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18th GIST 14 th -16 th May 2003 E Sawyer RAL

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

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18th GIST 14 th -16 th May 2003 E Sawyer RAL

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  1. 18th GIST 14th-16th May 2003E Sawyer RAL • Status of GERB1,2,3 and 4 • Descan mirror bearing life tests • Battery issues • Operations during eclipse

  2. 18th GIST 14th-16th May 2003E 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

  3. 18th GIST 14th–16th May 2003E Sawyer RAL Status • GERB2 • In orbit • Switched off for eclipse season • Back on 28th 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.

  4. 18th GIST 14th-16th May 2003E Sawyer RAL Status • GERB3 • Delivery to Alcatel 21/5/03 • Will be returned for battery modifications and calibration check

  5. 18th GIST 14th-16th May 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.

  6. 18th GIST 14th-16th May 2003E Sawyer RAL Bearing life test - Status

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  8. 18th GIST 14th-16th May 2003E 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

  9. 18th GIST 14th-16th May 2003E Sawyer RAL Bearing life test – Status continued • Post test torque measurements

  10. 18th GIST 14th-16th May 2003E 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

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  19. 18th GIST 14th-16th May 2003E 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.

  20. 18th GIST 14th-16th May 2003E 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.

  21. 18th GIST 14th-16th May 2003E 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.

  22. 18th GIST 14th-16th May 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) • Current plan is that during eclipse periods, GERB will be in sunblock mode for approximately 5 hours.

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