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THEMIS INSTRUMENTNITROGEN PURGE

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Purge Design Requirements

The purge system was designed to comply with the following standards:

NASA-STD-5005 Ground Support Equipment Design Criteria

EWR 127 Eastern and Western Range Safety Policies and Practices

PAIP THEMIS Performance Assurance Implementation Plan (UCB Document)

THM-SYS-011 THEMIS Configuration Management Plan (UCB Document)

THM-SYS-004 THEMIS Contamination Control Document (UCB Document)

SAI-PLAN- 0647 THEMIS Mission System Program Safety Plan (Swales Document)

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THEMIS Purge Overview

ESA & SST Instruments Require Nitrogen Purge

• Nitrogen Purge Required Two of the instruments on the THEMIS probes require high purity (99.999%) nitrogen

purging – the SST (Solid State Telescope) and ESA (Electrostatic Analyzer) instruments. The ESA microchannel plates are sensitive to condensable hydrocarbons, particulates, and water vapor. The SST detectors are sensitive mainly to particulates.

• Low Pressure / Very Low Flow (5 psi / 68sccm (.0024 cfm) per Probe)

• UCB SSL will supply all hardware Oxygen Sensor, 2-stage Regulator, Gages (Blow-Out-Back Type), Relief Valve (10 psi),

Shutoff Valve, Filter/Moisture Separator, Flow meter, Hose Assemblies with Quick Disconnects, Manifolds etc.

• UCB SSL Responsible for Purge With some assistance in monitoring gas supply and providing gas at non-UCB facilities.

• Purge up until PCA Integration When impractical to purge, 24 hr off-purge limit. Lumaloy bonnets on instruments when covers are off (up until PCA integration)/

• Bag PCA and Backfill With NitrogenReference THM-SYS-032 PURGE PLAN REV B for more detail

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Probe Purge

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Purge Hardware

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Purge Outline

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Purge Outline cont.

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PCA Bagging

1. Final Instrument Purge Just Prior to PCA integration

2. Bag PCA After Integration

3. Purge Bag For 24 Hours

4. Remove Purge Line.

5. Transport to Pad

6. Remove Bag Just Prior to Installing Shroud