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GRACE - Planned switch-on of MWA / ICU

21 October 2016

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

  • 11 October 2016, 14:12 UTC: GRACE-A ICU
  • 12 October 2016, 10:04 UTC: GRACE-A MWA
  • 13 October 2016, 09:53 UTC: GRACE-B MWA

Presently, the GRACE-B MWA is still off for about 47 minutes every orbit and the GRACE-B ICU is still completely off. Both off-times are due to reduced battery capacity on GRACE-B. The project is still working to improve this situation.*

*On 13 September 2015 two orbit manoeuvres have been executed on GRACE-A in order to accelerate the drift towards GRACE-B 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 280 m on 21 September - GRACE-B became the leading satellite. Two drift stop maneuvres (requiring 180 degree yaw turns) on GRACE-A on 25 September finished the swap.