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Space Observatory
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 (space telescope), 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 Observatory#Ground-based observatories, 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 ... [...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] |
Adaptive Optics
Adaptive optics (AO) is a technique of precisely deforming a mirror in order to compensate for light distortion. It is used in Astronomy, astronomical telescopes and laser communication systems to remove the effects of Astronomical seeing, atmospheric distortion, in microscopy, optical fabrication and in retinal imaging systems to reduce optical aberrations. Adaptive optics works by measuring the distortions in a wavefront and compensating for them with a device that corrects those errors such as a deformable mirror or a liquid crystal array. Adaptive optics should not be confused with active optics, which work on a longer timescale to correct the primary mirror geometry. Other methods can achieve resolving power exceeding the limit imposed by atmospheric distortion, such as speckle imaging, aperture synthesis, and lucky imaging, or by moving outside the atmosphere with space-based telescope, space telescopes, such as the Hubble Space Telescope. History Adaptive optics was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aperture
In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image of the aperture and focal length of an optical system determine the cone angle of a bundle of rays that comes to a focus in the image plane. An optical system typically has many structures that limit ray bundles (ray bundles are also known as ''pencils'' of light). These structures may be the edge of a lens or mirror, or a ring or other fixture that holds an optical element in place or may be a special element such as a diaphragm placed in the optical path to limit the light admitted by the system. In general, these structures are called stops, and the aperture stop is the stop that primarily determines the cone of rays that an optical system accepts (see entrance pupil). As a result, it also determines the ray cone angle and brightne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angular Resolution
Angular resolution describes the ability of any image-forming device such as an Optical telescope, optical or radio telescope, a microscope, a camera, or an Human eye, eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. It is used in optics applied to light waves, in antenna (radio), antenna theory applied to radio waves, and in acoustics applied to sound waves. The colloquial use of the term "resolution" sometimes causes confusion; when an optical system is said to have a high resolution or high angular resolution, it means that the perceived distance, or actual angular distance, between resolved neighboring objects is small. The value that quantifies this property, ''θ,'' which is given by the Rayleigh criterion, is low for a system with a high resolution. The closely related term spatial resolution refers to the precision of a measurement with respect to space, which is directly connected to angular resolution in imaging ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth's Atmosphere
The atmosphere of Earth is composed of a layer of gas mixture that surrounds the Earth's planetary surface (both lands and oceans), known collectively as air, with variable quantities of suspended aerosols and particulates (which create weather features such as clouds and hazes), all retained by Earth's gravity. The atmosphere serves as a protective buffer between the Earth's surface and outer space, shields the surface from most meteoroids and ultraviolet solar radiation, keeps it warm and reduces diurnal temperature variation (temperature extremes between day and night) through heat retention (greenhouse effect), redistributes heat and moisture among different regions via air currents, and provides the chemical and climate conditions allowing life to exist and evolve on Earth. By mole fraction (i.e., by quantity of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other trace gases (see Composition below ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scintillation (astronomy)
Twinkling, also called scintillation, is a generic term for variations in apparent brightness, colour, or position of a distant luminous object viewed through a medium.Wang, Ting-I; Williams, Donn"Scintillation technology bests NIST" , ''InTech'', May 1, 2005. If the object lies outside the Earth's atmosphere, as in the case of stars and planets, the phenomenon is termed ''astronomical scintillation''; for objects within the atmosphere, the phenomenon is termed ''terrestrial scintillation''. As one of the three principal factors governing astronomical seeing (the others being light pollution and cloud cover), atmospheric scintillation is defined as variations in illuminance only. In simple terms, twinkling of stars is caused by the passing of light through different layers of a turbulent atmosphere. Most scintillation effects are caused by anomalous atmospheric refraction caused by small-scale fluctuations in air density usually related to temperature gradients. Scinti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Radiation
In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ranging from radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. All forms of EMR travel at the speed of light in a vacuum and exhibit wave–particle duality, behaving both as waves and as discrete particles called photons. Electromagnetic radiation is produced by accelerating charged particles such as from the Sun and other celestial bodies or artificially generated for various applications. Its interaction with matter depends on wavelength, influencing its uses in communication, medicine, industry, and scientific research. Radio waves enable broadcasting and wireless communication, infrared is used in thermal imaging, visible light is essential for vision, and higher-energy radiation, such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include planets, natural satellite, moons, stars, nebulae, galaxy, galaxies, meteoroids, asteroids, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond atmosphere of Earth, Earth's atmosphere. Cosmology is a branch of astronomy that studies the universe as a whole. Astronomy is one of the oldest natural sciences. The early civilizations in recorded history made methodical observations of the night sky. These include the Egyptian astronomy, Egyptians, Babylonian astronomy, Babylonians, Greek astronomy, Greeks, Indian astronomy, Indians, Chinese astronomy, Chinese, Maya civilization, M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
