James Webb Space Telescope Integrated Science Instrument Module Thermal Vacuum/Thermal Balance Test Campaign at NASA’s Goddard Space Flight Center

Date

2016-07-10

Journal Title

Journal ISSN

Volume Title

Publisher

46th International Conference on Environmental Systems

Abstract

The James Webb Space Telescope is a large infrared telescope with a 6.5-meter primary mirror, designed as a successor to the Hubble Space Telescope when launched in 2018. Three of the four science instruments contained within the Integrated Science Instrument Module (ISIM) are passively cooled to their operational temperature range of 36K - 40K with radiators, and the fourth instrument is actively cooled to its operational temperature of approximately 6K. Thermal-vacuum testing of the flight science instruments at the ISIM element level has taken place in three separate highly challenging and extremely complex thermal tests within a gaseous helium-cooled shroud inside Goddard Space Flight Center’s Space Environment Simulator. Special data acquisition software was developed for these tests to monitor over 1700 flight and test sensor measurements, track over 50 gradients, component rates, and temperature limits in real time against defined constraints and limitations, and guide the complex transition from ambient to final cryogenic temperatures and back. This extremely flexible system has proven highly successful in safeguarding the nearly $2B science payload during the 3.5 month long thermal tests. Heat flow measurement instrumentation, or “Q”-meters, were also specially developed for these tests. These devices provide thermal boundaries to the flight hardware while measuring instrument heat loads up to 600 mW with an estimated uncertainty of < 2 mW in test, enabling accurate thermal model correlation, hardware design validation, and workmanship verification. The high accuracy heat load measurements provided first evidence of a potentially serious hardware design issue that was subsequently corrected. This paper provides an overview of the ISIM-level thermal-vacuum tests and thermal objectives; explains the thermal test configuration and thermal balances; describes special measurement instrumentation and monitoring and control software; presents key test thermal results; lists problems encountered during testing and lessons learned.

Description

United States
NASA GSFC
Comber Thermal Solutions, LLC
108
ICES108: Thermal Control of Cryogenic Instruments and Optical Systems
Vienna, Austria
The 46th International Conference on Environmental Systems was held in Vienna, Austria, USA on 10 July 2016 through 14 July 2016.
Stuart Glazer, NASA/Goddard Space Flight Center, USA
Brian Comber, Comber Thermal Solutions, LLC, USA

Keywords

JWST ISIM cryogenic thermal testing, heat load measurements, thermal model correlation, thermal design validation

Citation