It can be concluded that operation needs to be performed at a lower temperature when the wavelength is extended. The forbidden bandwidth is proportional to the temperature, and the cutoff wavelength is inversely proportional to the forbidden bandwidth. Taking a mercury cadmium telluride (Hg 1−xCd xTe, MCT) detector as an example, Formula ( 1) and ( 2) show the relationships among the cutoff wavelength ( \(\lambda_\)) and temperature (T) if the premise of component × is determined. If the detector needs to work in the longwave or very longwave infrared spectrum, the operating temperature needs to be decreased to approximately 40 K or 20 K and below the temperature region 3. Under normal circumstances, a shortwave detector works at approximately 150 K, and a medium wave detector works at approximately 77 K. Infrared detection wavelengths mainly consist of five categories: near infrared, shortwave infrared, medium wave infrared, longwave infrared (also called thermal infrared) and very longwave infrared. ![]() In general, the longer the infrared wavelength is, the lower the operating temperature of the detector will be. The radiation wavelength shifts toward the shortwave direction as the temperature rises. Wien’s displacement law is one of the basic laws of thermal radiation and is expressed as \(\lambda T = b\), where b is Wien’s constant, λ is the detection wavelength, and T is the low temperature. Finally, the development of cryogenic technology for future space exploration is summarized by comparing and analyzing the interdependent relationships between them in space projects.įull size image Relationship between infrared wavelength and low temperature The space coordination and symbiotic relationship of infrared detection technology and cryogenic technology is illuminated through the different temperature zones of the influence law of the detector. For example, the Improved Stratospheric and Mesosphere Sounder (ISAMS) on UARS was successfully launched in 1991, which realized the first space application of Oxford Stirling refrigerators 4 China’s Fengyun-4, Gaofen-5 and other satellites have also been launched for space application with long-life mechanical refrigerators 5, 6 their working lives have extended beyond the service lives of a low-temperature Dewar in the early Infrared Astronomical Satellite (IRAS) and Cosmic Background Explorer (COBE) 3.īased on the current development of cryogenic technology at different detection temperatures, this paper analyzes the influence of cryogenic technology on the infrared wavelengths and dark currents in detectors. The development of long-life (> 5 years) and highly reliable space cryogenic coolers is synergistic and symbiotic with the development of modern infrared detection technology. Therefore, infrared detectors require high reliability and long-life components, especially cryogenic cryocoolers, whose performance determines the service life of infrared detectors. However, the space environment is challenging, and it is extremely difficult to achieve device maintenance while in orbit. Therefore, detector instrument replacement requires an increasingly stringent cooling capacity and temperature range, and the development of cryogenic technologies, especially for large cooling capacity and deep cryogenic technology, has been greatly promoted. Cryogenic space refrigerators with large cooling capacities (the cooling capacity classification is shown in Table 1 in the Supplementary Information) have been develop rapidly, such as China's Fengyun series satellites and the United States’ Landsat and GOES series satellites. The detection performance has been greatly improved at the same time, the heat load of the device and heat radiation leakage has also increased, which requires a lower temperature and greater cooling power to guarantee the effectiveness of the detectors. Infrared detector units began with small-scale first-generation multivariate detectors, developed with second-generation line and small-scale array detectors, and now widely use third-generation large-scale focal plane (256 × 256 ~ 4 K × 4 K) multicolor detectors 3. ![]() Infrared detectors are core components for infrared detection technology, and cryogenic technology has been codeveloped with cryogenic infrared detectors. The operating temperatures of different types of cryogenic detectors are shown in Fig. ![]() ![]() Photon detectors are typically used in low-temperature environments because low temperature can effectively suppress dark current detection and background noise interference to improve detection performance. Photon detectors use incident photons to interact with bound electrons and are superior to thermal detectors in terms of sensitivity and response speed thus, they are commonly used in space exploration missions 2. Existing detectors include photon detectors and thermal detectors.
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