Eve M Wooldridge | Search NASA

NASA NTRS2022

An Overview of Contamination Control for the James Webb Space Telescope Launch Campaign

The James Webb Space Telescope (JWST) is a large, infrared space telescope operating at Lagrange point 2. JWST is a joint effort between NASA, ESA, and CSA and was launched from the Centre Spatial Guyanais (CSG) on an Ariane 5 rocket in December 2021. The three-month launch campaign utilized enhanced contamination controls to meet JWST’s strict cleanliness requirements. Prior to launch, JWST was permitted to only be exposed to ISO Class 7 cleanrooms, whereas the processing facilities at CSG are ISO Class 8. NASA, ESA, Arianespace, and CNES implemented temporary upgrades to the nominal contamination control operations for the launch campaign unique to JWST, including the use of vetted, portable High Efficiency Particulate Air (HEPA) filter walls, pre-entrance cleanliness acceptance surveys of each facility and the intra-plant transporter, tightened cleanroom protocols, upgraded garmenting and laundering techniques, cleaning of Self-Contained Atmospheric Protection Ensemble (SCAPE) suits, increased maintenance, staffed pre-cleaning stations, adaptation of the house purge network, and a contamination control enclosure atop the Ariane 5 launcher prior to fairing encapsulation. The Ariane 5 fairing interior and Vehicle Equipment Bay membrane also received multiple cleanings, detailed inspections, and verification sampling to achieve necessary cleanliness levels. The fairing itself was specially sealed to protect the inner environment with just a small, door porthole accessible via diving board for final closeout of the purge interface. All of these enhancements together allowed JWST to meet its contamination requirements for launch, ensuring successful post-separation deployments and mission science.

Contamination Control↗

NASA NTRS2022

Environmental Testing of Contamination Sensitive Instruments and Optics in Non-Cleanliness Controlled Facilities

The James Webb Space Telescope (JWST) Optical Telescope Element + Integrated Science Instrument Module (OTIS) went through environmental testing at the Goddard Space Flight Center. The vibration and acoustic tests occurred outside of cleanrooms. These areas are typically around ISO Class 8, far out of specifications for JWST. Through collaboration between the OTIS Mechanical and Contamination Engineering teams, a portable clean enclosure was designed, built, and verified to prevent contamination of the sensitive OTIS assembly. This manuscript describes the process of designing and building this enclosure, including materials selection and High Efficiency Particle Air (HEPA) filtration. This enclosure also provided environmental control with a portable air conditioning unit to control the relative humidity level enabling personnel to work within it. The manuscript emphasizes working in a systematic order to maintain cleanliness and integrity. “Clean as you go” during construction was a top priority to ensure that this critical Ground Support Equipment (GSE) was acceptable. The process of installing the walls and then sealing their internal and external surfaces with approved films was critical to maintaining OTIS integrity. This proved important because OTIS was in the enclosure for months longer than originally planned. This manuscript concludes by reviewing the process used to verify that the OTIS clean enclosure could achieve acceptable contamination level fallout accumulation for use during the vibration and acoustic testing and then verifying that the predicted performance was achieved after testing was complete.

Contamination Control, James Webb Space Telescope,↗

NASA NTRS2022

Clean Air Shower Curtain for Protection of Contamination Sensitive Telescopes on the Ariane 5 Launcher

The launch of the James Webb Space Telescope (JWST) was successfully performed by Ariane 5 from French Guiana on December 25th 2021. The unique nature of the JWST mission led to various adaptations of the Ariane 5 launch system to fulfill stringent cleanliness and hygrometry requirements all along the launch preparation. JWST integration and test activities in the Final Assembly Building (BAF) had to be performed in ISO Class 7 equivalent conditions under Volatile Organic Compounds (VOC) protection and monitoring. For this purpose, a dedicated air supply system equipped with Airborne Molecular Contamination (AMC) filters was installed in the umbilical mast. The fairing itself was specially sealed to protect the inner environment, and to, guarantee ISO Class 7, the BAF Composite Hall (BAF-HC) facilities were upgraded with a removable “Air Shower Curtain” (AShC) containment enclosure between the mobile platforms around JWST. The preparation of these Ariane 5 launch system adaptations started several years before the launch campaign with close cooperation and coordination between Arianespace, ArianeGroup, the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). This paper describes their specificities and addresses the challenges experienced to achieve the successful mission preparation.

Contamination Control, James Webb Space Telescope,↗

NASA NTRS2022

Clean Air Shower Curtain for Protection of Contamination Sensitive Telescopes on the Ariane 5 Launcher

The launch of the James Webb Space Telescope (JWST) was successfully performed by Ariane 5 from French Guiana on December 25th 2021. The unique nature of the JWST mission led to various adaptations of the Ariane 5 launch system to fulfill stringent cleanliness and hygrometry requirements all along the launch preparation. JWST integration and test activities in the Final Assembly Building (BAF) had to be performed in ISO Class 7 equivalent conditions under Volatile Organic Compounds (VOC) protection and monitoring. For this purpose, a dedicated air supply system equipped with Airborne Molecular Contamination (AMC) filters was installed in the umbilical mast. The fairing itself was specially sealed to protect the inner environment, and to, guarantee ISO Class 7, the BAF Composite Hall (BAF-HC) facilities were upgraded with a removable “Air Shower Curtain” (AShC) containment enclosure between the mobile platforms around JWST. The preparation of these Ariane 5 launch system adaptations started several years before the launch campaign with close cooperation and coordination between Arianespace, ArianeGroup, the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). This paper describes their specificities and addresses the challenges experienced to achieve the successful mission preparation.

Contamination Control, James Webb Space Telescope,↗

NASA NTRSDate not supplied

Study of Fallout Metrics for Contamination Analysis

A challenge present in assessing contamination accumulation on many missions is predicting fallout during ground processing given the multiple and various orientations possible for surfaces such as optics and instruments. The best practice assumption has been to quantify particle build up on vertical surfaces as approximately 1/10 that of horizontal surfaces. This fractional relation is important when considering contamination allocations necessary to meet cleanliness requirements since spacecraft can be in many orientations during integration and testing. There is insufficient data to provide confidence in the 1/10 approximation, yet its use can have a significant effect on mission end of life contamination level predictions, leading to expenditures of precious resources to meet mission requirements. A study was conducted to compare and analyze the fallout in horizontal and vertical orientations. Silicon wafers were deployed in four different facilities. Data sets from a long term deployment of wafers were analyzed from a cleanroom facility housing integration of the James Webb Space Telescope (JWST) as well as from a shorter term deployment of wafers in three cleanroom facilities at Goddard Space Flight Center with lower activity. There are many variables influencing the relationship between fallout on vertical and horizontal wafers, including wafer position with respect to air flow, air changes in the facility, duration of exposure, and activity workload. The goal of this continuing study is to develop a tool to inform particulate accumulation predictions for future projects.

Contamination↗

NASA NTRSDate not supplied

Molecular Accumulation during JWST’s Optical Telescope Cryogenic Thermal Vacuum Testing

Maintaining molecular cleanliness during the JWST’s Optical Telescope/Instrument Module (OTIS) Cryogenic Thermal Vacuum (TV) test campaign was critical to the success of its optical mission on orbit. In the thermal vacuum tests leading up to the final cryogenic test to validate the OTIS flight hardware, NASA Johnson Space Center’s (JSC’s) TV Chamber A was fully characterized for molecular contamination. It was found to contain common volatile condensable materials (VCM), including hydrocarbons, plasticizers, and silicones, all of which absorb in JWST’s infrared wavelength region. Due to the risks involved, cleaning molecular contamination from the OTIS mirrors was not an option and heating the Primary Mirror (PM) segments would have also been a risky and expensive endeavor. As a result, a monitoring process was developed and implemented during four different Pathfinder or risk reduction tests that were scheduled to occur prior to the flight hardware test. The goal was to quantify and assess the risk of molecular contamination depositing on the PM resulting from relatively warm chamber shrouds “leading” colder PM mirrors during warmup, by a margin of 10-50 Kelvin (K). This was accomplished using Cryogenic Quartz Crystal Microbalances (CQCMs), held at temperatures slightly cooler than the segments to signal the onset of contamination events. Per the JWST Contamination Control Plan (CCP)1, the total Primary Mirror molecular allocation requirement was 50 angstroms. In all tests, the results showed an average accumulated molecular contamination of <10 angstroms.

optics↗

NASA NTRSDate not supplied

Overview of Contamination Control for the James Webb Space Telescope Launch Campaign

The James Webb Space Telescope (JWST) is a large, infrared space telescope operating at Lagrange point 2. JWST is a joint effort between NASA, ESA, and CSA and was launched from the Centre Spatial Guyanais (CSG) on an Ariane 5 rocket in December 2021. The three-month launch campaign utilized enhanced contamination controls to meet JWST’s strict cleanliness requirements. Prior to launch, JWST was permitted to only be exposed to ISO Class 7 cleanrooms, whereas the processing facilities at CSG are ISO Class 8. NASA, ESA, Arianespace, and CNES implemented temporary upgrades to the nominal contamination control operations for the launch campaign unique to JWST, including the use of vetted, portable High Efficiency Particulate Air (HEPA) filter walls, pre-entrance cleanliness acceptance surveys of each facility and the intra-plant transporter, tightened cleanroom protocols, upgraded garmenting and laundering techniques, cleaning of Self-Contained Atmospheric Protection Ensemble (SCAPE) suits, increased maintenance, staffed pre-cleaning stations, adaptation of the house purge network, and a contamination control enclosure atop the Ariane 5 launcher prior to fairing encapsulation. The Ariane 5 fairing interior and Vehicle Equipment Bay membrane also received multiple cleanings, detailed inspections, and verification sampling to achieve necessary cleanliness levels. The fairing itself was specially sealed to protect the inner environment with just a small, doored porthole accessible via diving board for final closeout of the purge interface. All these enhancements together allowed JWST to meet its contamination requirements for launch, ensuring successful post-separation deployments and mission science.

James Webb Space Telescope↗