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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

Overview of STIS Repair Plans

Charles R. Proffitt

November 16, 2006

Stis history
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

Stis in hst with location of meb
STIS in HST with Location of MEB







Nov 16, 2006

Overview of stis repair plans








Flight STIS Instrument

EVA Handle


MEB Cover




STIS Closeup

MEB Cover



Nov 16, 2006

Overview of stis repair plans


STIS Main Electronics Box (MEB)

LVPS2 Board (Engineering Unit)

MEB1 with Cover Removed

MEB Structure (non-flight)

Nov 16, 2006

Lvps 2 interfaces
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

Functional overview of repair
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


Nov 16, 2006

Eva timeline
EVA Timeline

  • Goal from STIS Repair SRR was to get STIS repair and cooling to fit in one EVA day.

Nov 16, 2006

Stis aliveness test
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

Cooling system scs overview stis



STIK Support Bracket



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

Why install the scs
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

Challenges of stis repair
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

Status after pdr
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