Hendrik Linz, Luisa Buinhas, Roger Förstner, Matthias Lezius, Divya Bhatia, Simon Batz-dorfer;, Katja Beha, Ulf Bestmann, Bernd Eissfeller, Meltem Eren Copur, Eloi Ferrer, Kathrin Frankl, Oliver Krause, Yongjin Moon, Mathias Philips-Blum, Silvia Scheithauer, Meiko Steen,
https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10698/1069852/The-far-infrared-space-interferometer-study-IRASSI--motivation-principle/10.1117/12.2313801.short?SSO=1
The far-infrared (FIR) regime is one of the few
wavelength ranges where no astronomical data with sub-arcsecond spatial
resolution exist yet. Also medium-term satellite projects like SPICA,
Millimetron or OST will not resolve this malady. For many research areas,
however, information at high spatial and spectral resolution in the FIR, taken
from atomic fine-structure lines, from highly excited CO and especially from
water lines would open the door for transformative science. These demands call
for interferometric concepts. We present here first results of our feasibility
study IRASSI (Infrared Astronomy Satellite Swarm Interferometry) for an FIR
space interferometer. Extending on the principal concept of the previous study
ESPRIT, it features heterodyne interferometry within a swarm of 5 satellite
elements. The satellites can drift in and out within a range of several hundred
meters, thereby achieving spatial resolutions of <0.1 arcsec over the whole
wavelength range of 1–6 THz. Precise knowledge on the baselines will be ensured
by metrology employing laser frequency combs, for which first ground-based
tests have been designed by members of our study team. In this contribution, we
first give a motivation how the science requirements translated into operational
and design parameters for IRASSI. Our consortium has put much emphasis on the
navigational aspects of such a free-flying swarm of satellites operating in
relatively close vicinity. We hence present work on the formation geometry, the
relative dynamics of the swarm, and aspects of our investigation towards
attitude estimation. Furthermore, we discuss issues regarding the real-time
capability of the autonomous relative positioning system, which is an important
aspect for IRASSI where, due to the large raw data rates expected, the
interferometric correlation has to be done onboard, quasi in real-time. We also
address questions regarding the spacecraft architecture and how a first
thermomechanical model is used to study the effect of thermal perturbations on the
spacecraft. This will have implications for the necessary internal calibration
of the local tie between the laser metrology and the phase centres of the
science signals.
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