18th GIST 14 th -16 th May 2003 E Sawyer RAL Status of GERB1,2,3 and 4 Descan mirror bearing life tests Battery issues Operations during eclipse 18th GIST 14 th -16 th May 2003 E Sawyer RAL Status GERB1- Currently Integrated onto MSG 2 AIV programme complete Pre storage/flight readiness review started GERB returned for modifications and possible recalibration 18th GIST 14 th 16 th May 2003 E Sawyer RAL Status GERB2 In orbit Switched off for eclipse season Back on 28 th April 9/5/03 One anomalous switch off triggered by a scan mirror position error out of limits. MRB held, decision to switch back on with no modification. 18th GIST 14 th -16 th May 2003 E Sawyer RAL Status GERB3 Delivery to Alcatel 21/5/03 Will be returned for battery modifications and calibration check 18th GIST 14 th -16 th May 2003 E 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. 18th GIST 14 th -16 th May 2003 E Sawyer RAL Bearing life test - Status 18 g 18th GIST 14 th -16 th May 2003 E Sawyer RAL Bearing life test - Status The test is complete!! Centrifuge test started with two lead one grease lubricated bearing pairs. 230 million revs completed. 230 was the goal for a 7 year mission, plus 20% margin. One dry test bearing switched off at 138 million to give bench mark. Good performance from all bearings for the whole test 18th GIST 14 th -16 th May 2003 E Sawyer RAL Bearing life test Status continued Post test torque measurements LTM NoLubricationRevs completed Initial torque (gcm) Final Torque (gcm) 1Dry138M3974 2Grease75M Dry230M3871 18th GIST 14 th -16 th May 2003 E Sawyer RAL Bearing life test Status continued The bearing preload was measured and found to be very close to the initial setting less than 10% variation. Strip down and visual inspection carried out LTM1 some wear debris, mostly in the debris traps, moderate wear of ball pockets. LTM2 very little wear (only 75 million revs) LTM3 less wear than LTM1 18th GIST 14 th -16 th May 2003 E Sawyer RAL Other bearing issues Back up DSM mechanism, using grease lubricated bearings, has been constructed at Officini Galileo and is available for GERB 3 if required. Contamination studies show that the grease can evaporate under the in orbit conditions. If any grease gets on the mirror it will be fixed by the solar UV and significantly effect optical performance. This can be reviewed in the light of in orbit data. 18th GIST 14 th -16 th May 2003 E Sawyer RAL Battery GERB carries a battery to enable safe power down in the event of sudden loss of power and thus avoid sun damage to the detectors. During final tests of GERB on MSG 1 at Kourou, the battery was found to be discharged. GERB on MSG 1 was launched with a flat battery The discharge mechanism is not fully understood. Proposals have been discussed with ESA that enable safe switch down without battery power, these are being assessed by Alcatel. 18th GIST 14 th -16 th May 2003 E Sawyer RAL Battery continued Minor modifications will be required to GERB 1 and 3 GERB on MSG1 has no battery assisted power down capability Eumetsat intend to modify MSG software to minimise risk to GERB in the event of a spacecraft emergency. 18th GIST 14 th -16 th May 2003 E 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) Current plan is that during eclipse periods, GERB will be in sunblock mode for approximately 5 hours.