Thus, generally, the detection of IR radiation from the atmospheric gasses is done from space using satellites with variant altitudes. For example, CO2 has altitude ranges of about 10 to 100 km and H2O has altitude ranges of about 10 to 80 km from the earth’s surface. The concentration of the gasses in the atmosphere has some lifetime and varies with the altitude from the earth’s surface. The level of absorption by various gasses is described by Beer-Lambert law, it depends on the optical path of light to the gasses, concentration of the gasses, and absorption cross-section. The absorption spectrum of a molecule provides a unique “fingerprint” of the absorbances that can be used to deduce the chemical composition and concentrations of the atmospheric gasses. The position of the absorption peaks in an IR spectrum are characteristic of the chemical composition and the intensity of an absorption peak is proportional to the concentration of the samples. IR spectroscopy is a method to measure the absorption of an IR beam that has been passed through a sample. The attenuation of infrared radiation comes from the absorption of electromagnetic radiation by the atmospheric gasses in the IR spectral region. Outgoing infrared radiation is attenuated by atmospheric gasses, such as CO2, H2O, and O3. When radiation is absorbed, it is re-emitted in all directions where the amount of energy is dependent on the temperature and emissivity of the earth’s surface, clouds, aerosols, and gasses. Gasses absorb at some wavelengths and not others because of the energy gap between various vibrational and rotational states of the molecules. The atmosphere generally behaves as a selective absorber. Specifically for thermal sensing, the detector needs to be able to detect both cold and hot objects and be able to operate either sunlit or in shadow in a far distance. To compromise with the small area of spacecraft and space satellites, the dimensions of the detectors also should be small and compact. The detectors also need to have a short response time (< 6 s) for fast data acquisition and a long lifetime. Thus, the detectors need to be cooled to give a stable measurement result at a high range of ambient temperature and have a low power operation. Harsh environmental conditions in space by high-temperature fluctuations (-40oC to +85oC), shock, and vibration decrease the signal-to-noise ratio of the detectors.
The detector also should pass several standard evaluations subjected to environmental screening, including thermal cycling, radiation, vacuum compatibility, burning, and vibration testing. The detector appropriate for space application needs to have a wide spectral range with a small tolerance (+/- 1 μm) and the ability to enhance the optical signal. This paper describes some examples of the application of infrared detectors for space missions and the way to choose the best detectors provided by VIGO Photonics that suit your space exploration.ĭetector appropriate for space application VIGO Photonics is an expert in providing IR detectors and detector arrays from the SWIR to LWIR that support the space application. Thus, much infrared spectroscopy from space or near space with high altitude aircraft or remote objects, and also earth-based and earth-orbiting telescopes have been included in many space missions.ĭifferent astronomical phenomena in the infrared range correspond with different methods of observation and require specific detection. Many gaseous molecules are readily visible in the infrared range, which have their unique ways of rotation and vibration. Relatively cold objects also emit most strongly in the infrared spectrum.
In far-infrared, the emission of the dust itself becomes observable. The character of the near-infrared spectrum is dust transparent, so it is able to see cool stars and other celestial objects. The techniques of infrared astronomy make it possible to investigate many astronomical phenomena. Those are also extended farther away to observe nebulae, young stars, gas and dust in other galaxies, planets, and active galactic nuclei which need much effort to collect the data.
Those projects are not limited only to the earth’s surface and earth’s atmosphere, which have a direct impact on human beings and the environment. Several projects led by space agencies were built to expand our ability to observe many phenomena in space.
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