Design, implementation, and performance of the primary reflector for SALTUS

We describe the space observatory architecture and mission design of the Single Aperture Large Telescope for Universe Studies (SALTUS) mission, a National Aeronautics and Space Administration (NASA) Astrophysics Probe Explorer concept. SALTUS will address key far-infrared science using a 14-m diameter <45 K primary reflector (M1) and will provide unprecedented levels of spectral sensitivity for planet, solar system, and galactic evolution studies and cosmic origins. Drawing from Northrop Grumman's extensive NASA mission heritage, the observatory flight system is based on the LEOStar-3 spacecraft platform to carry the SALTUS Payload. The Payload is comprised of the inflation control system, sunshield module (SM), cold corrector module (CCM), warm instrument electronics module, and primary reflector module (PRM). The 14-m M1 is an off-axis inflatable membrane radiatively cooled by a two-layer sunshield (∼1000 m 2 per layer). The CCM corrects for residual aberration from M1 and delivers a focused beam to two instruments-the High-Resolution Receiver (HiRX) and SAFARI-Lite. The CCM and PRM reside atop a truss-based composite deck that also provides a platform for the attitude control system. The SALTUS 5-year mission lifetime is driven by a two-consumable architecture: the propellant system and the inflation control system. The core interface module (CIM), a multi-faceted composite truss structure, provides a load path with high stiffness, mechanical attachment, and thermal separation between the Payload and spacecraft. The SM attaches outside the CIM with its aft end integrating directly to the bus. The spacecraft maintains an attitude off M1's boresight with respect to the Sun line to facilitate the <45 K thermal environment. SALTUS will reside in a Sun-Earth halo L2 orbit with a maximum Earth slant range of 1.8 million km, thereby reducing orbit transfer delta-v. The instantaneous field of regard provides two continuous 20 deg viewing zones around the ecliptic poles, resulting in full sky coverage in 6 months.

SALTUS probe class space mission: observatory architecture and mission design

Harding,

Arenberg,

Donovan

et al. 2024

Milky Way and nearby galaxy science with the SALTUS space observatory

Levy,

Tielens,

Spilker

et al. 2024

We present an overview of the Milky Way (MW) and nearby galaxy science case for the Single Aperture Large Telescope for Universe Studies (SALTUS) far-infrared (IR) NASA probe-class mission concept. SALTUS offers enormous gains in spatial resolution and spectral sensitivity over previous far-IR missions due to its cold (<40 K) 14-m primary mirror. Key MW and nearby galaxy science goals for SALTUS focus on understanding the role of star formation in feedback in the local universe. In addition to this science case, SALTUS would open a new window to galactic and extragalactic communities in the 2030s, enabling fundamentally new questions to be answered, and would be a far-IR analog to the near-and mid-IR capabilities of the James Webb Space Telescope. We summarize the MW and nearby galaxy science case and plans for notional observing programs in both guaranteed and guest (open) times.

High-Resolution Receiver for the Single Aperture Large Telescope for Universe Studies

Silva,

Walker,

Kulesa

et al. 2024

The High-Resolution Receiver (HiRX) is one of two instruments of the Single Aperture Large Telescope for Universe Studies (SALTUS), a mission proposed to NASA's 2023 Astrophysics Probe Explorer. SALTUS employs a 14 m aperture, leading to a 16-fold increase in collecting area and a factor of 4 increase in the angular resolution with respect to the Herschel Space Telescope. It will be radiatively cooled to ≤ 45 K and has a planned duration of >5 years. HiRX consists of four bands of cryogenic heterodyne receivers with a high sensitivity and high spectral resolution, being able to observe the gaseous components of objects across the far-IR. HiRX is going to detect water, HD, and other relevant astrophysical lines while resolving them in velocity. HiRX covers the following frequency ranges: Band 1 from 455 to 575 GHz, Band 2 from 1.1 to 2.1 THz, Band 3 from 2.475 to 2.875 THz, and Band 4 for both 4.744 and 5.35 THz. Bands 1 to 3 contain single, high-performance mixers. Band 4 consists of an array of seven hexagonally packed pixels, where the central pixel operates as a heterodyne mixer. Band 1 utilizes superconductinginsulator-superconducting mixers (SIS), whereas Bands 2 to 4 use superconducting hot electron bolometers (HEB) mixers. The local oscillator (LO) system uses frequency-multiplier chains for Bands 1 and 2, and quantum cascade lasers for Bands 3 and 4. Autocorrelator spectrometers are used to process the intermediate frequency (IF) signals from each science band, providing instantaneous frequency coverage of 4 to 8 GHz for Band 1 and 0.5 to 4 GHz for Bands 2 to 4. SALTUS will also fly a chirp transform spectrometer system for high spectral resolution observations in Band 1.