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The Parker Solar Probe (PSP; previously Solar Probe, Solar Probe Plus or Solar Probe+) is a NASA space probe launched in 2018 with the mission of making observations of the outer corona of the Sun. It will approach to within 9.86 solar radii (6.9 million km or 4.3 million miles) from the center of the Sun, and by 2025 will travel, at closest approach, as fast as 690,000 km/h (430,000 mph) or 191 km/s, which is 0.064% the speed of light. It is the fastest object ever built. The project was announced in the fiscal 2009 budget year. The cost of the project is US$1.5 billion. Johns Hopkins University Applied Physics Laboratory designed and built the spacecraft, which was launched on 12 August 2018. It became the first NASA spacecraft named after a living (at the time) person, honoring physicist Eugene Newman Parker, professor emeritus at the University of Chicago. A memory card containing the names of over 1.1 million people was mounted on a plaque and installed below the spacecraft's high-gain antenna on 18 May 2018. The card also contains photos of Parker and a copy of his 1958 scientific paper predicting important aspects of solar physics. On 29 October 2018, at about 18:04 UTC, the spacecraft became the closest ever artificial object to the Sun. The previous record, 42.73 million kilometres (26.55 million miles) from the Sun's surface, was set by the Helios 2 spacecraft in April 1976. As of its perihelion 27 September 2023, the Parker Solar Probe's closest approach is 7.26 million kilometres (4.51 million miles). This will be surpassed after the remaining flyby of Venus. History The Parker Solar Probe concept originates in the 1958 report by the Fields and Particles Group (Committee 8 of the National Academy of Sciences' Space Science Board) which proposed several space missions including "a solar probe to pass inside the orbit of Mercury to study the particles and fields in the vicinity of the Sun". Studies in the 1970s and 1980s reaffirmed its importance, but it was always postponed due to cost. A cost-reduced Solar Orbiter mission was studied in the 1990s, and a more capable Solar Probe mission served as one of the centerpieces of the eponymous Outer Planet/Solar Probe (OPSP) program formulated by NASA in the late 1990s. The first three missions of the program were planned to be: the Solar Orbiter, the Pluto and Kuiper belt reconnaissance Pluto Kuiper Express mission, and the Europa Orbiter astrobiology mission focused on Europa. The original Solar Probe design used a gravity assist from Jupiter to enter a polar orbit which dropped almost directly toward the Sun. While this explored the important solar poles and came even closer to the surface (3 R☉, a perihelion of 4 R☉), the extreme variation in solar irradiance made for an expensive mission and required a radioisotope thermal generator for power. The trip to Jupiter also made for a long mission (3+1⁄2 years to first solar perihelion, 8 years to second). Following the appointment of Sean O'Keefe as Administrator of NASA, the entirety of the OPSP program was canceled as part of President George W. Bush's request for the 2003 United States federal budget. Administrator O'Keefe cited a need for a restructuring of NASA and its projects, falling in line with the Bush Administration's wish for NASA to refocus on "research and development, and addressing management shortcomings". In the early 2010s, plans for the Solar Probe mission were incorporated into a lower-cost Solar Probe Plus. The redesigned mission uses multiple Venus gravity assists for a more direct flight path, which can be powered by solar panels. It also has a higher perihelion, reducing the demands on the thermal protection system. In May 2017, the spacecraft was renamed the Parker Solar Probe in honor of astrophysicist Eugene Newman Parker, who had proposed the existence of nanoflares as an explanation of coronal heating as well as had developed a mathematical theory that predicted the existence of solar wind. The solar probe cost NASA US$1.5 billion. The launch rocket bore a dedication in memory of APL engineer Andrew A. Dantzler who had worked on the project. Spacecraft The Parker Solar Probe is the first spacecraft to fly into the low solar corona. It will assess the structure and dynamics of the Sun's coronal plasma and magnetic field, the energy flow that heats the solar corona and impels the solar wind, and the mechanisms that accelerate energetic particles. The spacecraft's systems are protected from the extreme heat and radiation near the Sun by a solar shield. Incident solar radiation at perihelion is approximately 650 kW/m2, or 475 times the intensity at Earth orbit.: 31  The solar shield is hexagonal, mounted on the Sun-facing side of the spacecraft, 2.3 m (7 ft 7 in) in diameter, 11.4 cm (4.5 in) thick, and is made of two panels of reinforced carbon–carbon composite with a lightweight 11-centimeter-thick (4.5 in) carbon foam core, which is designed to withstand temperatures outside the spacecraft of about 1,370 °C (2,500 °F). The shield weighs only 73 kilograms (160 lb) and keeps the spacecraft's instruments at 29 °C (85 °F). A white reflective alumina surface layer minimizes absorption. The spacecraft systems and scientific instruments are located in the central portion of the shield's shadow, where direct radiation from the Sun is fully blocked. If the shield were not between the spacecraft and the Sun, the probe would be damaged and become inoperative within tens of seconds. As radio communication with Earth will take about eight minutes in each direction, the Parker Solar Probe has to act autonomously and rapidly to protect itself. This will be done using four light sensors to detect the first traces of direct sunlight coming from the shield limits and engaging movements from reaction wheels to reposition the spacecraft within the shadow again. According to project scientist Nicky Fox, the team describe it as "the most autonomous spacecraft that has ever flown". The primary power for the mission is a dual system of solar panels (photovoltaic arrays). A primary photovoltaic array, used for the portion of the mission outside 0.25 au, is retracted behind the shadow shield during the close approach to the Sun, and a much smaller secondary array powers the spacecraft through closest approach. This secondary array uses pumped-fluid cooling to maintain operating temperature of the solar panels and instrumentation. Trajectory The Parker Solar Probe mission design uses repeated gravity assists at Venus to incrementally decrease its orbital perihelion to achieve a final altitude (above the surface) of approximately 8.5 solar radii, or about 6×10^6 km (3.7×10^6 mi; 0.040 au). The spacecraft trajectory will include seven Venus flybys over nearly seven years to gradually shrink its elliptical orbit around the Sun, for a total of 24 orbits. The near Sun radiation environ.... Discover the R J Parker popular books. Find the top 100 most popular R J Parker books.