Camera
A camera is an optical instrument to capture still images or to record moving images, which are stored in a physical medium such as in a digital system or on photographic film. A camera consists of a lens which focuses light from the scene, a camera body which holds the image capture mechanism; the still image camera is the main instrument in the art of photography and captured images may be reproduced as a part of the process of photography, digital imaging, photographic printing. The similar artistic fields in the moving image camera domain are film and cinematography; the word camera comes from camera obscura, which means "dark chamber" and is the Latin name of the original device for projecting an image of external reality onto a flat surface. The modern photographic camera evolved from the camera obscura; the functioning of the camera is similar to the functioning of the human eye. The first permanent photograph was made in 1825 by Joseph Nicéphore Niépce. A camera works with the light of the visible spectrum or with other portions of the electromagnetic spectrum.
A still camera is an optical device which creates a single image of an object or scene and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging/convex lens and an image is recorded on a light-sensitive medium. A shutter mechanism controls the length of time. Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, to control the exposure so that it is not too bright or too dim. On most digital cameras a display a liquid crystal display, permits the user to view the scene to be recorded and settings such as ISO speed and shutter speed. A movie camera or a video camera operates to a still camera, except it records a series of static images in rapid succession at a rate of 24 frames per second; when the images are combined and displayed in order, the illusion of motion is achieved. Traditional cameras capture light onto photographic film.
Video and digital cameras use an electronic image sensor a charge coupled device or a CMOS sensor to capture images which can be transferred or stored in a memory card or other storage inside the camera for playback or processing. Cameras that capture many images in sequence are known as movie cameras or as ciné cameras in Europe; however these categories overlap as still cameras are used to capture moving images in special effects work and many modern cameras can switch between still and motion recording modes. A wide range of film and plate formats have been used by cameras. In the early history plate sizes were specific for the make and model of camera although there developed some standardisation for the more popular cameras; the introduction of roll film drove the standardization process still further so that by the 1950s only a few standard roll films were in use. These included 120 film providing 8, 12 or 16 exposures, 220 film providing 16 or 24 exposures, 127 film providing 8 or 12 exposures and 135 providing 12, 20 or 36 exposures – or up to 72 exposures in the half-frame format or in bulk cassettes for the Leica Camera range.
For cine cameras, film 35 mm wide and perforated with sprocket holes was established as the standard format in the 1890s. It was used for nearly all film-based professional motion picture production. For amateur use, several smaller and therefore less expensive formats were introduced. 17.5 mm film, created by splitting 35 mm film, was one early amateur format, but 9.5 mm film, introduced in Europe in 1922, 16 mm film, introduced in the US in 1923, soon became the standards for "home movies" in their respective hemispheres. In 1932, the more economical 8 mm format was created by doubling the number of perforations in 16 mm film splitting it after exposure and processing; the Super 8 format, still 8 mm wide but with smaller perforations to make room for larger film frames, was introduced in 1965. Traditionally used to "tell the camera" the film speed of the selected film on film cameras, film speed numbers are employed on modern digital cameras as an indication of the system's gain from light to numerical output and to control the automatic exposure system.
Film speed is measured via the ISO system. The higher the film speed number the greater the film sensitivity to light, whereas with a lower number, the film is less sensitive to light. On digital cameras, electronic compensation for the color temperature associated with a given set of lighting conditions, ensuring that white light is registered as such on the imaging chip and therefore that the colors in the frame will appear natural. On mechanical, film-based cameras, this function is served by the operator's choice of film stock or with color correction filters. In addition to using white balance to register natural coloration of the image, photographers may employ white balance to aesthetic end, for example, white balancing to a blue object in order to obtain a warm color temperature; the lens of a camera brings it to a focus on the sensor. The design and manufacture of the lens is critical to the quality of the photograph being taken; the technological revolution in camera design in the 19th century revolutionized optical glass manufacture and lens design with great benefits for modern lens manufacture in a wide range of optical instruments from reading glasses to microscopes.
Pioneers included Leitz. Camera lenses are
Mars Science Laboratory
Mars Science Laboratory is a robotic space probe mission to Mars launched by NASA on November 26, 2011, which landed Curiosity, a Mars rover, in Gale Crater on August 6, 2012. The overall objectives include investigating Mars' habitability, studying its climate and geology, collecting data for a manned mission to Mars; the rover carries a variety of scientific instruments designed by an international team. MSL carried out the most accurate Martian landing of any known spacecraft, hitting a small target landing ellipse of only 7 by 20 km, in the Aeolis Palus region of Gale Crater. In the event, MSL achieved a landing 400 m north of the center of the target; this location is near the mountain Aeolis Mons. The rover mission is set to explore for at least 687 Earth days over a range of 5 by 20 km; the Mars Science Laboratory mission is part of NASA's Mars Exploration Program, a long-term effort for the robotic exploration of Mars, managed by the Jet Propulsion Laboratory of California Institute of Technology.
The total cost of the MSL project is about US$2.5 billion. Previous successful U. S. Mars rovers include Sojourner from the Mars Pathfinder mission and the Mars Exploration Rovers Spirit and Opportunity. Curiosity is about twice as long and five times as heavy as Spirit and Opportunity, carries over ten times the mass of scientific instruments; the MSL mission has four scientific goals: Determine the landing site's habitability including the role of water, the study of the climate and the geology of Mars. It is useful preparation for a future manned mission to Mars. To contribute to these goals, MSL has eight main scientific objectives: Biological Determine the nature and inventory of organic carbon compounds Investigate the chemical building blocks of life Identify features that may represent the effects of biological processes Geological and geochemical Investigate the chemical and mineralogical composition of the Martian surface and near-surface geological materials Interpret the processes that have formed and modified rocks and soilsPlanetary process Assess long-timescale Martian atmospheric evolution processes Determine present state and cycling of water and carbon dioxideSurface radiation Characterize the broad spectrum of surface radiation, including cosmic radiation, solar particle events and secondary neutrons.
As part of its exploration, it measured the radiation exposure in the interior of the spacecraft as it traveled to Mars, it is continuing radiation measurements as it explores the surface of Mars. This data would be important for a future manned mission. About one year into the surface mission, having assessed that ancient Mars could have been hospitable to microbial life, the MSL mission objectives evolved to developing predictive models for the preservation process of organic compounds and biomolecules; the spacecraft flight system had a mass at launch of 3,893 kg, consisting of an Earth-Mars fueled cruise stage, the entry-descent-landing system, a 899 kg mobile rover with an integrated instrument package. The MSL spacecraft includes spaceflight-specific instruments, in addition to utilizing one of the rover instruments — Radiation assessment detector — during the spaceflight transit to Mars. MSL EDL Instrument: The MEDLI project's main objective is to measure aerothermal environments, sub-surface heat shield material response, vehicle orientation, atmospheric density.
The MEDLI instrumentation suite was installed in the heatshield of the MSL entry vehicle. The acquired data will support future Mars missions by providing measured atmospheric data to validate Mars atmosphere models and clarify the lander design margins on future Mars missions. MEDLI instrumentation consists of three main subsystems: MEDLI Integrated Sensor Plugs, Mars Entry Atmospheric Data System and the Sensor Support Electronics. Curiosity rover has a mass of 899 kg, can travel up to 90 m per hour on its six-wheeled rocker-bogie system, is powered by a multi-mission radioisotope thermoelectric generator, communicates in both X band and UHF bands. Computers: The two identical on-board rover computers, called "Rover Compute Element", contain radiation-hardened memory to tolerate the extreme radiation from space and to safeguard against power-off cycles; each computer's memory includes 256 KB of EEPROM, 256 MB of DRAM, 2 GB of flash memory. This compares to 3 MB of EEPROM, 128 MB of DRAM, 256 MB of flash memory used in the Mars Exploration Rovers.
The RCE computers use the RAD750 CPU operating at 200 MHz. The RAD750 CPU is capable of up to 400 MIPS, while the RAD6000 CPU is capable of up to 35 MIPS. Of the two on-board computers, one is configured as backup, will take over in the event of problems with the main computer; the rover has an Inertial Measurement Unit that provides 3-axis information on its position, used in rover navigation. The rover's computers are self-monitoring to keep the rover operational, such as by regulating the rover's temperature. Activities such as taking pictures and operating the instruments are performed in a command sequence, sent from the flight team to the rover; the rover's computers function on a real-time operating system from Wind River Systems. During the trip to Mars, VxWorks ran
Baltimore
Baltimore is the largest city in the state of Maryland within the United States. Baltimore was established by the Constitution of Maryland as an independent city in 1729. With a population of 611,648 in 2017, Baltimore is the largest such independent city in the United States; as of 2017, the population of the Baltimore metropolitan area was estimated to be just under 2.808 million, making it the 20th largest metropolitan area in the country. Baltimore is located about 40 miles northeast of Washington, D. C. making it a principal city in the Washington-Baltimore combined statistical area, the fourth-largest CSA in the nation, with a calculated 2017 population of 9,764,315. Baltimore is the second-largest seaport in the Mid-Atlantic; the city's Inner Harbor was once the second leading port of entry for immigrants to the United States. In addition, Baltimore was a major manufacturing center. After a decline in major manufacturing, heavy industry, restructuring of the rail industry, Baltimore has shifted to a service-oriented economy.
Johns Hopkins Hospital and Johns Hopkins University are the city's top two employers. With hundreds of identified districts, Baltimore has been dubbed a "city of neighborhoods." Famous residents have included writers Edgar Allan Poe, Edith Hamilton, Frederick Douglass, Ogden Nash, H. L. Mencken. During the War of 1812, Francis Scott Key wrote "The Star-Spangled Banner" in Baltimore after the bombardment of Fort McHenry, his poem popularized as a song. Baltimore has more public statues and monuments per capita than any other city in the country, is home to some of the earliest National Register Historic Districts in the nation, including Fell's Point, Federal Hill, Mount Vernon; these were added to the National Register between 1969–1971, soon after historic preservation legislation was passed. Nearly one third of the city's buildings are designated as historic in the National Register, more than any other U. S. city. The city has 33 local historic districts. Over 65,000 properties are designated as historic buildings and listed in the NRHP, more than any other U.
S. city. The historical records of the government of Baltimore are located at the Baltimore City Archives; the city is named after Cecil Calvert, second Lord Baltimore of the Irish House of Lords and founding proprietor of the Province of Maryland. Baltimore Manor was the name of the estate in County Longford on which the Calvert family lived in Ireland. Baltimore is an anglicization of the Irish name Baile an Tí Mhóir, meaning "town of the big house." The Baltimore area had been inhabited by Native Americans since at least the 10th millennium BC, when Paleo-Indians first settled in the region. One Paleo-Indian site and several Archaic period and Woodland period archaeological sites have been identified in Baltimore, including four from the Late Woodland period. During the Late Woodland period, the archaeological culture, called the "Potomac Creek complex" resided in the area from Baltimore south to the Rappahannock River in present-day Virginia. In the early 1600s, the immediate Baltimore vicinity was sparsely populated, if at all, by Native Americans.
The Baltimore County area northward was used as hunting grounds by the Susquehannock living in the lower Susquehanna River valley. This Iroquoian-speaking people "controlled all of the upper tributaries of the Chesapeake" but "refrained from much contact with Powhatan in the Potomac region" and south into Virginia. Pressured by the Susquehannock, the Piscataway tribe, an Algonquian-speaking people, stayed well south of the Baltimore area and inhabited the north bank of the Potomac River in what are now Charles and southern Prince George's counties in the coastal areas south of the Fall Line. European colonization of Maryland began with the arrival of an English ship at St. Clement's Island in the Potomac River on March 25, 1634. Europeans began to settle the area further north, beginning to populate the area of Baltimore County; the original county seat, known today as "Old Baltimore", was located on Bush River within the present-day Aberdeen Proving Ground. The colonists engaged in sporadic warfare with the Susquehanna, whose numbers dwindled from new infectious diseases, such as smallpox, endemic among the Europeans.
In 1661 David Jones claimed the area known today as Jonestown on the east bank of the Jones Falls stream. The colonial General Assembly of Maryland created the Port of Baltimore at old Whetstone Point in 1706 for the tobacco trade; the Town of Baltimore, on the west side of the Jones Falls, was founded and laid out on July 30, 1729. By 1752 the town had just 27 homes, including two taverns. Jonestown and Fells Point had been settled to the east; the three settlements, covering 60 acres, became a commercial hub, in 1768 were designated as the county seat. Being a colony, the Baltimore street names were laid out to demonstrate loyalty to the mother country. For example King George, King and Caroline streets. Baltimore grew swiftly in the 18th century, its plantations producing grain and tobacco for sugar-producing colonies in the Caribbean; the profit from sugar encouraged the cultivation of cane in the Caribbean and the importation of food by planters there. As noted, Baltimore was as the county seat, in 1768 a courthouse was built to serve both the city and county.
Its square was a center of community discussions. Baltimore established its public market system in 1763. Lexington Market, founded in 1782, i
Panorama
A panorama is any wide-angle view or representation of a physical space, whether in painting, photography, seismic images or a three-dimensional model. The word was coined in the 18th century by the English painter Robert Barker to describe his panoramic paintings of Edinburgh and London; the motion-picture term panning is derived from panorama. A panoramic view is purposed for multi-media, cross-scale applications to an outline overview along and across repositories; this so-called "cognitive panorama" is a panoramic view over, a combination of, cognitive spaces used to capture the larger scale. The device of the panorama existed in painting in murals, as early as 20 A. D. in those found as a means of generating an immersive ` panoptic' experience of a vista. Cartographic experiments during the Enlightenment era preceded European panorama painting and contributed to a formative impulse toward panoramic vision and depiction; this novel perspective was conveyed to America by Benjamin Franklin, present for the first manned balloon flight by the Montgolfier brothers in 1783, by American born physician, John Jeffries who had joined French aeronaut Jean Pierre Blanchard on flights over England and the first aerial crossing of the English Channel in 1785.
In the mid-19th century, panoramic paintings and models became a popular way to represent landscapes, topographic views and historical events. Audiences of Europe in this period were thrilled by the aspect of illusion, immersed in a winding 360 degree panorama and given the impression of standing in a new environment; the panorama was a 360-degree visual medium patented under the title Apparatus for Exhibiting Pictures by the artist Robert Barker in 1787. The earliest that the word "panorama" appeared in print was on June 11, 1791 in the British newspaper The Morning Chronicle, referring to this visual spectacle. Barker created a painting, shown on a cylindrical surface and viewed from the inside, giving viewers a vantage point encompassing the entire circle of the horizon, rendering the original scene with high fidelity; the inaugural exhibition, a "View of Edinburgh", was first shown in that city in 1788 transported to London in 1789. By 1793, Barker had built "The Panorama" rotunda at the center of London's entertainment district in Leicester Square, where it remained until closed in 1863.
Inventor Sir Francis Ronalds developed a machine to remove errors in perspective that were created when a sequence of planar sketches was combined into a cylinder. It projected the cylindrical drawing onto the wall of the rotunda at much larger scale to enable its accurate painting; the apparatus was exhibited at the Royal Polytechnic Institution in the early 1840s. Large scale installations enhance the illusion for an audience of being surrounded with a real landscape; the Bourbaki Panorama in Lucerne, Switzerland was created by Edouard Castres in 1881. The painting measures about 10 metres in height with a circumference of 112 meters. In the same year of 1881, the Dutch marine painter Hendrik Willem Mesdag created and established the Panorama Mesdag of The Hague, Netherlands, a cylindrical painting more than 14 metres high and 40 meters in diameter. In the United States of America is the Atlanta Cyclorama, depicting the Civil War Battle of Atlanta, it was first displayed in 1887, is 42 feet high by 358 feet circumference.
On a gigantic scale, still extant, is the Racławice Panorama located in Wrocław, which measures 15 x 120 metres. In addition to these historical examples, there have been panoramas painted and installed in modern times. Panoramic photography soon came to displace painting as the most common method for creating wide views. Not long after the introduction of the Daguerreotype in 1839, photographers began assembling multiple images of a view into a single wide image. In the late 19th century, flexible film enabled the construction of panoramic cameras using curved film holders and clockwork drives to rotate the lens in an arc and thus scan an image encompassing 180 degrees. Pinhole cameras of a variety of constructions can be used to make panoramic images. A popular design is the "oatmeal box", a vertical cylindrical container in which the pinhole is made in one side and the film or photographic paper is wrapped around the inside wall opposite, extending right to the edge of, the pinhole; this generates an egg-shaped image with more than 180° view.
Popular in the 1970s and 1980s, but now superseded by digital presentation software, Multi-image 35mm slide projections onto one or more screens characteristically lent themselves to the wide screen panorama. They could run autonomously with silent synchronization pulses to control projector advance and fades, recorded beside an audio voice-over or music track. Overlapping slides placed in slide mounts with soft-edge density masks would merge seamlessly on the screen to create the panorama. Cutting and dissolving between sequential images generated animation effects in the panorama format. Digital photography of the late twentieth century simplified this assembly process, now known as image stitching; such stitched images may be fashioned into forms of virtual reality movies, using technologies such as Apple Inc.'s QuickTime VR, Java, or JavaScript. A rotating line camera such as the Panoscan allows the capture of high resolution panoramic images and eliminates the need for image stitching, but immersive "spherical" pa
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or light. A typical human eye will respond to wavelengths from about 380 to 740 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 430–770 THz; the spectrum does not contain all the colors. Unsaturated colors such as pink, or purple variations like magenta, for example, are absent because they can only be made from a mix of multiple wavelengths. Colors containing only one wavelength are called pure colors or spectral colors. Visible wavelengths pass unattenuated through the Earth's atmosphere via the "optical window" region of the electromagnetic spectrum. An example of this phenomenon is when clean air scatters blue light more than red light, so the midday sky appears blue; the optical window is referred to as the "visible window" because it overlaps the human visible response spectrum. The near infrared window lies just out of the human vision, as well as the medium wavelength infrared window, the long wavelength or far infrared window, although other animals may experience them.
In the 13th century, Roger Bacon theorized that rainbows were produced by a similar process to the passage of light through glass or crystal. In the 17th century, Isaac Newton discovered that prisms could disassemble and reassemble white light, described the phenomenon in his book Opticks, he was the first to use the word spectrum in this sense in print in 1671 in describing his experiments in optics. Newton observed that, when a narrow beam of sunlight strikes the face of a glass prism at an angle, some is reflected and some of the beam passes into and through the glass, emerging as different-colored bands. Newton hypothesized light to be made up of "corpuscles" of different colors, with the different colors of light moving at different speeds in transparent matter, red light moving more than violet in glass; the result is that red light is bent less than violet as it passes through the prism, creating a spectrum of colors. Newton divided the spectrum into six named colors: red, yellow, green and violet.
He added indigo as the seventh color since he believed that seven was a perfect number as derived from the ancient Greek sophists, of there being a connection between the colors, the musical notes, the known objects in the solar system, the days of the week. The human eye is insensitive to indigo's frequencies, some people who have otherwise-good vision cannot distinguish indigo from blue and violet. For this reason, some commentators, including Isaac Asimov, have suggested that indigo should not be regarded as a color in its own right but as a shade of blue or violet. Evidence indicates that what Newton meant by "indigo" and "blue" does not correspond to the modern meanings of those color words. Comparing Newton's observation of prismatic colors to a color image of the visible light spectrum shows that "indigo" corresponds to what is today called blue, whereas "blue" corresponds to cyan. In the 18th century, Johann Wolfgang von Goethe wrote about optical spectra in his Theory of Colours. Goethe used the word spectrum to designate a ghostly optical afterimage, as did Schopenhauer in On Vision and Colors.
Goethe argued. Where Newton narrowed the beam of light to isolate the phenomenon, Goethe observed that a wider aperture produces not a spectrum but rather reddish-yellow and blue-cyan edges with white between them; the spectrum appears only. In the early 19th century, the concept of the visible spectrum became more definite, as light outside the visible range was discovered and characterized by William Herschel and Johann Wilhelm Ritter, Thomas Young, Thomas Johann Seebeck, others. Young was the first to measure the wavelengths of different colors of light, in 1802; the connection between the visible spectrum and color vision was explored by Thomas Young and Hermann von Helmholtz in the early 19th century. Their theory of color vision proposed that the eye uses three distinct receptors to perceive color. Many species can see light within frequencies outside the human "visible spectrum". Bees and many other insects can detect ultraviolet light. Plant species that depend on insect pollination may owe reproductive success to their appearance in ultraviolet light rather than how colorful they appear to humans.
Birds, can see into the ultraviolet, some have sex-dependent markings on their plumage that are visible only in the ultraviolet range. Many animals that can see into the ultraviolet range cannot see red light or any other reddish wavelengths. Bees' visible spectrum ends at about 590 nm. Birds can see some red wavelengths; the popular belief that the common goldfish is the only animal that can see both infrared and ultraviolet light is incorrect, because goldfish cannot see infrared light. Dogs are thought to be color blind but they have been shown to be sensitive to colors, though not as many as humans; some snakes can "see" radiant heat at wavelengths between 5 and 30 μm to a degree of accuracy such that a blind rattlesnake can target vulnerable body parts of the prey at which it strikes, other snakes with the organ may detect warm bodies from a meter away. It may be used in thermoregulation and predator detection. (See
Endurance (crater)
Endurance is an impact crater lying situated within the Margaritifer Sinus quadrangle region of the planet Mars. This crater was visited by the Opportunity rover from May until December 2004. Mission scientists named the crater after the ship Endurance that sailed to the Antarctic through the Weddell Sea during the ill-fated 1914-1917 Imperial Trans-Antarctic Expedition, considered to be the last expedition of the Heroic Age of Antarctic Exploration organized by Ernest Shackleton; the rover entered the crater interior on its 134th mission sol, exited on the 315th sol. During this time it traversed various obstacles, steep inclines, overcame large wheel slippage when driving over fine sand. After arriving at the crater, Opportunity performed a survey of the crater to plan the further steps in exploring the local geology. A site dubbed "Karatepe" was chosen to investigate the layering of the bedrock; the picture to the right shows changes in the color of the bedrock layers. The layer "A" is closer to the rover and higher than the layers "B" to "E".
Texture and rock chemistry differed with depth. Thus scientists infer that the age of these layers is following a similar pattern, with the higher layers being younger than the lower layers. Opportunity went farther down into the crater to investigate the sand dunes. Various rock outcrops were investigated, it was decided not to drive for fear the rover might get stuck permanently. Instead, Opportunity did some work on some rocks surrounding the dunes before heading back up to the rim of the crater. On the way, it encountered a boulder, nicknamed'Wopmay', that provided inconclusive evidence that rocks near the bottom of the crater were affected by water before and after the crater formed; the rover headed off to Burns Cliff. Burns Cliff, named for the late mineralogist Roger Burns of MIT, was studied by Opportunity. High amounts of slippage prevented the rover from using its robotic arm, however high resolution imaging was conducted with the Pancam, it shows layers of sediment. The layers in the cliff would be followed south of the crater to identify it as a geologic formation, in this case the "Burns Formation".
These names are not official. Burns Cliff was the final science stop inside Endurance; the rover prevailed. Leaving Endurance it headed for its heat shield where it would find the Meridiani Planum meteorite, which happened to be the first meteorite discovered on another planet. Opportunity spent about half a year exploring Endurance. During that time, data collected by the rover supplanted and expanded on the history of water at Meridiani Planum, in addition to the confirmation that there had been liquid water here in ancient times. Endurance provided mission scientists with a cross-section of the bedrock on this part of Mars, showing that liquid water hadn't flowed across the surface just once, but was of an episodic nature, wasn't permanently present, with floods periodically washing over the landscape, drying up again. Interpretation of the materials in Endurance's evaporite outcrops led mission scientists to believe that this shallow sea was rather acidic in nature, but can't rule out that life couldn't have been present at some point.
Exploration of Mars Geography of Mars List of craters on Mars Opportunity mission timeline Grotzinger, J. P.. "Stratigraphy and sedimentology of a dry to wet eolian depositional system, Burns formation, Meridiani Planum, Mars". Earth and Planetary Science Letters. 240: 11–72. Bibcode:2005E&PSL.240...11G. Doi:10.1016/j.epsl.2005.09.039. The official Mars Exploration Rover Mission website Various papers on the geology encountered at Endurance Crater and the processes involved: The sedimentary rocks of Sinus Meridiani: Five key observations from data acquired by the Mars Global Surveyor and Mars Odyssey orbiters - proposes a theory on crater exhumation in the region Endurance crater and the surrounding plains of Meridiani Planum
Space telescope
A space telescope or space observatory is an instrument located in outer space to observe distant planets and other astronomical objects. Space telescopes avoid many of the problems of ground-based observatories, such as light pollution and distortion of electromagnetic radiation. In addition, ultraviolet frequencies, X-rays and gamma rays are blocked by the Earth's atmosphere, so they can only be observed from space. Theorized by Lyman Spitzer in 1946, the first operational space 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 are distinct from other imaging satellites pointed toward Earth for purposes of espionage, weather analysis and other types of information gathering. Wilhelm Beer and Johann Heinrich Mädler in 1837 discussed the advantages of an observatory on the Moon. In 1946, American theoretical astrophysicist Lyman Spitzer proposed a telescope in space, 11 years before the Soviet Union launched the first satellite, Sputnik 1.
Spitzer's proposal called for a large telescope. After lobbying in the 1960s and 70s for such a system to be built, Spitzer's vision materialized into the Hubble Space Telescope, launched on April 24, 1990 by the Space Shuttle Discovery. Performing astronomy from ground-based observatories on Earth is limited by the filtering and distortion of electromagnetic radiation due to the atmosphere; some terrestrial telescopes can reduce atmospheric effects with adaptive optics. A telescope orbiting Earth outside the atmosphere is subject neither to twinkling nor to light pollution from artificial light sources on Earth; as a result, the angular resolution of space telescopes is much smaller than a ground-based telescope with a similar aperture. Space-based astronomy is more important for frequency ranges which are outside the optical window and the radio window, the only two wavelength ranges of the electromagnetic spectrum that are not attenuated by the atmosphere. For example, X-ray astronomy is nearly impossible when done from Earth, has reached its current importance in astronomy only due to orbiting X-ray telescopes such as the Chandra observatory and the XMM-Newton observatory.
Infrared and ultraviolet are largely blocked. However, all these advantages do come with a price. Space telescopes are much more expensive to build than ground-based telescopes. Due to their location, space telescopes are extremely difficult to maintain; the Hubble Space Telescope was serviced by the Space Shuttle while many other space telescopes cannot be serviced at all. Space observatories can be divided into two classes: missions which map the entire sky, observatories which focus on selected astronomical objects or parts of the sky. Satellites have been launched and operated by NASA, ISRO, ESA, Japanese Space Agency and the Soviet space program succeeded by Roskosmos of Russia; as of 2018, many space observatories have completed their missions, while others continue operating on extended time. However, the availability of space telescopes and observatories in the future is threatened due to delays and budget cuts. While future space observatories are planned by NASA, JAXA and the China National Space Administration, scientists fear that there would be gaps in coverage that would not be covered by future projects and this would affect research in fundamental science.
Space observatories portal Airborne observatory Earth observation satellite List of telescope types Observatory Timeline of artificial satellites and space probes Timeline of telescopes and observing technology Ultraviolet astronomy X-ray astronomy satellite Neil English: Space Telescopes - Capturing the Rays of the Electromagnetic Spectrum. Springer, Cham 2017, ISBN 978-3-319-27812-4
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