Swarm debris manoeuvre aborted
25 January 2017
The orbital manoeuvre planned for 25 January has been cancelled.
Based on an assessment of information on hand as of late yesterday, it was clear that the conjunction - a close flyby - of a ca. 15-cm chunk of space debris expected tonight at 23:10:55 UTC would be too close to the Swarm-B spacecraft, in orbit at about 500 km altitude.
This morning, two new sets of information were received that helped make the cancellation decision.
First, during the same ground station communication slot when the manoeuvre commands were being uploaded, the Swarm-B spacecraft also downloaded a fresh set of GPS data recorded on board during the previous approximately 20 hours. The highly precise data provided a record the spacecraft's actual current orbit.
"This allowed us to conduct a fresh orbit determination, and this could be used to reduce uncertainty in the spacecraft's position at the forecast conjunction time this evening to very small values," says Detlef Sieg, the flight dynamics specialist assigned to Swarm.
Second, the Space Debris Office received a fresh set of tracking information from JSpOC, providing data on the object's orbital trajectory.
"As this was acquired less than 24 hours prior to tonight's forecast conjunction, it had lower uncertainty related to the object's position during the conjunction than previous tracking data," says Klaus Merz from the Space Debris Office.
"As a result of the reduced uncertainties in the object's trajectory, the risk of collision is now well below the missio's threshold," says Klaus.