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.
The Probe far-Infrared Mission for Astrophysics (PRIMA) contains two instruments: an imager (PRIMAGER) and a multi-band spectrometer (FIRESS). These two instruments require detector cooling to 100 mK and require parts of the optical train to operate at 1.0 K. From a base temperature of 4.5 K, provided by a JWST-like cryocooler, a 5-stage Continuous Adiabatic Demagnetization Refrigerator (CADR) will provide this cooling to both instruments. The PRIMA CADR is based on heritage parts from the Hitomi and the X-Ray Imaging and Spectroscopy Mission (XRISM) ADRs and from recent Strategic Astrophysics Technology (SAT)-developed hardware. The CADR will provide 700 microW of lift at 1.0 K and 9 microW of lift at 100 mK to meet the two instruments (PRIMAGER and FIRESS) cooling requirements with a factor of 2 margin. The CADR is designed to reject a maximum of 8 mW at the 4.5 K cryocooler heat sink. This paper will describe the CADR, its requirements, its operation, and its heritage.
The PRobe far Infrared Mission for Astrophysics (PRIMA) is a mission concept for a NASA cryogenic observatory in an Earth-Sun L2 halo orbit, designed to reveal how abundant elements are built up in galaxies over cosmic time. To achieve the target sensitivity in the wavelength range of 25 to at least 200 microns, its wideband spectrometer and multiband spectrophotometric imager/polarimeter need to operate at 0.1 K, and its primary mirror and relay optics need to be at 4.5 K. To meet these cooling needs, the PRIMA study team is designing a cryogen-free cooling system with a combination of passive radiators and thermal shields, a hybrid mechanical cooler and a continuous Adiabatic Demagnetization Refrigerator system. The PRIMA mechanical cooler is slightly modified JWST Mid-Infrared Instrument (MIRI) cooler that uses 3He as the working fluid in its JT stage. This paper first discusses the overall thermal requirements and the system's thermal architecture and then describes the main thermal subsystems in the cryocooling chain. Finally, the paper presents compressor and 3He Joule-Thomson (JT) effect test results to validate the predicted performance of PRIMA’s 4.5 K mechanical cryocooler.
The Galaxy Evolution Probe (GEP) is a concept for a mid- and far-infrared space observatory to measure key properties of large samples of galaxies with large and unbiased surveys. GEP will attempt to achieve zodiacal light and Galactic dust emission photon background-limited observations by utilizing a 6-K, 2.0-m primary mirror and sensitive arrays of kinetic inductance detectors (KIDs). It will have two instrument modules: a 10 to 400 μm hyperspectral imager with spectral resolution R = λ / Δλ ≥ 8 (GEP-I) and a 24 to 193 μm, R = 200 grating spectrometer (GEP-S). GEP-I surveys will identify star-forming galaxies via their thermal dust emission and simultaneously measure redshifts using polycyclic aromatic hydrocarbon emission lines. Galaxy luminosities derived from star formation and nuclear supermassive black hole accretion will be measured for each source, enabling the cosmic star formation history to be measured to much greater precision than previously possible. Using optically thin far-infrared fine-structure lines, surveys with GEP-S will measure the growth of metallicity in the hearts of galaxies over cosmic time and extraplanar gas will be mapped in spiral galaxies in the local universe to investigate feedback processes. The science case and mission architecture designed to meet the science requirements is described, and the KID and readout electronics state of the art and needed developments are described. This paper supersedes the GEP concept study report cited in it by providing new content, including: a summary of recent mid-infrared KID development, a discussion of microlens array fabrication for mid-infrared KIDs, and additional context for galaxy surveys. The reader interested in more technical details may want to consult the concept study report.
The Origins Survey Spectrometer (OSS) is a multi-purpose far-IR spectrograph for Origins. Operating at the photon background limit, OSS covers the 25- to 588-μm wavelength range instantaneously at a resolving power (R) of 300 using six logarithmically spaced grating modules. Each module couples at least 30 and up to 100 spatial beams simultaneously, enabling true [three-dimensional (3D)] spectral mapping. In addition, OSS provides two high-resolution modes. The first inserts a long-path Fourier-transform spectrometer (FTS) into a portion of the incoming light in advance of the grating backends, enabling R up to 43 , 000 × [ λ / 112 μm ] , while preserving the grating-based sensitivity for line detection. The second incorporates a scanning etalon in series with the FTS to provide R up to 300,000 for the 100-to 200-μm range.
OSS on Origins is designed to decode the cosmic history of nucleosynthesis, star formation, and supermassive black hole growth with wide-area spatial-spectral 3-D surveys in the 30 to 670 micron band. Six wideband grating modules combine to cover the full band at R=300, each couples a long slit with at least 30 beams on the sky. Two high-resolution modes are provided: one incorporates an interferometer in front of the gratings providing R of more than 40,000 at 112 microns, the other adds an etalon for R>300,000 at 112 microns. The full system design is presented, including optics, detector arrays, readouts, and the thermal design.
The OSS on the Origins Space Telescope is designed to decode the cosmic history of nucleosynthesis, star formation, and supermassive black hole growth with wide-area spatial-spectral 3-D surveys across the full 25 to 590 micron band. Six wideband grating modules combine to cover the full band at R=300, each couples a long slit with 60-190 beams on the sky. OSS will have a total of 120,000 background-limited detector pixels in the six 2-D arrays which provide spatial and spectral coverage. The suite of grating modules can be used for pointed observations of targets of interest, and are particularly powerful for 3-D spectral spectral surveys. To chart the transition from interstellar material, particularly water, to planetary systems, two high-spectral-resolution modes are included. The first incorporates a Fourier-transform spectrometer (FTS) in front of the gratings providing resolving power of 25,000 (δv = 12 km/s) at 179 µm to resolve water emission in protoplanetary disk spectra. The second boosts the FTS capability with an additional etalon (Fabry-Perot interferometer) to provide 2 km/s resolution in this line to enable detailed structural studies of disks in the various water and HD lines. Optical, thermal, and mechanical designs are presented, and the system approach to the detector readout enabling the large formats is described.
The Galaxy Evolution Probe (GEP) is a concept for a mid and far-infrared space observatory designed to survey sky for star-forming galaxies from redshifts of z = 0 to beyond z = 4. Furthering our knowledge of galaxy formation requires uniform surveys of star-forming galaxies over a large range of redshifts and environments to accurately describe star formation, supermassive black hole growth, and interactions between these processes in galaxies. The GEP design includes a 2 m diameter SiC telescope actively cooled to 4 K and two instruments: (1) An imager to detect star-forming galaxies and measure their redshifts photometrically using emission features of polycyclic aromatic hydrocarbons. It will cover wavelengths from 10 to 400 μm, with 23 spectral resolution R = 8 filter-defined bands from 10 to 95 μm and five R = 3.5 bands from 95 to 400 μm. (2) A 24 – 193 μm, R = 200 dispersive spectrometer for redshift confirmation, identification of active galactic nuclei, and interstellar astrophysics using atomic fine-structure lines. The GEP will observe from a Sun-Earth L2 orbit, with a design lifetime of four years, devoted first to galaxy surveys with the imager and second to follow-up spectroscopy. The focal planes of the imager and the spectrometer will utilize KIDs, with the spectrometer comprised of four slit-coupled diffraction gratings feeding the KIDs. Cooling for the telescope, optics, and KID amplifiers will be provided by solar-powered cryocoolers, with a multi-stage adiabatic demagnetization refrigerator providing 100 mK cooling for the KIDs.
KEYWORDS: Mirrors, Amplifiers, Thermal modeling, Space telescopes, Sensors, Telescopes, Beryllium, Space operations, James Webb Space Telescope, Galaxy evolution
The Galaxy Evolution Probe (GEP) is a proposed far infrared-optimized observatory designed for zodiacal-light-limited imaging and spectroscopy in the 10 to 250 micron band. The GEP telescopes and instruments are planned to be actively cooled with the system in a sun-earth L2 halo orbit. A detailed description of the GEP mission concept is documented in [1]. Crucial to the scientific performance of GEP is the thermal architecture; it must support a range of cryogenic elements, ranging from the full telescope optical assembly at around 4 K to the far-IR focal planes consisting of kinetic inductance detector (KID) arrays cooled to 100 mK. Given the mass operating at these low temperatures, the thermal system is one of the main drivers of mission cost and complexity. We present a solution to the GEP thermal design that is realizable within a probe-class envelope. The baseline system utilizes a multi-stage adiabatic demagnetization refrigerator (ADR) for the 100mK base; the ADR system also provides an intercept at 1K. ADR systems similar to that in our design have flown, and among sub-K options, ADRs offer high Carnot efficiency. The ADR rejects heat to a hybrid Joule Thompson (JT) and Stirling or PT Cryocooler with a lowtemperature stage at 4 K as well as an intercept at 20 K. These coolers are also mature systems with flight heritage on most subcomponents.
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