Simon Calcutt

Abstract:

Plain Language Summary: Earth absorbs energy emitted by the Sun, radiating some of that as heat back into space. The energy exchange between Earth and space drives weather and climate. Scientists measure and track this energy using satellite instruments that can identify which parts of Earth's surface and atmosphere emit specific portions of the overall heat radiated into space. But these instruments are complicated and expensive, and until now, no one has built a sensor that can look at and separate all of Earth's heat emissions in a systematic way. The Polar Radiant Energy in the Far‐InfraRed Experiment (PREFIRE) has developed a novel instrument that combines simple, miniaturized heat sensors with specially shaped optics and microelectronics to provide such measurements to further our understanding of the planet's weather and climate. Furthermore, implementation of the sensors has been done within a cost‐capped mission profile that encourages development of a sustainable sensor system for Earth monitoring. This manuscript describes the instrument design, including its components and their characteristics, the system and its functionality, its trade‐offs, cost limitations, and testing and performance information. PREFIRE began operating two of these instruments in space in 2024, in order to start quantifying the heat exchange processes in Earth's polar regions.

Abstract:

In this paper, the improved design of an Ice Giants Net Flux Radiometer (IG-NFR), for inclusion as a payload on a future Uranus probe mission, is given. IG-NFR will measure the net radiation flux, in seven spectral bands, each with a 10° Field-Of-View (FOV) and in five viewing angles as a function of altitude. Net flux measurements within spectral filter bands, ranging from solar to far-infrared, will help derive radiative heating and cooling profiles, and will significantly contribute to our understanding of the planet’s atmospheric heat balance and structure, tropospheric 3-D flow, and compositions and opacities of the cloud layers. The IG-NFR uses an array of non-imaging Winston cones integrated to a matched thermopile detector Focal Plane Assembly (FPA), with individual bandpass filters and windows, housed in a vacuum micro-vessel. The FPA thermopile detector signals are read out in parallel mode, amplified and processed by a multi-channel digitizer application specific integrated circuit (MCD ASIC) under field programmable gate array (FPGA) control. The vacuum micro-vessel rotates providing chopping between FOV’s of upward and downward radiation fluxes. This unique design allows for small net flux measurements in the presence of large ambient fluxes and rapidly changing temperatures during the probe descent to ≥10 bar pressure.

Abstract:

Based on preflight laboratory testing, an unexpectedly large positional offset between the two midinfrared (mid-IR) detector arrays in the Cassini composite infrared spectrometer (CIRS) instrument has been noted in the literature. A much smaller offset was measured in-flight. We investigate this discrepancy by estimating several spatial relationships among the detectors and comparing these results with three independent data sets. This enables us to infer the probable cause of this offset and to derive a new reduced value. We comment on the effect that this change could have on previously published results involving CIRS data. We also present a graphical display of the arrays projected on the sky as CIRS would see it.