ANITA2 – the Multicomponent Air Analyser on ISS – Gas Measurement Results From the ISS Air in 2024

The ANITA2 (Analysing Interferometer for Ambient Air) system is a trace gas analyser that operates onboard the ISS to monitor the cabin atmosphere. It started operation on March 9, 2022, as a demonstration system for exploration. After delivery of excellent and reliable multi-gas data for over two years, ANITA2’s role was formally upgraded in June 2024 to be an ISS system, as part of the CHeCS (Crew Health and Care System). At the time of writing, ANITA2 is monitoring 48 gases in parallel in the ISS cabin air. The pre-flight calibration included 37 gases. After start-up, the calibration has been extended stepwise to include new gases – either discovered in the ISS air by ANITA2 or expected or suspected to occur owing to information about e.g. operations, payloads, or visiting spacecraft. All work on recalibration has been performed on and from ground, without any astronaut involvement. The advantages of an ANITA-type instrument include very high selectivity, sensitivity, accuracy, precision, and reliability, and high time resolution of the measurement data. This has made it possible for ANITA1 (on the ISS in 2007-2008) as well as ANITA2 to discover new gases in the ISS air, and to reveal new and very useful knowledge about the ISS air dynamics. ANITA has no consumption except electrical power and no production of waste, and there is no need for any on-board calibration gas. As intended, ANITA2 makes a steppingstone into the future, as a precursor system for crewed stations, bases, and exploration missions, including the Lunar Gateway and to/on the Moon and Mars. ANITA3 has already been selected by ESA as the air monitoring system in ESA’s I-HAB module on the Gateway. This paper describes ANITA2’s properties and the applied calibration and presents the gas measurement results from the ISS air in 2024.