query: why did scientists use radio telescopes to bounce radar pulses off of venus

pos: Radar astronomy have a relatively good ephemeris of the target before observing it. The Moon is comparatively close and was detected by radar soon after the invention of the technique in 1946. Measurements included surface roughness and later mapping of shadowed regions near the poles. The next easiest target is Venus. This was a target of great scientific value, since it could provide an unambiguous way to measure the size of the astronomical unit, which was needed for the nascent field of interplanetary spacecraft. In addition such technical prowess had great public relations value, and was an excellent demonstration to funding agencies.

neg: Microwave radio sources; planets, stars, galaxies, and nebulas are studied in radio astronomy with large dish antennas called radio telescopes. In addition to receiving naturally occurring microwave radiation, radio telescopes have been used in active radar experiments to bounce microwaves off planets in the solar system, to determine the distance to the Moon or map the invisible surface of Venus through cloud cover. A recently completed microwave radio telescope is the Atacama Large Millimeter Array, located at more than 5,000 meters (16,597 ft) altitude in Chile, observes the universe in the millimetre and submillimetre wavelength ranges. The world's largest ground-based astronomy

neg: Lovell Telescope from these original objectives, and are outlined in the following sections. In Autumn 1958, the telescope was used to bounce "Hellos" off the Moon for a demonstration in Lovell's third Reith Lecture. The telescope was also used to receive messages bounced off the Moon (a "moonbounce") as part of the 50th anniversary First Move festival. In April 1961, a radar echo from Venus was achieved using the telescope while the planet was at a close approach, confirming measurements of the distance of the planet made by American telescopes. The 21 cm hydrogen line was discovered during the telescope's construction; the

neg: Mercury (planet) observations. Many of the planet's surface features, particularly the albedo features, take their names from Antoniadi's map. In June 1962, Soviet scientists at the Institute of Radio-engineering and Electronics of the USSR Academy of Sciences, led by Vladimir Kotelnikov, became the first to bounce a radar signal off Mercury and receive it, starting radar observations of the planet. Three years later, radar observations by Americans Gordon Pettengill and R. Dyce, using the 300-meter Arecibo Observatory radio telescope in Puerto Rico, showed conclusively that the planet's rotational period was about 59 days. The theory that Mercury's rotation was synchronous had become

neg: Shapiro time delay by Irwin Shapiro. Shapiro proposed an observational test of his prediction: bounce radar beams off the surface of Venus and Mercury and measure the round-trip travel time. When the Earth, Sun, and Venus are most favorably aligned, Shapiro showed that the expected time delay, due to the presence of the Sun, of a radar signal traveling from the Earth to Venus and back, would be about 200 microseconds, well within the limitations of 1960s-era technology. The first tests, performed in 1966 and 1967 using the MIT Haystack radar antenna, were successful, matching the predicted amount of time delay. The experiments

neg: Frequency agility Frequency agility Frequency agility is the ability of a radar system to quickly shift its operating frequency to account for atmospheric effects, jamming, mutual interference with friendly sources, or to make it more difficult to locate the radar broadcaster through radio direction finding. The term can also be applied to other fields, including lasers or traditional radio transceivers using frequency-division multiplexing, but it remains most closely associated with the radar field and these other roles generally use the more generic term "frequency hopping". Radar systems generally operate by sending out short pulses of radio energy and then turning off the

neg: Venus the first measurements of the rotation period, which were close to the modern value. Radar observations in the 1970s revealed details of the Venusian surface for the first time. Pulses of radio waves were beamed at the planet using the radio telescope at Arecibo Observatory, and the echoes revealed two highly reflective regions, designated the Alpha and Beta regions. The observations also revealed a bright region attributed to mountains, which was called Maxwell Montes. These three features are now the only ones on Venus that do not have female names. The first robotic space probe mission to Venus, and the

neg: Lunar distance (astronomy) the radio waves echoed off the surface of the Moon, the return signal was detected and the delay time measured. From that measurement, the distance could be calculated. In practice, however, the signal-to-noise ratio was so low that an accurate measurement could not be reliably produced. The experiment was repeated in 1958 at the Royal Radar Establishment, in England. Radar pulses lasting were transmitted with a peak power of 2 megawatts, at a repetition rate of 260 pulses per second. After the radio waves echoed off the surface of the Moon, the return signal was detected and the delay time

neg: AI Mk. VIII radar the "sunrise pattern". For unknown reasons, the team did not decide to use the same system for radio beacon use, as they had under Mk. IV. Instead, at meetings on the 13th and 14 July 1941, Hodgkin and Clegg decided to use the radar's own frequency for this role. This would require new transponders on the ground to support the AIS-equipped night fighters. The radar was adapted too, adding a switch that changed the pulse repetition frequency from 2,500 to 930 Hz, stretching the maximum range to . To offset the fact that fewer pulses were being sent, the pulse

neg: Radio GPS position. Search radars scan a wide area with pulses of short radio waves. They usually scan the area two to four times a minute. Sometimes search radars use the Doppler effect to separate moving vehicles from clutter. Targeting radars use the same principle as search radar but scan a much smaller area far more often, usually several times a second or more. Weather radars resemble search radars, but use radio waves with circular polarization and a wavelength to reflect from water droplets. Some weather radar use the Doppler effect to measure wind speeds. Most new radio systems are digital,

neg: Observations and explorations of Venus the rotation of Venus was retrograde (it rotates in the opposite direction to that in which it orbits the Sun). The radar observations also allowed astronomers to determine that the rotation period of Venus was 243.1 days, and that its axis of rotation was almost perpendicular to its orbital plane. It was also established that the radius of the planet was , some less than the best previous figure obtained with terrestrial telescopes. Interest in the geological characteristics of Venus was stimulated by the refinement of imaging techniques between 1970 and 1985. Early radar observations suggested merely that the surface

neg: Pulse repetition frequency utilized extensively in automated machine control systems (e.g. electric eyes controlling a garage door, conveyor sorting gates, etc.), and those that use pulse rate detection and ranging are at heart, the same type of system as a radar—without the bells and whistles of the human interface. Unlike lower radio signal frequencies, light does not bend around the curve of the earth or reflect off the ionosphere like C-band search radar signals, and so lidar is useful only in line of sight applications like higher frequency radar systems. Pulse repetition frequency The pulse repetition frequency (PRF) is the number of pulses

neg: Pulse repetition frequency Pulse repetition frequency The pulse repetition frequency (PRF) is the number of pulses of a repeating signal in a specific time unit, normally measured in pulses per second. The term is used within a number of technical disciplines, notably radar. In radar, a radio signal of a particular carrier frequency is turned on and off; the term "frequency" refers to the carrier, while the PRF refers to the number of switches. Both are measured in terms of cycle per second, or hertz. The PRF is normally much lower than the frequency. For instance, a typical World War II radar like

neg: History of radar three fully steerable radio telescopes became operational just in time to radar track "Sputnik 1", the first artificial satellite, in October 1957. History of radar The history of radar (where radar stands for RAdio Detection And Ranging) started with experiments by Heinrich Hertz in the late 19th century that showed that radio waves were reflected by metallic objects. This possibility was suggested in James Clerk Maxwell's seminal work on electromagnetism. However, it was not until the early 20th century that systems able to use these principles were becoming widely available, and it was German inventor Christian Hülsmeyer who first used

neg: Vid Flumina scientists at NASA were expecting to find some evidence for liquid methane because of Titan's surface temperature and its methane-rich atmosphere. However, "Cassini" early findings that were focused on Titan's equator revealed no traces of seas or rivers. The early disappointment changed as the "Cassini" orbit shifted and allowed the researchers at NASA to bounce radar off other regions of the moon. The radar signals were then routinely reflected off angled, rough features such as sand dunes and rocks and cliffs, but when the radar reached the polar regions of Titan, the regular signals ceased. These non-reflecting dark spots where

neg: Cleopatra (crater) data which shows surfaces with different elevations from the "Magellan" mission. Prior to improved satellite imagery from the "Magellan" spacecraft mapping mission to Venus in 1994, the topography of Venus was interpreted from lower quality images received from radio telescopes and altimetric data. This data allowed for a misinterpretation of the crater; however, it is important to understand what was seen geometrically to explain why certain hypotheses withstood many years. It was found that the topographic elevation on Maxwell Montes resulted from a combination of horizontal compression and vertical crustal thickening, which in combination allowed for the lower crust to

neg: Robert Price (engineer) system, the Lincoln F9C (1950). Price and Green also attempted to bounce radar waves off the planet Venus (1958). With Gordon Pettengill, the two of them worked out a theory of range-Doppler mapping that was used on the Magellan probe mapping of Venus' surface 20 years later. In 1965 he left the Lincoln Laboratory to join the Sperry Research Center in Sudbury, Massachusetts. He later worked at M/A-COM Government Systems and at Raytheon. Price was elected to the National Academy of Engineering (1985). He was a Life Fellow of the IEEE. Robert Price (engineer) Robert Price (7 July 1929 –

neg: ASM-135 ASAT In order to complete an ASAT test before an expected Congressional ban took effect (as it did in October 1985), the DoD chose to use the existing Solwind astrophysics satellite as a target. NASA worked with the DoD to monitor the effects of the tests using two orbital debris telescopes and a reentry radar deployed to Alaska. NASA assumed the torn metal would be bright. Surprisingly, the Solwind pieces turned out to appear so dark as to be almost undetectable. Only two pieces were seen. NASA Scientists theorized that the unexpected Solwind darkening was due to carbonization of organic compounds

neg: Paul Green (engineer) and were followed by Ph.D. from M.I.T. (1953) on a thesis on spread spectrum, supervised by Wilbur Davenport, Robert Fano and Jerome Wiesner. This involved co-creating the Rake receiver (with Robert Price) and supervision of its deployment in a first-ever spread-spectrum system, the Lincoln F9C (1950). Following his studies, Green and Price (at MIT Lincoln Laboratory), attempting to bounce radar waves off the planet Venus (1958). With Gordon Pettengill, he worked out a theory of range-Doppler mapping that was used on the Magellan probe mapping of Venus' surface twenty years later. He also designed the LASA (Large Aperture Seismic Array)

neg: Shukrayaan-1 be deployed from an orbiter and take prolonged observations while floating in the relatively mild upper atmosphere of the planet. ISRO accepted to consider the proposal to use a balloon probe carrying payload to study the Venusian atmosphere at altitude. The science payload would have a mass of and would consist of instruments from India and other countries. The pre-selected proposals from India are listed below. Some of these would be selected to fly: NASA may provide terahertz devices to generate powerful radar pulses. The proposal has not been formalized. Shukrayaan-1 Shukrayaan-1 ("Venus craft") is a proposed orbiter to Venus

neg: Pulsed radiofrequency pulse rate) with a gated pulse width of 42 µs. The pulse packet frequency in this example is 27.125 megahertz (MHz) of RF energy. The duty cycle for a pulsed radio frequency is the percent time the RF packet is on, 4.2% for this example ([0.042 ms X 1000 pulses divided by 1000 ms/s] X 100). The pulse packet form can be a square, triangle, sawtooth or sine wave. In several applications of pulse radio frequency, such as radar, times between pulses can be modulated. The best understood and applied use of pulse radio frequency electromagnetic energy is their use

neg: EnVision (spacecraft) EnVision (spacecraft) EnVision is a proposed orbital mission to Venus that would perform high-resolution radar mapping and atmospheric studies. The mission would help scientists understand the relationships between its geological activity and the atmosphere, and it would investigate why Venus and Earth took such different evolutionary paths. The concept was selected in May 2018 as a finalist to become the fifth Medium-class mission (M5) of the Cosmic Vision programme by the European Space Agency (ESA). The other two finalists are SPICA, an infrared space telescope, and THESEUS, a gamma-ray space observatory. The winner will be selected in 2021 and it

neg: Ground-penetrating radar Ground-penetrating radar Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This nondestructive method uses electromagnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR can have applications in a variety of media, including rock, soil, ice, fresh water, pavements and structures. In the right conditions, practitioners can use GPR to detect subsurface objects, changes in material properties, and voids and cracks. GPR uses high-frequency (usually polarized) radio waves, usually in the range 10 MHz to 2.6 GHz. A GPR transmitter and antenna

neg: Magellan (spacecraft) an eleven-year gap in U.S. interplanetary probe launches. Beginning in the late 1970s, scientists pushed for a radar mapping mission to Venus. They first sought to construct a spacecraft named the "Venus Orbiting Imaging Radar" (VOIR), but it became clear that the mission would be beyond the budget constraints during the ensuing years. The VOIR mission was canceled in 1982. A simplified radar mission proposal was recommended by the Solar System Exploration Committee, and this one was submitted and accepted as the Venus Radar Mapper program in 1983. The proposal included a limited focus and a single primary scientific instrument.

neg: Radar each other, and it is not easy to combine both good short range and good long range in a single radar. This is because the short pulses needed for a good minimum range broadcast have less total energy, making the returns much smaller and the target harder to detect. This could be offset by using more pulses, but this would shorten the maximum range. So each radar uses a particular type of signal. Long-range radars tend to use long pulses with long delays between them, and short range radars use smaller pulses with less time between them. As electronics have

neg: Radar signal characteristics process where the time between interrogations from radar changes slightly, "in a patterned and readily-discernible repeating manner." The change of repetition frequency allows the radar, on a pulse-to-pulse basis, to differentiate between returns from its own transmissions and returns from other radar systems with the same PRF and a similar radio frequency. Consider a radar with a constant interval between pulses; target reflections appear at a relatively constant range related to the flight-time of the pulse. In today's very crowded radio spectrum, there may be many other pulses detected by the receiver, either directly from the transmitter or as reflections

neg: Venus Orbiting Imaging Radar Venus Orbiting Imaging Radar Venus Orbiting Imaging Radar (VOIR; also called Venus Orbital Imaging Radar) was a planned 1983 U.S. spacecraft mission to Venus that was primarily intended to use a microwave imaging radar to perform mapping of the Venusian surface. The goal was to map up to 50% of the planet's surface down to a resolution of 2 km with the eventual goal of targeting landers and atmospheric probes. A 1978 study evaluated the potential use of synthetic aperture radar to achieve 200 meter resolution. The spacecraft was to be launched from the Space Shuttle using a twin stage

neg: Edwin King Stodola Project Diana, a Signal Corps project to investigate long range radar. Led by John H. DeWitt, Jr., this group consisted of a five-man team with Stodola as the chief scientist. During a test on January 10, 1946, this team became the first to bounce a radio signal off the moon and detect the resulting echo (Earth-Moon-Earth or EME). He left the Signal Corps in 1947 and became an engineer with Reeves Instrument Corporation. Stodola received the Presidential Citation from Cooper Union in 1987 in recognition of his contributions to radar and radar tracking systems, and the Radio Club of America's

neg: Cavity magnetron in widespread use in roles which require high power, but where precise control over frequency and phase is unimportant. In a radar set, the magnetron's waveguide is connected to an antenna. The magnetron is operated with very short pulses of applied voltage, resulting in a short pulse of high power microwave energy being radiated. As in all primary radar systems, the radiation reflected off a target is analyzed to produce a radar map on a screen. Several characteristics of the magnetron's output make radar use of the device somewhat problematic. The first of these factors is the magnetron's inherent instability

neg: Maxwell Montes in relation to other compressional mountain ranges around Lakshmi Planum suggests that its origin is more complex. Most of Maxwell Montes has a bright radar return which is common on Venus at high altitudes. This phenomenon is thought to result from the presence of a mineral, possibly a metallic snow. Early suggestions included pyrite and tellurium; more recently, lead sulfide and bismuth sulfide have been proposed. By using radar to probe through the permanent and thick clouds in the Venusian atmosphere and make observations of the surface, scientists at the American Arecibo Radio Telescope in Puerto Rico discovered the extensive

neg: Radar display Radar display A radar display is an electronic device to present radar data to the operator. The radar system transmits pulses or continuous waves of electromagnetic radiation, a small portion of which backscatter off targets (intended or otherwise) and return to the radar system. The receiver converts all received electromagnetic radiation into a continuous electronic analog signal of varying (or oscillating) voltage that can be converted then to a screen display. Modern systems typically use some sort of raster scan display to produce a map-like image. Early in radar development, however, numerous circumstances made such displays difficult to produce. People

neg: Radar display guided toward it. Radar display A radar display is an electronic device to present radar data to the operator. The radar system transmits pulses or continuous waves of electromagnetic radiation, a small portion of which backscatter off targets (intended or otherwise) and return to the radar system. The receiver converts all received electromagnetic radiation into a continuous electronic analog signal of varying (or oscillating) voltage that can be converted then to a screen display. Modern systems typically use some sort of raster scan display to produce a map-like image. Early in radar development, however, numerous circumstances made such displays difficult

neg: Venus Orbiting Imaging Radar it exceeded its budget limit. In 1983, it was replaced by a less ambitious mission called the Venus Radar Mapper, which was later renamed Magellan. Venus Orbiting Imaging Radar Venus Orbiting Imaging Radar (VOIR; also called Venus Orbital Imaging Radar) was a planned 1983 U.S. spacecraft mission to Venus that was primarily intended to use a microwave imaging radar to perform mapping of the Venusian surface. The goal was to map up to 50% of the planet's surface down to a resolution of 2 km with the eventual goal of targeting landers and atmospheric probes. A 1978 study evaluated the

neg: Gordon Pettengill Arecibo Observatory in Puerto Rico. At Arecibo, Pettengill with Rolf Dyce, used radar pulses to measure the spin rate of Mercury and found that Mercury's 'day' was 59 Earth days, not 88 as had been previously thought. He was appointed Professor of Planetary Physics in the Department of Earth and Planetary Sciences at MIT in 1970. In the late 1960s and early 1970s, Pettengill led ground-based radar studies of the surface properties of all of the inner planets, including the Earth's (via a "triple-bounce" experiment: Moon-Earth-Moon). Pettengill also played a leading role in the first radar studies of an asteroid

neg: Magellan (spacecraft) nadir, emitted thousands of microwave pulses that passed through the clouds and to the surface of Venus, illuminating a swath of land. The Radar System then recorded the brightness of each pulse as it reflected back off the side surfaces of rocks, cliffs, volcanoes and other geologic features, as a form of backscatter. To increase the imaging resolution, "Magellan" recorded a series of data bursts for a particular location during multiple instances called, "looks". Each "look" slightly overlapped the previous, returning slightly different information for the same location, as the spacecraft moved in orbit. After transmitting the data back to

neg: Radio telescope They may be used singly or linked together electronically in an array. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night. Since astronomical radio sources such as planets, stars, nebulas and galaxies are very far away, the radio waves coming from them are extremely weak, so radio telescopes require very large antennas to collect enough radio energy to study them, and extremely sensitive receiving equipment. Radio observatories are preferentially located far from major centers of population to avoid electromagnetic interference (EMI) from radio, television, radar, motor vehicles, and other manmade electronic devices. Radio

neg: Apache Point Observatory Lunar Laser-ranging Operation Apache Point Observatory Lunar Laser-ranging Operation The Apache Point Observatory Lunar Laser-ranging Operation, or APOLLO, is a project at the Apache Point Observatory in New Mexico. It is an extension and advancement of previous Lunar Laser Ranging experiments, which use retroreflectors on the Moon to track changes in lunar orbital distance and motion. Using telescopes on Earth, the reflectors on the Moon, and accurate timing of laser pulses, by the early 2000s scientists could measure and predict the orbit of the Moon to an accuracy of a few centimeters. This already impressive accuracy (the Moon is typically about 385,000 km

neg: Yevpatoria RT-70 radio telescope Yevpatoria RT-70 radio telescope The Yevpatoria RT-70 radio telescope (P-2500, RT-70) is an RT-70 radio telescope and planetary radar at the Center for Deep Space Communications, Yevpatoria, Crimea. In the scientific literature is often called Evpatoria Planetary Radar (EPR). With its 70-meter antenna diameter, it is among the largest single dish radio telescopes in the world. It has an advantage in comparison with other large radio telescopes in the fact that the complex includes powerful transmitters that allow active space experiments. Powerful electromagnetic beams can be accurately targeted and the signals received can be analyzed. For this reason, the Yevpatoria

neg: AI Mk. VIII radar separate radio system for transmitting and receiving these pulses, the "interrogator". When the radar operator pressed a button on their console, the interrogator began sending out pulses synchronised with those of the radar unit. The IFF unit in the target aircraft then responded with pulses with the same timing. The output of the interrogator's receiver was mixed with the radar's, causing the blip to extend as before. When this was added to the spiral scan display, instead of stretching the blip, the IFF signal appeared as a series of short line segments extending outward from the middle of the display,

neg: Project Diana early 1960s. Since then it has been used by amateur radio operators. Today, the Project Diana site is part of the Camp Evans Historic District, InfoAge Science History Learning Center and Museum, and is maintained by the Ocean-Monmouth Amateur Radio Club. The antenna array was removed earlier and is now presumably lost. Project Diana Project Diana, named for the Roman moon goddess Diana, was an experimental project of the US Army Signal Corps in 1946 to bounce radar signals off the Moon and receive the reflected signals. This was the first experiment in radar astronomy and the first active attempt

neg: Radar signal characteristics from elsewhere. Because their apparent "distance" is defined by measuring their time relative to the last pulse transmitted by "our" radar, these "jamming" pulses could appear at any apparent distance. When the PRF of the "jamming" radar is very similar to "our" radar, those apparent distances may be very slow-changing, just like real targets. By using stagger, a radar designer can force the "jamming" to jump around erratically in apparent range, inhibiting integration and reducing or even suppressing its impact on true target detection. Without staggered PRF, any pulses originating from another radar on the same radio frequency might appear

neg: Raman Research Institute one of the few largest telescopes that operate at the wavelength of 10 metre and is being used by RRI scientists to study radio emission from various types of celestial objects such as the Sun, Jupiter and similar radio sources in Milky Way and other galaxies. Other radio telescopes that are being used by RRI scientists for observations are the Ooty Radio Telescope, at Ooty, and Giant Metrewave Radio Telescope (GMRT), near Pune, both set up by the Tata Institute of Fundamental Research (TIFR). RRI also played an active role in building the Mauritius Radio Telescope, a low-frequency radio telescope

neg: Associated Universities, Inc. as its director. Pending submission, review, and approval of a supplemental funding request, AUI will continue managing each under a separate cooperative agreement for the next two years, while NSF decides the long-term future of these facilities. The National Radio Astronomy Observatory (NRAO), headquartered in Charlottesville, VA, is a Federally Funded Research and Development Center (FFRDC) operated by Associated Universities, Inc. under cooperative agreement with the United States National Science Foundation. NRAO designs, builds, and operates high sensitivity radio telescopes for use by scientists around the world. NRAO telescopes are open to all astronomers regardless of institutional or national affiliation.

neg: Polarization (waves) horizontal and vertical polarizations. AM and FM broadcast radio usually use vertical polarization, while television uses horizontal polarization. At low frequencies especially, horizontal polarization is avoided. That is because the phase of a horizontally polarized wave is reversed upon reflection by the ground. A distant station in the horizontal direction will receive both the direct and reflected wave, which thus tend to cancel each other. This problem is avoided with vertical polarization. Polarization is also important in the transmission of radar pulses and reception of radar reflections by the same or a different antenna. For instance, back scattering of radar

neg: Lada Terra as well as many other features that scientists use to attempt to piece together the history of this complex planet. The distinctive cross-cutting relationships found in the bedding of Lada Terra have been important in realizing relative ages of the extensional belts and coronae, as well as the complex tesserae features present planet-wide. In 1990 the Venus Radar Mapper revealed the largest outflow channel system on the planet located in the northern region of Lada Terra. Although Lada Terra is generally considered a highland of Venus, the topography is much lower-lying than its northern counterparts Ishtar Terra and Aphrodite Terra.

neg: Automatic dependent surveillance – broadcast continuously transmits high power radio frequency (RF) pulses. Bearing is measured by the position of the rotating radar antenna when it receives the RF pulses that are reflected from the aircraft skin. Range is measured by measuring the time it takes for the RF energy to travel to and from the aircraft. Primary surveillance radar does not require any cooperation from the aircraft. It is robust in the sense that surveillance outage failure modes are limited to those associated with the ground radar system. Secondary surveillance radar depends on active replies from the aircraft. Its failure modes include the transponder

neg: Mapping of Venus After collection of the images of the Venusian surface, scientists started to map and identify different geologic materials and units according to distinctive surface features. Different groups of scientists analysed different mapping areas, schemes and interpretation of features observed, to produce a classification of the units and comparison of their mapping. Before the development of radar-based observation, the thick yellow Venusian atmosphere hid surface features. In the 1920s, the first Venus ultraviolet project captured the thick atmosphere of Venus, but provided no information about the surface. From 1961 to 1984, the Soviet Union developed the "Venera" probes for surface mapping

neg: Amateur astronomy built radio telescope in the late 1930s to follow up on the discovery of radio wavelength emissions from space by Karl Jansky. Non-visual amateur astronomy includes the use of infrared filters on conventional telescopes, and also the use of radio telescopes. Some amateur astronomers use home-made radio telescopes, while others use radio telescopes that were originally built for astronomical research but have since been made available for use by amateurs. The One-Mile Telescope is one such example. Amateur astronomers use a range of instruments to study the sky, depending on a combination of their interests and resources. Methods include simply

neg: H2S (radar) of various Marks featuring one or more of these additional corrections. These delays had not been expected, and Lovell later noted: Radar operates by sending out very short pulses of a radio signal from a transmitter, then turning the transmitter off and listening for echoes in a receiver. The output of the receiver is sent to an oscilloscope's brightness input, so strong echoes cause a spot on the screen to light up. To make the spots correspond to locations in space, the oscilloscope quickly scans from the centre to the outside of the display; echoes that return later in time

neg: Pulse repetition frequency the Type 7 GCI radar had a basic carrier frequency of 209 MHz (209 million cycles per second) and a PRF of 300 or 500 pulses per second. A related measure is the pulse width, the amount of time the transmitter is turned on during each pulse. The PRF is one of the defining characteristics of a radar system, which normally consists of a powerful transmitter and sensitive receiver connected to the same antenna. After producing a brief pulse of radio signal, the transmitter is turned off in order for the receiver units to hear the reflections of that signal

neg: RAF Chenies the game volleyball would be played where players were permitted to bounce the ball off the walls. In the 1980s the station was used as the site for a Met Office weather radar station with a 'golf ball' styled Radome, still in use today. As of September 2012, the site is being transformed to accommodate housing. All of the derelict buildings have been demolished, the antenna tower has been removed and construction is underway on at least two houses. The active radar installation is still securely fenced off inside the larger compound. RAF Chenies RAF Chenies is a former Royal

neg: Radio telescope other radio sources. The rapid development of radar during World War II created technology which was applied to radio astronomy after the war, and radio astronomy became a branch of astronomy, with universities and research institutes constructing large radio telescopes. The range of frequencies in the electromagnetic spectrum that makes up the radio spectrum is very large. This means that the types of antennas that are used as radio telescopes vary widely in design, size, and configuration. At wavelengths of 30 meters to 3 meters (10 MHz - 100 MHz), they are generally either directional antenna arrays similar to "TV

neg: ASR-11 closer than six nautical miles from the radar cannot be located with the long range pulse system built into the ASR-11. Installing additional radar equipment to the same antenna is required for close range location and weather detection. The second advantage of using an ASR-11 is the radar's ability to utilize a pulse sequence diversity. This gives the radar system the capability to limit processing dwells to a small number of pulses. This feature becomes most important when monitoring air traffic is the primary use of the radar. Reducing the number of pulses sent out by the radar system also

neg: Radar ways depending on the size (wavelength) of the radio wave and the shape of the target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a mirror. If the wavelength is much longer than the size of the target, the target may not be visible because of poor reflection. Low-frequency radar technology is dependent on resonances for detection, but not identification, of targets. This is described by Rayleigh scattering, an effect that creates Earth's blue sky and red sunsets. When the two length

neg: Astronomy small minority experiment with wavelengths outside the visible spectrum. This includes the use of infrared filters on conventional telescopes, and also the use of radio telescopes. The pioneer of amateur radio astronomy was Karl Jansky, who started observing the sky at radio wavelengths in the 1930s. A number of amateur astronomers use either homemade telescopes or use radio telescopes which were originally built for astronomy research but which are now available to amateurs ("e.g." the One-Mile Telescope). Amateur astronomers continue to make scientific contributions to the field of astronomy and it is one of the few scientific disciplines where amateurs

neg: Radar the receiver) and the speed of the signal. Since radio waves travel close to the speed of light, accurate distance measurement requires high-speed electronics. In most cases, the receiver does not detect the return while the signal is being transmitted. Through the use of a duplexer, the radar switches between transmitting and receiving at a predetermined rate. A similar effect imposes a maximum range as well. In order to maximize range, longer times between pulses should be used, referred to as a pulse repetition time, or its reciprocal, pulse repetition frequency. These two effects tend to be at odds with

neg: Gordon Pettengill a radar altimeter to map Venus and contributed key technical ideas. The results, in part, were detailed reflectivity and topographic maps of virtually the entire planet of Venus, providing geologists and geophysicists with lifetimes of work to understand the development of Venus' crust and the history of its interior. Many planetary scientists feel he is one of the individuals most responsible for our present knowledge of Venus (aside from its atmosphere). His observations have embraced Mercury, Venus, Mars, several asteroids and comets, the Galilean satellites of Jupiter and the rings of Saturn. He won the Charles A. Whitten Medal from

neg: Extraterrestrial liquid water least one gravitational study on Cassini data, Dione has an ocean 100 kilometers below the surface. Scientists have detected liquid water using radio signals. The Radar Detection And Ranging (RADAR) instrument of the Cassini probe was used to detect the existence of a layer of liquid water and ammonia beneath the surface of Saturn's moon Titan that are consistent with calculations of the moon's density. Ground penetrating radar and dielectric permittivity data from the MARSIS instrument on Mars Express indicates a 20-kilometer-wide stable body of briny liquid water in the Planum Australe region of planet Mars. Planetary scientists can use

neg: Ambiguity function would observe in a radar system) is a Doppler cut, with constant frequency given by the target's Doppler shift: formula_10. Pulse-Doppler radar equipment sends out a series of radio frequency pulses. Each pulse has a certain shape (waveform)—how long the pulse is, what its frequency is, whether the frequency changes during the pulse, and so on. If the waves reflect off a single object, the detector will see a signal which, in the simplest case, is a copy of the original pulse but delayed by a certain time formula_11—related to the object's distance—and shifted by a certain frequency formula_12—related to

neg: Space debris is difficult. Most debris remain unobserved. The NASA Orbital Debris Observatory tracked space debris with a liquid mirror transit telescope. FM Radio waves can detect debris, after reflecting off them onto a receiver. Optical tracking may be a useful early-warning system on spacecraft. The U.S. Strategic Command keeps a catalog of known orbital objects, using ground-based radar and telescopes, and a space-based telescope (originally to distinguish from hostile missiles). The 2009 edition listed about 19,000 objects. Other data come from the ESA Space Debris Telescope, TIRA, the Goldstone, Haystack, and EISCAT radars and the Cobra Dane phased array radar, to

neg: Parabolic antenna are also used in radio telescopes. The other large use of parabolic antennas is for radar antennas, in which there is a need to transmit a narrow beam of radio waves to locate objects like ships, airplanes, and guided missiles, and often for weather detection. With the advent of home satellite television receivers, parabolic antennas have become a common feature of the landscapes of modern countries. The parabolic antenna was invented by German physicist Heinrich Hertz during his discovery of radio waves in 1887. He used cylindrical parabolic reflectors with spark-excited dipole antennas at their focus for both transmitting and

neg: Heterodyne is used very widely in communications engineering to generate new frequencies and move information from one frequency channel to another. Besides its use in the superheterodyne circuit found in almost all radio and television receivers, it is used in radio transmitters, modems, satellite communications and set-top boxes, radar, radio telescopes, telemetry systems, cell phones, cable television converter boxes and headends, microwave relays, metal detectors, atomic clocks, and military electronic countermeasures (jamming) systems. In large scale telecommunication networks such as telephone network trunks, microwave relay networks, cable television systems, and communication satellite links, large bandwidth capacity links are shared by many

neg: Radar configurations and types Radar configurations and types Radar configurations and types is an article about listing the different uses of radars. Radar come in a variety of configuration in the emitter, the receiver, the antenna, wavelength, scan strategies, etc. Search radars scan great volumes of space with pulses of short radio waves. They typically scan the volume two to four times a minute. The waves are usually less than a meter long. Ships and planes are metal, and reflect radio waves. The radar measures the distance to the reflector by measuring the time of the roundtrip from emission of a pulse to reception,

neg: Lada Terra corona, make relative age dating very difficult for scientists. However, using cross cutting relationships obtained from the radar data received from the missions to Venus has allowed scientists to draw complex correlations. The unique tessera terrain, which is interpreted to be a deformation product of the high regional stresses on Venus, is the oldest type of terrain found in the Lada Terra Region. The extensional belts and several corona, including the Quetzalpetlatl Corona, are observed to be cutting across the tessera terrain, implying these structures to be formed after this heavily deformed material. The extensional belts in some areas cross

neg: AI Mk. VIII radar Another issue was the desire to start using the new Sutton tubes for switching, which was expected to greatly increase the range of the system. Also desired was some way to use IFF and radio beacons with the AIS systems, as previous transponders had been deliberately designed to listen and respond on the original AI Mk. IV frequencies around 193 MHz. The transponder problem had been growing before the introduction of AIS. IFF worked on the basis of a small receiver/transmitter set that listened for pulses from a radar and produced a low-power pulse broadcast on the same frequency but

neg: Maxwell Montes highland on Venus that came to be called Maxwell Montes in 1967. In 1978, the space probe Pioneer Venus 1 went into orbit around Venus for the purpose of making radar observations of the Venusian surface. These observations made possible the creation of the first topographic map of the surface of Venus, and confirmed that a point within Maxwell Montes is the highest point above the average level of the planet's surface. Maxwell Montes is named for James Clerk Maxwell whose work in mathematical physics predicted the existence of radio waves, which made radar, and thus the surface observations of

neg: Jet Propulsion Laboratory Development Ephemeris crunched by JPL to derive the ephemeris began to move away from limited-accuracy telescopic observations and more toward higher-accuracy radar-ranging of the planets, radio-ranging of spacecraft, and very-long-baseline-interferometric (VLBI) observations of spacecraft, especially for the four inner planets. Telescopic observations remained important for the outer planets because of their distance, hence the inability to bounce radar off of them, and the difficulty of parking a spacecraft near them. The perturbations of 300 asteroids were included, vs DE118/DE200 which included only the five asteroids determined to cause the largest perturbations. Better values of the planets' masses had been found since DE118/DE200,

neg: Continuous wave constant during each code element. At the receiver, the received signal is mixed with a heterodyne signal from a BFO (beat frequency oscillator) to change the radio frequency impulses to sound. Though most commercial traffic has now ceased operation using Morse it is still popular with amateur radio operators. Non-directional beacons (NDB) and VHF omnidirectional radio range (VOR) used in air navigation use Morse to transmit their identifier. Morse code is all but extinct outside the amateur service, so in non-amateur contexts the term CW usually refers to a continuous-wave radar system, as opposed to one transmitting short pulses. Some

neg: Lightning of study. During the Soviet Venera and U.S. Pioneer missions of the 1970s and 1980s, signals suggesting lightning may be present in the upper atmosphere were detected. Although the Cassini–Huygens mission fly-by of Venus in 1999 detected no signs of lightning, the observation window lasted mere hours. Radio pulses recorded by the spacecraft Venus Express (which began orbiting Venus in April 2006) may originate from lightning on Venus. Thunder is heard as a rolling, gradually dissipating rumble because the sound from different portions of a long stroke arrives at slightly different times. When the local electric field exceeds the dielectric

neg: National Radio Astronomy Observatory National Radio Astronomy Observatory The National Radio Astronomy Observatory (NRAO) is a Federally Funded Research and Development Center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc for the purpose of radio astronomy. NRAO designs, builds, and operates its own high sensitivity radio telescopes for use by scientists around the world. The NRAO headquarters is located on the campus of the University of Virginia. The North American ALMA Science Center and the NRAO Technology Center are also located in Charlottesville, Virginia. NRAO was, until October 2016, the operator of the world's largest fully steerable

neg: Nike Hercules proposed a series of changes: The addition of the TRR solved a problem with early pulse radar units. It is relatively easy to jam a conventional radar by sending out additional pulses of radio signal on the same frequency. Unless the transmitter has encoded some additional form of information in the signal, the receiver cannot determine which pulse it sent out and which is from the jammer. Note that this has no effect on the determination of the "direction" to the target, which is the same for both the original and jammer pulses. However, it makes the determination of range

neg: Venera 16 the planet (local vertical) and the SAR would be looking off to the side at 10 degrees. A bulge at the opposite end of the cylinder held fuel tanks and propulsion units. Two square solar arrays extended like wings from the sides of the cylinder. A radio dish antenna for communications was also attached to the side of the cylinder. The spacecraft each weighed . Both Venera 15 and 16 were equipped with a Synthetic Aperture Radar (SAR). A radar was necessary in this mission because nothing else would be able to penetrate the dense clouds of Venus. The probes

neg: Pulse repetition frequency off distant targets. Since the radio signal has to travel out to the target and back again, the required inter-pulse quiet period is a function of the radar's desired range. Longer periods are required for longer range signals, requiring lower PRFs. Conversely, higher PRFs produce shorter maximum ranges, but broadcast more pulses, and thus radio energy, in a given time. This creates stronger reflections that make detection easier. Radar systems must balance these two competing requirements. Using older electronics, PRFs were generally fixed to a specific value, or might be switched among a limited set of possible values. This gives

neg: Radar signal characteristics data. In simple ranging radars, the carrier will be pulse modulated and in continuous wave systems, such as Doppler radar, modulation may not be required. Most systems use pulse modulation, with or without other supplementary modulating signals. Note that with pulse modulation, the carrier is simply switched on and off in sync with the pulses; the modulating waveform does not actually exist in the transmitted signal and the envelope of the pulse waveform is extracted from the demodulated carrier in the receiver. Although obvious when described, this point is often missed when pulse transmissions are first studied, leading to misunderstandings

neg: Ground plane the ground connection of all the components are at the same reference potential. In digital and radio frequency PCBs, the major reason for using large ground planes is to reduce electrical noise and interference through ground loops and to prevent crosstalk between adjacent circuit traces. When digital circuits switch state, large current pulses flow from the active devices (transistors or integrated circuits) through the ground circuit. If the power supply and ground traces have significant impedance, the voltage drop across them may create noise voltage pulses that disturb other parts of the circuit (ground bounce). The large conducting area of

neg: History of radar provided directional information to objects over short ranges, were developed over the next two decades. The development of systems able to produce short pulses of radio energy was the key advance that allowed modern radar systems to come into existence. By timing the pulses on an oscilloscope, the range could be determined and the direction of the antenna revealed the angular location of the targets. The two, combined, produced a "fix", locating the target relative to the antenna. In the 1934–1939 period, eight nations developed independently, and in great secrecy, systems of this type: the United Kingdom, Germany, the United

neg: Beat frequency oscillator switching the transmitter on and off rapidly using a switch called a telegraph key. This was the first type of radio transmission, and during the early 20th century was widely used for private person-to-person messages by amateurs and commercial telegram traffic. With the rise of other types of modulation its use has declined, and CW is now only used for personal hobbyist messages by radio amateurs and is becoming obsolete. Since the pulses of carrier have no audio modulation, a CW signal received by an AM radio receiver simply sounds like silence. In order to make the carrier pulses audible

neg: Jodrell Bank Observatory mostly used for moon radar experiments. It has been decommissioned. An reflecting optical telescope was donated to the observatory in 1951 but was not used much, and was donated to the Salford Astronomical Society around 1971. The Multi-Element Radio Linked Interferometer Network (MERLIN) is an array of radio telescopes spread across England and the Welsh borders. The array is run from Jodrell Bank on behalf of the Science and Technology Facilities Council as a National Facility. The array consists of up to seven radio telescopes and includes the Lovell Telescope, the Mark II, Cambridge, Defford, Knockin, Darnhall, and Pickmere (previously

neg: Lee Harvey Oswald was my radio on my motorcycle, why did it not record the revving up at high speed plus my siren when we immediately took off for Parkland Hospital?'" In 1982, a panel of twelve scientists appointed by the National Academy of Sciences, including Nobel laureates Norman Ramsey and Luis Alvarez, unanimously concluded that the acoustic evidence submitted to the HSCA was "seriously flawed", was recorded after the shots, and did not indicate additional gunshots. Their conclusions were published in the journal "Science". In a 2001 article in the journal "Science & Justice", D.B. Thomas wrote that the NAS investigation was

neg: Arecibo Observatory include locating Soviet radar installations by detecting their signals bouncing off the Moon. Limited amateur radio operations have occurred, using "moon bounce" or Earth–Moon–Earth communication, in which radio signals aimed at the Moon are reflected back to Earth. The first of these operations was on June 13–14, 1964, using the call KP4BPZ. A dozen or so two-way contacts were made on 144 and 432 MHz. On July 3 and July 24, 1965, KP4BPZ was again activated on 432 MHz, making approximately 30 contacts on 432 MHz during the limited time slots available. For these tests, a very wide-band instrumentation recorder

neg: Synthetic-aperture radar power spectral density (PSD) than the fast Fourier transform (FFT)-based methods. Backprojection Algorithm is computationally expensive. It is specifically attractive for sensors that are wideband, wide-angle, and/or have long coherent apertures with substantial off-track motion. The basic design of a synthetic aperture radar system can be enhanced to collect more information. Most of these methods use the same basic principle of combining many pulses to form a synthetic aperture, but may involve additional antennas or significant additional processing. SAR requires that echo captures be taken at multiple antenna positions. The more captures taken (at different antenna locations) the more reliable

neg: Tessera (Venus) and further extensive studies of Venus's surface are necessary to fully understand this complex terrain. Pioneer Venus Orbiter detected regions of anomalous radar properties and high backscatter. Using SAR imaging, the Venera 15 and Venera 16 orbiters revealed these regions to be chaotically tiled terrain, which Soviet scientists named "parquet" (tiled floors), later known as "Tesserae". The most recent data concerning tessera terrain comes from the Magellan Mission, in which the majority of Venus's surface was mapped in high resolution (~100 m/pixel). Future missions to Venus would allow for further understanding of tessera terrain. Tesserae are recognized as covering 7.3%

neg: 1769 Transit of Venus observed from Tahiti phase was when Venus began "touching" the outside rim of the sun. In the second phase, Venus was completely within the sun's disc, but was still "touching" the outer rim. In the third phase, Venus has crossed the sun, was still completely within the disc, but was "touching" the opposite rim. Finally in the fourth phase, Venus was completely off the sun, but was still "touching" its outer rim. On the day of the transit, the sky was clear. Independent observations were made by James Cook, Green and Solander with their own telescopes. Because of the rarity of the event,

neg: DAVINCI would help scientists understand why Venus and Earth took such different paths as they matured, and provide another point of comparison for studies of rocky planets in other star systems (exoplanets). "DAVINCI" "in situ" measurements would answer multiple questions regarding Venus atmospheric composition as currently formulated for the National Research Council Planetary Science Decadal Survey's Venus In Situ Explorer (VISE). "DAVINCI" is designed to address high-priority NASA decadal science by targeting noble gases, trace gases, and their isotopes, as well as temperature, pressure, winds, and imaging at Venus. "DAVINCI" Venus Analytic Laboratory (VAL) instruments would provide high-fidelity synergistic measurements throughout

neg: David Felder the variety of his means and aims makes it useful to have, almost like a museum guide taking us through the collection... Paul Griffiths delves into Felder's ability to creatively manage musical inheritances and use the basic elements of Western music in fresh and original ways in his liner notes to the 2009 Albany Records release, "BoxMan", Another musical gene these pieces share, already implicated in the above, is their rhythmic dynamism, the way pulses bounce off tight metrical frames. Yet another is the containment of rhythmic—and harmonic—tensions in small motifs, out of which a whole stretch of music can

neg: SIRE Radar optical or laser sensor system because they are not hindered by the presence of fog or dust blocking their line of sight. However, most radar systems use high-frequency microwave radiation, which have difficulty penetrating grass and other foliage. In contrast, the SIRE radar can penetrate foliage, various media, and even the ground to detect hidden or buried IEDs due to its use of low-frequency microwave radiation. The data acquisition cycle for the SIRE radar consist of the following steps: The transmitters used in the SIRE radar are transversal electromagnetic (TEM) horns that generate short, 1 nanosecond-long radar pulses with a

neg: John F. Kennedy assassination conspiracy theories acoustical evidence has since been discredited. Officer H.B. McLain, from whose motorcycle radio the HSCA acoustic experts said the Dictabelt evidence came, has repeatedly stated that he was not yet in Dealey Plaza once the assassination occurred. McLain asked the Committee, If it was my radio on my motorcycle, why did it not record the revving up at high speed plus my siren when we immediately took off for Parkland Hospital? In 1982, a panel of 12 scientists appointed by the National Academy of Sciences, including Nobel laureates Norman Ramsey and Luis Alvarez, unanimously concluded that the acoustic evidence submitted

neg: Electronic counter-countermeasure the radar receiver. The outgoing radar pulses are chirped, that is, the frequency of the carrier is varied within the pulse, much like the sound of a cricket chirping. When the pulse reflects off a target and returns to the receiver, the signal is processed to add a delay as a function of the frequency. This has the effect of 'stacking' the pulse so it seems stronger, but shorter in duration, to further processors. The effect can increase the received signal strength to above that of noise jamming. Similarly, jamming pulses (used in deception jamming) will not typically have the

neg: Low-probability-of-intercept radar useless against AESA radars, which is why AESA's are also known as "'low probability of intercept radar"s. Modern RWRs must be made highly sensitive (small angles and bandwidths for individual antennas, low transmission loss and noise) and add successive pulses through time-frequency processing to achieve useful detection rates. Ways of reducing the profile of a radar include using wider bandwidth (wideband, Ultra-wideband), frequency hopping, using FMCW, and using only the minimum power required for the task. Using pulse compression also reduces the probability of detection, since the peak transmitted power is lower while the range and resolution is the same.

neg: Arecibo, Puerto Rico The lower story is rusticated, with arched openings; the three doorways in the center giving the effect of a "loggia." The upper windows all have segmental pediments and balconies; the central trio share one long balcony. Architectural detailing is modest, but the building is graceful and charming. In 1898 the Spaniards built the Arecibo Lighthouse. It was automated in 1964 and is still in use. A small park, Arecibo Lighthouse and Historical Park, has been established around it. The Arecibo Observatory is the largest single-unit radio telescope ever constructed and one of the world's most powerful radar-radio telescopes. The observatory's

neg: Weather radar in 2003, the National Science Foundation established the Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), a multidisciplinary, multi-university collaboration of engineers, computer scientists, meteorologists, and sociologists to conduct fundamental research, develop enabling technology, and deploy prototype engineering systems designed to augment existing radar systems by sampling the generally undersampled lower troposphere with inexpensive, fast scanning, dual polarization, mechanically scanned and phased array radars. Weather radars send directional pulses of microwave radiation, on the order of a microsecond long, using a cavity magnetron or klystron tube connected by a waveguide to a parabolic antenna. The wavelengths of

neg: PSR B0943+10 with the European Space Agency's XMM-Newton X-ray observatory and ground-based radio telescopes revealed that it exhibits variations in its X-ray emission that mimic in reverse the changes seen in radio waves—the pulsar has a weaker non-pulsing X-ray luminosity during the radio bright mode and is actually brighter during the radio quite mode emitting distinct X-ray pulses. Such changes can only be explained if the pulsar's magnetosphere (which may extend up to 52,000 km from the surface) quickly switches between two extreme states. The change happens on a few seconds timescale, far faster than most pulsars. Despite being one of the

neg: Switch Contact bounce (also called "chatter") is a common problem with mechanical switches and relays. Switch and relay contacts are usually made of springy metals. When the contacts strike together, their momentum and elasticity act together to cause them to bounce apart one or more times before making steady contact. The result is a rapidly pulsed electric current instead of a clean transition from zero to full current. The effect is usually unimportant in power circuits, but causes problems in some analogue and logic circuits that respond fast enough to misinterpret the on‑off pulses as a data stream. The effects of

neg: Onsala Space Observatory It was completed in 2011. The Onsala Space Observatory currently hosts the Nordic ALMA node, which is part of the European ALMA regional centre (ARC). The Nordic ALMA node provides face-to-face support for any astronomer that wants to use the ALMA telescope and primarily supports the Nordic scientific community. Onsala Space Observatory Onsala Space Observatory (OSO), the Swedish National Facility for Radio Astronomy, provides scientists with equipment to study the Earth and the rest of the Universe. The observatory operates two radio telescopes in Onsala, 45 km south of Gothenburg, and takes part in several international projects. Examples of activities:

neg: Ground-penetrating radar a locked room}) The "Mineseeker Project" seeks to design a system to determine whether landmines are present in areas using ultra wideband synthetic aperture radar units mounted on blimps. An overview of scientific and engineering applications can be found in: A general overview of geophysical methods in archaeology can be found in the following works: Ground-penetrating radar Ground-penetrating radar (GPR) is a geophysical method that uses radar pulses to image the subsurface. This nondestructive method uses electromagnetic radiation in the microwave band (UHF/VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR can have applications

neg: Air traffic control radar beacon system as "track jitter." The jitter problem makes software tracking algorithms problematic, and is the reason why monopulse was implemented. Interrogations consist of three pulses, 0.8 μs in duration, referred to as P1, P2 and P3. The timing between pulses P1 and P3 determines the mode (or question) of the interrogation, and thus what the nature of the reply should be. P2 is used in side-lobe suppression, explained later. Mode 3/A uses a P1 to P3 spacing of 8.0 μs, and is used to request the "beacon code", which was assigned to the aircraft by the controller to identify it. Mode

neg: Aleksandr Leonidovich Zaitsev study of Venus, Mars, and Mercury; near-Earth asteroid radar research; and interstellar radio messaging, his current field of research. He retired in 2013. Zaitsev observed the asteroid 4179 Toutatis in December 1992 using the 70-m Yevpatorian Planetary Radar in Crimea (Ukraine), as a sounding signal transmitter, and the 100-m radio telescope in Effelsberg, Germany, as a receiver of the asteroid's radar echo. In June 1995, Zaitsev was responsible for initiating the world's first intercontinental radar astronomy experiment; the radar groups participating in this experiment were led by Steven Ostro at JPL, Zaitsev in Yevpatoria, and Yasuhiro Koyama in Kashima, Japan.

neg: Radar configurations and types Radar range and wavelength can be adapted for different surveys of bird and insect migration and daily habits. They can have other uses too in the biological field. Radar configurations and types Radar configurations and types is an article about listing the different uses of radars. Radar come in a variety of configuration in the emitter, the receiver, the antenna, wavelength, scan strategies, etc. Search radars scan great volumes of space with pulses of short radio waves. They typically scan the volume two to four times a minute. The waves are usually less than a meter long. Ships and planes

neg: Fort Monmouth was built in 1928. Other structures were built to house units the Army consolidated at Fort Monmouth. In 1928 the first radio-equipped meteorological balloon reached the upper atmosphere, a forerunner of weather sounding techniques universally used today. In 1938 the U.S. Army's first radio-based aircraft detection and ranging system (later called radar) was developed on post. A production model of this equipment detected the oncoming Japanese air attack on Pearl Harbor, but the warning it provided was discounted. In 1946 celestial communication was proved feasible, when the radar developed by the Project Diana team was used to bounce radio signals

neg: Automatic soap dispenser energy and waits for the energy to reflect back. In a stagnant situation, the energy will bounce back in a normal pattern. When hands are placed in the basin, the energy emitted from the sensor will bounce back irregularly which triggers the dispensation of soap. Modern sensors used in electronic faucets, electronic flush valves and electronic soap dispensers use Infrared light with wavelength in the range of 850 nm. The sensor employs an emitter and a collector. The emitter emits pulses of infrared light while the collector, which is positioned to face in the same direction as the emitter, "sits"