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GRACE operational issue: Planned switch-on of Microwave Assemblies

19 January 2015

The GRACE-A and -B Microwave Assemblies (MWA) and Accelerometer Instrument Control Units (ICU) have been switched-on again on:

  • 07 January 2015, 12:03 UTC: GRACE-A and GRACE-B ICU
  • 13 January 2015, 5:32 UTC: GRACE-A MWA (continuously on since 23:40, before ca. 7-12 minutes off each orbit)
  • 13 January 2015, 5:32 UTC: GRACE-B MWA (continuously on since 06:42)

Additionally on 15 December 2014 an orbit manoeuvre was executed on GRACE-B in order to accelerate the drift towards GRACE-A as initiation of a satellite switch. The satellite swap intends to save fuel on GRACE-B by staying on the better performing GRACE-B star camera for the first half of 2015.

During the manoeuvre the two satellites had a minimum distance of 251 m on 28 December.

A drift stop manoeuvre followed by a 180 degree yaw turn of both satellites on 15 January finished the swap.