Interferometer with single-axis robot: design, alignment and performance

An interferometer is an essential subsystem of the Fourier-transform spectrometer (FTS). We describe an FTS Instrument to operate at the surface of Mars based on a Michelson interferometer with hollow retroreflectors. The instrument will operate in two different regimes, observing the solar disc through the atmosphere to measure trace gases, and measuring the thermal emission from the atmosphere to study the planetary boundary layer (PBL). The interferometer has an aperture of 1 inch, operates in the spectral range 1.7-17 μm, and features low mass and volume (≤1 kg with all necessary subsystems). Beam splitter and compensator are made of potassium Bromide (KBr). A single-axis robot with stepper motor drive provides a linear movement of the retroreflector (the Speed stability is about 2%) and enables a maximal optical path difference (MOPD) of 15 cm. A reference channel with a distributed-feedback laser diode (0.76 μm) and a photodiode (Si) supports the interferogram sampling and the speed stabilization loop. The time to measure one interferogram with a best spectral resolution of about 0.05 cm–1 is 500 s (the sun tracking regime). In the thermal sounding regime, one measurement of a two-side interferogram (with the spectral resolution of ~1 cm–1) takes less than 1 min. Laboratory calibrations with a black body and a laser confirm the design parameters of the instrument

ACS/TIRVIM: Calibration and first results.

Atmospheric Chemistry Suite (ACS) is a part of Russian contribution to ExoMars Trace Gas Orbiter (TGO) ESA-Roscosmos mission. ACS includes three separate infrared spectrometers (MIR, NIR and TIRVIM) with a different spectral coverage and targeted to the different science goals. ACS TIRVIM is a Fourier-transform spectrometer based on 2-inch double pendulum interferometer. It operates in the spectral range of 1.7-7 μm with the best spectral resolution 0.13 cm-1 for solar occultation (SO) mode and 0.8 cm-1 for nadir mode. In nadir mode TIRVIM is purposed to thermal sounding of the Martian atmosphere and aerosol properties retrieval. In SO mode TIRVIM is dedicated to trace gases measurements complementing to ACS MIR. After successful launch of ExoMars TGO on 16 April 2016 there were three time slots for turning on science instruments during cruise phase to execute necessary checks and calibration measurements. In March 2018 the nominal science orbit was reached after cruise and aerobraking phases. The first results of TIRVIM data processing show high performance of the Instrument

Monitoring of the atmosphere of Mars with ACS TIRVIM nadir observations on ExoMars TGO.

The ExoMars Trace Gas Orbiter (TGO), a mission by ESA and Roscosmos started its operational scientific phase in March 2018. The Atmospheric Chemistry Suite (ACS) is a set of three spectrometers (NIR, MIR, and TIRVIM) designed to observe the Martian atmosphere in solar occultation, nadir and limb geometry [1]. The thermal infrared channel — TIRVIM is a Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm, with the best spectral resolution 0.13 cm−1. In nadir operation mode, the primary goal of TIRVIM is the long-term monitoring of atmospheric temperature and aerosol (dust and ice clouds) state from the surface to approximately 60 km. We present the results of the first half year operation in orbit around Mars