1. Hubble Space Telescope Servicing Mission Four (HST SM4): Unique Challenges for STS-125
Bob Dedalis, HST Payload Safety Manager
Miranda Cooter, HST Lead Flight Safety Engineer
Patrick Mitchell, Payload Safety Review Panel Executive Secretary
William Hill, HST Lead Ground Safety Engineer
Phillip Adkins, Systems Safety Engineer

2. 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

3. Major Tasks Impact to Hubble Task Install WFC3 – Wide Field Camera 3
Installed 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 by
replacing circuit boards.
Repair ACS
Restored critical scientific functionality to the Advanced Camera for Surveys
by replacing power supply and circuit boards.
Replace Rate Sensor Units (RSU) (gyroscopes)
Completed change-out of all six gyroscopes, the heart of HST's pointing
system, 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 are
steadily 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/Science
Data Formatter (CU/SDF).

4. Payload Bay Equipment Four Full Equipment Carriers
Science Instrument Control and Data Handling Unit
Flight Support System pivots and rotates to enable in-bay servicing
Four Full Equipment Carriers
Included a servicing platform

5. Payload Safety Review Process
Hazard Report
Verify Hardware
As Built
Implement Controls
Payload Organization
Concurrence
NSTS
Safety Review
Phase III
Delivery
Flight Safety Verification
Tracking Log
Track Verification of
Items To Be Conducted
After Phase III Review
Payload Organization
Approval
NSTS Review
Hazard Report
Verify Design
Implement Controls
Payload Organization
Concurrence
NSTS
Safety Review
Phase II
CDR
Hazard Report
Identify Hazard
Controls
Payload Organization
Concurrence
NSTS
Safety Review
Phase I
PDR
Preliminary Hazard
Reports
Identification of
Hazards
Safety Review
Phase 0
Design Concept
Update
Only
Update
Only
For
Each
Hazard

6. Hazard Identification Process
Postulate Failure (PHA/FMEA/FTA)
NSTS Requirements
Change Design
Not Approved
System/ Sub-system/Interfaces
Hazard to Crew/STS
Requirements Met
Perform Hazard Assessment
Write HR
Yes No
Critical No
Yes (Generic Hazard)
Catastrophic
Confirm Fault Tolerance or DFMR in Design/Operations No
Hazard
Write HR
Review with JSC
Approved
1 Fault-Tolerant
2 Fault-Tolerant
Redesign
Write HR
Verify Controls
* 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 *
Document for CoFR
4/25/2017

7. Final Flight Safety Post Phase III/Part 4

8. 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

9. Soft Capture Mechanism and Battery Isolation Switch
Miranda Cooter

10. 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

11. Soft Capture Mechanism
Berthing Latch outside SCM attach mechanisms
Servicing Platform
Soft Capture Mechanism
Berthing Latches
and
SCM Attach Points
Crew-Activated Remote Drive
Soft Capture Mechanism Detail on Next Slide

12. SCM Mechanism Detail Radial Out View Radial In View FSS Override Assy
HST Release Override
HST Attach Override
FSS Release Override
FSS Override Assy
FSS Attach Override
Sill Plate Adapter

13. Final SCM Fault Tolerance
Separated Mission Success issues from Safety concerns
Mission Success is single fault tolerant
Flight Safety must be dual fault tolerant

14. Batteries Launched charged Battery Isolation Switch (BIS) Installed
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)

15. BIS Design

16. Modifications to BIS BIS Not Fail-safe Conducted Hazard Analysis
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

17. IMAX Accommodations and Science Instrument Control and Data Handling
Phillip Adkins

18. ORUC with IMAX Accommodations

19. 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

20. MULE Picture

21. 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

22. EVA Safety Considerations
Bill Hill

23. 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

24. EVA Timeline
Five long days of EVA with four astronauts participating

25. Tool Development Process
Tools Developed and designed with crew and safety participation
Design and development includes full review and verification

26. STIS Repair Tools

27. FCP After Removal On-orbit

28. Shuttle Specific Challenges
Patrick Mitchell

29. 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

30. Launch On Need STS-400

31. 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

32. HST After SM4 Deployment