An ultra-stable mid-infrared detector array for space-based exoplanet transit and phase curve spectroscopy

MIRASET (Mid-IR Array Spectrometer demonstration for Exoplanet Transits) is an ultra-stable laboratory spectrometer. Its purpose is to demonstrate a novel approach for isolating mid-infrared spectral lines detected in the atmospheres of transiting planets orbiting M-stars. Certain combinations of these spectral lines could potentially indicate the existence of life on these planets. To achieve this objective, we employ a black body source as a calibration standard, which also mimics the emission of an M-star in our lab setup. The power range of the black body emission can be adjusted to emit the same power on the detectors as would be observed from Proxima Cen B and Trappist-1 if they were observed using space-based observatories like ORIGINS or specialized MIR exoplanet missions like MIRECLE. All major elements in the experiment at all relevant stages can be temperature controlled, from the detector package, spectrometer, to the photo diode that monitors the output of the black body source in the visible, thereby measuring the temperature on the Wien side of the BB curve, which yields a higher temperature to emission ratio than in the MIR, which is on the Rayleigh Jeans part of the curve. With this experimental setup we have demonstrated the ability to monitor the black body emission over about an hour with a photometric precision of about 2 ppm in the MIR. Over more than 6 hours of integration, the noise floor still remains well below 5 ppm, which is the requirement for the detection of important atmospheric lines from earth-like planets around M-stars (~5 ppm).