The Thermo-Mechanical Control and Analysis of the TOLIMAN Space Telescope

Abstract

The Telescope for Orbital Locus Interferometric Monitoring of our Astronomical Neighborhood (TOLIMAN) is a microsatellite mission that aims to detect habitable exoplanets in the Alpha Centauri star system. TOLIMAN is designed around a 13 cm Ritchey–Chrétien telescope in low Earth orbit that uses a reformulation of an optical configuration known as a ``diffractive pupil'' to measure the micro-arcsecond angular deflections between stars. TOLIMAN aims to address a critical blind spot in our astronomy cabability; answering the basic question of whether there are Earth-analog exoplanets orbiting our nearest-neighbour star systems. This innovative mission concept requires an optical system with thermo-mechanical stability previously unseen in this class of telescope.

This thesis introduces the design and analysis of a ``cold bias'' thermal control system for TOLIMAN. Through extensive simulations, candidate orbits are studied, exploring the trade space between thermal performance and viewing time on the science target. Parametric thermal models and optimisation routines are used for the determination of worst case orbit conditions and optimal design choices. Reduced order thermal models are also created based on finite element models for the design of an active heater control system. These thermal models and their results are integrated with structural models to assess the dimensional stability of the primary mirror. The proposed design can achieve on orbit temperature stability of 20 +/- 0.05 deg C on the primary mirror, and 20 +/- 0.25 deg C on the metering structure through a synthesis of active and passive control techniques. The final outcome of a predicted RMS dimensional stability of better than 5 nm on the primary mirror is highly encouraging for the precision optical measurements required to accomplish the core mission science.