Close encounter # 2

Erik Clacey

It has now been approximately 3 weeks since our close encounter with the object COSMOS 2251 DEB (SSC# 34544). We have now had our second close encounter on Saturday 24 July, 09:42 UTC. This time it was with debris from a Zenith-2/SL-16 launcher (SSC# 22437). It was launched on 25 December 1992 and carried a COSMOS-2227 satellite.

 

The warning received from Joint Space Operations Center (JSpOC) showed that we would be much closer than in the previous encounter. The uncertainties of the position of PRISMA and the other object were however smaller this time thus allowing us to take the decision to remain in our orbit and not “wake up” PRISMA from its safe sun routine mode.

 

The latest warning that we received from JSpOC showed:

 

Overall miss distance: 113 meters

Radial (dU) miss distance: -103 meters

In-Track (dV) miss distance: -48 meters

Cross-track (dW) miss distance: 12 meters

 

We are developing strategies to enhance our responsiveness to such warnings and to aid us in taking decisions whether or not to actively change our orbit during a future close encounter.