Description: The PALETTE PRR for LuSEE-Night project is a follow-on to the Planetary and Lunar Environment Thermal Toolbox Elements (PALETTE) project, which was a 3-year effort (from April 2020 to July 2023) that successfully developed passive thermal management tools necessary for future instrument/system operation in extreme environments. One of those key tools was an affordable, easily fabricated, low sink temperature parabolic reflector radiator (PRR). The goal of the PALETTE PRR for LuSEE-Night project is to adapt PALETTE PRR technology to the Lunar Surface Electromagnetics Experiment Night Version (LuSEE-Night) mission, which will perform radio astronomy (21 cm cosmology) from an ultra-quiet low latitude lunar farside site in 2026. The key PALETTE PRR for LuSEE-Night technology area to be advanced is the design and development of flight-ready PRRs for low latitude lunar missions. ThePALETTE PRR for LuSEE-Night project is a 14-month effort to design, build, test, and deliver flight PRR reflectors to the LuSEE-Night mission. This project will also design, build, and test a subscale PRR (1/9th of full-size) that will be random vibration (RV) and thermal vacuum (TVAC) tested. The LuSEE-Night mission will land at a 20 degree South latitude site on the farside of the Moon in 2026 and plans to operate there for 24 lunar day/night cycles (2 Earth years). Due to its top mounted solar panels and science equipment, LuSEE-Night needs a side-facing, low sink temperature PRR to reject heat during the hot lunar day, where surface temperatures at lunar noon can reach 385 K. The key performance parameter (KPP) for this project is a PRR radiative sink temperature of 231 K. In TVAC testing, the measured PRR radiative sink temperature that was achieved with the subscale PRR test unit was 239 K. This level of PRR performance, while falling a little short of the project goal, will still (easily) enable the LuSEE-Night instrument to stay within its temperature limits over the course of the entire mission.

Benefits: The primary benefit of the PRR is allowing science payloads at low latitude sides with side-facing radiators to achieve low radiative sink temperatures and thus enable their internal components to stay within operating limits during the lunar day. At the lunar equator for example, where surface temperatures at lunar noon can reach 400 K, the radiative sink temperature provided by a conventional (non-PRR) side-facing radiator, one thatdivides its radiative view equally between the lunar surface at 400 K and space at 0 K, is 336 K. This high sink temperature would simply not be viable for typical science payloads that utilize electronics and batteries that must be kept below 313 K. Conceptually, a PRR works by reflecting both radiated IR (heat from the instrument) and surface IR (heat from the lunar surface). The PALETTE PRR is a very simple two-piece design involving a finned radiator plate and a reflector with parabolic blades. To achieve a low sink temperature, a PRR must reflect away a large percentage of the lunar surface IR flux. Typically, a minimum of 95% of the lunar surface IR flux must be reflected away. With this level of performance, a PRR can potentially achieve sink temperatures in the range of 225-245 K. A PRR thus allows lunar instruments with side-facing radiators operating at low latitude sites on the lunar surface to run at temperatures of less than 300 K.