The GRACE Operations Status depends on the health of the battery and the duration within each orbit when the battery is in use. The Status will be updated here approximately every week.

CURRENT STATUS:

Science Instrument Status:
• All instruments (GPS, KBR, accelerometer, and star cameras) operating nominally since Apr 11, 2013
• The Accelerometers were turned on at UTC 09:44 Apr 05, 2013 (GRACE-1) and UTC 08:49 Apr 04, 2013 (GRACE-2)
• The K-Band ranging systems were turned on at UTC 08:58 Apr 11, 2013 (GRACE-1) and UTC 09:37, Apr 10, 2013 (GRACE-2)
• The GPS receivers and star cameras continue nominal operation


Both satellites are operating with minimal thermal control (Table-H).
GRACE-1 in Table-H since October 5, 2012
GRACE-2 in Table-H since October 5, 2012


beta_prime: 44 deg; Altitude: 435 km; Separation: 259 km

PEAK beta_prime=70 deg, Jun 10, 2013
NEXT beta_prime=0 event, August 28, 2013
PEAK beta_prime=-75 deg, Nov 16, 2013

SCIENCE DATA PRODUCTS:

• 2011: Level-2 and Level-1B data products were delivered for every month except the following spans, for which only partial Level-1B data were delivered:
  • Jan-01 to Feb-06, 2011
  • Jun-01 to Jul-06, 2011
  • Nov-17 to Dec-12, 2011
• 2012: Level-2 and Level-1B data products were delivered for every month except the following spans, for which only partial Level-1B data were delivered:
  • Apr-20 to May-31, 2012
  • Sep-26 to Nov-05, 2012
• Jan 2013: All Level-2 and Level-1B data products delivered to archives
• Feb 2013: All Level-2 and Level-1B (until Feb 26, 2013) delivered to archives

BACKGROUND:

The GRACE Science Operations concept for the remainder of the mission is driven by the intersection of two factors. First is the project decision to operate the spacecrafts in a manner that maximizes the remaining lifetime, so that the longest possible climate data record is available from GRACE. The second is the degraded battery capacity that limits the availability of the power in certain orbital configurations.

The GRACE orbit plane precesses at -1.117 degrees/day relative to the Sun, such that the Sun is in the orbit plane every 161 days. Due to the power system status and desire for longevity, this event will henceforth define a 161-day work cycle for science operations. As long as the beta_prime angle (angle between the orbit plane and the Earth-Sun line) is greater than 69 degrees, the satellite operates using power only from its solar array. For smaller beta_prime angles, the satellites operates partly using the arrays, and partly using the battery. When beta_prime is near zero (i.e. Sun is in the orbit plane), the battery may be used for as much a 40 minutes out of 90 minutes in each orbit. Near beta_prime=0 events, the mission operations status depends on the battery health and operating environment.

This Status will be updated here approximately every week.