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 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 . 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.
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.