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GERB 4 Instrument Status GIST 25 23rd October 2006

GERB 4 Instrument Status GIST 25 23rd October 2006. Presenter: N Morris. GERB-4 Status. IEU built completed in March 2005 Successfully passed vibration tests TVAC test will be done together with IOU, so is currently on hold until IOU is finished

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GERB 4 Instrument Status GIST 25 23rd October 2006

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  1. GERB 4 Instrument Status GIST 25 23rd October 2006 Presenter: N Morris

  2. GERB-4 Status • IEU built completed in March 2005 • Successfully passed vibration tests • TVAC test will be done together with IOU, so is currently on hold until IOU is finished • IOU fully assembled with FM1 Focal Plane Assembly in March 2005 • Following IOU vibration test a problem was found on the Quartz Filter Mechanism • Unit returned to Galileo Avionica for repair.

  3. QFM Anomaly • Extensive investigation into QFM conducted • Out of tolerance parts plus suspected movement of the Stator under vibration caused Rotor and Stator to come into contact • Selection of in-tolerance parts plus a redesign of the Stator Clamp is expected to fix the problem • Vibration levels for the IOU will be notched at critical frequencies to avoid overtesting the QFM at IOU level • QFM vibration tests (to qualification levels in one axis) are being performed this week • Provided there are no other problems, the QFM should be back at RAL by the beginning of December 2006.

  4. FPA Status • Currently FM1 FPA is fitted in the IOU • There was some concern that the pixels exhibited a very long time constant, due to the high thickness of the gold black coating • Decision was taken to replace the detector with FM3, which had lower time constants and slightly less noisy response, but one pixel response was suspect (#193) • Because of problem with QFM the swap out of FPAs could take place before the instrument level tests were completed (original plan was to retrofit the FM3 detector) • Leicester University have been busy calibrating FM3 and should be ready for delivery to RAL this week. • Calibration of FM2 will follow. This will be the flight spare. • John Remedios will present some results on the detector spectral response tomorrow.

  5. GERB-4 Schedule • FM3 FPA will be fitted in the next two weeks • Most of IOU can be re-assembled because the QFM is the last subsystem to be fitted • QFM delivered back to RAL in December • IOU assembly and functional tests completed in Jan 2007 • IOU + IEU environmental test campaign will take ~ 3 weeks • GERB-4 Delivery Review Board February 2007 • Will then go into storage until start of calibration in June 2007 • After calibration the instrument will return to RAL and stored until launch (2013).

  6. GERB-3 Status • GERB-3 IEU is currently on MSG-4 to assist with check-out at spacecraft level • Will be returned to RAL when spacecraft testing completed (Jan 2007?) • Minor updates are needed to IEU to bring to the same build standard as the GERB-4 IEU. • Proposal into EUMETSAT for the re-calibration of the GERB 1/2/3 flight spare detector. • If significant differences found between GERB-4 detector and GERB spare then EUMETSAT may consider re-calibrating the GERB-3 detector. • The GERB-3 QFM is showing some similar anomalies to those found recently on GERB-4, so we may have to make some minor repairs. • GERB-3 instrument re-calibration will take place after GERB-4 (and after the detector re-calibration if needed).

  7. Mirror Pitting Update • Concern raised over pitting seen on GERB-3 Flight Spare Telescope mirrors • This was just prior to the launch of GERB-1 on MSG-2 • Qualitative assessment made at Kourou of GERB-1 DSM mirror confirmed that there was not a significant problem (hopefully the data from GERB-1 now confirms this). • Still a concern remains about whether pitting (or corrosion) of the mirror surfaces on GERB-3 and GERB-4 will continue up to launch • To help answer this question a detailed survey of some of the GERB coating witness samples was carried out using microscopy techniques. • Each sample was photographed over an area of approximately 32mm2 with a resolution of 0.32 microns • The photographs were individually assessed using image processing software to look for defects up to 5 microns in diameter • Ratio of max to min diameter was set at >0.2 to exclude scratches • Area of defects calculated for each sample as well as histograms of defect size.

  8. Defects under bright field illumination

  9. Mirror Survey Results • H5A29 1447 defects Defect area = 246970 mm2 Area % defects 0.08 • H8I26 2065 defects Defect area = 135106 mm2 Area % defects 0.04 • H9I40 660 defects Defect area = 76761 mm2 Area % defects 0.02 • H9J13 2699 defects Defect area = 324656 mm2 Area % defects 0.1

  10. Mirror Pitting • Will re-measure samples every 12 months and look for signs of defects increasing in number or size. • Evidence to date suggests the defects to not grow, but reach a finite size and then stop. • GERB 3 and 4 instruments will be stored under vacuum, so this should help reduce growth rate if it is still happening.

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