A document describes a three-stage passive radiative cooler for a cryogenic spectrometer to be launched into a low orbit around the Moon. This cooler is relatively lightweight and compact, and its basic design is scalable and otherwise adaptable to other applications in which there are requirements for cooling instrumentation in orbit about planets.
The cooler includes multiple lightweight flat radiator blades alternating with cylindrical parabolic infrared reflectors. The radiator blades are oriented at an angle chosen to prevent infrared loading from the Moon limb at the intended orbital altitude and attitude. The reflectors are shaped and oriented to position their foci outside the radiator surfaces. There are six radiatorblade/ reflector pairs — two pairs for each stage of cooling. The radiator blades and reflectors are coated on their front and back surfaces with materials having various infrared emissivities, infrared reflectivities, and solar reflectivities so as to maximize infrared radiation to cold outer space and minimize inadvertent solar heating. The radiator blades and reflectors are held in place by a lightweight support structure, the components of which are designed to satisfy a complex combination of thermal and mechanical requirements.
This work was done by Jose I. Rodriguez of Caltech for NASA's Jet Propulsion Laboratory.
Refer NPO-44960.
This Brief includes a Technical Support Package (TSP).
Multistage Passive Cooler for Spaceborne Instruments
(reference NPO-44960) is currently available for download from the TSP library.
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Overview
The document outlines the development and technical specifications of a Multistage Passive Cooler designed for spaceborne instruments, particularly for NASA's Moon Mineralogy Mapper (M3) instrument, which is part of India's Chandrayaan-1 mission. The cooler is intended to meet the stringent thermal requirements of cryogenic spectrometers, which require cooling at temperatures of 150K for detectors and 180K for optical benches, with a critical stability requirement of 250mK for the optical bench's orbital temperature gradient.
The passive cooler operates without electrical power, generating no vibration and boasting a long lifespan, making it ideal for applications requiring cooling above 80K. It utilizes the emissive power of radiator surfaces with high emissivity thermo-optical coatings to reject heat effectively. The design incorporates multiple stages of cooling, with each stage thermally isolated to enhance overall system performance. The cooler's effectiveness is influenced by the energy balance between cooling power, parasitic heat loads, and radiated power.
Key components of the cooler include parabolic reflectors and radiator blades, which are designed for high thermal efficiency and low emissivity surfaces. The reflectors are crucial for directing thermal radiation, while the radiator blades are constructed with high aspect ratios and mounted on a lightweight frame to minimize heat loads. The design also features flexible conductive thermal links to reduce the impact of mechanical loads on sensitive optics and detectors.
The document emphasizes the importance of minimizing parasitic heat loads, which can arise from internal conduction, radiation, and external environmental factors. By positioning the passive cooler on the anti-sun side of the spacecraft, direct solar flux can be effectively neglected, further enhancing cooling efficiency.
Overall, this innovation represents a significant advancement in cryogenic cooling technology for space applications, providing a reliable and efficient solution for future NASA missions and other aerospace endeavors. The document serves as a technical support package, detailing the cooler's design, functionality, and potential applications in the field of space science.
