# Presentation: 662022

## Section 23	

_***Section 23***_***	***
***Contamination***

*** ******. . . Michael Woronowicz***
* *

## Outline

***Outline***

***Contamination Perspective***
***Thermal Balance/Thermal Vacuum Test***
***contamination-related equipment***
***measurements***
***Pulsed Plasma Thruster***
***Inertial Reference Units***
***Purge Requirements***
***Cleanliness Maintenance***
***Open Issues***

## Contamination Perspective

***Contamination Perspective***

***Contamination staff concerned with deposition of foreign materials***
***Particulates***
***Molecular films***
***On sensitive surfaces***
***Instruments***
***Optics***
***Thermal control surfaces***
***Sources considered for EO-1***
***On-orbit***
*Outgassing from non-metallic materials*
*PPT operations*
***During ground operations***
*contaminants in ambient atmosphere*
*residue from handling and testing*

## TB/TV Parameters

***TB/TV Parameters***

***Chamber 238 instrumentation ***
***2 TQCM’s (usually collected @ -35 °C)***
***scavenger plate @ 90 K***
***coldfinger (collected @ 90 K for 10.25 hrs)***
***TQCM’s placed above nadir deck to measure outgassing for general external requirement***
***one faced upward near Hyperion aperture***
***another faced downward near ALI***
***Demonstrate contaminant desorption during TQCM warmup to satisfy instrumenters’ concerns***

## TB/TV TQCM Placement

**S-Band**
**Antenna**

**TQCM #1**

**Hyperion**

**TQCM #2**

**X-Band**
**Antenna**

**ALI**

**Nadir Deck**
**Heater Panels**

## TB/TV Contamination Results

***TB/TV Contamination Results***

***Hot thermal balance TQCM requirement (1.3 ************ 10******-8****** g/cm******2******/hr deposition @ -35 °C) easily met (by factor of six)***
***continued to monitor outgassing throughout test***
***Desorption readily demonstrated during TQCM warmup to 40 °C***
***near end of hot T/B plateau***
***during final T/V cycle hot plateau ***
***final TQCM frequencies indicated slight net loss***
***Post-test chemical analyses performed on coldfinger indicated little deposition (at edge of resolution)***

## Pulsed Plasma Thruster

***Pulsed Plasma Thruster***

***Concern over S/C degradation due to plume products from PPT firing***
***uses Teflon******®****** for fuel ************ fluorinated products possibly corrosive to S/C materials***
***some plume product fraction will be ionized***
***Effects measured on S/C mockup with strategically-placed S/C materials during lifetime acceptance test***
***Test performed in vacuum at NASA-Glenn***
***Results indicate negligible degradation after 10******5****** pulses***

## IRU Helium Issue

***IRU Helium Issue***

***Inertial reference units (IRU’s) absorb helium, changing required driving voltage***
***Ambient Helium in Bldg 7 highbay high enough to cause IRU voltage to exceed operating specifications***
***IRU Helium desorption rate considerably less than absorption rate***
***Nitrogen purge to IRU box halted He absorption***
***Special Topic discussed on PSR Day 2***
***This was our most significant contamination issue***

## Purge Requirements

***Purge Requirements***

***IRU box***
***Science instruments***
***N******2****** boil-off (better than MIL-P-27401C Grade B, 2**********m absolute filtered)***
***MIT-LL provided purge cart (all three instruments)***
***protects against accidental exposure to condensable hydrocarbons***

## Cleanliness Maintenance

***Cleanliness Maintenance***

***Spacecraft cleaned during I&T flow as work is performed***
***external requirements ***
*1.86% obscuration (particulate), 2 mg/ft**2** (molecular)*
***current levels***
*< 1% obscuration, 1 mg/ft**2** molecular*
***Thorough inspection and cleaning performed at critical milestones***
***before and after movement between facilities***
***before thermal vacuum test***
***before launch***
***Spacecraft bagged when not in cleanroom***

## Open Issues

***Open Issues***

***No open issues***
***No contamination liens***
***Ready to ship***