Flight Operations for GOCE, ESA’s Gravity Mission
C. Steiger, R. Floberghagen, M. Fehringer, J. Piñeiro, P.P. Emanuelli
Complexity and Specifics of GOCE
Complexity of GOCE:• 2487 telecommands• 42000 telemetry parameters• 991 procedures written by ESOC to operate the S/C
What sets GOCE flight operations apart:• Low orbit => short ground station contact times• Atmospheric drag => orbit prediction intricate, S/C heavily affected
by (changes in) the environment• Complex S/C with no clear distinction between ‘platform’ and
‘payload’ => high level of expertise required in case of anomalies• Routine science operations consist of letting the S/C fly in drag-free
mode (no complex payload operations campaigns)
GOCE Flight Operations at ESOC
• 7 to 8 contacts per day• Low altitude => short contacts• Pass operations automated• Orbit prediction based on SSTI
data• Strict requirements on complete-
ness of science data
Commissioning Overview
30/03 to 03/04: checkout of ion propulsion assembly
May/June: checkout of drag-free modes
17/03/2009: launch from Plesetsk/RU on ROCKOT17/03 to 20/03: launch and early orbit phase
13/09: stop of decay at 259.6 km
23/06: Resumption of decay
20/03 to 27/03: AOCS unit calibrations
03/04 to 07/04: gradiometer commissioning
Telecommands Sent in Commissioning
10000
30000
50000
40000
20000
60000
70000
80000
90000
100000
About 600 TCs / day sent in commissioning (30% routine activities, 70% special ops)
Orbit Prediction during Orbit Decay
S/C attitude error around Yaw [deg] Orbit decay rate [m/day]
• Performance of attitude control impacts orbit when not drag-free• ±100 m/day => variation of ±2 sec per day in contact predictions
Routine Operations in Drag-free Mode
05-Apr-2010: strong geomagnetic storm
Oct-2009: drag-free mode interruption, decay 250m/day
Feb-2010: drag-free mode interruption, decay 500m/day
Mean altitude [km] Average IPA thrust level [mN]
• Drag-free mode is working well• DFM interruption requires rapid intervention from ground (e.g.
update of orbit prediction to ensure correct pointing of antennas)
Conclusions
• Main challenges for flight operations were due to the unique features of GOCE:– Low orbit– Operations in a drag environment– High S/C complexity (no distinction between platform and
payload)• Intense commissioning phase successfully completed, GOCE is in
routine since October 2009• ESOC’s flight operations approach for GOCE is working well• ESOC is looking forward to supporting a possible mission extension