September 16, 2022

MicroCarb instrument begins thermal vacuum testing

The MicroCarb instrument began thermal vacuum testing at Airbus Defence & Space (ADS) in Toulouse in September. The instrument is being put through its paces in different conditions for 40 days to test optical performance before delivery to Thales Alenia Space UK. MicroCarb is a French mission led by the French space agency CNES and funded by the national research agency ANR in partnership with the United Kingdom Space Agency (UKSA). The mission will map global sources and sinks of carbon dioxide (CO2), the main greenhouse gas. Elodie Cansot, in charge of the instrument, explains what these thermal vacuum tests entail.

© CNES / Airbus DS 2022

Goals

The first goal of the tests is to qualify temperature control of the instrument in a range of operational and other conditions. In particular, they will be verifying the thermal performance of the cryostat cooling system, taking it down to a temperature of 150 Kelvin (–123.15°C) in all test environments. Once the cryostat has reached this temperature, the MicroCarb instrument’s optical performance will be checked and validated using optical ground systems developed by ADS to test geometric, spectral and radiometric performance.

The next goal is to make sure the instrument works as intended in scenarios representative of flight conditions, for which two tests will be run. The first consists in illuminating the instrument with a signal sent through a gas cell containing CO2, and the second is a sun pointing end-to-end test during which sunlight is directed at the entrance of the instrument via a suite of telescopes and optical fibres.

Élodie Cansot, MicroCarb instrument manager

Key test steps

© CNES / Airbus DS 2022

Optical performance will be measured during different temperature phases representing the temperatures the instrument will encounter on its mission.
These tests will involve two key steps: characterization of the instrument’s spectral response and remanence measurements to determine how it responds to rapid variations in brightness. These two steps are expected to last 10 days.

Two days have also been set aside for solar measurements that require clear skies and parallel measurements by ground instruments on the roof of the clean room. The objective here is to obtain reference measurements of CO2 concentration and solar illumination for comparison with MicroCarb’s measurements.

Test management

Airbus Defence & Space is in charge of these tests. CNES is also contributing with support from laboratories belonging to the national scientific research centre CNRS: the LERMA astrophysical and atmospheric radiation and matter research laboratory, the LOA applied optics laboratory and the GSMA molecular and atmospheric spectrometry laboratory for solar and gas cell tests.

Once thermal vacuum testing is complete, project teams will be moving on to the next key milestone: delivery of the instrument to Thales Alenia Space UK in Harwell for integration with the Myriade spacecraft bus.