Performance of Short Wave Cutoff MBE HgCdTe 2-D Arrays; Space Borne Application for Sensing OH Airglow Wave Structure

摘要

Passive radiative cooling is desirable for space borne detectors because it is generally cheaper, less massive and power consumptive than cooling by a mechanical refrigerator or expendable cryogens. Our interest is space borne nadir imaging the OH airglow in Q-branch features of the 9- > 6 band at ～ 1382.3 nm, and the 2- > 0 band at ～ 1434.4 nm with sufficient signal to noise (S/N) to quantitatively retrieve wave structure. Low noise 256 X 256 - 40 micrometer pitch HgCdTe detector arrays are available for our application. E.g., the Rockwell Science Center (RSC) standard 2.5 μm PACE~i product bonded on to the PICNIC read out mux satisfies our high sensitivity and low read noise requirements, but would require a mechanical refrigerator or expendable cryogen to cool sufficiently (to about 80K) to satisfy our dark current requirement (< 50e/s/pixel). To demonstrate an option that would provide our required performance at viable passive radiative cooling temperature, we have procured examples of the more recent RSC double layer planar heterogeneous (DLPH) HgCdTe 2-D arrays with shorter wavelength cutoff and produced by molecular beam epitaxy (MBE) on a CdZnTe substrate, an bonded to the PICNIC mux. Here we describe our test procedures and results that these at relatively warm temperature, the order 160 to 170K, satisfy the requirements for our OH airglow wave imaging application. We describe an instrument model and observational operations to observe the OH airglow wave structure with signal to noise (S/N) > 100.