XMM reaches its final orbit
17 December 1999On 16 December at 11:30 UT, the final orbit trim for XMM was performed on schedule, bringing the spacecraft into its operational orbit, from where it will be ready to start the instrument commissioning phase, due to commence in the new year. XMM Ground Segment Manager Howard Nye describes the atmosphere during this final manoeuvre...
In the Main Control Room of the Operations Control Centre at ESOC, the Flight Control team loaded the control parameters provided by their Flight Dynamics colleagues onto the command display.
In the calm and professional way they had already performed the previous four orbit manoeuvres, the controllers were about to execute the last of the planned series of orbit control manoeuvres.
"I confirm the values of command parameters are correct" reports Gottlob Gienger, the Flight Dynamics Coordinator on the voice loop. It was then the turn of the Spacecraft Operations Manager, Dietmar Heger, to authorise uplink to the spacecraft before making the last, now routine go/no-go check of his team.
"All Front Row positions, please give me your go/no-go status for the apogee lowering manoeuvre". His team responds like clockwork one by one. As soon as the appointed time is reached, the Spacecraft Controller uplinks the command to start the manoeuvre.
"Manoeuvre has started at 11:30:00" announces the Spacecraft Operations Engineer, Mark Seymour, as he monitors the reports send down from the spacecraft in telemetry.
The huge spacecraft lurches momentarily as the thrusters start to fire, but all is as expected and the on board control system keeps the spacecraft in trim and within the required bounds.
Unlike the previous orbit control manoeuvres, this last one will last only 92 seconds, making the final fine adjustment needed to bring the orbit into exact synchronicity with the earth rotation, and to ensure that the ground station visibility is maximised for later the science observation programme, specifically for those periods when XMM altitude is higher than 40 000 Km, the low altitude limit for instrument operations.
Very quickly, we hear the same voice announcing "Manoeuvre has ended at 13:00:02". Dietmar Heger jumps in "Flight Dynamics, this is SOM. XMM has now reached its operational orbit, congratulations to you all." His voice is temporarily drowned out by the applause in the Main Control Room, but we hear him continuing: "I don't think that we need any more orbit control commands, as we plan to stay here for the next ten years".