A HgCdTe detector-based mid-infrared spectrometer for space-based exoplanet transit and phase curve observations

We present a modified HgCdTe detector-based laboratory demonstration of an ultra-stable mid-IR array spectrometer for exoplanet transits. The instrument includes a calibration system that enables the 1/f stability required for the detection of atmospheric bio-signatures in habitable-zone planets around M-dwarfs. We have already demonstrated the required stability of 5 ppm with Transition Edge Sensors (TES) over days in an identical spectrometer. However, TES require sub-K cooling. In 2019 Cabrera et al. demonstrated a long-wavelength cut-off of 16.7 μm for a new HgCdTe-based detector, and Mandell et al., 2022, demonstrated that this long-wavelength cutoff would be sufficient to measure surface temperature, radius, and multiple atmospheric tracers. We use this particular array in our demonstration. Here, we provide an overview of the testbed and present first results from ongoing tests and compare these to the performance we achieved with TES detectors.