# Presentation: 502365

## Section 3

_***Section 3***_
***Residual Risk***

*** ******. . . Bryant Cramer***
*EO-1 Mission Implementation Manager*

## Residual Risk

***Residual Risk***

***Residual Risk is that risk remaining at launch after all mitigation efforts have been completed***
***The Red Team is charged to “ascertain and document all residual risks, judged to be any level higher than low, that are remaining in the mission”***
***NASA Administrator has asked that 3 system engineering tools be used to estimate the likelihood of occurrence and the overall mission risk associated with the predominant failure modes as identified by:***
***Failure Modes and Effects Analyses***
***Fault Tree Analysis***
***Probabilistic Risk Analysis***
***Red Team Charter focuses on single-point failure mechanisms as a major source of residual risk***

## Three System Engineering Tools

***Three System Engineering Tools***

***NASA Administrator has asked that we evaluate residual risk through the use of:***
***Failure Modes and Effects Analyses (FMEA)***
***Failure Tree Analysis (FTA)***
***Probabilistic Risk Analysis (PRA)***
***These are normally used during design definition to support the system engineering process***
***These tools were not used to develop the EO-1 design:***
***Single string design by policy***
***Hard cost cap and lots of schedule pressure***
***Redundancy was largely out-of-bounds -- by policy, by budget, by schedule, and by available staff***
***We utilized selective redundancy within the existing constraints as best we could***
***We used these 3 tools in a complementary abbreviated application to evaluate the likelihood of successfully completing the EO-1 Minimal Mission***
***The results were presented to the Red Team on June 13, 2000***
***Red Team Charter requires that they be assembled in a separate document to be delivered by the Chairman to the Center Director at the MRR***

## EO-1 Minimal Mission

***EO-1 Minimal Mission***

***Described in EO-1 Mission Success Criteria:***
***Our evaluation focuses only on the EO-1 Minimal Mission***

## EO-1 Residual Risk Assessment

***Fault-Tree Analysis:***
*Failure of the Minimal Mission*
*Includes all mission segments*
*Product is mission element failures that disable the Minimal Mission*
***FMEA:***
*Down to box, board or service level, as appropriate*
*Used to survey single-point failures*
*Product is all single-point board failures disabling the Minimal Mission*
***Probability Risk Assessment:***
*Classified by similarity*
*Reliability Block Diagram*
*Product is probability of single-point failures that disable Minimal Mission*

***Risk Mitigation Strategies***

***Fault Tree Analysis of Minimal Mission***

***Single-Point Failures of Minimal Mission within each Mission Element***

***Probabilistic Classification of Single-Point Failures by Similarity***

***Reliability***
***Block Diagram for Minimal Mission***

***Residual Risk Assessment of EO-1 Minimal Mission***

***Flight Segment***
***Ground Segment***
***Launch Unique Segment***

***F***
***M***
***E***
***A***

## Assumptions For All FMEAs

***Assumptions For All FMEAs***

***One failure at a time***
***All required inputs are nominal***
***All consumables are present in sufficient quantities***
***Nominal power is available (except when the availability of power is part of the failure(s) being considered)***
***Only the launch separation and on-orbit phase of the mission has been treated***
***Connector failures are not treated***
*(Adapted from GSFC P-302-720 and GSFC S-302-89-01)*

## Failure Severity Criticality Categories for FMEAs

***Failure Severity Criticality Categories for FMEAs***

***Severity criticality codes for these FMEAs are defined as follows:***
***1 =******	******Effective loss of the Minimal Mission (non-recoverable complete loss of ALI data)***
***2 =******	******Loss of the Hyperion (non-recoverable complete loss of Hyperion data)***
***3 =******	******Serious degradation, but still meets some of the Level I ALI and/or Hyperion requirements***
***4 =******	******Some degradation or operations impact, but still achieves the baseline mission***
***5 =******	******Little or no impact to mission success or mission operations***
***Some examples are:***
***Category 1:******	******Power System, ACS, WARP, or ALI instrument failing completely***
***Category 2:******	******Hyperion instrument failing by itself***
***Category 3:******	******A Hyperion ASP failure, or an X-Band Phased Array failure***
***Category 4:******	******Heaters***
***Category 5:******	******PPT, GPS, AC, etc.***

## EO-1 Minimal Mission ElementsCategory 1 Failures

## EO-1 Minimal Mission ElementsCategory 1 Failures(continued)

## EO-1 Minimal MissionReliability Block Diagram

- = Has  Consequence Category 1 from FMEA

**Attitude Control**
**Subsystem**
**(ACS)**

**Electrical Power**
**Subsystem**
**(EPS)**

**Communications**
**Subsystem (CS)**

**Command & Data**
**Handling**
**Subsystem**
**(C&DHS)**

**Reaction Control**
**Subsystem (RCS)**

**ALI**

**WARP**

**0.9490**

**0.9679**

**0.9535**

**0.9638**

**0.8960**

**0.9846**

**Reliability @ 1 year = 0.7447**
**Failure Likelihood   = 0.2553**

**Has Redundancy**

**0.9999**

## 0.75

**0.75**

## PRA Summary

***PRA Summary***

***Reliability at 1 year for FMEA Category 1 = 0.7491***
***Reliability at 1 year for FMEA Category 1R = 0.9941***
***Redundant 1R items have small impact on reliability***
***Reliability at 1 year for Category 1 & 1R = 0.7447***
***If 1R items were not redundant then R = 0.6917***
***Category 1 single point failures are primary drivers of residual risk.***

## Special Topic:

***Accelerated Minimal Mission***

*** ******. . . Bryant Cramer***
*EO-1 Mission Implementation Manager*

## Overview

***Overview***

***The EO-1 Accelerated Mission is a change in operations to maximize the likelihood of flight validating the ALI & WARP (Minimal Mission)***
***The concept is an outgrowth of our Probabilistic Risk Assessment (PRA)***
***EO-1 is a largely single-string design and for such a mission the reliability typically decreases to about 0.70 at the end of one year***
***Due to selective redundancy, our reliability is at 0.75 @ 12 months***
***By increasing the data collection rate from 4 to 8 Data Collection Events (DCEs) during the first four months aloft, we can increase the probability of completing the Minimal Mission from 0.75 to 0.90***
***The cost is roughly $600K ***

## Reliability vs. Mission Success Criteria

- Minimal Mission

- Completely Successful Mission

- Successful Mission

- Months After Launch

- Successful Mission

- Completely Successful Mission

- Probability

***Reliability vs. Mission Success Criteria***

**4 DCEs / Day**

**8 DCEs / Day**

## EO-1 Accelerated Mission

***EO-1 Accelerated Mission***

**COST ($K)**

**MONTHS**

- Accelerated Mission
- Science Validation Facility (SVF)
- Normal Ops

**$600K**

## Summary

***Summary***

***Accelerated Mission capitalizes on the early reliability of the observatory***
***Maximizes the likelihood of completing the Minimal Mission***
***Cost-effective -- can be supported from existing resources***
***Leaves the option for an extended mission still intact***
***Facilitates DCEs in Southern Hemisphere***
***Strengthens the overall science validation***

## Special Topic:

***WARP Back-Up Solid State Recorder***

*** ******. . . Irving Linares***
*EO-1 BSSR Lead*

## Background

***Background***

***WARP failed on 1/4/00 and subsequent troubleshooting found a connector with a bent pin and socket corrosion that was repaired***
***WARP failed again on 2/26/00 and this time an LM136 regulator failed and overstressed adjacent parts***
***This regulator was the true cause of the first failure***
***A new regulator board was built, integrated, and tested, and the WARP returned to the spacecraft on 5/16/00***
***After the second WARP failure, it was decided that EO-1 would pursue a Backup Solid State Recorder (BSSR) as a prudent risk mitigation***

## What is the BSSR

***What is the BSSR***

***Backup Solid State Recorder is a high-reliability, stand-alone CCSDS-compatible unit packaged as a single card to fit directly into the WARP***
***4.6 Gb of solid state memory***
***Interfaces: MIL-STD-1773; +28V power input; RS-422 science data input/output***
***3:1 mux for input science data***
***Maximum science data input rate of 165 Mbps***
***No processor, no internal software, therefore design is simple and independent of flight hardware & software***
***Design incorporates radiation-hardened mil-spec EEE parts to gain a reliability prediction of 95% over two years   ***
***Team Members:***

## Interface Block Diagram

## BSSR Board Layout

***Preliminary PWB layout***

## Board Placement Within WARP

## Enhanced WARP Reliability

***Enhanced WARP Reliability***

## Current Status of BSSR Development

***Current Status of BSSR Development***

***BSSR Team has completed ~75% of the detailed electrical design effort***
***CDR held on 7/20/00 ***
***Remaining items to complete design under current task (8/31/00):***
***FPGA designs and simulations***
***Analog simulations***
***Deliverables under current task:***
***Electrical schematics, FPGA fuse files***
***CDR Package and Action Item responses ***
***EO-1 ICD-068 “EO-1 BSSR ICD and Performance Specification” ***
***Draft BSSR Qualification and Acceptance Test Plan***
***Preliminary PWB area study, Design Guidelines/Critical Routings***
***Detailed Parts list complete, Long-Lead parts identified and quoted***
***Reliability and Thermal Analysis***

## Cost to Date, Cost & Schedule to Complete Design

***Cost to Date, Cost & Schedule to Complete Design***

***Costs to date:***
***July 31, 2000***
* **$299K for CDR and preliminary design*
***August 31, 2000***
*Additional $100K for complete electrical design*
***February 28, 2001 ***
*Additional $900K for WARP/BSSR Integration *
***Major development milestones include:***
***Complete BSSR Design and conduct Peer Reviews:******	******8/31/00***
***Complete assembly of the flight BSSR: ******	******10/30/00***
***Complete BIT at Litton and Deliver to GSFC:******	******11/20/00***
***Complete BSSR Performance and environmental test; integrate ******	******1/9/01***
***	******to the WARP: ******	***
***Complete WARP/BSSR testing and ready to integrate to EO-1: ******	******2/19/01***
***Complete Observatory I&T:******	******6/29/01***
***Launch Readiness Date:******	******8/23/01***

**Plan to Halt Here**