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Space Telescopes
A space telescope (also known as space observatory) is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launched in 1968, and the Soviet Orion 1 ultraviolet telescope aboard space station Salyut 1 in 1971. Space telescopes avoid several problems caused by the atmosphere, including the absorption or scattering of certain wavelengths of light, obstruction by clouds, and distortions due to atmospheric refraction such as twinkling. Space telescopes can also observe dim objects during the daytime, and they avoid light pollution which ground-based observatories encounter. They are divided into two types: Satellites which map the entire sky (astronomical survey), and satellites which focus on selected astronomical objects or parts of the sky and beyond. Space telescopes are distinct from Earth imaging satellites, which point toward Earth f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength Sensitivity Of Hubble, Webb, Roman, And Other Observatories (01FEBQTM8Y4FESTQ4N2AFQDBXH)
In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves), phase'' on the wave, such as two adjacent crests, troughs, or zero crossings. Wavelength is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The multiplicative inverse, inverse of the wavelength is called the ''spatial frequency''. Wavelength is commonly designated by the Greek letter lambda (''λ''). For a modulated wave, ''wavelength'' may refer to the carrier wavelength of the signal. The term ''wavelength'' may also apply to the repeating envelope (mathematics), envelope of modulated waves or waves formed by Interference (wave propagation), interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed phase velocity, wave speed, wavelength is inversely proportion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Remote Sensing
Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring information about Earth and other planets. Remote sensing is used in numerous fields, including geophysics, geography, land surveying and most Earth science disciplines (e.g. exploration geophysics, hydrology, ecology, meteorology, oceanography, glaciology, geology). It also has military, intelligence, commercial, economic, planning, and humanitarian applications, among others. In current usage, the term ''remote sensing'' generally refers to the use of satellite- or airborne-based sensor technologies to detect and classify objects on Earth. It includes the surface and the atmosphere and oceans, based on wave propagation, propagated signals (e.g. electromagnetic radiation). It may be split into "active" remote sensing (when a signal is emitted b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Window
The radio window is the region of the radio spectrum that penetrate the Earth's atmosphere. Typically, the lower limit of the radio window's range has a value of about 10 MHz (λ ≈ 30 m); the best upper limit achievable from optimal terrestrial observation sites is equal to approximately 1 THz (λ ≈ 0.3 mm). It plays an important role in astronomy; up until the 1940s, astronomers could only use the visible and near infrared spectra for their measurements and observations. With the development of radio telescopes, the radio window became more and more utilizable, leading to the development of radio astronomy that provided astrophysicists with valuable observational data. Factors affecting lower and upper limits The lower and upper limits of the radio window's range of frequencies are not fixed; they depend on a variety of factors. Absorption of mid-IR The upper limit is affected by the vibrational transitions of atmospheric molecules such as oxygen (O2), carbon dioxid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Window
The optical window is the portion of the optical spectrum that is blocked by the Earth's atmosphere. The window runs from around 300 nanometers ( ultraviolet-B) up into the range the human eye can detect, roughly 400–700 nm and continues up to approximately 2 μm. Sunlight mostly reaches the ground through the optical atmospheric window; the Sun is particularly active in most of this range (44% of the radiation emitted by the Sun falls within the visible spectrum and 49% falls within the infrared spectrum). Definition The Earth's atmosphere is not totally transparent and is in fact 100% opaque to many wavelengths (see plot of Earth's opacity); the wavelength ranges to which it is transparent are called atmospheric windows. Disambiguation of the term 'optical spectrum' Although the word ''optical'', deriving from Ancient Greek ὀπτῐκός (optikós, "of or for sight"), generally refers to something visible or visual, the term ''optical spectrum'' is used to descr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
