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Uranus Pathfinder
Uranus Pathfinder was a mission concept for the Uranian system evaluated in the 2010s by the European Space Agency. In 2011, scientists from the Mullard Space Science Laboratory in the United Kingdom proposed the joint NASA–ESA ''Uranus Pathfinder'' mission to Uranus. It would be a medium-class (M-class) mission to be launched in 2022, and was submitted to the ESA in December 2010 with the signatures of 120 scientists from around the globe. ESA caps the cost of M-class missions at €470 million. Uranus Pathfinder was proposed in support of ESA's Cosmic Vision 2015–2025. The mission study including several possible combinations of launch dates, trajectories, and flybys (gravity assists), including flybys of Earth, Venus, and of the planet Saturn. Indeed, the study noted the velocity change requirements are only marginally higher than for typical missions to Saturn of this period. In the baseline concept, UP is an ESA–NASA bilateral mission and it would launch on an At ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waves In Plasmas
In plasma physics, waves in plasmas are an interconnected set of particles and fields which propagate in a periodically repeating fashion. A Plasma (physics), plasma is a Plasma (physics)#Plasma_potential, quasineutral, electrical conductivity, electrically conductive fluid. In the simplest case, it is composed of electrons and a single species of positive ions, but it may also contain multiple ion species including negative ions as well as neutral particles. Due to its electrical conductivity, a plasma couples to electric field, electric and magnetic fields. This complex of particles and fields supports a wide variety of wave phenomena. The electromagnetic fields in a plasma are assumed to have two parts, one static/equilibrium part and one oscillating/perturbation part. Waves in plasmas can be classified as electromagnetic or electrostatic according to whether or not there is an oscillating magnetic field. Applying Faraday's law of induction to plane waves, we find \mathbf\times\ti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MUSE (spacecraft)
MUSE (Mission to Uranus for Science and Exploration) is a European proposal for a dedicated mission to the planet Uranus to study its atmosphere, interior, moons, rings, and magnetosphere. It is proposed to be launched with an Ariane 6 in 2026, travel for 16.5 years to reach Uranus in 2044, and would operate until 2050. The European Space Operations Centre would monitor and control the mission, as well as generate and provide the raw data sets. In 2012, the cost was estimated at €1.8 billion. The mission addresses the themes of the ESA Cosmic Vision 2015–2025. This was designed as an L-Class flagship level mission; however, it is constrained by the need for RTGs. MUSE was also analyzed in the US as an Enhanced New Frontiers class mission in 2014. Orbiter The orbiter science phase would consist on the Uranus Science Orbit (USO) phase of approximately 2 years in a highly elliptic polar orbit to provide best gravimetry data, during which 36 Uranus orbits are performed. Subs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moons Of Uranus
Uranus, the seventh planet of the Solar System, has 27 known moons, most of which are named after characters that appear in, or are mentioned in, the works of William Shakespeare and Alexander Pope. Uranus's moons are divided into three groups: thirteen inner moons, five major moons, and nine irregular moons. The inner and major moons all have prograde orbits, while orbits of the irregulars are mostly retrograde. The inner moons are small dark bodies that share common properties and origins with Uranus's rings. The five major moons are ellipsoidal, indicating that they reached hydrostatic equilibrium at some point in their past (and may still be in equilibrium), and four of them show signs of internally driven processes such as canyon formation and volcanism on their surfaces. The largest of these five, Titania, is 1,578 km in diameter and the eighth-largest moon in the Solar System, about one-twentieth the mass of the Earth's Moon. The orbits of the regular moons are near ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exploration Of Uranus
The exploration of Uranus has, to date, been through telescopes and a lone probe by NASA's ''Voyager 2'' spacecraft, which made its closest approach to Uranus on January 24, 1986. ''Voyager 2'' discovered 10 moons, studied the planet's cold atmosphere, and examined its ring system, discovering two new rings. It also imaged Uranus' five large moons, revealing that their surfaces are covered with impact craters and canyons. A number of dedicated exploratory missions to Uranus have been proposed, but none have been approved. ''Voyager 2'' ''Voyager 2'' made its closest approach to Uranus on January 24, 1986, coming within of the planet's cloud tops. This was the probe's first solo planetary flyby, since ''Voyager 1'' ended its tour of the outer planets at Saturn's moon Titan. Uranus is the third-largest planet in the Solar System. It orbits the Sun at a distance of about and completes one orbit every 84 years. The length of a day on Uranus as measured by ''Voyager 2'' is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmosphere Of Uranus
The atmosphere of Uranus is composed primarily of hydrogen and helium. At depth it is significantly enriched in volatiles (dubbed "ices") such as water, ammonia and methane. The opposite is true for the upper atmosphere, which contains very few gases heavier than hydrogen and helium due to its low temperature. Uranus's atmosphere is the coldest of all the planets, with its temperature reaching as low as 49 K. The Uranian atmosphere can be divided into five main layers: the troposphere, between altitudes of −300 and 50 km and pressures from 100 to 0.1 bar; the stratosphere, spanning altitudes between 50 and 4000 km and pressures of between and the hot thermosphere (and exosphere) extending from an altitude of 4,056 km to several Uranian radii from the nominal surface at 1 bar pressure. Unlike Earth's, Uranus's atmosphere has no mesosphere. The troposphere hosts four cloud layers: methane clouds at about 1.2 bar, hydrogen sulfide and ammonia clou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Advanced Stirling Radioisotope Generator
The advanced Stirling radioisotope generator (ASRG) is a radioisotope power system first developed at NASA's Glenn Research Center. It uses a Stirling power conversion technology to convert radioactive-decay heat into electricity for use on spacecraft. The energy conversion process used by an ASRG is about four times more efficient than in previous radioisotope systems to produce a similar amount of power, and allows it to use about one quarter of the plutonium-238 as other similar generators. Despite termination of the ASRG flight development contract in 2013, NASA continues a small investment testing by private companies. Flight-ready Stirling-based units are not expected before 2028. Development Development was undertaken in 2000 under joint sponsorship by the United States Department of Energy (DoE), Lockheed Martin Space Systems, and the Stirling Research Laboratory at NASA's Glenn Research Center (GRC) for potential future space missions. In 2012, NASA chose a solar-powere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multi-mission Radioisotope Thermoelectric Generator
The multi-mission radioisotope thermoelectric generator (MMRTG) is a type of radioisotope thermoelectric generator (RTG) developed for NASA space missions such as the Mars Science Laboratory (MSL), under the jurisdiction of the United States Department of Energy's Office of Space and Defense Power Systems within the Office of Nuclear Energy. The MMRTG was developed by an industry team of Aerojet Rocketdyne and Teledyne Energy Systems. Background Space exploration missions require safe, reliable, long-lived power systems to provide electricity and heat to spacecraft and their science instruments. A uniquely capable source of power is the radioisotope thermoelectric generator (RTG) – essentially a nuclear battery that reliably converts heat into electricity. Radioisotope power has been used on eight Earth orbiting missions, eight missions to the outer planets, and the Apollo missions after Apollo 11 to the Moon. The outer Solar System missions are the ''Pioneer 10'' and ''11'', ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Americium-241
Americium-241 (, Am-241) is an isotope of americium. Like all isotopes of americium, it is radioactive, with a half-life of . is the most common isotope of americium as well as the most prevalent isotope of americium in nuclear waste. It is commonly found in ionization type smoke detectors and is a potential fuel for long-lifetime radioisotope thermoelectric generators (RTGs). Its common parent nuclides are β− from , EC from , and α from . is fissile and the critical mass of a bare sphere is and a sphere diameter of . Americium-241 has a specific activity of . It is commonly found in the form of americium-241 dioxide (). This isotope also has one meta state, , with an excitation energy of and a half-life of . The presence of americium-241 in plutonium is determined by the original concentration of plutonium-241 and the sample age. Because of the low penetration of alpha radiation, americium-241 only poses a health risk when ingested or inhaled. Older samples of plutoni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radioisotope Thermoelectric Generator
A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This type of generator has no moving parts. RTGs have been used as power sources in satellites, space probes, and uncrewed remote facilities such as a series of lighthouses built by the Soviet Union inside the Arctic Circle. RTGs are usually the most desirable power source for unmaintained situations that need a few hundred watts (or less) of power for durations too long for fuel cells, batteries, or generators to provide economically, and in places where solar cells are not practical. Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit. The expense of RTGs tends to limit their use to niche applications in rare or special situations. Beca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravity Assist
In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft, typically to save propellant and reduce expense. Gravity assistance can be used to accelerate a spacecraft, that is, to increase or decrease its speed or redirect its path. The "assist" is provided by the motion of the gravitating body as it pulls on the spacecraft. Any gain or loss of kinetic energy and velocity by a passing spacecraft is correspondingly lost or gained by the gravitational body, in accordance with Newton's Third Law. The gravity assist maneuver was first used in 1959 when the Soviet probe Luna 3 photographed the far side of Earth's Moon and it was used by interplanetary probes from Mariner 10 onward, including the two Voyager probes' notable flybys of Jupiter and Saturn. Explanation A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ka Band
The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum defined as frequencies in the range 26.5–40 gigahertz (GHz), i.e. wavelengths from slightly over one centimeter down to 7.5 millimeters. The band is called Ka, short for "K-above" because it is the upper part of the original NATO K band, which was split into three bands because of the presence of the atmospheric water vapor resonance peak at 22.24 GHz (1.35 cm), which made the center unusable for long range transmission. The 30/20 GHz band is used in communications satellite uplinks in either the 27.5 GHz and 31 GHz bands, and high-resolution, close-range targeting radars aboard military airplanes. Some frequencies in this radio band are used for vehicle speed detection by law enforcement. The Kepler Mission used this frequency range to downlink the scientific data collected by the space telescope. The designation "Ka ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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