Evaluation of thermal performance of window materials for satellite payloads in low earth orbit (LEO)

Council for Scientific and Industrial Research (CSIR), Optronic Sensor Systems (OSS), PO Box 395, 0001, South Africa

^* Corresponding author: abaloyi3@csir.co.za

Abstract

Selecting the appropriate window materials for use in space products such as Low Earth Orbit (LEO) satellite optical payloads is of critical importance. Windows on satellite optical payloads are essential for mission success and functionality. They serve a dual purpose: shielding the optical instrument’s interior from environmental hazards and physical damage, while allowing beneficial radiation to pass through, ensuring optimal performance. However, temperature gradients can deform an inherently plane-parallel window and turn it into a weak meniscus, introducing Optical Path Difference (OPD) into the wavefront. This may lead to defocusing, thereby reducing the payload’s performance. Design considerations to account for thermal stresses to prevent window damages such as “cracking”, “crazing” and “delamination” due to “thermal cycling” are vital. This paper analyses the thermal performance of ULE Corning 7972 and Fused Silica window materials for LEO satellite optical payloads, considering solar radiation, Earth’s Albedo (solar reflection), and Earth infrared radiation. ULE Corning 7972 outperformed Fused Silica due to its near-zero CTE, exhibiting less deformation and lower thermal stress. This analysis offers valuable insights into window material selection for enhanced reliability, durability, and functionality for LEO satellite optical payloads.