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Overview of STIS Repair Plans

Overview of STIS Repair Plans. Charles R. Proffitt November 16, 2006. STIS History. Installed during SM2, Feb 14, 1997 Side 1 Failed May 16, 2001 (after ~ 4.5 yrs) Short across power input leads Probably failed tantalum capacitor Side 1 electronics not accessible w/o removing STIS

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Overview of STIS Repair Plans

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  1. Overview of STIS Repair Plans Charles R. Proffitt November 16, 2006

  2. STIS History • Installed during SM2, Feb 14, 1997 • Side 1 Failed May 16, 2001 (after ~ 4.5 yrs) • Short across power input leads • Probably failed tantalum capacitor • Side 1 electronics not accessible w/o removing STIS • Side 2 failed Aug 3, 2004 (after ~ 3 yrs) • Interpoint converter in low voltage power supply failed • Supplied power to most instrument mechanisms - aperture wheel, MSM, CCD shutter, etc. • Can’t get light to the detectors • Need to replace LVPS2 card in MEB1 • Can be accessed w/o removing STIS Nov 16, 2006

  3. STIS in HST with Location of MEB +V2 STIS NICMOS MEB Cover NCC Nov 16, 2006

  4. +V3 Side MEB-2 +V2 Side MEB-1 STIS Flight STIS Instrument EVA Handle L-Handle MEB Cover Extension MEB-1 Cover STIS Closeup MEB Cover Extension Clamp Nov 16, 2006

  5. LVPS-2 STIS Main Electronics Box (MEB) LVPS2 Board (Engineering Unit) MEB1 with Cover Removed MEB Structure (non-flight) Nov 16, 2006

  6. LVPS-2 Interfaces • Circuit board LVPS-2 has 3 main functions • Supply Heater Power • +15 volts to Thermal Control Zone A and B • Supply Calibration Lamp Power • +30 volts to Calibration Lamp Controller • Supply Mechanism Power • +5 volts to Mechanism Optical Coupler • +15 volts to Mechanism Drivers • +30 Volts to Mechanism motors • LVPS-2R will connect to MEB motherboard Nov 16, 2006

  7. Functional Overview of Repair Major activities to be performed to repair STIS • Open the +V2 Aft Shroud doors • Remove STIS EVA Handrail • Remove MEB Cover Clamp • Install the Fastener Capture Plate (FCP) Tool • Release MEB cover fasteners (111) • Remove MEB Cover and FCP Tool • Remove failed LVPS-2 board • Install replacement LVPS-2R board • Install replacement MEB cover • Perform Aliveness Test • Install the STIS Thermal Interface Kit (STIK) • Install the STIK Radiator (STIKER) • Close the +V2 Aft Shroud doors HST +V2 Nov 16, 2006

  8. EVA Timeline • Goal from STIS Repair SRR was to get STIS repair and cooling to fit in one EVA day. Nov 16, 2006

  9. STIS Repair - NBL 06.2 Images Nov 16, 2006

  10. STIS Aliveness Test (This is when we find out if it worked) • To be conducted during EVA • Verify connectivity of LVPS-2R board to MEB motherboard. • Ensure that major functions of LVPS-2R all work • Verify heaters enabled • Enable SES telemetry collection • Enable (close) mechanism and lamp relays and verify output voltages • Less Than 10 minutes in duration. • Macro started at beginning of test will ensure auto-shutdown • Isolate any failure to specific pin. Nov 16, 2006

  11. NICMOS STIS STIK Support Bracket NCC STIKER Cooling System (SCS) Overview STIS • The STIS Cooling System (SCS) is intended to conduct heat away from the MAMA detector radiator and radiate it into the aft-shroud. • Evolved from the STIK interface to the Aft Shroud Cooling System • Three part assembly: • SCS Mounting Bracket (SMB) • The STIS Thermal Interface Kit (STIK • An actuator forces STIK pressure plate against STIS radiator • Soft thermal interface material on the pressure plate conducts heat to heat pipes. • The STIK Extended Radiator (STIKER) • Spreader heat pipes on the STIKER conduct and radiate heat away from the instrument. Nov 16, 2006

  12. Why install the SCS? • Without SCS would expect a significant increase in MAMA tube temperature over previous side-2 values (~ 4 C). • Substantial increase in MAMA dark rates • New temperature regime for detectors • SCS should keep tube temperatures ~ 2 C lower than were seen in 2003-2004. • Should reduce MAMA detector dark currents. Nov 16, 2006

  13. Challenges of STIS Repair • STIS repair requires a whole EVA • If fewer EVAs than expected are available, STIS repair will be the first thing deleted! • Removal of 111 MEB Cover Fasteners • Need to be prepared to handle stripped or jammed fasteners • Removal of MEB cover • RFI gasket • Removal of LVPS-2 card • Card Locks may stick - studies indicate card can be removed anyway • Insertion of LVPS-2R • Tolerances very tight, need all active pins to connect • Need enough force to engage pins, but not enough to break anything • Debris generated by fastener, cover plate, and card removal • Determined to be within acceptable limits • HST PCS analysis of SCS Jitter and STIKER mass control ongoing • Failed SCS installation could cause jitter. Nov 16, 2006

  14. Status after PDR • Hardware shown to meet requirements • NBL tests successfully demonstrated execution of STIS Repair with high-fidelity hardware • 10 successful completions of LVPS-2 change-out • 2 successful completions of SCS installation • Extensive testing and analysis performed to show compliance with HST Contamination requirements • Test results for high-risk tasks (Card Extraction and Insertion) and resulting requirements • The STIS Repair Team has defined and implemented plans, processes, tools, and has in place the organization to proceed to CDR (January 2007). Nov 16, 2006

  15. STIS Repair Top-level Schedule Nov 16, 2006

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