SWAP (solar wind around Pluto) is a science instrument aboard the unmanned New Horizons space probe, which was designed to fly by dwarf planet Pluto. [1] SWAP was designed to record Solar Wind en route, at, and beyond Pluto. [1] At Pluto, SWAP's purpose was to record the relationship between the solarwind and ions and/or material entering space from the atmosphere of Pluto. [2]
The atmosphere of Pluto was discovered in 1988, but it remained enigmatic and it was hard to understand an atmosphere existing in such low temperatures (45 K, −230 °C, −380 °F). [3] One of the ideas about Pluto is atmospheric loss, with Pluto being compared to losses from comets. [2] [3] The idea of atmospheric loss was suggested in 1980, even before the atmosphere was discovered. [2] One idea is the photoionization of escaping neutral particles might alter the flow solar wind around the dwarf planet. [2] The atmosphere was known to be very tenuous compared to Earth, and one of the questions was how the gases were interacting with the solar wind and sunlight, likewise weaker at Pluto's orbit than at Earth's. [4] One of the ideas was that Pluto's atmosphere would be stripped away by the solar wind over time. [5]
By the 2010s, only three other spacecraft besides New Horizons have collected extensive data about the solar wind beyond 10 AU, Voyager 2 , Pioneer 10 , and Pioneer 11 . [6]
SWAP is designed to be able to detect the sparse solar wind concentration at 32 AU, which is about three orders of magnitude less than near Earth (1 AU). [2] However, at that distance the flow of the Solar Wind is still supersonic, and thus liable to create a bow shock around an obstacle (at the distance of about 4.5 Pluto radii from the surface). [2] One of the areas of investigation is the relationship between high altitude atmospheric loss and the solar wind. [2] After the July 2015 flyby of Pluto by New Horizons, data from SWAP was used to study the nature of Pluto's interaction with the solar wind. [7] It was determined that NH crossed the plutopause, that separates the solar wind plasma from one bound to Pluto, and then passed through a heavy ion tail. [7]
Earlier in the mission SWAP was intended to observe the Solar Wind around Jupiter. [8] SWAP was also designed to be used in conjunction with PEPPSI and REX, to study how the solar wind changes with greater distance from the Sun. [8] SWAP took only limited observations before 2012, but after that took a greater amount of data. [9]
Starting in 2012, while the rest of the spacecraft was in hibernation most of the time, SWAP was turned on to collect data about the Solar wind as it journeyed out to Pluto at 33 AU. [10] SWAP recorded data about solar wind in the outer solar system and beyond Pluto, and some of the data that is sought about the solar wind are the proton density, speed, and temperature. [9]
One of the observations made with SWAP was that the cross-section of the Pluto's interaction region was limited to about six Pluto radii (about 7000 kilometers); this was smaller than expected. [11] [3]
SWAP is a top-hat electrostatic analyzer. [9] SWAP has a barrier known as the Retarding Potential Analyzer (RPA) that can be open or shut depending on the conditions. [9] When closed ions must pass through the RPA before reaching the inner detectors. [9] Beyond the orbit of Jupiter, it was not necessary to have the RPA engaged for measurements to protect the sensors from being overloaded. [9] The RPA can protect the sensors from being overloaded by solar wind intensities that are too strong, as the device is also required to measure much fainter solar wind fluxes at 33 AU from Sun where Pluto would be at the time of the flyby, and even beyond. [9] SWAP can detect ions up to 6.5 kiloelectron volts (keV). [12]
SWAP weighs 3.3 kilograms (7.3 pounds) and uses an average of 2.3 watts of spacecraft electrical power. [12]
Overall swap is designed to study the solar wind, including at the distant of 32 AU, and to study atmospheric loss from the atmosphere of Pluto. [13]
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. The composition of the solar wind plasma also includes a mixture of materials found in the solar plasma: trace amounts of heavy ions and atomic nuclei of elements such as C, N, O, Ne, Mg, Si, S, and Fe. There are also rarer traces of some other nuclei and isotopes such as P, Ti, Cr, and 58Ni, 60Ni, and 62Ni. Superimposed with the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field. The boundary separating the corona from the solar wind is called the Alfvén surface.
Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume, by a small margin, but is less massive than Eris. Like other Kuiper belt objects, Pluto is made primarily of ice and rock and is much smaller than the inner planets. Pluto has only one sixth the mass of Earth's moon, and one third its volume.
Charon, known as (134340) Pluto I, is the largest of the five known natural satellites of the dwarf planet Pluto. It has a mean radius of 606 km (377 mi). Charon is the sixth-largest known trans-Neptunian object after Pluto, Eris, Haumea, Makemake, and Gonggong. It was discovered in 1978 at the United States Naval Observatory in Washington, D.C., using photographic plates taken at the United States Naval Observatory Flagstaff Station (NOFS).
New Horizons is an interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a team led by Alan Stern, the spacecraft was launched in 2006 with the primary mission to perform a flyby study of the Pluto system in 2015, and a secondary mission to fly by and study one or more other Kuiper belt objects (KBOs) in the decade to follow, which became a mission to 486958 Arrokoth. It is the fifth space probe to achieve the escape velocity needed to leave the Solar System.
The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun. It takes the shape of a vast, tailed bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstellar medium. The "bubble" of the heliosphere is continuously "inflated" by plasma originating from the Sun, known as the solar wind. Outside the heliosphere, this solar plasma gives way to the interstellar plasma permeating the Milky Way. As part of the interplanetary magnetic field, the heliosphere shields the Solar System from significant amounts of cosmic ionizing radiation; uncharged gamma rays are, however, not affected. Its name was likely coined by Alexander J. Dessler, who is credited with the first use of the word in the scientific literature in 1967. The scientific study of the heliosphere is heliophysics, which includes space weather and space climate.
15810 Arawn (provisional designation 1994 JR1) is a trans-Neptunian object (TNO) from the inner regions of the Kuiper belt, approximately 133 kilometres (83 mi) in diameter. It belongs to the plutinos, the most populous class of resonant TNOs. It was named after Arawn, the ruler of the underworld in Welsh mythology, and was discovered on 12 May 1994, by astronomers Michael Irwin and Anna Żytkow with the 2.5-metre Isaac Newton Telescope at Roque de los Muchachos Observatory in the Canary Islands, Spain.
The exploration of Jupiter has been conducted via close observations by automated spacecraft. It began with the arrival of Pioneer 10 into the Jovian system in 1973, and, as of 2023, has continued with eight further spacecraft missions in the vicinity of Jupiter. All of these missions were undertaken by the National Aeronautics and Space Administration (NASA), and all but two were flybys taking detailed observations without landing or entering orbit. These probes make Jupiter the most visited of the Solar System's outer planets as all missions to the outer Solar System have used Jupiter flybys. On 5 July 2016, spacecraft Juno arrived and entered the planet's orbit—the second craft ever to do so. Sending a craft to Jupiter is difficult, mostly due to large fuel requirements and the effects of the planet's harsh radiation environment.
The study of extraterrestrial atmospheres is an active field of research, both as an aspect of astronomy and to gain insight into Earth's atmosphere. In addition to Earth, many of the other astronomical objects in the Solar System have atmospheres. These include all the gas giants, as well as Mars, Venus and Titan. Several moons and other bodies also have atmospheres, as do comets and the Sun. There is evidence that extrasolar planets can have an atmosphere. Comparisons of these atmospheres to one another and to Earth's atmosphere broaden our basic understanding of atmospheric processes such as the greenhouse effect, aerosol and cloud physics, and atmospheric chemistry and dynamics.
MAVEN is a NASA spacecraft orbiting Mars to study the loss of that planet's atmospheric gases to space, providing insight into the history of the planet's climate and water. The name is an acronym for "Mars Atmosphere and Volatile Evolution" while the word maven also denotes "a person who has special knowledge or experience; an expert". MAVEN was launched on an Atlas V rocket from Cape Canaveral Air Force Station, Florida, on 18 November 2013 UTC and went into orbit around Mars on 22 September 2014 UTC. The mission is the first by NASA to study the Mars atmosphere. The probe is analyzing the planet's upper atmosphere and ionosphere to examine how and at what rate the solar wind is stripping away volatile compounds.
The atmosphere of Pluto consists mainly of nitrogen (N2), with minor amounts of methane (CH4) and carbon monoxide (CO), all of which are vaporized from their ices on Pluto's surface. It contains layered haze, probably consisting of heavier compounds which form from these gases due to high-energy radiation. The atmosphere of Pluto is notable for its strong and not completely understood seasonal changes caused by peculiarities of the orbital and axial rotation of Pluto.
Jovian Infrared Auroral Mapper (JIRAM) is an instrument on the Juno spacecraft in orbit of the planet Jupiter. It is an image spectrometer and was contributed by Italy. Similar instruments are on ESA Rosetta, Venus Express, and Cassini-Huygens missions. The primary goal of JIRAM is to probe the upper layers of Jupiter's atmosphere down to pressures of 5–7 bars at infrared wavelengths in the 2–5 μm interval using an imager and a spectrometer. The Jupiter's atmosphere and auroral regions are targeted for study. In particular it has been designed to study the dynamics and chemistry in the atmosphere, perhaps determining the how Jovian hot spots form.
JEDI (Jupiter Energetic-particle Detector Instrument) is an instrument on the Juno spacecraft orbiting planet Jupiter. JEDI coordinates with the several other space physics instruments on the Juno spacecraft to characterize and understand the space environment of Jupiter's polar regions, and specifically to understand the generation of Jupiter's powerful aurora. It is part of a suite of instruments to study the magnetosphere of Jupiter. JEDI consists of three identical detectors that use microchannel plates and foil layers to detect the energy, angle, and types of ion within a certain range. It can detect electrons between 40 and 500 keV (Kilo electron-volts), and hydrogen and oxygen from a few tens of keV to less than 1000 keV (1 MeV). JEDI uses radiation hardened Application Specific Integrated Circuits (ASIC)s. JEDI was turned on in January 2016 while still en route to Jupiter to also study interplanetary space. JEDI uses solid state detectors (SSD's) to measure the total energy (E) of both the ions and the electrons. The MCP anodes and the SSD arrays are configured to determine the directions of arrivals of the incoming charged particles. The instruments also use fast triple coincidence and optimum shielding to suppress penetrating background radiation and incoming UV foreground.
The geography of Pluto is mainly focused the distribution of physical features across Pluto. On 14 July 2015, the New Horizons spacecraft became the first spacecraft to fly by Pluto. During its brief flyby, New Horizons made detailed geographical measurements and observations of Pluto and its moons.
A flyby is a spaceflight operation in which a spacecraft passes in proximity to another body, usually a target of its space exploration mission and/or a source of a gravity assist to impel it towards another target. Spacecraft which are specifically designed for this purpose are known as flyby spacecraft, although the term has also been used in regard to asteroid flybys of Earth for example. Important parameters are the time and distance of closest approach.
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Jovian Auroral Distributions Experiment (JADE) is an instrument that detects and measures ions and electrons around the spacecraft. It is a suite of detectors on the Juno Jupiter orbiter. JADE includes JADE-E, JADE-I, and the EBox. JADE-E and JADE-I are sensors that are spread out on the spacecraft, and the EBox is located inside the Juno Radiation Vault. EBox stands for Electronics Box. JADE-E is for detecting electrons from 0.1 to 100 keV, and there are three JADE-E sensors on Juno. JADE-I is for detecting ions from 5 eV to 50 keV. It is designed to return data in situ on Jupiter's auroral region and magnetospheric plasmas, by observing electrons and ions in this region. It is primarily focused on Jupiter, but it was turned on in January 2016 while still en route to study inter-planetary space.
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Amy Simon is an American planetary scientist at NASA's Goddard Space Flight Center, involved in several missions of the Solar System Exploration Program.
Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI), is an instrument on the New Horizons space probe to Pluto and beyond, it is designed to measure ions and electrons. Specifically, it is focused on measuring ions escaping from the atmosphere of Pluto during the 2015 flyby. It is one of seven major scientific instruments aboard the spacecraft. The spacecraft was launched in 2006, flew by Jupiter the following year, and went onto flyby Pluto in 2015 where PEPSSI was able to record and transmit back to Earth its planned data collections.
REX or Radio Science Experiment is an experiment on the New Horizons space probe to measure properties of the atmosphere of Pluto during the 2015 flyby.
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