Emu: A Case Study for TDI-like Imaging for Infrared Observation from Space

TL;DR

The Emu space telescope employs TDI-like imaging with advanced infrared detectors from the ISS to survey cool stars at 1.4 μm, enabling new astrophysical insights into stellar properties and compositions.

Contribution

This paper introduces the Emu mission's TDI-like imaging technique using SAPHIRA detectors for infrared sky surveys from space, a novel approach for studying cool stars.

Findings

Demonstrated the feasibility of TDI-like imaging in space-based infrared observations.

Simulated the instrument's capability to measure water absorption in cool stars.

Outlined the science potential for understanding stellar compositions and galaxy formation.

Abstract

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 $\mu$m) 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 $\mu$m. Here we present the TDI-like imaging capability of Emu mission, its science objectives, instrument details and simulation results.