This PDF file contains the front matter associated with SPIE Proceedings Volume 13146, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Multiple new technologies relevant to sensing, calibration, and data exploitation are now coming online that have the potential to enable higher-performance observing systems (better resolution and sensitivity, broader coverage, etc.) that are also smaller and offer cost savings relative to conventional approaches for development, launch, and operations. Pre-flight laboratory prototyping and demonstration are the logical first steps in bringing these new technologies along a path to infusion in a flight mission, but it is often the case that some form of in-space validation is needed to prove out all relevant elements of a new observing system in an operational context. CubeSats and SmallSats, coupled with relatively low-cost launch options now available on rideshares, are facilitating this validation in multiple ways. Here we discuss two NASA earth observing projects that are in two very different phases of mission implementation: TROPICS, an earth venture mission now in its operational phase, and CREWSR, an instrument prototyping project funded by the NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP). TROPICS was preceded by multiple in-space validation missions (most recently the Pathfinder mission), and CREWSR is now proceeding successfully along a path to be ready for a future in-space validation mission. In this paper, we provide some experiences, conclusions, and lessons learned from each of these two efforts along their project lifecycles.

PolSIR is the latest Earth Venture Instrument class missions to addresses key research priorities related to uncertainties in our current understanding in ice clouds. The PolSIR mission consists of two 16U CubeSats, each equipped with a cross-track scanning polarized submillimeter radiometer near 325 and 684 GHz. The two PolSIR satellites fly in separate, 52-degree inclination, non-sun-synchronous orbits, to measure the diurnal variation of cloud ice and its microphysical properties on a monthly basis in the tropics and sub-tropics.

The mission is PI-led by Vanderbilt University. NASA Goddard will provide the project management team that builds the two instruments, while science operations will be conducted by the Space Science and Engineering Center at the University of Wisconsin. The two spacecraft will be built by Blue Canyon Technologies. Launch of the two satellites is currently anticipated for late 2027.

The Libera instrument is being developed as part of a NASA Earth Venture Continuity mission for extending Earth radiation budget (ERB) measurements by the currently operational Clouds and the Earth’s Radiant Energy System (CERES) instruments into the future. Libera will be launched on NOAA’s JPSS-4 satellite. Libera introduces several new technologies, including advanced VACNT detectors, a split-shortwave channel to quantify shortwave near-IR and visible radiation, and a wide field of view camera (WFC) that advance the state-of-the-art in Earth radiation budget measurements. The WFC is a monochromatic wide field of view camera operating at 555nm over a 123-degree field of view that will continuously observe the full Earth disk from low-earth orbit. The WFC provides a unique capability for scene identification and Angular Distribution Model (ADM) generation that complements similar measurements from the VIIRS instrument that will fly on JPSS-4 with Libera. By demonstrating that Libera’s WFC provides the data required for ADM development, a path forward for future free-flier ERB measurements will be explored. We focus on the development of the WFC, its science objectives, unique design features, its current state of development, and how it could help to enable a constellation of smaller, more cost-effective ERB instruments for the future.

The NASA Earth Science Technology Office (ESTO) selected the Pyro-atmosphere Infrared Sounder (PIRS) airborne demonstration as part of its FireTech program in May of 2023. Upon completion, the PIRS will be flown in an aircraft to measure temperature and water vapor profiles, and total column carbon monoxide, above and in the vicinity of wildfires to support fire prediction and suppression efforts and scientific investigations of the meteorology of wildfires. The PIRS incorporates a wide field all refractive grating spectrometer operating in the MWIR region of the spectrum with 640 spectral channels from 4.08-5.13μm. The PIRS optics assembly was developed by BAE SYSTEMS for the CubeSat Infrared Atmospheric Sounder (CIRAS) project, as part of an earlier NASA and NOAA technology maturation program in support of reducing the size of infrared sounding instruments for space applications. Through the PIRS airborne flight development and demonstration, the full performance capabilities of the CIRAS instrument will have been demonstrated and build confidence in the performance expected from a future CIRAS spaceflight mission.

Catastrophic bushfires are becoming increasingly prevalent as climate change advances. Impacts extend beyond national borders. Multinational efforts can inform new science and management practices. Space-based sensors and integrated data facilities will play an important role. This paper describes a collaborative project between a consortium of Australian universities and NASA Centers to develop and implement a small satellite platform comprising highly integrated thermal and lightning sensors coupled with AI-based edge computing to help predict, detect, and track bushfires, supporting mitigation activities. This will fill an important capability gap since Australia does not currently have any sovereign Earth observation satellites. This program is enabled by and builds on Australia-NASA collaboration and will also support fire science and management activities in the broader global context.

Determining the abundance, origin, movement, and storage of water on the Moon with far greater certainty is an ongoing primary goal of lunar exploration. Essential constraints would come from measuring water absorption features repeatedly over the same swaths as a function of time of day from a nearly polar orbit with equatorial periapsis, the goal proposed for BIRCHES (Broadband InfraRed Compact High Resolution Exploration Spectrometer) on the original Lunar Ice Cube mission. Establishing these constraints would be the goal of CLEW, Compact Lunar Explorer for Water, the instrument described in this paper. CLEW has mass, volume, and power requirements comparable but performance, including imaging capability, greatly improved relative to BIRCHES. High heritage CLEW would utilize the NASA GSFC Compact Thermal Imager (CTI), state of the art self-calibrating focal plane array combined with SIDECAR ASIC instrument electronics, combined with an active cooling system and optics similar to CLuHME (Compact Lunar Hydration and Mineralogy Experiment). The platform would likely be significantly more robust and ‘roomy’, due to availability of high-performance thermal protection components and a larger 12U platform. Planned addition of a compact context camera would enhance image interpretation.

The presence of water hydrating the Moon’s regolith is now well established, with an observed maximum abundance in the polar regions and near the terminator at all latitudes, reducing to a minimum near surface temperature maximum at equatorial noon. The next major step forward will be to determine the distribution of neutral water and hydroxyl radicals (total water) on the Moon, to understand its variability with time and location, to quantify its abundance, and to determine its resupply mechanisms, if any. Of particular interest is identifying the mineral context of regolith hosting water and determining which mineral resources, if any, may also be superior water resources. We describe the value of a global mapping campaign to achieve these goals with suitable instrumentation to detect and distinguish between neutral water and hydroxyl in surface mineral hydrates. Future targeted measurements at high spatial resolution can be fit into the context of global processes.

Past and current laser altimeter instruments in planetary research have high requirements in terms of mass, power and volume. We present a novel less resource-demanding concept based on single-photon counting techniques. The instrument concept was utilized in a flight campaign of which the setup and the data analysis is presented. A small-satellite mission to the Moon is outlined as well as further potential for miniaturization of the instrument concept.

Pointing, Acquisition, and Tracking (PAT) are critical aspects of both uplink and downlink Free Space Optical (FSO) communications systems, ensuring precise targeting of the optical signal from the transmitter to the receiver. PAT systems provide steering and tracking capabilities in order to establish and maintain an optical link, compensating for the relative satellite motion, atmospheric turbulence, vibration and jitter.

A novel method for achieving closed loop control between the steering mirrors of a dual channel free space optical communications terminal is presented. By modifying an off-the-shelf open loop stick-slip actuator, the control system achieves a pointing resolution of 0.002° with under a 15% increase in mass, resulting in a light weight solution suitable for small satellites.

A NASA-ESTO SLI-T grant-funded effort for Improved Radiometric calibration of Imaging Systems (IRIS), was awarded to Raytheon and developed in partnership with LabSphere to address the demonstration of a compact, high-performance, full-spectrum VNIR-to-LWIR Jones source prototype calibrator for use in spaceborne payloads. The resulting IRIS calibrator system employs LEDs, SLDs, and an integrated blackbody source, and has been advanced to a performance-validated state. The IRIS system enables accurate entrance pupil aperture radiometric calibration of telescope-acquired imagery on-demand in wavelengths from <0.4microns to >13microns. This system is of particular value to small earth observing payloads that lack radiometric fidelity in their imagery, or that rely on infrequent non-contemporaneous vicarious methods for radiometric knowledge. IRIS calibrator test results are discussed, including a summary of tests and lessons-learned in fabrication of this small, lightweight integrated system, that when fielded will provide substantial value to SmallSat imaging payloads now and over the coming decades.

5 mm diameter silicon photodiodes having 30-50 nm electrically active thicknesses were fabricated on silicon-on insulator (SOI) wafers to realize solar blind UV photodiodes (UVTN). Their responsivity measurements in the 200-1100 nm range indicated that responsivities drop sharply after 350 nm. Silicon direct bandgap is 3.5 eV which corresponds to 354 nm. Thus, these devices act as wide band gap semiconductor photodiodes like SiC, GaN, AlGaN, diamond etc. UV/VUV/EUV filters can be directly deposited on UVTN detectors to limit their response to specific wavelengths. Four filtered UVTN photometers devoid of chronic red leak and associated electronics will fit in a 1 U CubeSat which can be used to make solar UV/VUV/EUV spectral measurements. Because of their minuscule silicon thickness, UVTN detectors will have low responsivity to x-rays and other space radiation and also will be very hard to space radiation. Thus, these devices are expected to survive in the deep space environment for several decades for applications like water detection (165 nm strong reflection) on small bodies as desired by NASA’s Small Bodies Assessment Group. As the solar blind material is silicon which is high volume manufacturing compatible, this is a disruptive technology development and will have numerous application in space research. For example, one may use UVTN pixels in an imaging array to get a true solar blind (no red leak) UV/VUV/EUV imager with 100% IQE.