The thermal-vacuum and security system of the characterization facility for MAJIS/JUICE VIS-NIR FM and SM detectors

Abstract

MAJIS is part of the science payload of the JUICE mission to be launched in 2022. BIRA-IASB and ROB contribute to MAJIS with the characterization of the VIS-NIR Flight Model (FM) and Spare Model (SM) detectors, including the design, development, and validation of the setup, as well as the data processing pipeline. The VIS-NIR detectors are thermalized within a temperature range from 125 K to 150 K during their characterization campaigns. Moreover, the temperature of their electronic units must always remain above 120 K to avoid any irreparable damage, and below 160 K for operative conditions. Likewise, to avoid any risk of contamination, the detector should preferably be operated below 10-5 mbar of vacuum. To fulfill these requirements, a complete security system was developed; it includes redundant thermal control loops, alarms from every pressure and temperature monitoring devices in use, and a robust semi-automatic control system for the pumping and cryocooling equipment. Moreover, the security system is complemented by the Temperature Ground Support Equipment (TGSE), which provides a LabVIEW user-friendly interface to communicate the status of the detector and the vacuum chamber in real-time. This subsystem was successfully validated in May 2020, before the delivery of the FM detector in June 2020. In this paper, we summarize the design, implementation and validation tests of the security system as well as the thermal and vacuum performances of the facility. We also show the thermal behavior of the detector during acquisitions representative of typical MAJIS observations.