Radiation heat transfer analysis of spectrometer's Dewar Cooling Assembly

Abstract

Optical spectrometers have been of interest in remote sensing because of their ability to decipher an image scene based on its spectrum. Fore-optics, glass window, cold shield, order sorting filters (OSF), focal plane array (FPA) and cryo-cooler are integral parts of a spectrometer assembly. It can be divided into two parts: Fore optics & Integrated Detector Dewar Cooling Assembly (IDDCA). Optimum size of cryo-cooler ought to be known as weight constraints are critical in payload design. Cooling load on cryo-cooler depends on the ability of assembly's parts to absorb, transmit and radiate energy emanating from distant scene and incident on spectrometer's aperture. The experimentation with small scale components is expensive and requires sophisticated measuring and calibration techniques. Efforts have been made to develop a computational model which can hypothesize thermal parameters of IDDCA and their interdependency. This study has been carried out for the assembly using Ray optics and Heat transfer modules of COMSOL Multiphysics in the wavelength range of 800 to 5000 nm. This model examines the distribution of temperature and total heat flux on FPA in order to maintain its low temperature 90 K) for maintaining image resolution.