loud laughs and cheers bursts through the room. We are safe.

The day shift
It’s almost 09:00 and the day shift guys arrive. Briefing. A bit of incredulity, someone in the day shift team is heard saying, “These guys, they will never change? They are making it up, can’t be true, come on!”

Finally, the formal hand-over is complete and everybody goes to their position. And then, something unexpected happens: the night shift guys don’t want to leave their positions! A bit of discussion, then the boss, Pier Paolo, declares a ‘general briefing’ for the night shift guys in the adjacent room, where the refreshments are.

Everybody executes the orders. That’s the moment: the ‘day shift’ guys are in place at the consoles. Everyone in the night shift group gets half a cup of the remaining coffee that once, a long time ago, had been warm. And then something really exceptional happens – we are drinking the best ever coffee in our lives; how is this possible?

Another ordinary night in the Sentinel-1 project life over, it is the turn of  the day shift team to play with the baby now.

Post from the Sentinel-1A team, 7 April 2014