Optical interferometry from space is arguably the most exciting prospect for high angular resolution astrophysics; including the analysis of exoplanet atmospheres. This was highlighted in the recent ESA Voyage 2050 plan, which pointed out the exciting potential of this technology, but also indicated the critical need for technological demonstrators. Here we present the Pyxis interferometer; a ground-based pathfinder for a CubeSat space interferometer, currently being built at Mt Stromlo Observatory. We outline its technological and scientific potential as the only visible wavelength interferometer in the Southern Hemisphere, and the optical systems designed to provide CubeSat compatible metrology for formation flying.
KEYWORDS: Stars, Sensors, Infrared radiation, Infrared imaging, Telescopes, Absorption, Space operations, Infrared telescopes, Infrared detectors, Signal to noise ratio
A wide-field zenith-looking telescope operating in a mode similar to time-delay-integration (TDI) or drift scan imaging can perform an infrared sky survey without active pointing control, but it requires a high-speed, low-noise infrared detector. Operating from a hosted payload platform on the International Space Station (ISS), the Emu space telescope employs the paradigm-changing properties of the Leonardo SAPHIRA electron avalanche photodiode array to provide powerful new observations of cool stars at the critical water absorption wavelength (1.4 μm) largely inaccessible to ground-based telescopes due to the Earth’s own atmosphere. Cool stars, especially those of spectral-type M, are important probes across contemporary astrophysics, from the formation history of the Galaxy to the formation of rocky exoplanets. Main sequence M-dwarf stars are the most abundant stars in the Galaxy and evolved M-giant stars are some of the most distant stars that can be individually observed. The Emu sky survey will deliver critical stellar properties of these cool stars by inferring oxygen abundances via measurement of the water absorption band strength at 1.4 μm. Here, we present the TDI-like imaging capability of Emu mission, its science objectives, instrument details, and simulation results.
Cool stars, especially spectral-type M, are important probes across contemporary astrophysics, from the forma- tion history of the galaxy to the coalescence of rocky exoplanets. Main sequence M-dwarf stars are one of the most abundant stars in the galaxy, and evolved M-giant stars are some of the most distant stars that can be individually observed. The Emu sky survey, described here, will deliver critical stellar properties of these cool stars by inferring the oxygen abundance via measurement of the water band strength at 1.4 μm. A relatively wide field zenith-looking telescope with time delay integration capability can perform such a survey without active pointing but requires a fast and low-noise detector. Emu employs the paradigm-changing properties of the Leonardo SAPHIRA electron avalanche photodiode array, to provide these powerful new observations at the critical water absorption wavelength inaccessible to ground-based telescopes due to the Earth's own atmosphere. Here we will present Emu mission concept, science objectives, instrument details and simulation results.
KEYWORDS: Sensors, Photometry, Stars, Electronics, Image processing, Space operations, Earth's atmosphere, Field programmable gate arrays, Cryocoolers, Control systems design
‘Emu’ is a compact wide-field photometer destined for a 6-month mission on the exterior of the International Space Station (ISS), commencing in 2021. Emu will undertake a sky survey in the 1.4 μm ‘water band’, as a method of estimating oxygen abundance in the atmospheres of cool stars down to a magnitude of mAB≈13 (H-band).
The Leonardo SAPHIRA is a HgCdTe linear avalanche photodiode array enabling high frame rate, high sensitivity, low noise, and low dark current imaging at near-infrared wavelengths. The ANU utilised the Leonardo SAPHIRA to develop a high cadence “Lucky Imager” which was successfully tested on sky at Siding Spring Observatory. The cryogenic electronics and cryostat were designed and built by the ANU. The cryostat was cooled with a compact Stirling cycle cryocooler with active vibration damping. Various detector control systems were tested, including an ESO 'NGC' system and also a 32 channel ARC SDSU Series III. Images were ultimately captured at a windowed frame rate of 2.2 kHz with the ESO NGC controller.
Ground-based infrared observations are often limited by atmospheric absorption and emission. Space-based instruments avoid this, but introduce unique technical challenges. We present the design of a flexible, compact, and cost-effective detector controller for space, based on commercial off-the-shelf components. Its architecture provides up to 50 configurable clock sequences and 16 biases, 32 16-bit video channels and several genera lpurpose ports. This allows for full control of CMOS detectors including Leonardo ‘SAPHIRA’ avalanche photodiode arrays (APD) which represent current state of the art in low-noise infrared imaging.
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