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GRACE operational: Switch-on of MWA/ICU and orbit manoeuvre

18 December 2015

Following the switch-off in October, the GRACE-A and -B Microwave Assemblies (MWA) and Accelerometer Instrument Control Units (ICU) have been switched-on again:

  • 08 December 2015, 07:35 UTC: GRACE-A and GRACE-B ICU
  • 10 December 2015, 23:32 UTC: GRACE-A MWA
  • 10 December 2015, 23:51 UTC: GRACE-B MWA

The GRACE-B MWA has been ON in sunlight and OFF for 29 minutes during eclipse. GRACE-B MWA time OFF has progressively been decreased since then. Permanent operations were resumed on 18 December at 05:11.

Since 11 December 2015 21:02 UTC, after a commanded reboot of the GRACE-A Instrument Processor Unit (IPU), the Ka-band microwave link is in lock again.

On 03 November 2015 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 coming months. The two satellites had a minimum distance of 220 m on 17 November - GRACE-B became the leading satellite. Two drift stop manoeuvres (requiring 180 degree yaw turns) on GRACE-B on 02 December finished the swap.