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