19th GIST 27th-29th August 2003E Sawyer RAL

• Status of GERB1,2,3 and 4• Battery issues• Operations during eclipse• Stray light• NOT bearing life test

19th GIST 27th-29th August 2003E Sawyer RAL

Status• GERB1-

– GERB has been returned for modifications and recalibration.

– Re-calibration first at Imperial– Battery mods, TBC tomorrow.

19th GIST 27th-29th August 2003E Sawyer RAL

Status• GERB2

– In orbit– Switched off for eclipse season– Back on 28th April– Off again now

19th GIST 27th-29th August 2003E Sawyer RAL

Status• GERB3

– Delivered to Alcatel in June– Now integrated onto MSG 3– Will be returned for battery modifications and

calibration check

19th GIST 27th-29th August 2003E Sawyer RAL

Status• GERB4

– ATP received from Eumetsat for 70% funding to match the approval by Eumetsat council.

– Some activities started, parts procurement, detector blacking.

– Some electronics manufacture will start at RAL.

– Most subsystems will kick of Jan 04.

19th GIST 27th-29th August 2003E Sawyer RAL

Battery

• Proposals have been discussed with ESA that enable safe switch down without battery power, these have been assessed by Alcatel.

• Agreement has now been reached on the implementation, a kick-off meeting for GERB 1 will be held tomorrow.

• Relatively simple modifications will be incorporated and the unit re-qualified.

• GERB 3 will undergo similar treatment.

19th GIST 27th-29th August 2003E Sawyer RAL

Battery continued

• GERB on MSG1 has no battery assisted power down capability

• GERB software patch has been coded to detect sun close to the field of view and perform safe switch down, first test failed, some more work to do.

• Eumetsat may be able to modify MSG software to minimise risk to GERB in the event of a spacecraft emergency. The schedule for this is not defined

19th GIST 27th-29th August 2003E Sawyer RAL

Eclipse

• First Sun avoidance period started 12 February

• No battery safe switch down

• GERB switched to SAFE mode

• No MSG modified software

• There was one unplanned switch off of GERB during this period

• Strategy for next eclipse period (end August to end Oct) is to switch down to SUNBLOCK mode

• Current plan is that during eclipse periods, GERB will be in SUNBLOCK mode for approximately 5 hours.

19th GIST 27th-29th August 2003E Sawyer RAL

Stray light• Two issues

– Contamination when sun is close to FOV

– Contamination due to sun illumination of Black Body.

19th GIST 27th-29th August 2003E Sawyer RAL

Stray light

Close to FOV

+/- 20 degrees

16.2 degrees

19th GIST 27th-29th August 2003E Sawyer RAL

Stray light

Contamination of blackbody signal

19th GIST 27th-29th August 2003E Sawyer RAL

Stray light

Contamination of blackbody signal

19th GIST 27th-29th August 2003E Sawyer RAL

Evolution of GERB• One in orbit, data is now available• Two complete instruments on the ground• One more to build• Minor hardware or software mods, no redesign• No funding, but potential opportunity• Inputs sought from the GIST and GOT