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111-457: The Tropical Rainfall Measuring Mission ( TRMM ) was a joint space mission between NASA and JAXA designed to monitor and study tropical rainfall . The term refers to both the mission itself and the satellite that the mission used to collect data. TRMM was part of NASA's Mission to Planet Earth , a long-term, coordinated research effort to study the Earth as a global system. The satellite

222-647: A band being used for Milstar . Global Navigation Satellite Systems (GNSS) including the Chinese Beidou , the American Global Positioning System (introduced in 1978) and the Russian GLONASS broadcast navigational signals in various bands between about 1.2 GHz and 1.6 GHz. Radar is a radiolocation technique in which a beam of radio waves emitted by a transmitter bounces off an object and returns to

333-421: A spaceport (cosmodrome), which may be equipped with launch complexes and launch pads for vertical rocket launches and runways for takeoff and landing of carrier airplanes and winged spacecraft. Spaceports are situated well away from human habitation for noise and safety reasons. ICBMs have various special launching facilities. A launch is often restricted to certain launch windows . These windows depend upon

444-516: A standing wave is present, they may also be used to measure the distance between the nodes , which is equal to half the wavelength. The precision of this method is limited by the determination of the nodal locations. Microwaves are non-ionizing radiation, which means that microwave photons do not contain sufficient energy to ionize molecules or break chemical bonds, or cause DNA damage, as ionizing radiation such as x-rays or ultraviolet can. The word "radiation" refers to energy radiating from

555-496: A sub-orbital spaceflight the spacecraft reaches space and then returns to the atmosphere after following a (primarily) ballistic trajectory. This is usually because of insufficient specific orbital energy , in which case a suborbital flight will last only a few minutes, but it is also possible for an object with enough energy for an orbit to have a trajectory that intersects the Earth's atmosphere, sometimes after many hours. Pioneer 1

666-512: A "time buffer" and substantially widened the allowable launch windows . The parking orbit gave the crew and controllers time to thoroughly check out the spacecraft after the stresses of launch before committing it for a long journey to the Moon. Robotic missions do not require an abort capability and require radiation minimalization only for delicate electronics, and because modern launchers routinely meet "instantaneous" launch windows, space probes to

777-406: A . Microwaves travel solely by line-of-sight paths; unlike lower frequency radio waves, they do not travel as ground waves which follow the contour of the Earth, or reflect off the ionosphere ( skywaves ). Although at the low end of the band they can pass through building walls enough for useful reception, usually rights of way cleared to the first Fresnel zone are required. Therefore, on

888-431: A computer-controlled array of antennas that produces a beam that can be electronically steered in different directions. At microwave frequencies, the transmission lines which are used to carry lower frequency radio waves to and from antennas, such as coaxial cable and parallel wire lines , have excessive power losses, so when low attenuation is required, microwaves are carried by metal pipes called waveguides . Due to

999-443: A counter measure to United States bomber planes in the 1950s. The Tsiolkovsky-influenced Sergey Korolev became the chief rocket designer, and derivatives of his R-7 Semyorka missiles were used to launch the world's first artificial Earth satellite , Sputnik 1 , on October 4, 1957. The U.S., after the launch of Sputnik and two embarrassing failures of Vanguard rockets , launched Explorer 1 on February 1, 1958. Three years later,

1110-416: A flight that normally lasts over twenty hours , could be traversed in less than one hour. While no company offers this type of transportation today, SpaceX has revealed plans to do so as early as the 2020s using Starship . Suborbital spaceflight over an intercontinental distance requires a vehicle velocity that is only a little lower than the velocity required to reach low Earth orbit. If rockets are used,

1221-535: A frequency near 2.45 GHz (12 cm) through food, causing dielectric heating primarily by absorption of the energy in water. Microwave ovens became common kitchen appliances in Western countries in the late 1970s, following the development of less expensive cavity magnetrons . Water in the liquid state possesses many molecular interactions that broaden the absorption peak. In the vapor phase, isolated water molecules absorb at around 22 GHz, almost ten times

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1332-422: A harmonic generator and a mixer. The accuracy of the measurement is limited by the accuracy and stability of the reference source. Mechanical methods require a tunable resonator such as an absorption wavemeter , which has a known relation between a physical dimension and frequency. In a laboratory setting, Lecher lines can be used to directly measure the wavelength on a transmission line made of parallel wires,

1443-451: A launch tower and flame trench. It is surrounded by equipment used to erect, fuel, and maintain launch vehicles. Before launch, the rocket can weigh hundreds of tons. The Space Shuttle Columbia , on STS-1 , weighed 2030 metric tons (4,480,000 lb) at takeoff. The most commonly used definition of outer space is everything beyond the Kármán line , which is 100 kilometers (62 mi) above

1554-595: A liquid-fueled rocket on March 16, 1926. During World War II , the first guided rocket, the V-2 , was developed and employed as a weapon by Nazi Germany . During a test flight in June 1944, one such rocket reached space at an altitude of 189 kilometers (102 nautical miles), becoming the first human-made object to reach space. At the end of World War II, most of the V-2 rocket team, including its head, Wernher von Braun , surrendered to

1665-530: A place in the electromagnetic spectrum with frequency above ordinary radio waves , and below infrared light: In descriptions of the electromagnetic spectrum , some sources classify microwaves as radio waves, a subset of the radio wave band, while others classify microwaves and radio waves as distinct types of radiation. This is an arbitrary distinction. Bands of frequencies in the microwave spectrum are designated by letters. Unfortunately, there are several incompatible band designation systems, and even within

1776-611: A pre-programmed list of operations that will be executed unless otherwise instructed. A robotic spacecraft for scientific measurements is often called a space probe or space observatory . Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn , Uranus , and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are

1887-515: A receiver, allowing the location, range, speed, and other characteristics of the object to be determined. The short wavelength of microwaves causes large reflections from objects the size of motor vehicles, ships and aircraft. Also, at these wavelengths, the high gain antennas such as parabolic antennas which are required to produce the narrow beamwidths needed to accurately locate objects are conveniently small, allowing them to be rapidly turned to scan for objects. Therefore, microwave frequencies are

1998-449: A source and not to radioactivity . The main effect of absorption of microwaves is to heat materials; the electromagnetic fields cause polar molecules to vibrate. It has not been shown conclusively that microwaves (or other non-ionizing electromagnetic radiation) have significant adverse biological effects at low levels. Some, but not all, studies suggest that long-term exposure may have a carcinogenic effect. During World War II , it

2109-597: A subsequent recommendation from the National Research Council panel that the mission be extended despite the risk of an uncontrolled entry. Battery issues began to limit the spacecraft in 2014 and the mission operations team had to make decisions about how to ration power. In March 2014, the VIRS instruments was turned off to extend the battery life. In July 2014, with propellant on TRMM running low, NASA decided to cease station-keeping maneuvers and allow

2220-574: A system the frequency ranges corresponding to some of the letters vary somewhat between different application fields. The letter system had its origin in World War 2 in a top-secret U.S. classification of bands used in radar sets; this is the origin of the oldest letter system, the IEEE radar bands. One set of microwave frequency bands designations by the Radio Society of Great Britain (RSGB),

2331-492: A vacuum under the influence of controlling electric or magnetic fields, and include the magnetron (used in microwave ovens ), klystron , traveling-wave tube (TWT), and gyrotron . These devices work in the density modulated mode, rather than the current modulated mode. This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream of electrons. Low-power microwave sources use solid-state devices such as

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2442-591: A wide swath will serve both TRMM as well as the continuing measurements being made by the SSM/I and radiometers flying on the NASA's EOS-PM ( Aqua (satellite) ) and the Japanese ADEOS II satellites. The Visible and Infrared Scanner (VIRS) was one of the three instruments in the rain-measuring package and serves as a very indirect indicator of rainfall. VIRS, as its name implies, sensed radiation coming up from

2553-566: Is also more bandwidth in the microwave spectrum than in the rest of the radio spectrum; the usable bandwidth below 300 MHz is less than 300 MHz while many GHz can be used above 300 MHz. Typically, microwaves are used in remote broadcasting of news or sports events as the backhaul link to transmit a signal from a remote location to a television station from a specially equipped van. See broadcast auxiliary service (BAS), remote pickup unit (RPU), and studio/transmitter link (STL). Most satellite communications systems operate in

2664-416: Is also used to perform rotational spectroscopy and can be combined with electrochemistry as in microwave enhanced electrochemistry . Microwave frequency can be measured by either electronic or mechanical techniques. Frequency counters or high frequency heterodyne systems can be used. Here the unknown frequency is compared with harmonics of a known lower frequency by use of a low-frequency generator,

2775-491: Is done by a set of orbital maneuvers called space rendezvous . After rendezvousing with the space station, the space vehicle then docks or berths with the station. Docking refers to joining of two separate free-flying space vehicles, while berthing refers to mating operations where an inactive vehicle is placed into the mating interface of another space vehicle by using a robotic arm . Vehicles in orbit have large amounts of kinetic energy. This energy must be discarded if

2886-887: Is effective mainly because of its ability to sustain thrust even as the atmosphere thins. Many ways to reach space other than rocket engines have been proposed. Ideas such as the space elevator , and momentum exchange tethers like rotovators or skyhooks require new materials much stronger than any currently known. Electromagnetic launchers such as launch loops might be feasible with current technology. Other ideas include rocket-assisted aircraft/spaceplanes such as Reaction Engines Skylon (currently in early stage development), scramjet powered spaceplanes, and RBCC powered spaceplanes. Gun launch has been proposed for cargo. On some missions beyond LEO (Low Earth Orbit) , spacecraft are inserted into parking orbits, or lower intermediary orbits. The parking orbit approach greatly simplified Apollo mission planning in several important ways. It acted as

2997-470: Is important for weather and climate prediction, as this precipitation contains three-fourths of the energy that drives atmospheric wind circulation. Prior to TRMM, the distribution of rainfall worldwide was known to only a 50% of certainty. The concept for TRMM was first proposed in 1984. The science objectives, as first proposed, were: Japan joined the initial study for the TRMM mission in 1986. Development of

3108-586: Is impossible. To date several academics have studied intergalactic travel in a serious manner. Spacecraft are vehicles designed to operate in space. The first 'true spacecraft' is sometimes said to be Apollo Lunar Module , since this was the only crewed vehicle to have been designed for, and operated only in space; and is notable for its non-aerodynamic shape. Spacecraft today predominantly use rockets for propulsion , but other propulsion techniques such as ion drives are becoming more common, particularly for uncrewed vehicles, and this can significantly reduce

3219-555: Is inversely proportional to the transmitted frequency. Microwaves are used in spacecraft communication, and much of the world's data, TV, and telephone communications are transmitted long distances by microwaves between ground stations and communications satellites . Microwaves are also employed in microwave ovens and in radar technology. Before the advent of fiber-optic transmission, most long-distance telephone calls were carried via networks of microwave radio relay links run by carriers such as AT&T Long Lines . Starting in

3330-541: Is known as Kessler syndrome . There are several terms that refer to a flight into or through outer space . A space mission refers to a spaceflight intended to achieve an objective. Objectives for space missions may include space exploration , space research , and national firsts in spaceflight. Space transport is the use of spacecraft to transport people or cargo into or through outer space. This may include human spaceflight and cargo spacecraft flight. The first theoretical proposal of space travel using rockets

3441-424: Is limited to a few kilometers. A spectral band structure causes absorption peaks at specific frequencies (see graph at right). Above 100 GHz, the absorption of electromagnetic radiation by Earth's atmosphere is so effective that it is in effect opaque , until the atmosphere becomes transparent again in the so-called infrared and optical window frequency ranges. In a microwave beam directed at an angle into

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3552-647: Is more fuel-efficient for a craft to burn its fuel as close as possible to its periapsis (lowest point); see Oberth effect . Astrodynamics is the study of spacecraft trajectories, particularly as they relate to gravitational and propulsion effects. Astrodynamics allows for a spacecraft to arrive at its destination at the correct time without excessive propellant use. An orbital maneuvering system may be needed to maintain or change orbits. Non-rocket orbital propulsion methods include solar sails , magnetic sails , plasma-bubble magnetic systems , and using gravitational slingshot effects. The term "transfer energy" means

3663-455: Is not generally recognized by the public that the increase in potential energy required to pass the Kármán line is only about 3% of the orbital energy (potential plus kinetic energy) required by the lowest possible Earth orbit (a circular orbit just above the Kármán line.) In other words, it is far easier to reach space than to stay there. On May 17, 2004, Civilian Space eXploration Team launched

3774-554: Is not the result of any instrument improvements, but rather a function of the lower altitude of TRMM 402 kilometers compared to 860 kilometers of SSM/I). TMI has a 878-kilometer wide swath on the surface. The higher resolution of TMI on TRMM, as well as the additional 10.7 GHz frequency, makes TMI a better instrument than its predecessors. The additional information supplied by the Precipitation Radar further helps to improve algorithms. The improved rainfall products over

3885-432: Is tabulated below: Other definitions exist. The term P band is sometimes used for UHF frequencies below the L band but is now obsolete per IEEE Std 521. When radars were first developed at K band during World War 2, it was not known that there was a nearby absorption band (due to water vapor and oxygen in the atmosphere). To avoid this problem, the original K band was split into a lower band, K u , and upper band, K

3996-650: Is the fifth spacecraft put on an escape trajectory leaving the Solar System . Voyager 1 , Voyager 2 , Pioneer 10 , Pioneer 11 are the earlier ones. The one farthest from the Sun is Voyager 1 , which is more than 100 AU distant and is moving at 3.6 AU per year. In comparison, Proxima Centauri , the closest star other than the Sun, is 267,000 AU distant. It will take Voyager 1 over 74,000 years to reach this distance. Vehicle designs using other techniques, such as nuclear pulse propulsion are likely to be able to reach

4107-617: Is the range between 1 and 100 GHz (wavelengths between 30 cm and 3 mm), or between 1 and 3000 GHz (30 cm and 0.1 mm). The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range; rather, it indicates that microwaves are small (having shorter wavelengths), compared to the radio waves used in prior radio technology . The boundaries between far infrared , terahertz radiation , microwaves, and ultra-high-frequency (UHF) are fairly arbitrary and are used variously between different fields of study. In all cases, microwaves include

4218-616: The Big Bang , and is one of the few sources of information about conditions in the early universe. Due to the expansion and thus cooling of the Universe, the originally high-energy radiation has been shifted into the microwave region of the radio spectrum. Sufficiently sensitive radio telescopes can detect the CMBR as a faint signal that is not associated with any star, galaxy, or other object. A microwave oven passes microwave radiation at

4329-524: The Earth Observing System (EOS) AM (Terra) and PM (Aqua) satellites.) The Lightning Imaging Sensor (LIS) was a small, highly sophisticated instrument that detects and locates lightning over the tropical region of the globe. The lightning detector was a compact combination of optical and electronic elements including a staring imager capable of locating and detecting lightning within individual storms. The imager's field of view allowed

4440-484: The Tsiolkovsky rocket equation , can be used to find the total Δ v {\displaystyle \Delta v} , or potential change in velocity. This formula, which is still used by engineers, is a key concept of spaceflight. Spaceflight became a practical possibility with the work of Robert H. Goddard 's publication in 1919 of his paper A Method of Reaching Extreme Altitudes . His application of

4551-461: The USSR made one orbit around the Earth. In official Soviet documents, there is no mention of the fact that Gagarin parachuted the final seven miles. As of 2020, the only spacecraft regularly used for human spaceflight are Soyuz , Shenzhou , and Crew Dragon . The U.S. Space Shuttle fleet operated from April 1981 until July 2011. SpaceShipOne has conducted three human suborbital space flights. On

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4662-536: The cloud water, and the rainfall intensity in the atmosphere . It was a relatively small instrument that consumed little power. This, combined with the wide swath and the quantitative information regarding rainfall made TMI the "workhorse" of the rain-measuring package on Tropical Rainfall Measuring Mission. TMI is not a new instrument. It is based on the design of the highly successful Special Sensor Microwave/Imager (SSM/I) which has been flying continuously on Defense Meteorological Satellites since 1987. The TMI measures

4773-457: The de Laval nozzle to liquid-fuel rockets improved efficiency enough for interplanetary travel to become possible. After further research, Goddard attempted to secure an Army contract for a rocket-propelled weapon in the first World War but his plans were foiled by the November 11, 1918 armistice with Germany . After choosing to work with private financial support, he was the first to launch

4884-577: The field-effect transistor (at least at lower frequencies), tunnel diodes , Gunn diodes , and IMPATT diodes . Low-power sources are available as benchtop instruments, rackmount instruments, embeddable modules and in card-level formats. A maser is a solid-state device which amplifies microwaves using similar principles to the laser , which amplifies higher frequency light waves. All warm objects emit low level microwave black-body radiation , depending on their temperature , so in meteorology and remote sensing , microwave radiometers are used to measure

4995-438: The 2.3 GHz, 2.5 GHz, 3.5 GHz and 5.8 GHz ranges. Mobile Broadband Wireless Access (MBWA) protocols based on standards specifications such as IEEE 802.20 or ATIS/ANSI HC-SDMA (such as iBurst ) operate between 1.6 and 2.3 GHz to give mobility and in-building penetration characteristics similar to mobile phones but with vastly greater spectral efficiency. Some mobile phone networks, like GSM , use

5106-425: The 5 GHz range. Licensed long-range (up to about 25 km) Wireless Internet Access services have been used for almost a decade in many countries in the 3.5–4.0 GHz range. The FCC recently carved out spectrum for carriers that wish to offer services in this range in the U.S. — with emphasis on 3.65 GHz. Dozens of service providers across the country are securing or have already received licenses from

5217-689: The 95 GHz focused beam heats the skin to a temperature of 54 °C (129 °F) at a depth of 0.4 millimetres ( 1 ⁄ 64  in). The United States Air Force and Marines are currently using this type of active denial system in fixed installations. Microwave radiation is used in electron paramagnetic resonance (EPR or ESR) spectroscopy, typically in the X-band region (~9 GHz) in conjunction typically with magnetic fields of 0.3 T. This technique provides information on unpaired electrons in chemical systems, such as free radicals or transition metal ions such as Cu(II). Microwave radiation

5328-437: The C, X, K a , or K u bands of the microwave spectrum. These frequencies allow large bandwidth while avoiding the crowded UHF frequencies and staying below the atmospheric absorption of EHF frequencies. Satellite TV either operates in the C band for the traditional large dish fixed satellite service or K u band for direct-broadcast satellite . Military communications run primarily over X or K u -band links, with K

5439-483: The Earth in five spectral regions, ranging from visible to infrared , or 0.63 to 12 mm . VIRS was included in the primary instrument package for two reasons. First was its ability to delineate rainfall. The second, and even more important reason, was to serve as a transfer standard to other measurements that are made routinely using Polar Operational Environmental Satellites (POES) and Geostationary Operational Environmental Satellite (GOES) satellites. The intensity of

5550-403: The Earth's surface. (The United States defines outer space as everything beyond 50 miles (80 km) in altitude.) Rocket engines remain the only currently practical means of reaching space, with planes and high-altitude balloons failing due to lack of atmosphere and alternatives such as space elevators not yet being built. Chemical propulsion, or the acceleration of gases at high velocities,

5661-457: The FCC to operate in this band. The WIMAX service offerings that can be carried on the 3.65 GHz band will give business customers another option for connectivity. Metropolitan area network (MAN) protocols, such as WiMAX (Worldwide Interoperability for Microwave Access) are based on standards such as IEEE 802.16 , designed to operate between 2 and 11 GHz. Commercial implementations are in

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5772-697: The Gemini program ended just before the Apollo 1 tragedy. Following multiple uncrewed test flights of the Saturn 1B and the Saturn V , the U.S. launched the crewed Apollo 7 mission into low earth orbit . Shortly after its successful completion, the U.S. launched Apollo 8 (first mission to orbit the moon), Apollo 9 (first Apollo mission to launch with both the CSM and the LEM ) and Apollo 10 (first mission to nearly land on

5883-459: The GoFast rocket on a suborbital flight, the first amateur spaceflight. On June 21, 2004, SpaceShipOne was used for the first privately funded human spaceflight . Point-to-point, or Earth to Earth transportation, is a category of sub-orbital spaceflight in which a spacecraft provides rapid transport between two terrestrial locations. A conventional airline route between London and Sydney ,

5994-539: The Moon and developed continuous crewed human presence in space with a series of space stations , ranging from the Salyut program to the International Space Station . Rockets are the only means currently capable of reaching orbit or beyond. Other non-rocket spacelaunch technologies have yet to be built, or remain short of orbital speeds. A rocket launch for a spaceflight usually starts from

6105-423: The Moon and other planets generally use direct injection to maximize performance by limiting the boil off of cryogenic propellants . Although some might coast briefly during the launch sequence, they do not complete one or more full parking orbits before the burn that injects them onto an Earth escape trajectory. The escape velocity from a celestial body decreases as the distance from the body increases. However, it

6216-514: The USA on the 20th anniversary of Yuri Gagarin 's flight, on 12 April 1981. During the Shuttle era, six orbiters were built, all of which flown in the atmosphere and five of which flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 and gliding to deadstick landings at Edwards AFB, California . The first Space Shuttle to fly into space

6327-537: The USSR launched Vostok 1, carrying cosmonaut Yuri Gagarin into orbit. The US responded with the suborbital launch of Alan Shepard on May 5, 1961, and the orbital launch of John Glenn on February 20, 1962. These events were followed by a pledge from U.S. President John F. Kennedy to go to the moon and the creation of the Gemini and Apollo programs. After successfully performing a rendezvous and docking and an EVA ,

6438-644: The United States, and were expatriated to work on American missiles at what became the Army Ballistic Missile Agency , producing missiles such as Juno I and Atlas . The Soviet Union , in turn, captured several V2 production facilities and built several replicas, with 5 of their 11 rockets successfully reaching their targets. (This was relatively consistent with Nazi Germany's success rate.) The Soviet Union developed intercontinental ballistic missiles to carry nuclear weapons as

6549-490: The body. The lens and cornea of the eye are especially vulnerable because they contain no blood vessels that can carry away heat. Exposure to microwave radiation can produce cataracts by this mechanism, because the microwave heating denatures proteins in the crystalline lens of the eye (in the same way that heat turns egg whites white and opaque). Exposure to heavy doses of microwave radiation (as from an oven that has been tampered with to allow operation even with

6660-592: The case of uncrewed spacecraft in high-energy orbits, to boost themselves into graveyard orbits . Used upper stages or failed spacecraft, however, often lack the ability to deorbit themselves. This becomes a major issue when large numbers of uncontrollable spacecraft exist in frequently used orbits, increasing the risk of debris colliding with functional satellites. This problem is exacerbated when large objects, often upper stages, break up in orbit or collide with other objects, creating often hundreds of small, hard to find pieces of debris. This problem of continuous collisions

6771-508: The door open) can produce heat damage in other tissues as well, up to and including serious burns that may not be immediately evident because of the tendency for microwaves to heat deeper tissues with higher moisture content. Microwaves were first generated in the 1890s in some of the earliest radio wave experiments by physicists who thought of them as a form of "invisible light". James Clerk Maxwell in his 1873 theory of electromagnetism , now called Maxwell's equations , had predicted that

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6882-516: The early 1950s, frequency-division multiplexing was used to send up to 5,400 telephone channels on each microwave radio channel, with as many as ten radio channels combined into one antenna for the hop to the next site, up to 70 km away. Wireless LAN protocols , such as Bluetooth and the IEEE 802.11 specifications used for Wi-Fi, also use microwaves in the 2.4 GHz ISM band , although 802.11a uses ISM band and U-NII frequencies in

6993-819: The earth's surface as ground waves , or reflect from the ionosphere , so terrestrial microwave communication links are limited by the visual horizon to about 40 miles (64 km). At the high end of the band, they are absorbed by gases in the atmosphere, limiting practical communication distances to around a kilometer. Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks , microwave radio relay networks, radar , satellite and spacecraft communication , medical diathermy and cancer treatment, remote sensing , radio astronomy , particle accelerators , spectroscopy , industrial heating, collision avoidance systems , garage door openers and keyless entry systems , and for cooking food in microwave ovens . Microwaves occupy

7104-528: The entire super high frequency (SHF) band (3 to 30 GHz, or 10 to 1 cm) at minimum. A broader definition includes UHF and extremely high frequency (EHF) ( millimeter wave ; 30 to 300 GHz) bands as well. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S , C , X , K u , K , or K a band , or by similar NATO or EU designations. Microwaves travel by line-of-sight ; unlike lower frequency radio waves , they do not diffract around hills, follow

7215-408: The final time on 1 April 2015 and the final scientific sensor, LIS, was turned off on 15 April 2015. Re-entry occurred on 16 June 2015 at 06:54 UTC. The Precipitation Radar (PR) was the first space-borne instrument designed to provide three-dimensional maps of storm structure. The measurements yielded information on the intensity and distribution of the rain, on the rain type, on the storm depth and on

7326-414: The frequency can then be calculated. A similar technique is to use a slotted waveguide or slotted coaxial line to directly measure the wavelength. These devices consist of a probe introduced into the line through a longitudinal slot so that the probe is free to travel up and down the line. Slotted lines are primarily intended for measurement of the voltage standing wave ratio on the line. However, provided

7437-406: The frequency of the microwave oven. Microwave heating is used in industrial processes for drying and curing products. Many semiconductor processing techniques use microwaves to generate plasma for such purposes as reactive ion etching and plasma-enhanced chemical vapor deposition (PECVD). Microwaves are used in stellarators and tokamak experimental fusion reactors to help break down

7548-458: The gas into a plasma and heat it to very high temperatures. The frequency is tuned to the cyclotron resonance of the electrons in the magnetic field, anywhere between 2–200 GHz, hence it is often referred to as Electron Cyclotron Resonance Heating (ECRH). The upcoming ITER thermonuclear reactor will use up to 20 MW of 170 GHz microwaves. Microwaves can be used to transmit power over long distances, and post- World War 2 research

7659-415: The height at which the snow melts into rain. The estimates of the heat released into the atmosphere at different heights based on these measurements can be used to improve models of the global atmospheric circulation. The PR operated at 13.8 GHz and measured the 3-D rainfall distribution over land and ocean surfaces. It defined a layer depth of perception and hence measured rainfall that actually reached

7770-459: The high cost and maintenance requirements of waveguide runs, in many microwave antennas the output stage of the transmitter or the RF front end of the receiver is located at the antenna. The term microwave also has a more technical meaning in electromagnetics and circuit theory . Apparatus and techniques may be described qualitatively as "microwave" when the wavelengths of signals are roughly

7881-427: The intensity of radiation at five separate frequencies: 10.7, 19.4, 21.3, 37.0, 85.5 GHz. These frequencies are similar to those of the SSM/I, except that TMI has the additional 10.7 GHz channel designed to provide a more-linear response for the high rainfall rates common in tropical rainfall. The other main improvement that is expected from TMI is due to the improved ground resolution. This improvement, however,

7992-411: The latent heat of atmosphere. It had a 4.3 km resolution at radii with 220 km swath. The TRMM Microwave Imager (TMI) was a passive microwave sensor designed to provide quantitative rainfall information over a wide swath under the TRMM satellite. By carefully measuring the minute amounts of microwave energy emitted by the Earth and its atmosphere , TMI was able to quantify the water vapor ,

8103-577: The low-microwave/high-UHF frequencies around 1.8 and 1.9 GHz in the Americas and elsewhere, respectively. DVB-SH and S-DMB use 1.452 to 1.492 GHz, while proprietary/incompatible satellite radio in the U.S. uses around 2.3 GHz for DARS . Microwave radio is used in point-to-point telecommunications transmissions because, due to their short wavelength, highly directional antennas are smaller and therefore more practical than they would be at longer wavelengths (lower frequencies). There

8214-759: The main frequencies used in radar. Microwave radar is widely used for applications such as air traffic control , weather forecasting, navigation of ships, and speed limit enforcement . Long-distance radars use the lower microwave frequencies since at the upper end of the band atmospheric absorption limits the range, but millimeter waves are used for short-range radar such as collision avoidance systems . Microwaves emitted by astronomical 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

8325-409: The moon). These events culminated with the first crewed moon landing, Apollo 11 , and six subsequent missions, five of which successfully landed on the moon. Spaceflight has been widely employed by numerous government and commercial entities for placing satellites into orbit around Earth for a broad range of purposes. Certain government agencies have also sent uncrewed spacecraft exploring space beyond

8436-406: The nearest star significantly faster. Another possibility that could allow for human interstellar spaceflight is to make use of time dilation , as this would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. However, attaining such high speeds would still require

8547-402: The only way to explore them. Telerobotics also allows exploration of regions that are vulnerable to contamination by Earth micro-organisms since spacecraft can be sterilized. Humans can not be sterilized in the same way as a spaceship, as they coexist with numerous micro-organisms, and these micro-organisms are also hard to contain within a spaceship or spacesuit. The first uncrewed space mission

8658-520: The origin of the Universe . Microwave technology is extensively used for point-to-point telecommunications (i.e., non-broadcast uses). Microwaves are especially suitable for this use since they are more easily focused into narrower beams than radio waves, allowing frequency reuse ; their comparatively higher frequencies allow broad bandwidth and high data transmission rates , and antenna sizes are smaller than at lower frequencies because antenna size

8769-399: The position of celestial bodies and orbits relative to the launch site. The biggest influence is often the rotation of the Earth. Once launched, orbits are normally located within relatively constant flat planes at a fixed angle to the axis of the Earth, and the Earth rotates within this orbit. A launch pad is a fixed structure designed to dispatch airborne vehicles. It generally consists of

8880-425: The printed circuit inverted F antenna (PIFA) used in cell phones. Their short wavelength also allows narrow beams of microwaves to be produced by conveniently small high gain antennas from a half meter to 5 meters in diameter. Therefore, beams of microwaves are used for point-to-point communication links, and for radar . An advantage of narrow beams is that they do not interfere with nearby equipment using

8991-616: The radiation in the various spectral regions (or bands) can be used to determine the brightness (visible and near infrared) or temperature (infrared) of the source. Clouds and the Earth's Radiant Energy System (CERES) measured the energy at the top of the atmosphere , as well as estimates energy levels within the atmosphere and at the Earth's surface. The CERES instrument was based on the successful Earth Radiation Budget Experiment (ERBS) which used three satellites to provide global energy budget measurements from 1984 to 1993. Using information from very high resolution cloud imaging instruments on

9102-464: The remainder heats the atmosphere. The Mercury , Gemini , and Apollo capsules splashed down in the sea. These capsules were designed to land at relatively low speeds with the help of a parachute. Soviet/Russian capsules for Soyuz make use of a big parachute and braking rockets to touch down on land. Spaceplanes like the Space Shuttle land like a glider . After a successful landing,

9213-639: The same as the dimensions of the circuit, so that lumped-element circuit theory is inaccurate, and instead distributed circuit elements and transmission-line theory are more useful methods for design and analysis. As a consequence, practical microwave circuits tend to move away from the discrete resistors , capacitors , and inductors used with lower-frequency radio waves . Open-wire and coaxial transmission lines used at lower frequencies are replaced by waveguides and stripline , and lumped-element tuned circuits are replaced by cavity resonators or resonant stubs . In turn, at even higher frequencies, where

9324-406: The same frequency, allowing frequency reuse by nearby transmitters. Parabolic ("dish") antennas are the most widely used directive antennas at microwave frequencies, but horn antennas , slot antennas and lens antennas are also used. Flat microstrip antennas are being increasingly used in consumer devices. Another directive antenna practical at microwave frequencies is the phased array ,

9435-496: The same spacecraft, CERES determines cloud properties, including cloud-amount, altitude , thickness, and the size of the cloud particles. These measurements are important to understanding the Earth's total climate system and improving climate prediction models. It only operated during January–August 1998, and in March 2000, so the available data record is quite brief (although later CERES instruments were flown on other missions such as

9546-584: The satellite became a joint project between the space agencies of the United States and Japan, with Japan providing the Precipitation Radar (PR) and H-II launch vehicle, and the United States providing the satellite bus and remaining instruments. The project received formal support from the United States Congress in 1991, followed by spacecraft construction from 1993 through 1997. TRMM launched from Tanegashima Space Center on 27 November 1997. The Tropical Rainfall Measuring Mission (TRMM), one of

9657-532: The sensor to observe a point on the Earth or a cloud for 80 seconds, a sufficient time to estimate the flashing rate, which told researchers whether a storm was growing or decaying. Space mission Spaceflights include the launches of Earth observation and telecommunications satellites, interplanetary missions , the rendezvouses and dockings with space stations , and crewed spaceflights on scientific or tourist missions. Spaceflight can be achieved conventionally via multistage rockets , which provide

9768-463: The size of the rocket relative to the payload is similar to an Intercontinental Ballistic Missile (ICBM). Any intercontinental spaceflight has to surmount problems of heating during atmospheric re-entry that are nearly as large as those faced by orbital spaceflight. A minimal orbital spaceflight requires much higher velocities than a minimal sub-orbital flight, and so it is technologically much more challenging to achieve. To achieve orbital spaceflight,

9879-898: The sky, a small amount of the power will be randomly scattered as the beam passes through the troposphere . A sensitive receiver beyond the horizon with a high gain antenna focused on that area of the troposphere can pick up the signal. This technique has been used at frequencies between 0.45 and 5 GHz in tropospheric scatter (troposcatter) communication systems to communicate beyond the horizon, at distances up to 300 km. The short wavelengths of microwaves allow omnidirectional antennas for portable devices to be made very small, from 1 to 20 centimeters long, so microwave frequencies are widely used for wireless devices such as cell phones , cordless phones , and wireless LANs (Wi-Fi) access for laptops , and Bluetooth earphones. Antennas used include short whip antennas , rubber ducky antennas , sleeve dipoles , patch antennas , and increasingly

9990-651: 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, which observes the universe in the millimeter and submillimeter wavelength ranges. The world's largest ground-based astronomy project to date, it consists of more than 66 dishes and

10101-486: The spacecraft in the NASA Earth Probe series of research satellites, is a highly focused, limited-objective program aimed at measuring monthly and seasonal rainfall over the global tropics and subtropics. TRMM is a joint project between the United States and Japan to measure rainfall between 35.0° North and 35.0° South at 350 km altitude. To extend TRMM's mission life beyond its primary mission, NASA boosted

10212-433: The spacecraft's orbit altitude to 402.5 km in 2001. In 2005, NASA director Michael Griffin decided to extend the mission again by using the propellant originally intended for a controlled descent. This came after a 2002 NASA risk review put the probability of a human injury or death caused by TRMM's uncontrolled re-entry at 1-in-5,000, about twice the casualty risk deemed acceptable for re-entering NASA satellites; and

10323-411: The spacecraft's orbit to slowly decay, while continuing to collect data. The remaining fuel, initially reserved to avoid collisions with other satellites or space debris, was depleted in early March 2015. Re-entry was originally expected sometime between May 2016 and November 2017, but occurred sooner due to heightened solar activity. The probe's primary sensor, the precipitation radar, was switched off for

10434-640: The spacecraft, its occupants, and cargo can be recovered. In some cases, recovery has occurred before landing: while a spacecraft is still descending on its parachute, it can be snagged by a specially designed aircraft. This mid-air retrieval technique was used to recover the film canisters from the Corona spy satellites. Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control , or remote guidance. They may also be autonomous , in which they have

10545-433: The surface of the Earth, microwave communication links are limited by the visual horizon to about 30–40 miles (48–64 km). Microwaves are absorbed by moisture in the atmosphere, and the attenuation increases with frequency, becoming a significant factor ( rain fade ) at the high end of the band. Beginning at about 40 GHz, atmospheric gases also begin to absorb microwaves, so above this frequency microwave transmission

10656-610: The tangential velocity around the Earth is as important as altitude. In order to perform a stable and lasting flight in space, the spacecraft must reach the minimal orbital speed required for a closed orbit . Interplanetary spaceflight is flight between planets within a single planetary system . In practice, the use of the term is confined to travel between the planets of our Solar System . Plans for future crewed interplanetary spaceflight missions often include final vehicle assembly in Earth orbit, such as NASA's Constellation program and Russia's Kliper / Parom tandem. New Horizons

10767-464: The temperature of objects or terrain. The sun and other astronomical radio sources such as Cassiopeia A emit low level microwave radiation which carries information about their makeup, which is studied by radio astronomers using receivers called radio telescopes . The cosmic microwave background radiation (CMBR), for example, is a weak microwave noise filling empty space which is a major source of information on cosmology 's Big Bang theory of

10878-495: The thrust to overcome the force of gravity and propel spacecraft onto suborbital trajectories . If the mission is orbital , the spacecraft usually separates the first stage and ignites the second stage , which propels the spacecraft to high enough speeds that it reaches orbit. Once in orbit, spacecraft are at high enough speeds that they fall around the Earth rather than fall back to the surface. Most spacecraft, and all crewed spacecraft, are designed to deorbit themselves or, in

10989-411: The total amount of energy imparted by a rocket stage to its payload. This can be the energy imparted by a first stage of a launch vehicle to an upper stage plus payload, or by an upper stage or spacecraft kick motor to a spacecraft . In order to reach a space station , a spacecraft would have to arrive at the same orbit and approach to a very close distance (e.g. within visual contact). This

11100-460: The use of some new, advanced method of propulsion . Dynamic soaring as a way to travel across interstellar space has been proposed as well. Intergalactic travel involves spaceflight between galaxies, and is considered much more technologically demanding than even interstellar travel and, by current engineering terms, is considered science fiction . However, theoretically speaking, there is nothing to conclusively indicate that intergalactic travel

11211-413: The vehicle is to land safely without vaporizing in the atmosphere. Typically this process requires special methods to protect against aerodynamic heating . The theory behind reentry was developed by Harry Julian Allen . Based on this theory, reentry vehicles present blunt shapes to the atmosphere for reentry. Blunt shapes mean that less than 1% of the kinetic energy ends up as heat reaching the vehicle, and

11322-460: The vehicle's mass and increase its delta-v . Launch systems are used to carry a payload from Earth's surface into outer space. Most current spaceflight uses multi-stage expendable launch systems to reach space. The first reusable spacecraft, the X-15 , was air-launched on a suborbital trajectory on 19 July 1963. The first partially reusable orbital spacecraft, the Space Shuttle , was launched by

11433-410: The wavelength of the electromagnetic waves becomes small in comparison to the size of the structures used to process them, microwave techniques become inadequate, and the methods of optics are used. High-power microwave sources use specialized vacuum tubes to generate microwaves. These devices operate on different principles from low-frequency vacuum tubes, using the ballistic motion of electrons in

11544-453: Was Sputnik , launched October 4, 1957 to orbit the Earth. Nearly all satellites , landers and rovers are robotic spacecraft. Not every uncrewed spacecraft is a robotic spacecraft; for example, a reflector ball is a non-robotic uncrewed spacecraft. Space missions where other animals but no humans are on-board are called uncrewed missions. The first human spaceflight was Vostok 1 on April 12, 1961, on which cosmonaut Yuri Gagarin of

11655-480: Was NASA's first space probe intended to reach the Moon. A partial failure caused it to instead follow a suborbital trajectory to an altitude of 113,854 kilometers (70,746 mi) before reentering the Earth's atmosphere 43 hours after launch. The most generally recognized boundary of space is the Kármán line 100 km (62 mi) above sea level. (NASA alternatively defines an astronaut as someone who has flown more than 80 km (50 mi) above sea level.) It

11766-416: Was built in an international collaboration by Europe, North America, East Asia and Chile. A major recent focus of microwave radio astronomy has been mapping the cosmic microwave background radiation (CMBR) discovered in 1964 by radio astronomers Arno Penzias and Robert Wilson . This faint background radiation, which fills the universe and is almost the same in all directions, is "relic radiation" from

11877-443: Was done to examine possibilities. NASA worked in the 1970s and early 1980s to research the possibilities of using solar power satellite (SPS) systems with large solar arrays that would beam power down to the Earth's surface via microwaves. Less-than-lethal weaponry exists that uses millimeter waves to heat a thin layer of human skin to an intolerable temperature so as to make the targeted person move away. A two-second burst of

11988-546: Was launched on 27 November 1997 from the Tanegashima Space Center in Tanegashima , Japan. TRMM operated for 17 years, including several mission extensions, before being decommissioned on 15 April 2015. TRMM re-entered Earth's atmosphere on 16 June 2015. Tropical precipitation is a difficult parameter to measure, due to large spatial and temporal variations. However, understanding tropical precipitation

12099-493: Was observed that individuals in the radiation path of radar installations experienced clicks and buzzing sounds in response to microwave radiation. Research by NASA in the 1970s has shown this to be caused by thermal expansion in parts of the inner ear. In 1955, Dr. James Lovelock was able to reanimate rats chilled to 0 and 1 °C (32 and 34 °F) using microwave diathermy. When injury from exposure to microwaves occurs, it usually results from dielectric heating induced in

12210-663: Was published by Scottish astronomer and mathematician William Leitch , in an 1861 essay "A Journey Through Space". More well-known is Konstantin Tsiolkovsky 's work, " Исследование мировых пространств реактивными приборами " ( The Exploration of Cosmic Space by Means of Reaction Devices ), published in 1903. In his work, Tsiolkovsky describes the fundamental rocket equation: Δ v = v e ln ⁡ m 0 m f {\displaystyle \Delta v=v_{e}\ln {\frac {m_{0}}{m_{f}}}} Where: This equation, known as

12321-908: Was the Columbia , followed by the Challenger , Discovery , Atlantis , and Endeavour . The Endeavour was built to replace the Challenger , which was lost in January 1986. The Columbia broke up during reentry in February 2003. Microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequencies between 300 MHz and 300 GHz, broadly construed. A more common definition in radio-frequency engineering

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