Impacts of laser cooling for low earth orbit observation satellites: An analysis in terms of size, weight and power

Abstract

Laser cooling in solids is a breakthrough technology allowing vibration-free cooling down to a temperature of 100 K in a miniaturized way. It appears as a promising technology to improve future observation satellites performances e.g. in SWIR and NIR domains.In this paper, integration of a laser cooler onboard an observation satellite is studied for the first time. Our study focuses on size, weight and power (SWaP) criteria, at both satellite payload and platform levels. Its goal is to assess the interest of using an optical cryocooler over a mechanical cryocooler for low earth orbit (LEO) infrared observation missions.A preliminary space-borne laser cooler (LC) architecture is proposed. It is composed of two parts. The first part is the cooling head, based on state-of-the-art cooling crystals 10%Yb:YLF and an astigmatic multipass cavity. The second part is the cryocooler opto-electronics, based on redundant laser diodes and fiber coupled to the cooling head. The cooling power is estimated for a small focal plane, taking into account the thermal load of an infrared detector and the parasitic heat fluxes inside the cryostat. The required optical and electrical powers of the laser cooler are then estimated considering the crystal efficiency, the thermal link losses and the opto-electronics efficiency.Assuming a 5-year long LEO microsatellite mission, the sizing of the electrical power systems (PCDU, solar array, batteries) and thermal control systems (heatpipes, radiators) is performed. An additional mass margin is added to take mechanical support structures into account. At the end, payload and platform masses and volumes are summed respectively to obtain a SWaP balance at satellite level, representative of the overall impact of a laser cooler. The study is repeated for the case of a Miniature Pulse Tube Cooler (MPTC) architecture under the same mission and platform assumptions. Finally, the two architectures are compared. It is shown that even if the power requirement of a laser cooler is high, the reduction of mass and internal volume makes it possible for small satellite payloads.