Verification Testing of a Helium Gas-Gap Heat-Switch Controlled Calibration Target

Date
2017-07-16
Journal Title
Journal ISSN
Volume Title
Publisher
47th International Conference on Environmental Systems
Abstract

The Meteosat series of spacecraft are meteorological satellites, providing data that inform weather forecasts across Europe. Meteosat Third Generation (MTG) is expected to allow data to be collected into the 2030s. The Flexible Combined Imager (FCI) and Infrared Sounder (IRS) instruments will be flying on the MTG spacecraft. The ground based calibration targets used to calibrate these instruments are being designed at the Science and Technology Facilities Council’s Rutherford Appleton Laboratory Space Department (STFC RAL Space). They are designed to operate in vacuum over a temperature range from 160 K to 370 K, with an additional capability to operate at ~100 K as a point of near-zero radiance. The overall blackbody design is based upon a helium gas-gap heat switch, which reduces the total power budget and allows operation over the entire range. A Breadboard Model (BBM) was designed and built as part of the verification process. The testing of the BBM took place at STFC RAL Space between November 2015 and March 2016, and during August 2016. Overall, the testing demonstrated that a helium gas-gap can be used to successfully control over the entire temperature range desired, meeting both temperature uniformity and stability requirements essential to achieving the instrument calibrations. This paper will present the lessons learnt and the solutions implemented following these series of tests. In particular, it will focus upon the complications associated with the use of helium gas as the heat-switch: sealing the helium into the gas-gap, controlling the pressure of the helium accurately, induced arcing across the connectors due to helium breakdown, and steps required to mitigate these effects.

Description
ICES203: Thermal Testing
The 47th International Conference on Environmental Systems was held in South Carolina, USA on 16 July 2017 through 20 July 2017
Nicole Melzack, Rutherford Appleton Laboratory (RAL), United Kingdom
Jane G Hurley, Rutherford Appleton Laboratory (RAL), United Kingdom
Elliot Newman, Rutherford Appleton Laboratory (RAL), United Kingdom
Edward Jones, Rutherford Appleton Laboratory (RAL), United Kingdom
Daniel M Peters, Rutherford Appleton Laboratory (RAL), United Kingdom
Sean Keen, Rutherford Appleton Laboratory (RAL), United Kingdom
Jago Stokes, Rutherford Appleton Laboratory (RAL), United Kingdom
Sandy Fok, Rutherford Appleton Laboratory (RAL), United Kingdom
Keywords
calibration target, variable conductance, blackbody, gas conduction, heat switch, testing, verification, lessons learnt
Citation