Description: The Planetary and Lunar Environment Thermal Toolbox Elements (PALETTE) project was a 3-year effort (completed in July 2023) to develop the passive thermal management tools necessary for future instrument/system operation in extreme environments. The overarching objective was to ensure that a full "palette" of TRL6 or higher thermal "toolbox" elements is available so that engineers are able to create passive, ultra-isolative thermal designs for science instruments on a variety of carriers in lunar/planetary extreme environments. PALETTE technology focus areas have included: 1-enclosures; 2-radiators; 3-insulation/MLI; 4-thermal isolators; 5-gimbals; 6-thermal switches; 7-thermal transport devices; 8-thermal storage devices; 9-deployables/antennae; and 10-low heat loss feed-throughs. PALETTE was programmatically structured with 4 design/build/test efforts (Tasks 1-4), which have been completed, and 4 analysis/study efforts (Tasks 5-8),which have also been completed. Task 1 has focused on thermally-switched enclosures (TSE) composed of high performance radiative/conductive isolation that uses a new MLI (from Task 3) and Vectran tension cable (VTC) structural supports, in concert with a passive thermal switching system that employs a reverse-operation DTE thermal switch (ROD-TSW) in series with a propylene miniaturized loop heat pipe (mini-LHP). Task 2 has developed/demonstrated affordable parabolic reflector radiators (PRR) that can provide a low radiative sink temperature to keep mid-to-low latitude lunar payloads cool. Task 3 has developed/demonstrated new high-performance radiative insulation known as "spacerless MLI" that is at least 13X better than conventional MLI. Task 4 has developed/demonstrated new low conductance thermal isolators composed of low thermal conductivity 3D-printable polymers. Task 5 analytically studied gimbaled IR cameras that can search for lunar water. Task 6 analytically studied combinations of thermal transport/switching/storage that can solve key problems. Task 7 analytically studied configurations to systematically reduce the heat leak due to wiring and apertures. Lastly, Task 8 analytically studied scalability, extensibility, and planetary use. Following the conclusion of PALETTE in July 2023, NASA STMD initiated a follow-on GCD project involving the flight demonstration of PALETTE Task 2 PRR technology in support of the Lunar Surface Electromagnetics Experiment Night Version (LuSEE-Night). LuSEE-Night is slated to land at a low latitude site on the lunar farside in 2026 and to operate there for 24 lunar day/night cycles (2 Earth years). LuSEE-Night will make 21 cm radio astronomy measurements from the quiet RF environment afforded by the lunar farside. LuSEE-Night needs a PRR to provide a low sink temperature for operation during the exceedingly hot lunar day, where surface temperatures at its low latitude site will reach 380 K or higher.

Benefits: NASA has a renewed emphasis on lunar/planetary exploration that has resulted in science instruments being developed that are smaller, distributed, and possibly networked. If radioisotopes are to be avoided in thermally managing these payloads in extreme environments such as the Moon and inner/outer planetary destinations, existing thermal management capabilities will not meet future needs. Science instruments include magnetometers, seismometers, IR spectrometers, radiation detectors, particle analyzers, electric field instruments, and others. PALETTE was structured to meet the need by increasing thermal toolbox element TRL via four design/build/test tasks and four analysis/study tasks. The specific design/build/test task benefits that were targeted and were ultimately achieved during the PALETTE project include development of new thermal toolbox elements such as (1) low heat loss thermally-switched enclosures (TSE), (2) highly affordable low sink temperature parabolic reflector radiators (PRR), (3) ultra-low effective emissivity spacerless multilayer insulation (SMLI), and (4) ultra-low conductance thermal isolators (LCTI). The specific analysis/study task benefits that were targeted and were ultimately achieved during the PALETTE project include the development of quantitative methods for ranking (a) gimbaled IR camera architectures, (b) combined thermal transport/switching/storage architectures, (c) low heat loss feed-through architectures, and (d) scalability/extensibility/planetary use architectures. Mission infusion during PALETTE has been very rapid as PALETTE technologies are already being used on the Farside Seismic Suite (FSS) and the Lunar Surface Electromagnetics Experiment Night Version (LuSEE-Night), which are currently scheduled to travel to the lunar farside (FSS to a high latitude site and LuSEE-Night to a low latitude site) in 2025 and 2026, respectively.