Goddard Space Flight Center September 1, 2009CHART 1 Hubble Space Telescope Servicing Mission Four...

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Goddard Space Flight Center

September 1, 2009 CHART 1

Hubble Space Telescope Servicing Mission Four (HST SM4):

Unique Challenges for STS-125

Bob Dedalis, HST Payload Safety ManagerMiranda Cooter, HST Lead Flight Safety Engineer

Patrick Mitchell, Payload Safety Review Panel Executive Secretary

William Hill, HST Lead Ground Safety EngineerPhillip Adkins, Systems Safety Engineer

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Introduction

• Mission Overview– SM4 first time in seven years HST serviced

» Nominal design called for once every 3 years

– More new hardware than any previous mission

» SIC&DH added very late

– First time since Columbia a shuttle was not used for ISS construction

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Major Tasks

Task Impact to HubbleInstall WFC3 –

Wide Field Camera 3Installed a high-resolution/wide-field camera with continuous coverage of wavelengths or colors of light from the ultraviolet to the near-infrared.

Install COS – Cosmic Origins Spectrograph Installed the most sensitive ultraviolet spectrograph ever to fly on HST.

Repair STIS Restored the Space Telescope Imaging Spectrograph to operational status byreplacing circuit boards.

Repair ACS Restored critical scientific functionality to the Advanced Camera for Surveysby replacing power supply and circuit boards.

Replace Rate Sensor Units (RSU) (gyroscopes)

Completed change-out of all six gyroscopes, the heart of HST's pointingsystem, and HST's main wear-out items.

FGS - Fine Guidance Sensor Last in a series of changed-out units that allow fine pointing of HST.

Replace Batteries Replaced the six batteries originally launched with Hubble in 1990, which aresteadily losing capacity as they age.

Install Soft Capture and Rendezvous System

Installed the Soft Capture Mechanism on the bottom of Hubble to enable NASA to pursue options for the safe disposal of Hubble.

Install New Outer Blanket Layers (NOBLs)

Installed NOBL covers to thermally protect the exterior blankets and maintain

normal operating temperatures of Hubble's electronic equipment.

Replace Science Instrument Control & Data Handler (SIC&DH) unit

Replaced the original unit launched with Hubble in 1990 to insure redundancy

of operations after September 2008 failure of Side A Control Unit/ScienceData Formatter (CU/SDF).

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Payload Bay Equipment

• Four Full Equipment Carriers

• Included a servicing platform

Flight Support System pivots and rotates to enable in-bay servicing

Science Instrument Control and Data Handling Unit

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Payload Safety Review Process

Preliminary Hazard Reports

Identification of Hazards

Preliminary Hazard Reports

Identification of Hazards

Safety ReviewPhase 0

Design Concept

Hazard Report

Identify Hazard Controls

Payload Organization Concurrence

NSTS Concurrence

Hazard Report

Identify Hazard Controls


NSTS Concurrence

Safety ReviewPhase IPDR

ForEachHazard

UpdateOnly

UpdateOnly

Hazard Report

Verify HardwareAs Built

Implement Controls


NSTS Concurrence

Hazard Report

Verify HardwareAs Built

Implement Controls


NSTS Concurrence

Safety ReviewPhase IIIDelivery

Hazard Report

Verify Design Implement Controls


NSTS Concurrence

Hazard Report

Verify Design Implement Controls


NSTS Concurrence

Safety ReviewPhase II

CDR

Flight Safety Verification Tracking Log

Track Verification of Items To Be ConductedAfter Phase III Review

Payload Organization Approval

NSTS Review

Flight Safety Verification Tracking Log

Track Verification of Items To Be ConductedAfter Phase III Review

Payload Organization Approval

NSTS Review

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Hazard Identification Process

04/18/23

System/ Sub-system/Interfaces

System/ Sub-system/Interfaces

Hazard to Crew/STSHazard to Crew/STS

Postulate Failure (PHA/FMEA/FTA)

NoHazard

NoHazard

Yes Requirements Met

Requirements Met

Yes (Generic Hazard)

WriteHR

WriteHR

Perform Hazard Assessment

Perform Hazard Assessment

No

NSTS Requirements

Confirm Fault Tolerance or DFMR in

Design/Operations

Confirm Fault Tolerance or DFMR in

Design/Operations

Catastrophic

1 Fault-Tolerant

ARHR *ARHR *

2 Fault-Tolerant

Write HRWrite HR

Critical WriteHR

WriteHR

Review with JSCReview

with JSC

Not Approved

ApprovedApproved

Change Design

Change Design

Verify ControlsVerify

Controls

Document for CoFR

Document for CoFR

No

RedesignRedesign

* ARHR (Accepted Risk Hazard Report): New to the PSRP documentation process for SM4. Method for Shuttle program to accept the risk of safety non-compliant conditions

* ARHR (Accepted Risk Hazard Report): New to the PSRP documentation process for SM4. Method for Shuttle program to accept the risk of safety non-compliant conditions

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Final Flight Safety Post Phase III/Part 4

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Safety Challenges

• Soft Capture Mechanism (SCM)

• Batteries

• Late addition of Science Instrument Control and Data Handler (SIC&DH)

• Complex on-orbit Repairs–STIS

–Advanced Camera for Surveys (ACS)

• Lack of Shuttle Safe-Haven

• Increased chance of on-orbit debris

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Soft Capture Mechanism and Battery Isolation Switch

Miranda Cooter

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Soft Capture Mechanism

• Designed to enable controlled de-orbit– HST originally designed to be returned in payload

bay

– HST does not have propulsion system

• Installed onto Aft Shroud– Flew on FSS between HST and FSS support ring

– Was risk of connecting HST to FSS via SCM (inability to close shuttle payload bay doors)

• Systems Safety participated in initial design– Performed Initiating Event Tree Analysis

– Insured that each major function included crew-activated override

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Servicing Platform

Berthing Latches

andSCM Attach

Points

Crew-Activated Remote Drive

Berthing Latch outside SCM attach mechanisms

Soft Capture Mechanism Detail on Next Slide

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SCM Mechanism Detail

HST Attach Override

HST Release Override

FSS Release Override

FSS Attach Override

Sill Plate Adapter

FSS Override Assy

Radial In View Radial Out View

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Final SCM Fault Tolerance

• Separated Mission Success issues from Safety concerns– Mission Success is single fault tolerant– Flight Safety must be dual fault tolerant

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Batteries

• Launched charged– 88 amp-hour batteries– Nickel Hydrogen

• Battery Isolation Switch (BIS) Installed

– COTS product– Based on military

headlight switch– Not designed to be fail-

safe

• Barrier Analysis applied

Battery Isolation Switches (BIS)

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BIS DesignBIS Cut-Away

UPPER HOUSING NON-CONDUCTIVE

PAINT, 10E12 OHMS@ 100V

Not To Scale DP 092706

BIS CUTAWAY.CV5

HANDLE NON-CONDUCTIVE

WHITE PAINT A276 COATING

FRACTURE CRITICAL VESPEL

LOCKINGFASTERNER,

HEAD COATED WITH ARATHANE 5753

BMA LID

SUPPORT TUBE BRACKET

G10

Cd PLATED LOWER HOUSING

ARATHANE

YELLOW = CAD PLATE

RTV 1142

RTV 1142

LOCKING NUT (TYP)

JAM NUT TOOTH WASHER FLAT WASHER STACK (TYP)

Cd Plated Parts

Fracture Critical

Paint; Non-Conductive, White

Paint; Non-Conductive, Black

Mechanical:Locking & Split Washers

Mechanical:Split & Notched

Washers

Ag

Ag

Zinc plate washer & cap screw

Grease, silicone based oil with thickener

KAPTON or other barrier

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Modifications to BIS• BIS Not Fail-safe

– Failure causes switch to be closed (i.e. ON)

– Identified as a safety issue

• Conducted Hazard Analysis– No Backaway prevention on handle

– Possibility of Whiskers

» Cadmium and Zinc coatings

– Potential for “hot” handle if internal failure

» Not visually identifiable to crew

• Hazard process improved design– Staked handle fastener to prevent backaway

– Detailed analysis of potential for whiskers» Found whiskers in non-flight version of BIS

» Through analysis & test, determined that, for this design, whiskers cannot sustain arc

– Added non-conductive paint to handles

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IMAX Accommodations and Science Instrument Control and

Data Handling

Phillip Adkins

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ORUC with IMAX Accommodations

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Steps to Certify IMAX

• Previous IMAX flights reviewed with new analysis/testing done as needed–Proof Pressure Testing

–Vibration

–Functional Test

–Thermal Vacuum Test

• New Carrier Electrical Harness

• IMAX presented as a separate reflown payload

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MULE Picture

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Late Addition of SIC&DH

• Reduced time for final certification– Six month certification cycle

• Flight safety closely integrated with design and development to insure success

– Safety documentation available from unit certifications

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EVA Safety Considerations

Bill Hill

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Extra-Vehicular Activities (EVA)

• Included instrument and equipment exchange–Done on each previous servicing mission

• New techniques and tools developed for on-orbit, in situ repairs of instrument–Highly complex operations–Required specially designed tools to enable

delicate repairs to circuit boards tailored to crew needs

–Flight safety engineers participated in tool development beginning with design

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EVA Timeline

• Five long days of EVA with four astronauts participating

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Tool Development Process

• Tools Developed and designed with crew and safety participation• Design and development includes full review and verification

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STIS Repair Tools

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FCP After Removal On-orbit

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Shuttle Specific Challenges

Patrick Mitchell

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Shuttle-Specific Safety Challenges

• ISS was not available for Safe-Haven– Launch-on-need (LON) shuttle processed and

available for rescue

• Enhanced Micro-Meteorite On-orbit Debris (MMOD) Risk

– Shuttle flew protected attitudes when HST specific operations permitted

• Shuttle inspections performed – Tile inspections performed before and after servicing

– Insures no damage during ascent or from MMOD

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Launch On Need STS-400

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Solutions Applied

• Safety Systems Analysis Techniques Used– Initiating Event Tree Analysis (IETA)– Barrier Analyses– Fault Tolerance Analyses

• JSC Safety Requirements and Processes• Safety engineer integration into hardware

design teams resulted in safe hardware by design

Successful application of System Safety techniques contributed to a successful Servicing

Mission

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HST After SM4 Deployment

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Goddard Space Flight Center September 1, 2009CHART 1 Hubble Space Telescope Servicing Mission Four...

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