A Michelson interferometer spectrometer cooled to 10° by liquid helium was flown into an IBC class III aurora on 1 April 1976 from Poker Flat, Alas. The sensor, HIRIS, covered the spectral range 455–2500 wave numbers (4–22 μm) with a spectral resolution of 1.8 cm−1 and an NESR of 5 × 10−12 W/cm2 scrm−1 at 1000 cm−1. An atmospheric emission spectrum was obtained every 0.7 sec over an altitude range of 70–125 km. Atmospheric spectra were obtained of CO2(ν3), NO(Δν = 1), O3(ν3) and CO2(ν2). Auroral produced excitations were observed for each band, this being the first known measurement of auroral enhancements of O3(ν3), 9.6 μm, and CO2(ν2). 15 μm, emissions.

Rocketborne cryogenic (10 K) high-resolution interferometer spectrometer flight HIRIS: auroral and atmospheric IR emission spectra

Quantum well IR photodetectors (QWIPs) have been pro- posed for use in space-based sensing applications. These space sys- tems place stringent performance requirements on IR detectors due to low-irradiance environments and the associated requirement for low- temperature operation. We demonstrate that under these conditions, the responsivity of a QWIP detector depends on frequency and that the shape of the frequency response varies with operational conditions. This nonlinear frequency response is empirically similar to dielectric relax- ation effects observed in bulk extrinsic silicon and germanium photocon- ductors under similar operational conditions. Radiometric characteriza- tion data demonstrate how the frequency response varies with temperature, photon irradiance, and bias voltage. These data also show that at low irradiances and temperatures, the detector response is ex- tremely slow, with response times on the order of seconds. The perfor- mance of the QWIP detector is described using standard figures of merit including responsivity, noise, and specific detectivity (D*). We also de- scribe the performance of an IR focal plane array (IRFPA) made with QWIP detectors, under operational conditions that result in long re- sponse times. The dependence of this time constant on photon irradi- ance and operating temperature is also described. © 2000 Society of Photo- Optical Instrumentation Engineers. (S0091-3286(00)02410-7)

Nonlinear response of quantum well infrared photodetectors under low-background and low-temperature conditions

: Calibration experiments were conducted with the SPIRIT III infrared instrument on the Midcourse Space Experiment (MSX) against a number of infrared standard stars and five emissive reference spheres that were ejected at various times during the mission The physical properties of the 2 cm diameter aluminum spheres, such as the Bond albedo and thermal emissivity of the Martin Black coating, were measured in the laboratory The thermal balance equation between total flux absorbed and that emitted by the sphere was solved to obtain the time dependent temperature of the sphere under the assumption that the sphere radiates as a blackbody at this temperature with a mean infrared emissivity The estimated uncertainties in the modeling of the sphere are estimated to be about 1K in the thermal component and 3% for the geometry contribution MSX also measured more than 150 averaged fluxes on eight standard infrared calibration stars during the 10-month mission The photometric spectral energy distributions of the stars are measured to be within the uncertainties assigned to absolute fluxes adopted for these stars, with a few exceptions However, the small MSX measurement uncertainties did reveal statistically significant deviations from the recommended values Beta Peg was the only calibrations star that was found to be variable MSX also observed excess fluxes for Vega in the 121, 147 and 213 um spectral bands; the excesses in the latter two bands are consistent with the published thermal model for the dust ring around this star The absolute calibration of the fluxes of the stellar standards based on the average of the measurements of the spheres over all MSX bands and the five experiments agrees with the predictions to within the uncertainties The zero magnitude absolute fluxes proposed by Cohen et al (1992) are validated if the flux from Sirius is increased by 1%

Absolute Infrared Calibration of Standard Stars by the Midcourse Space Experiment

Quantum Well Infrared Photodetectors (QWIPs) have been proposed for use in space based remote sensing applications. These space systems place stringent performance requirements on infrared detectors due to the low irradiance environments and the associated requirement for low temperature operation. This study demonstrates that, under these space conditions, the responsivity of a QWIP detector depends on frequency and that the shape of the frequency response depends on the operational conditions. The non-flat frequency response is empirically similar to dielectric relaxation effects observed in bulk extrinsic silicon and germanium photoconductors under similar operational conditions. Data from four QWIP detectors, obtained from four independent sources, demonstrate how the frequency response of QWIP detectors vary with temperature, photon irradiance, and bias voltage, and how the shape of the frequency response depends on the dynamic resistance of the detector. This QWIP frequency response results in a detector signal that is nonlinear with irradiance for some combinations of detector bias, photon irradiance, and operating temperature.

Nonlinear response of QWIP detectors: summary of data from four manufacturers

A revised model is described for computing the nonlinear response of low-background Si:X photoconductive detectors to a given flux variation. The model gives results in good agreement with measured responses to large-amplitude sine wave and square wave flux modulations and implies a simple measurement procedure for calibrating a detector's nonlinear response.

Nonlinear response of low-background extrinsic silicon detectors. 2: A revised model

Extrinsic photoconductive silicon detectors operated in the infrared at low-background flux and high bias voltage respond nonlinearly to strongly modulated illumination. They can exhibit a dc nonlinear response even at low bias. We present a simple mathematical prescription for computing the output corresponding to a given input signal. This phenomenological model predicts results in reasonable agreement with measured response data for square wave input modulation.

Nonlinear response of low-background extrinsic silicon detectors. 1: A phenomenological model.

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Nonlinear response of low-background extrinsic silicon detectors. 1: A phenomenological model.