The Southern African Large Telescope (SALT) is a 10-m class fixed-elevation telescope with a primary mirror composed of 91 spherically figured one metre segments. A prime focus tracker assembly carries the spherical aberration corrector (SAC) and two of SALT’s instruments, SALTICAM (the acquisition and imaging camera) and the multi-purpose Robert Stobie spectrograph (RSS). Included in the tracker payload is a fibre-instrument feed, that positions ~45m long fibre cables coupled to the spectrographs in thermal enclosures beneath the telescope. These are the High-Resolution Spectrograph (HRS) and NIRWALS (Near InfraRed Washburn Astronomical Laboratories Spectrograph). The other major undertaking is a custom-built laser frequency comb and precision radial velocity data pipeline for the HRS, due in 2025. A novel RSS slit-mask IFU was recently commissioned, adding optical IFU spectroscopy to SALT’s capabilities. Work is also underway to develop a new red channel to turn the RSS into a dual-beam spectrograph. A study done in 2021 investigated the feasibility of building deployable robotic arms equipped with mini SACs to take advantage of SALT’s huge uncorrected field of view. Lastly, a pre-study is now underway to explore options for replacing the SAC and prime focus payload on the tracker to improve telescope performance and make provision for future instrument development.
The Southern African Large Telescope (SALT) is developing precision radial velocity capability for its high-resolution spectrograph (HRS). The instrument's high-stability (HS) mode includes a fibre double scrambler and makes provision for simultaneous thorium-argon (ThAr) injection into the calibration fibre. Given the limitations associated with ThAr lamps, as well as the cost and complexity of turn-key commercial laser frequency combs (LFCs), we are in the process of designing and building a bespoke LFC for the Red channel of the HRS (555-890 nm). At a later stage we plan to extend the wavelength range of the LFC to include parts of the blue channel (370-555 nm) as well. A data reduction pipeline capable of delivering precision radial velocity results for the HS mode is also currently under development. We aim to have the LFC and PRV pipeline available for science operations in early 2024.
With a focus on off-the-shelf components, Twinkle is the first in a series of cost competitive small satellites managed and financed by Blue Skies Space Ltd. The satellite is based on a high-heritage Airbus platform that will carry a 0.45 m telescope and a spectrometer which will provide simultaneous wavelength coverage from 0.5–4.5 μm. The spacecraft prime is Airbus Stevenage while the telescope is being developed by Airbus Toulouse and the spectrometer by ABB Canada. Scheduled to begin scientific operations in 2025, Twinkle will sit in a thermally-stable, sun-synchronous, low-Earth orbit. The mission has a designed operation lifetime of at least seven years and, during the first three years of operation, will conduct two large-scale survey programmes: one focused on Solar System objects and the other dedicated to extrasolar targets. Here we present an overview of the architecture of the mission, refinements in the design approach, and some of the key science themes of the extrasolar survey.
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