On-orbit absolute temperature calibration using multiple phase change materials: overview of recent technology advancements

Results from recent vacuum testing of an on-orbit absolute radiance standard (OARS) intended for the next generation of infrared remote sensing instruments

“…The concept for using miniature phase transition cells to calibrate imbedded blackbody cavity thermistors is illustrated in Figure 3, which shows a typical transient temperature response (signature) from one of the blackbody cavity thermistors during a gallium (<1 gram) melt event. 10,11 At the start of the melt process the blackbody cavity is brought to thermal stability in the constant temperature mode about 50 mK under the expected phase change temperature. Then the blackbody controller is switched into constant power mode using a power level that would bring the cavity to about 100 mK above the expected phase change temperature.…”

“…This allows the melt behavior for a given system to be fully characterized, and was used as a metric in the validation of the housing design that underwent extensive accelerated lift testing designed to simulate 7 years on orbit. 10,11 A thermistor temperature sensor is calibrated using this scheme by measuring its resistance during the mid melt plateau.…”

The University of Wisconsin Space Science and Engineering Center Absolute Radiance Interferometer (ARI): instrument overview and radiometric performance

“…The OARS uses transient temperature melt signatures from three (or more) different phase change materials to provide absolute calibration for the blackbody thermistor sensors covering a wide, continuous range of temperatures [7][8][9]. The system uses very small masses of phase change material (<1 g), making it well suited for spaceflight application.…”

“…The OARS is a source that will be used to maintain SI traceability of the radiance spectra measured by the calibrated interferometer sensor [7][8][9]; (2) On-orbit Cavity Emissivity Modules (OCEMs), providing a source (quantum cascade laser (QCL) or "Heated Halo") to measure any change in the cavity emissivity of the OARS and calibration reference sources [10][11][12][13];…”

On-orbit absolute radiance standard for the next generation of IR remote sensing instruments

“…This allows the melt behavior for a given system to be fully characterized, and was used as a metric in the validation of the housing design that underwent extensive accelerated lift testing designed to simulate 7 years on orbit. 17 A thermistor temperature sensor is calibrated using this scheme by measuring its resistance during the mid melt plateau.…”