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观测技术[Observational Techniques] [2005-9-15]
iamet 发表在 ¤〖天文〗
| Ground-based telescopes include optical and radio. Optical telescopes are used to observe atomic spectra and orbits, diameters, and surface features of planets and satellites. Limitations include diffraction, atmospheric blurring (to about  ), faintness of distant objects, and limited atmospheric viewing windows. Radio telescopes are used to measure non-thermal radio emission and determine surface features of nearby objects (especially Venus and the Moon) with radar.
Lander instruments include anemometers (measure wind speed and direction), barometers (measure pressure), biological sensors (search for biological activity), gamma ray spectrometers (measure gamma ray flux), mass spectrometers (determine chemical composition), nephelometers (determine the nature and density of clouds), radiation flux sensors (measure radiation intensity), seismometers (measure seismic activity), temperature sensors (measure temperature), and X-ray spectrometers (measure X-ray flux).
Orbiter and flyby instruments include CCDs (charge coupled devices) which record the light falling on individual pixels. Typical spacecraft cameras digitize 8 bits per pixel ( shades of gray), have 6-12 filters available, and take exposures over times longer than 0.1 s. Charged particle detectors measure intensity of the solar wind Infrared radiometers measure total infrared flux infrared spectrometers: measure flux as a function of wavelength and can determine atmospheric and surface composition by detecting reflected radiation). Magnetometers measure the strength of the magnetic field Ultraviolet spectrometers measure the composition of the upper atmosphere and detect auroral phenomena. Videcons take pictures by scanning (used on Viking but now supplanted by CCD's). |
学好数理化，走遍天下都不怕！ | |
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