System Design and Thermal Stability Analysis for the IRASSI Infrared Space Interferometer

摘要

IRASSI, the InfraRed Astronomy Satellite Swarm Interferometer, is a mission currently in the feasibility study phase that consists of 5 satellites operating from the L_2 point of the Sun-Earth system to perform space-based interferometry. The main advantage of using interferometry to make astronomic observations is that the achieved spatial resolution does not depend on the size of the telescopes, but on the distance between different collectors. Applying this technique from space would allow the observation of the far-infrared spectrum at spatial resolutions that were never achieved by previous missions. These observations would be particularly interesting to better understand the chemical and physical processes related to planet and star formation, which can be observed at such infrared frequencies. From a spacecraft design point of view, the main challenges of this mission are twofold. First, it is required to measure the distances between different spacecraft very accurately in order to perform interferometry. Thanks to the detection method used in IRASSI an active control of this distance is not required. The second challenge is the compliance with the required telescope pointing accuracy to observe an infrared source. Due to the scientific requirements of IRASSI, the distance between spacecraft shall be measured at an accuracy of 5 μm and an absolute pointing error below 0.4 arcsec shall be reached. In order to assess the feasibility of the mission, a preliminary spacecraft architecture that meets the mission requirements and minimizes the perturbations onboard the spacecraft is presented. This architecture is taken as a baseline to develop a thermomechanical model of the spacecraft and analyze the effect of thermal perturbations on the spacecraft operations and performance.