Bringing a single spacecraft into operation is quite a complex procedure. Simultaneously commissioning four scientific spacecraft can be a logistical nightmare.
Sandro Matussi, Cluster spacecraft operations manager at the European Space Operations Centre (ESOC) in Darmstadt, Germany, found time to describe how things were progressing, one month into the three-month-long commissioning phase of ESA’s unique mission to explore the magnetosphere.
"We have to get all of the payloads in the correct configuration, but there are 44 payloads for us and the PIs (principal investigators) to check out and monitor, so it’s a major operation. We’ve had a few problems here and there, but overall we’re on target and we plan to meet the deadline of completing commissioning by the end of November or beginning of December, he said.
There are seven engineers in the ESOC team who provide support for the commissioning, with five of them responsible for one or two payloads on each spacecraft. It’s their job to coordinate the activities for their payloads in the overall commissioning plan. They hold separate meetings with the Project Scientist and the individual PIs to determine the activities to be undertaken that day or the next day.
My job is to bring together their requests and coordinate the overall timeline. It means a lot of planning and replanning. We often have to switch procedures because of minor problems with a particular payload, but this is not easy since we have a small team and limited flexibility.
The communication periods with the four spacecraft vary considerably from day to day, depending on their orbital location and the position of the Earth. This period of visibility can range from five hours to 19 or 20 hours a day. We communicate with them whenever possible, using the NASA ground station at Canberra (Australia) and the VIL-1 antenna in Spain, but we have to bear in mind that Canberra is shared with many other missions. VIL-2 also gives support, when needed, to download data from the onboard solid state recorders.
At present we’re well into the boom deployment stage. On both Rumba and Salsa, one pair of wire booms has been extended to their full length of 41 metres and the other two have reached 20 metres. All of them will be fully deployed by the end of next week.
We’ve had a few surprises but this is accepted as a normal part of a commissioning campaign. No matter how many tests you do in a vacuum chamber, they won’t fully reflect the behaviour of payloads in space.
For example, we couldn’t measure the exact deployment length of one pair of booms with the principal sensors, so we had to switch over to the back-up sensors and quickly put everything back on track.
In the case of EDI, a large part of the software was modified after launch, so in the last week or two we’ve been uploading it from the ground and it works perfectly."
So how do you feel about the way things are going?
"We’re tired but happy," was Sandro’s succinct reply.
* Cluster scientific commissioning updates from ESOC * Cluster ground operations
* The instruments onboard Cluster