Speaker
Description
SOLSTICE is a UK-led programme developing novel miniaturised scientific payloads for the high-resolution profiling of atmospheric composition. One of these payloads is the High-resolution InfraRed Occultation Sounder (HIROS). This presentation describes the thermal design and verification of the instrument, with particular focus on its demanding thermal control requirements.
HIROS is a thermal infrared laser heterodyne spectro-radiometer using a quantum cascade laser (QCL) as local oscillator. To ensure it operates within its selected spectral micro-window, HIROS must maintain its QCL within ±3 K of a set temperature, while achieving a thermal stability of <3 mK/s for periods of up to 120 s. In addition, the detector must be cooled below −66 °C using a TEC-based cooling system. Such requirements present a significant challenge within a compact 7.9 dm³ payload architecture, further constrained by a limited power budget, restricted radiator area, and the highly localised dissipation of 2.5 W within the mm²-scale QCL package.
Initial payload-level thermal-vacuum testing identified difficulties in meeting these requirements. A dedicated thermal test campaign was subsequently conducted to characterise the instrument’s thermal behaviour, investigate the underlying causes, and assess compliance with operational requirements. The campaign identified the thermal mechanisms preventing compliance with the ±3 K temperature requirement, demonstrated compliance with the QCL thermal stability requirement (<3 mK/s) and highlighted conductive thermal limitations affecting detector cooling. The presentation describes the test methodology, key findings, and lessons learned applicable to the thermal control and verification of miniaturised scientific instruments.