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121-476: The Explorers program is a NASA exploration program that provides flight opportunities for physics, geophysics , heliophysics , and astrophysics investigations from space. Launched in 1958, Explorer 1 was the first spacecraft of the United States to achieve orbit. Over 90 space missions have been launched since. Starting with Explorer 6 , it has been operated by NASA, with regular collaboration with

242-612: A U.S. Army proposal ( Project Orbiter ) to place a "civilian" artificial satellite into orbit during the International Geophysical Year (IGY). Although that proposal was rejected in favor of the U.S. Navy 's Project Vanguard , which made the first sub-orbital flight Vanguard TV0 in December 1956, the Soviet Union 's launch of Sputnik 1 on 4 October 1957 (and the resulting " Sputnik crisis ") and

363-440: A magnetic crochet . The latter term derives from the french word crochet meaning hook reflecting the hook-like disturbances in magnetic field strength observed by ground-based magnetometers . These disturbances are on the order of a few nanoteslas and last for a few minutes, which is relatively minor compared to those induced during geomagnetic storms. For astronauts in low Earth orbit , an expected radiation dose from

484-401: A class is noted by a numerical suffix ranging from 1 up to, but excluding, 10, which is also the factor for that event within the class. Hence, an X2 flare is twice the strength of an X1 flare, an X3 flare is three times as powerful as an X1. M-class flares are a tenth the size of X-class flares with the same numeric suffix. An X2 is four times more powerful than an M5 flare. X-class flares with

605-628: A decade of reliance on the Russians. In 2019, NASA announced the Artemis program , intending to return to the Moon and establish a permanent human presence. This was paired with the Artemis Accords with partner nations to establish rules of behavior and norms of space commercialization on the Moon. In 2023, NASA established the Moon to Mars Program office. The office is designed to oversee

726-485: A helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy in this reconnection is the origin of the particle acceleration. The unconnected magnetic helical field and the material that it contains may violently expand outwards forming a coronal mass ejection. This also explains why solar flares typically erupt from active regions on the Sun where magnetic fields are much stronger. Although there

847-593: A lesser extent, that of Venus . The impacts on other planets in the Solar System are little studied in comparison. As of 2024, research on their effects on Mercury have been limited to modeling of the response of ions in the planet's magnetosphere , and their impact on Jupiter and Saturn have only been studied in the context of X-ray radiation back scattering off of the planets' upper atmospheres. Enhanced XUV irradiance during solar flares can result in increased ionization , dissociation , and heating in

968-647: A month after the Soviet Yuri Gagarin became the first human in space, executing a full orbital spaceflight. NASA's first orbital spaceflight was conducted by John Glenn on February 20, 1962, in the Friendship 7 , making three full orbits before reentering. Glenn had to fly parts of his final two orbits manually due to an autopilot malfunction. The sixth and final Mercury mission was flown by Gordon Cooper in May 1963, performing 22 orbits over 34 hours in

1089-555: A peak flux that exceeds 10 W/m may be noted with a numerical suffix equal to or greater than 10. This system was originally devised in 1970 and included only the letters C, M, and X. These letters were chosen to avoid confusion with other optical classification systems. The A and B classes were added in the 1990s as instruments became more sensitive to weaker flares. Around the same time, the backronym moderate for M-class flares and extreme for X-class flares began to be used. An earlier classification system, sometimes referred to as

1210-583: A permanently manned space station and to do it within a decade. In 1985, NASA proposed the Space Station Freedom , which both the agency and President Reagan intended to be an international program. While this would add legitimacy to the program, there were concerns within NASA that the international component would dilute its authority within the project, having never been willing to work with domestic or international partners as true equals. There

1331-650: A possible source of antimatter at the center of the Milky Way and observing that the majority of gamma-ray bursts occur outside of the Milky Way galaxy. The Chandra X-ray Observatory was launched from the Columbia on STS-93 in 1999, observing black holes, quasars , supernova , and dark matter . It provided critical observations on the Sagittarius A* black hole at the center of the Milky Way galaxy and

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1452-540: A space station since the agency was created. In 1973, following the end of the Apollo lunar missions, NASA launched its first space station, Skylab , on the final launch of the Saturn   V. Skylab reused a significant amount of Apollo and Saturn hardware, with a repurposed Saturn   V third stage serving as the primary module for the space station. Damage to Skylab during its launch required spacewalks to be performed by

1573-599: A total NASA cost cap of US$ 70 million. The Small Explorers class was implemented in 1989 specifically to fund space exploration missions that cost no more than US$ 120 million . The missions are managed by the Explorers Project at the Goddard Space Flight Center (GSFC). The first set of three SMEX missions were launched between 1992 and 1998. The second set of two missions were launched in 1998 and 1999. These early missions were managed by

1694-505: A variety of other institutions, including many international partners. Launchers for the Explorer program have included Juno I , Juno II , various Thor , Scout , Delta and Pegasus launch vehicles, and Falcon 9 . The program has three classes: Medium-Class Explorers (MIDEX), Small Explorers (SMEX), and University-Class Explorers (UNEX), with select Missions of Opportunity operated with other agencies. The Explorer program began as

1815-487: Is a general agreement on the source of a flare's energy, the mechanisms involved are not well understood. It is not clear how the magnetic energy is transformed into the kinetic energy of the particles, nor is it known how some particles can be accelerated to the GeV range (10 electron volt ) and beyond. There are also some inconsistencies regarding the total number of accelerated particles, which sometimes seems to be greater than

1936-475: Is absorbed by the daylight side of Earth's upper atmosphere, in particular the ionosphere , and does not reach the surface. This absorption can temporarily increase the ionization of the ionosphere which may interfere with short-wave radio communication. The prediction of solar flares is an active area of research. Flares also occur on other stars, where the term stellar flare applies. Solar flares are eruptions of electromagnetic radiation originating in

2057-562: Is an independent agency of the U.S. federal government responsible for the civil space program , aeronautics research, and space research. Established in 1958 , it succeeded the National Advisory Committee for Aeronautics (NACA) to give the U.S. space development effort a distinct civilian orientation, emphasizing peaceful applications in space science . It has since led most of America's space exploration programs, including Project Mercury , Project Gemini ,

2178-413: Is then classified taking S or a number that represents its size and a letter that represents its peak intensity, v.g.: Sn is a normal sunflare. A common measure of flare duration is the full width at half maximum (FWHM) time of flux in the soft X-ray bands 0.05 to 0.4 and 0.1 to 0.8 nm measured by GOES. The FWHM time spans from when a flare's flux first reaches halfway between its maximum flux and

2299-550: Is thought to be continued by prolonged heating present after the eruption and during the flare's decay stage. In sufficiently powerful flares, typically of C-class or higher, the loops may combine to form an elongated arch-like structure known as a post-eruption arcade . These structures may last anywhere from multiple hours to multiple days after the initial flare. In some cases, dark sunward-traveling plasma voids known as supra-arcade downflows may form above these arcades. The frequency of occurrence of solar flares varies with

2420-590: The Faith 7 . The Mercury Program was wildly recognized as a resounding success, achieving its objectives to orbit a human in space, develop tracking and control systems, and identify other issues associated with human spaceflight. While much of NASA's attention turned to space, it did not put aside its aeronautics mission. Early aeronautics research attempted to build upon the X-1's supersonic flight to build an aircraft capable of hypersonic flight . The North American X-15

2541-693: The Army Ballistic Missile Agency would launch Explorer 1 , America's first satellite, on February 1, 1958. The Eisenhower Administration decided to split the United States' military and civil spaceflight programs, which were organized together under the Defense Department 's Advanced Research Projects Agency . NASA was established on July 29, 1958, with the signing of the National Aeronautics and Space Act and it began operations on October 1, 1958. As

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2662-803: The Bell X-1 in a joint program with the U.S. Air Force . NACA's interest in space grew out of its rocketry program at the Pilotless Aircraft Research Division. The Soviet Union's launch of Sputnik 1 ushered in the Space Age and kicked off the Space Race . Despite NACA's early rocketry program, the responsibility for launching the first American satellite fell to the Naval Research Laboratory 's Project Vanguard , whose operational issues ensured

2783-677: The Big Bang . The James Webb Space Telescope , named after the NASA administrator who lead the Apollo program, is an infrared observatory launched in 2021. The James Webb Space Telescope is a direct successor to the Hubble Space Telescope, intended to observe the formation of the first galaxies. Other space telescopes include the Kepler space telescope , launched in 2009 to identify planets orbiting extrasolar stars that may be Terran and possibly harbor life. The first exoplanet that

2904-698: The Earth Observing System ; advancing heliophysics through the efforts of the Science Mission Directorate 's Heliophysics Research Program; exploring bodies throughout the Solar System with advanced robotic spacecraft such as New Horizons and planetary rovers such as Perseverance ; and researching astrophysics topics, such as the Big Bang , through the James Webb Space Telescope ,

3025-797: The Environmental Science Services Administration on a series of weather satellites and the agency launched its experimental Applications Technology Satellites into geosynchronous orbit. NASA's first dedicated Earth observation satellite, Landsat , was launched in 1972. This led to NASA and the National Oceanic and Atmospheric Administration jointly developing the Geostationary Operational Environmental Satellite and discovering Ozone depletion . NASA had been pursuing spaceplane development since

3146-630: The Europa and observed that the moon may hold ice or liquid water. A joint NASA- European Space Agency - Italian Space Agency mission, Cassini–Huygens , was sent to Saturn 's moon Titan , which, along with Mars and Europa, are the only celestial bodies in the Solar System suspected of being capable of harboring life. Cassini discovered three new moons of Saturn and the Huygens probe entered Titan's atmosphere. The mission discovered evidence of liquid hydrocarbon lakes on Titan and subsurface water oceans on

3267-784: The Johnson Space Center as the lead center for the design, development, and manufacturing of the Space Shuttle orbiter , while the Marshall Space Flight Center would lead the development of the launch system. NASA's series of lifting body aircraft, culminating in the joint NASA-U.S. Air Force Martin Marietta X-24 , directly informed the development of the Space Shuttle and future hypersonic flight aircraft. Official development of

3388-664: The Mars Global Surveyor orbiter and Mars Pathfinder , deploying the first Mars rover, Sojourner . During the early 2000s, the 2001 Mars Odyssey orbiter reached the planet and in 2004 the Sprit and Opportunity rovers landed on the Red Planet. This was followed in 2005 by the Mars Reconnaissance Orbiter and 2007 Phoenix Mars lander. The 2012 landing of Curiosity discovered that

3509-925: The NSSDC master catalog , typically assigned to each spacecraft in a mission. These numbers were not officially assigned until after 1975. Many missions are proposed, but not selected. For example, in 2011, the Explorers Program received 22 full missions solicitations, 20 Missions of Opportunity, and 8 USPI. Sometimes mission are only partially developed but must be stopped for financial, technological, or bureaucratic reasons. Some missions failed upon reaching orbit including WIRE and TERRIERS. Examples of missions that were not developed or cancelled were: Recent examples of conclusions of launched missions, cancelled due to budgetary constraints: Number of launches per decade: NASA The National Aeronautics and Space Administration ( NASA / ˈ n æ s ə / )

3630-565: The Orbiting Geophysical Observatory in the 1960s and 1970s to look down at Earth and observe its interactions with the Sun. The Uhuru satellite was the first dedicated x-ray telescope, mapping 85% of the sky and discovering a large number of black holes . Launched in the 1990s and early 2000s, the Great Observatories program are among NASA's most powerful telescopes. The Hubble Space Telescope

3751-658: The STS-1 mission, designed to serve as a flight test for the new spaceplane. NASA intended for the Space Shuttle to replace expendable launch systems like the Air Force's Atlas , Delta , and Titan and the European Space Agency 's Ariane . The Space Shuttle's Spacelab payload, developed by the European Space Agency, increased the scientific capabilities of shuttle missions over anything NASA

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3872-635: The STS-60 mission in 1994 and the Discovery rendezvoused, but did not dock with, the Russian Mir in the STS-63 mission. This was followed by Atlantis' STS-71 mission where it accomplished the initial intended mission for the Space Shuttle, docking with a space station and transferring supplies and personnel. The Shuttle- Mir program would continue until 1998, when a series of orbital accidents on

3993-417: The Space Race when the Soviet Union gave up its lunar ambitions. As the first human to step on the surface of the Moon, Neil Armstrong uttered the now famous words: That's one small step for man, one giant leap for mankind. NASA would conduct six total lunar landings as part of the Apollo program, with Apollo   17 concluding the program in 1972. Wernher von Braun had advocated for NASA to develop

4114-620: The Space Shuttle began in 1972, with Rockwell International contracted to design the orbiter and engines, Martin Marietta for the external fuel tank , and Morton Thiokol for the solid rocket boosters . NASA acquired six orbiters: the Enterprise , Columbia , Challenger , Discovery , Atlantis , and Endeavour The Space Shuttle program also allowed NASA to make major changes to its Astronaut Corps . While almost all previous astronauts were Air Force or Naval test pilots,

4235-620: The United States Congress created the Aviation Section of the U.S. Army Signal Corps in 1914 and established NACA in 1915 to foster aeronautical research and development. Over the next forty years, NACA would conduct aeronautical research in support of the U.S. Air Force , U.S. Army , U.S. Navy , and the civil aviation sector. After the end of World War II , NACA became interested in the possibilities of guided missiles and supersonic aircraft, developing and testing

4356-623: The University-Class Explorer (UNEX) program for much cheaper missions, which is regarded as a successor to STEDI. The Explorer missions were at first managed by the Small Explorer Project Office at NASA's Goddard Space Flight Center (GSFC). In early 1999, that office was closed and with the announcement of opportunity for the third set of SMEX missions NASA converted the SMEX class so that each mission

4477-406: The flare importance , was based on H-alpha spectral observations. The scheme uses both the intensity and emitting surface. The classification in intensity is qualitative, referring to the flares as: faint (f), normal (n), or brilliant (b). The emitting surface is measured in terms of millionths of the hemisphere and is described below. (The total hemisphere area A H = 15.5 × 10 km .) A flare

4598-405: The inner planets . Despite these successes, Congress was unwilling to fund further interplanetary missions and NASA Administrator James Webb suspended all future interplanetary probes to focus resources on the Apollo program. Following the conclusion of the Apollo program, NASA resumed launching interplanetary probes and expanded its space science program. The first planet tagged for exploration

4719-528: The ionospheres of Earth and Earth-like planets. On Earth, these changes to the upper atmosphere, collectively referred to as sudden ionospheric disturbances , can interfere with short-wave radio communication and global navigation satellite systems (GNSS) such as GPS , and subsequent expansion of the upper atmosphere can increase drag on satellites in low Earth orbit leading to orbital decay over time. Flare-associated XUV photons interact with and ionize neutral constituents of planetary atmospheres via

4840-399: The plasma medium. Evidence suggests that the phenomenon of magnetic reconnection leads to this extreme acceleration of charged particles. On the Sun, magnetic reconnection may happen on solar arcades – a type of prominence consisting of a series of closely occurring loops following magnetic lines of force. These lines of force quickly reconnect into a lower arcade of loops leaving

4961-466: The 11-year solar cycle . It can typically range from several per day during solar maxima to less than one every week during solar minima . Additionally, more powerful flares are less frequent than weaker ones. For example, X10-class (severe) flares occur on average about eight times per cycle, whereas M1-class (minor) flares occur on average about 2000 times per cycle. Erich Rieger discovered with coworkers in 1984, an approximately 154 day period in

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5082-524: The 1960s, blending the administration's dual aeronautics and space missions. NASA viewed a spaceplane as part of a larger program, providing routine and economical logistical support to a space station in Earth orbit that would be used as a hub for lunar and Mars missions. A reusable launch vehicle would then have ended the need for expensive and expendable boosters like the Saturn V . In 1969, NASA designated

5203-728: The 1968–1972 Apollo Moon landing missions, the Skylab space station, and the Space Shuttle . Currently, NASA supports the International Space Station (ISS) along with the Commercial Crew Program , and oversees the development of the Orion spacecraft and the Space Launch System for the lunar Artemis program . NASA's science division is focused on better understanding Earth through

5324-679: The 44 commercial companies that contracted with NASA to deploy their satellites to return to expendable launch vehicles. When the Space Shuttle returned to flight with the STS-26 mission, it had undergone significant modifications to improve its reliability and safety. Following the collapse of the Soviet Union, the Russian Federation and United States initiated the Shuttle- Mir program . The first Russian cosmonaut flew on

5445-630: The Air Force as the military space lead. Plans for human spaceflight began in the U.S. Armed Forces prior to NASA's creation. The Air Force's Man in Space Soonest project formed in 1956, coupled with the Army's Project Adam, served as the foundation for Project Mercury . NASA established the Space Task Group to manage the program, which would conduct crewed sub-orbital flights with the Army's Redstone rockets and orbital flights with

5566-501: The Air Force's Atlas launch vehicles. While NASA intended for its first astronauts to be civilians, President Eisenhower directed that they be selected from the military. The Mercury 7 astronauts included three Air Force pilots, three Navy aviators, and one Marine Corps pilot. On May 5, 1961, Alan Shepard became the first American to enter space, performing a suborbital spaceflight in the Freedom 7 . This flight occurred less than

5687-410: The Apollo program. Despite attacks on the goal of landing astronauts on the Moon from the former president Dwight Eisenhower and 1964 presidential candidate Barry Goldwater , President Kennedy was able to protect NASA's growing budget, of which 50% went directly to human spaceflight and it was later estimated that, at its height, 5% of Americans worked on some aspect of the Apollo program. Mirroring

5808-685: The Army Ballistic Missile Agency's original Saturn   I . The Apollo spacecraft was designed and built by North American Aviation , while the Apollo Lunar Module was designed and built by Grumman . To develop the spaceflight skills and equipment required for a lunar mission, NASA initiated Project Gemini . Using a modified Air Force Titan   II launch vehicle, the Gemini capsule could hold two astronauts for flights of over two weeks. Gemini pioneered

5929-774: The Corona and Heliosphere (PUNCH). In June 2019 NASA selected TRACERS and PUNCH for flight. Missions of Opportunity (MO) are investigations characterized by being part of a non-NASA space mission of any size and having a total NASA cost of under $ 55 million. These missions are conducted on a no-exchange-of-funds basis with the organization sponsoring the mission. NASA solicits proposals for Missions of Opportunity on SMEX, MIDEX and UNEX investigations. Three satellites were planned in this series: Beacon Explorer-A , Beacon Explorer-B , Beacon Explorer-C . A series of three Geodetic Earth Orbiting Satellite (GEOS) were put in orbit: GEOS 1 , GEOS 2 , GEOS 3 . Explorer name numbers can be found in

6050-485: The Department of Defense's program management concept using redundant systems in building the first intercontinental ballistic missiles, NASA requested the Air Force assign Major General Samuel C. Phillips to the space agency where he would serve as the director of the Apollo program. Development of the Saturn   V rocket was led by Wernher von Braun and his team at the Marshall Space Flight Center , derived from

6171-456: The IMP-D ( Explorer 33 ) in 1966 was the first to use MOSFETs. Over the following two decades, NASA has launched over 50 Explorer missions, some in conjunction to military programs, usually of an exploratory or survey nature or had specific objectives not requiring the capabilities of a major space observatory. Explorer satellites have made many important discoveries on: Earth's magnetosphere and

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6292-574: The Keplar space telescope confirmed was Kepler-22b , orbiting within the habitable zone of its star. NASA also launched a number of different satellites to study Earth, such as Television Infrared Observation Satellite (TIROS) in 1960, which was the first weather satellite. NASA and the United States Weather Bureau cooperated on future TIROS and the second generation Nimbus program of weather satellites. It also worked with

6413-558: The Martian interior. The 2021 Perseverance rover carried the first extraplanetary aircraft, a helicopter named Ingenuity . NASA also launched missions to Mercury in 2004, with the MESSENGER probe demonstrating as the first use of a solar sail . NASA also launched probes to the outer Solar System starting in the 1960s. Pioneer 10 was the first probe to the outer planets, flying by Jupiter , while Pioneer 11 provided

6534-402: The Moon and going to Mars. Embracing this approach, NASA's Commercial Crew Program started by contracting cargo delivery to the International Space Station and flew its first operational contracted mission on SpaceX Crew-1 . This marked the first time since the retirement of the Space Shuttle that NASA was able to launch its own astronauts on an American spacecraft from the United States, ending

6655-404: The Moon and returning him safely to Earth by the end of the 1960s and installed James E. Webb as NASA administrator to achieve this goal. On May   25, 1961, President Kennedy openly declared this goal in his "Urgent National Needs" speech to the United States Congress, declaring: I believe this Nation should commit itself to achieving the goal, before this decade is out, of landing a man on

6776-427: The Moon and returning him safely to Earth. No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish. Kennedy gave his " We choose to go to the Moon " speech the next year, on September   12, 1962 at Rice University , where he addressed the nation hoping to reinforce public support for

6897-409: The Russians be included. In 1993, the Clinton Administration announced that the Space Station Freedom would become the International Space Station in an agreement with the Russian Federation. This allowed the Russians to maintain their space program through an infusion of American currency to maintain their status as one of the two premier space programs. While the United States built and launched

7018-507: The Russians to fly to the International Space Station for four days, despite the opposition of NASA to the idea. Advocates of this new commercial approach for NASA included former astronaut Buzz Aldrin , who remarked that it would return NASA to its roots as a research and development agency, with commercial entities actually operating the space systems. Having corporations take over orbital operations would also allow NASA to focus all its efforts on deep space exploration and returning humans to

7139-691: The Small Explorer Project Office at Goddard Space Flight Center. In early 1999, that office was closed and with the announcement of opportunity for the third set of SMEX missions NASA converted the program so that each mission was managed by its Principal Investigator , with oversight by the GSFC Explorers Project. NASA funded a competitive study of five candidate heliophysics Small Explorers missions for flight in 2022. The proposals were Mechanisms of Energetic Mass Ejection – eXplorer (MEME-X), Focusing Optics X-ray Solar Imager (FOXSI), Multi-Slit Solar Explorer (MUSE), Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS), and Polarimeter to Unify

7260-422: The Solar System. Mars has long been a planet of intense fascination for NASA, being suspected of potentially having harbored life. Mariner 5 was the first NASA spacecraft to flyby Mars, followed by Mariner 6 and Mariner 7 . Mariner 9 was the first orbital mission to Mars. Launched in 1975, Viking program consisted of two landings on Mars in 1976. Follow-on missions would not be launched until 1996, with

7381-404: The Space Shuttle Columbia disaster in 2003, NASA was forced to rely on Russian Soyuz launches for its astronauts and the 2011 retirement of the Space Shuttle accelerated the station's completion. In the 1980s, right after the first flight of the Space Shuttle, NASA started a joint program with the Department of Defense to develop the Rockwell X-30 National Aerospace Plane. NASA realized that

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7502-418: The Space Shuttle allowed NASA to begin recruiting more non-military scientific and technical experts. A prime example is Sally Ride , who became the first American woman to fly in space on STS-7 . This new astronaut selection process also allowed NASA to accept exchange astronauts from U.S. allies and partners for the first time. The first Space Shuttle flight occurred in 1981, when the Columbia launched on

7623-443: The Space Shuttle and expand space exploration beyond low Earth orbit. Constellation was intended to use a significant amount of former Space Shuttle equipment and return astronauts to the Moon. This program was canceled by the Obama Administration . Former astronauts Neil Armstrong , Gene Cernan , and Jim Lovell sent a letter to President Barack Obama to warn him that if the United States did not get new human spaceflight ability,

7744-478: The Space Shuttle began flying, selling it as an orbital laboratory, repair station, and a jumping off point for lunar and Mars missions. NASA found a strong advocate in President Ronald Reagan , who declared in a 1984 speech: America has always been greatest when we dared to be great. We can reach for greatness again. We can follow our dreams to distant stars, living and working in space for peaceful, economic, and scientific gain. Tonight I am directing NASA to develop

7865-444: The Space Shuttle, while a massive technological accomplishment, would not be able to live up to all its promises. Designed to be a single-stage-to-orbit spaceplane, the X-30 had both civil and military applications. With the end of the Cold War , the X-30 was canceled in 1992 before reaching flight status. Following the Space Shuttle Columbia disaster in 2003, President Bush started the Constellation program to smoothly replace

7986-483: The Space Shuttle. Due to technical challenges, the spacecraft was cancelled in 2001. Despite this, it was the first time a commercial space company directly expended a significant amount of its resources into spacecraft development. The advent of space tourism also forced NASA to challenge its assumption that only governments would have people in space. The first space tourist was Dennis Tito , an American investment manager and former aerospace engineer who contracted with

8107-507: The Space Station Freedom was controversial, with much of the debate centering on cost. Several redesigns to reduce cost were conducted in the early 1990s, stripping away much of its functions. Despite calls for Congress to terminate the program, it continued, in large part because by 1992 it had created 75,000 jobs across 39 states. By 1993, President Bill Clinton attempted to significantly reduce NASA's budget and directed costs be significantly reduced, aerospace industry jobs were not lost, and

8228-446: The Sun with wavelengths shorter than 300 nm, space-based telescopes allowed for the observation of solar flares in previously unobserved high-energy spectral lines. Since the 1970s, the GOES series of satellites have been continuously observing the Sun in soft X-rays, and their observations have become the standard measure of flares, diminishing the importance of the H-alpha classification. Additionally, space-based telescopes allow for

8349-482: The Sun's atmosphere. They affect all layers of the solar atmosphere ( photosphere , chromosphere , and corona ). The plasma medium is heated to >10 kelvin , while electrons , protons , and heavier ions are accelerated to near the speed of light . Flares emit electromagnetic radiation across the electromagnetic spectrum , from radio waves to gamma rays . Flares occur in active regions , often around sunspots , where intense magnetic fields penetrate

8470-504: The Sun, are thought to occur and have been observed on other Sun-like stars . Flares produce radiation across the electromagnetic spectrum, although with different intensity. They are not very intense in visible light, but they can be very bright at particular spectral lines . They normally produce bremsstrahlung in X-rays and synchrotron radiation in radio. Solar flares were first observed by Richard Carrington and Richard Hodgson independently on 1 September 1859 by projecting

8591-399: The U.S. risked become a second or third-rate space power. As early as the Reagan Administration, there had been calls for NASA to expand private sector involvement in space exploration rather than do it all in-house. In the 1990s, NASA and Lockheed Martin entered into an agreement to develop the Lockheed Martin X-33 demonstrator of the VentureStar spaceplane, which was intended to replace

8712-536: The US's premier aeronautics agency, NACA formed the core of NASA's new structure by reassigning 8,000 employees and three major research laboratories. NASA also proceeded to absorb the Naval Research Laboratory's Project Vanguard, the Army's Jet Propulsion Laboratory (JPL), and the Army Ballistic Missile Agency under Wernher von Braun . This left NASA firmly as the United States' civil space lead and

8833-605: The ambient electrons and neutral species and via secondary ionization due to collisions with the latter, or so-called photoelectron impact ionization . In the process of thermalization, photoelectrons transfer energy to neutral species, resulting in heating and expansion of the neutral atmosphere. The greatest increases in ionization occur in the lower ionosphere where wavelengths with the greatest relative increase in irradiance—the highly penetrative X-ray wavelengths—are absorbed, corresponding to Earth's E and D layers and Mars's M 1 layer. The temporary increase in ionization of

8954-447: The background flux and when it again reaches this value as the flare decays. Using this measure, the duration of a flare ranges from approximately tens of seconds to several hours with a median duration of approximately 6 and 11 minutes in the 0.05 to 0.4 and 0.1 to 0.8 nm bands, respectively. Flares can also be classified based on their duration as either impulsive or long duration events ( LDE ). The time threshold separating

9075-424: The daylight side of Earth's atmosphere, in particular the D layer of the ionosphere , can interfere with short-wave radio communications that rely on its level of ionization for skywave propagation. Skywave, or skip, refers to the propagation of radio waves reflected or refracted off of the ionized ionosphere. When ionization is higher than normal, radio waves get degraded or completely absorbed by losing energy from

9196-404: The distance from its source region . The excess ionizing radiation , namely X-ray and extreme ultraviolet (XUV) radiation, is known to affect planetary atmospheres and is of relevance to human space exploration and the search for extraterrestrial life. Solar flares also affect other objects in the Solar System. Research into these effects has primarily focused on the atmosphere of Mars and, to

9317-632: The early 1980s. In 1988, the Small Explorer (SMEX) class was established with a focus on frequent flight opportunities for highly focused and relatively inexpensive space science missions in the disciplines of astrophysics and space physics. The first three SMEX missions were chosen in April 1989 out of 51 candidates, and launched in 1992, 1996 and 1998 The second set of two missions were announced in September 1994 and launched in 1998 and 1999. In

9438-674: The electromagnetic radiation emitted during a solar flare is about 0.05 gray , which is not immediately lethal on its own. Of much more concern for astronauts is the particle radiation associated with solar particle events. The impacts of solar flare radiation on Mars are relevant to exploration and the search for life on the planet . Models of its atmosphere indicate that the most energetic solar flares previously recorded may have provided acute doses of radiation that would have been almost harmful or lethal to mammals and other higher organisms on Mars's surface. Furthermore, flares energetic enough to provide lethal doses, while not yet observed on

9559-473: The event. Using these magnetometer readings, its soft X-ray class has been estimated to be greater than X10 and around X45 (±5). In modern times, the largest solar flare measured with instruments occurred on 4 November 2003 . This event saturated the GOES detectors, and because of this, its classification is only approximate. Initially, extrapolating the GOES curve, it was estimated to be X28. Later analysis of

9680-730: The failure of the Vanguard 1 launch attempt resulted in the Army program being funded to match the Soviet space achievements. Explorer 1 was launched on the Juno I on 1 February 1958, becoming the first U.S. satellite, as well as discovering the Van Allen radiation belt . Four follow-up satellites of the Explorer series were launched by the Juno I launch vehicle in 1958, of which Explorer 3 and Explorer 4 were successful, while Explorer 2 and Explorer 5 failed to reach orbit. The Juno I vehicle

9801-420: The first close up view of the planet. Both probes became the first objects to leave the Solar System. The Voyager program launched in 1977, conducting flybys of Jupiter and Saturn , Neptune , and Uranus on a trajectory to leave the Solar System. The Galileo spacecraft, deployed from the Space Shuttle flight STS-34 , was the first spacecraft to orbit Jupiter, discovering evidence of subsurface oceans on

9922-515: The first crew to make it habitable and operational. Skylab hosted nine missions and was decommissioned in 1974 and deorbited in 1979, two years prior to the first launch of the Space Shuttle and any possibility of boosting its orbit. In 1975, the Apollo–Soyuz mission was the first ever international spaceflight and a major diplomatic accomplishment between the Cold War rivals, which also marked

10043-402: The first humans to see the Earth as a globe in space, the first to witness an Earthrise , and the first to see and manually photograph the far side of the Moon. The first lunar landing was conducted by Apollo   11. Commanded by Neil Armstrong with astronauts Buzz Aldrin and Michael Collins , Apollo   11 was one of the most significant missions in NASA's history, marking the end of

10164-534: The first launch under this new class was FUSE in 1999. In May 1994, NASA started the Student Explorer Demonstration Initiative (STEDI) pilot program, to demonstrate that high-quality space science can be carried out with small, low-cost missions. Of the three selected missions, SNOE was launched in 1998 and TERRIERS in 1999, but the latter failed after launch. The STEDI program was terminated in 2001. Later, NASA established

10285-470: The four Great Observatories , and associated programs. The Launch Services Program oversees launch operations for its uncrewed launches . NASA traces its roots to the National Advisory Committee for Aeronautics (NACA). Despite being the birthplace of aviation, by 1914 the United States recognized that it was far behind Europe in aviation capability. Determined to regain American leadership in aviation,

10406-457: The image of the solar disk produced by an optical telescope through a broad-band filter. It was an extraordinarily intense white light flare , a flare emitting a high amount of light in the visual spectrum . Since flares produce copious amounts of radiation at H-alpha , adding a narrow (≈1 Å) passband filter centered at this wavelength to the optical telescope allows the observation of not very bright flares with small telescopes. For years Hα

10527-417: The ionosphere's dayside E layer inducing small-amplitude diurnal variations in the geomagnetic field. These ionospheric currents can be strengthened during large solar flares due to increases in electrical conductivity associated with enhanced ionization of the E and D layers. The subsequent increase in the induced geomagnetic field variation is referred to as a solar flare effect ( sfe ) or historically as

10648-525: The ionospheric effects suggested increasing this estimate to X45. This event produced the first clear evidence of a new spectral component above 100 GHz. Current methods of flare prediction are problematic, and there is no certain indication that an active region on the Sun will produce a flare. However, many properties of active regions and their sunspots correlate with flaring. For example, magnetically complex regions (based on line-of-sight magnetic field) referred to as delta spots frequently produce

10769-499: The largest flares. A simple scheme of sunspot classification based on the McIntosh system for sunspot groups, or related to a region's fractal complexity is commonly used as a starting point for flare prediction. Predictions are usually stated in terms of probabilities for occurrence of flares above M- or X-class within 24 or 48 hours. The U.S. National Oceanic and Atmospheric Administration (NOAA) issues forecasts of this kind. MAG4

10890-451: The last flight of the Apollo capsule. Flown in 1975, a U.S. Apollo spacecraft docked with a Soviet Soyuz capsule. During the 1960s, NASA started its space science and interplanetary probe program. The Mariner program was its flagship program, launching probes to Venus , Mars , and Mercury in the 1960s. The Jet Propulsion Laboratory was the lead NASA center for robotic interplanetary exploration, making significant discoveries about

11011-451: The launches, the MIDEX class has a current mission cap cost of US$ 250 million in 2018, with future MIDEX missions being capped at US$ 350 million. The cost cap for SMEX missions in 2017 was US$ 165 million. UNEX missions are capped at US$ 15 million. A sub-project called Missions of Opportunity (MO) has funded science instruments or hardware components of onboard non-NASA space missions, and have

11132-515: The majority of the International Space Station, Russia, Canada, Japan, and the European Space Agency all contributed components. Despite NASA's insistence that costs would be kept at a budget of $ 17.4, they kept rising and NASA had to transfer funds from other programs to keep the International Space Station solvent. Ultimately, the total cost of the station was $ 150 billion, with the United States paying for two-thirds.Following

11253-527: The mid-1990s, NASA initiated the Medium-class Explorer (MIDEX) to enable more frequent flights. These are larger than SMEX missions and were to be launched aboard a new kind of medium-light class launch vehicle. This new launch vehicle was not developed and instead, these missions were flown on a modified Delta II rocket. The first announcement opportunity for MIDEX was issued in March 1995, and

11374-634: The moon of Enceladus , which could harbor life. Finally launched in 2006, the New Horizons mission was the first spacecraft to visit Pluto and the Kuiper Belt . Beyond interplanetary probes, NASA has launched many space telescopes . Launched in the 1960s, the Orbiting Astronomical Observatory were NASA's first orbital telescopes, providing ultraviolet, gamma-ray, x-ray, and infrared observations. NASA launched

11495-548: The more frequent collisions with free electrons. The level of ionization of the atmosphere correlates with the strength of the associated solar flare in soft X-ray radiation. The Space Weather Prediction Center , a part of the United States National Oceanic and Atmospheric Administration , classifies radio blackouts by the peak soft X-ray intensity of the associated flare. During non-flaring or solar quiet conditions, electric currents flow through

11616-429: The observation of extremely long wavelengths—as long as a few kilometres—which cannot propagate through the ionosphere. The most powerful flare ever observed is thought to be the flare associated with the 1859 Carrington Event. While no soft X-ray measurements were made at the time, the magnetic crochet associated with the flare was recorded by ground-based magnetometers allowing the flare's strength to be estimated after

11737-517: The occurrence of gamma-ray emitting solar flares at least since the solar cycle 19 . The period has since been confirmed in most heliophysics data and the interplanetary magnetic field and is commonly known as the Rieger period . The period's resonance harmonics also have been reported from most data types in the heliosphere . The frequency distributions of various flare phenomena can be characterized by power-law distributions . For example,

11858-522: The peak fluxes of radio, extreme ultraviolet, and hard and soft X-ray emissions; total energies; and flare durations (see § Duration ) have been found to follow power-law distributions. The modern classification system for solar flares uses the letters A, B, C, M, or X, according to the peak flux in watts per square metre (W/m ) of soft X-rays with wavelengths 0.1 to 0.8 nanometres (1 to 8 ångströms ), as measured by GOES satellites in geosynchronous orbit . The strength of an event within

11979-598: The photosphere to link the corona to the solar interior. Flares are powered by the sudden (timescales of minutes to tens of minutes) release of magnetic energy stored in the corona. The same energy releases may also produce coronal mass ejections (CMEs), although the relationship between CMEs and flares is not well understood. Associated with solar flares are flare sprays. They involve faster ejections of material than eruptive prominences , and reach velocities of 20 to 2000 kilometers per second. Flares occur when accelerated charged particles, mainly electrons, interact with

12100-456: The process of photoionization . The electrons that are freed in this process, referred to as photoelectrons to distinguish them from the ambient ionospheric electrons, are left with kinetic energies equal to the photon energy in excess of the ionization threshold . In the lower ionosphere where flare impacts are greatest and transport phenomena are less important, the newly liberated photoelectrons lose energy primarily via thermalization with

12221-570: The radiation levels on Mars were equal to those on the International Space Station , greatly increasing the possibility of Human exploration, and observed the key chemical ingredients for life to occur. In 2013, the Mars Atmosphere and Volatile Evolution ( MAVEN ) mission observed the Martian upper atmosphere and space environment and in 2018, the Interior exploration using Seismic Investigations Geodesy, and Heat Transport ( InSight ) studied

12342-507: The satellites were repaired and relaunched. Despite ushering in a new era of spaceflight, where NASA was contracting launch services to commercial companies, the Space Shuttle was criticized for not being as reusable and cost-effective as advertised. In 1986, Challenger disaster on the STS-51L mission resulted in the loss of the spacecraft and all seven astronauts on launch, grounding the entire space shuttle fleet for 36 months and forced

12463-676: The separation of dark and regular matter during galactic collisions. Finally, the Spitzer Space Telescope is an infrared telescope launched in 2003 from a Delta II rocket. It is in a trailing orbit around the Sun, following the Earth and discovered the existence of brown dwarf stars . Other telescopes, such as the Cosmic Background Explorer and the Wilkinson Microwave Anisotropy Probe , provided evidence to support

12584-560: The setback caused by the Apollo   1 fire, which killed three astronauts, the program proceeded. Apollo   8 was the first crewed spacecraft to leave low Earth orbit and the first human spaceflight to reach the Moon . The crew orbited the Moon ten times on December   24 and   25, 1968, and then traveled safely back to Earth . The three Apollo   8 astronauts— Frank Borman , James Lovell , and William Anders —were

12705-505: The shape of its gravity field ; the solar wind ; properties of micrometeoroids raining down on the Earth ; ultraviolet, cosmic and X-rays from the Solar System and beyond; ionospheric physics ; Solar plasma ; solar energetic particles ; and atmospheric physics . These missions have also investigated air density, radio astronomy, geodesy , and gamma-ray astronomy . With decreases in NASA's budget, Explorer missions became infrequent in

12826-549: The space shuttle be retired. In 2006, the Space Shuttle returned to flight, conducting several mission to service the Hubble Space Telescope , but was retired following the STS-135 resupply mission to the International Space Station in 2011. NASA never gave up on the idea of a space station after Skylab's reentry in 1979. The agency began lobbying politicians to support building a larger space station as soon as

12947-481: The space station spelled an end to the program. In 2003, a second space shuttle was destroyed when the Columbia was destroyed upon reentry during the STS-107 mission, resulting in the loss of the spacecraft and all seven astronauts. This accident marked the beginning of the retiring of the Space Shuttle program, with President George W. Bush directing that upon the completion of the International Space Station,

13068-425: The total number in the coronal loop. After the eruption of a solar flare, post-eruption loops made of hot plasma begin to form across the neutral line separating regions of opposite magnetic polarity near the flare's source. These loops extend from the photosphere up into the corona and form along the neutral line at increasingly greater distances from the source as time progresses. The existence of these hot loops

13189-406: The two is not well defined. The SWPC regards events requiring 30 minutes or more to decay to half maximum as LDEs, whereas Belgium's Solar-Terrestrial Centre of Excellence regards events with duration greater than 60 minutes as LDEs. The electromagnetic radiation emitted during a solar flare propagates away from the Sun at the speed of light with intensity inversely proportional to the square of

13310-579: The use of fuel cells instead of batteries, and conducted the first American spacewalks and rendezvous operations . The Ranger Program was started in the 1950s as a response to Soviet lunar exploration, however most missions ended in failure. The Lunar Orbiter program had greater success, mapping the surface in preparation for Apollo landings and measured Selenography , conducted meteoroid detection, and measured radiation levels. The Surveyor program conducted uncrewed lunar landings and takeoffs, as well as taking surface and regolith observations. Despite

13431-458: The various projects, mission architectures and associated timelines relevant to lunar and Mars exploration and science. Solar flare Solar flares are thought to occur when stored magnetic energy in the Sun's atmosphere accelerates charged particles in the surrounding plasma . This results in the emission of electromagnetic radiation across the electromagnetic spectrum . The extreme ultraviolet and X-ray radiation from solar flares

13552-461: Was Venus , sharing many similar characteristics to Earth. First visited by American Mariner 2 spacecraft, Venus was observed to be a hot and inhospitable planet. Follow-on missions included the Pioneer Venus project in the 1970s and Magellan , which performed radar mapping of Venus' surface in the 1980s and 1990s. Future missions were flybys of Venus, on their way to other destinations in

13673-489: Was a joint NASA–U.S. Air Force program, with the hypersonic test aircraft becoming the first non-dedicated spacecraft to cross from the atmosphere to outer space. The X-15 also served as a testbed for Apollo program technologies, as well as ramjet and scramjet propulsion. Escalations in the Cold War between the United States and Soviet Union prompted President John F. Kennedy to charge NASA with landing an American on

13794-683: Was able to previously accomplish. NASA launched its first commercial satellites on the STS-5 mission and in 1984, the STS-41-C mission conducted the world's first on-orbit satellite servicing mission when the Challenger captured and repaired the malfunctioning Solar Maximum Mission satellite. It also had the capability to return malfunctioning satellite to Earth, like it did with the Palapa B2 and Westar 6 satellites. Once returned to Earth,

13915-545: Was also a concern with sharing sensitive space technologies with the Europeans, which had the potential to dilute America's technical lead. Ultimately, an international agreement to develop the Space Station Freedom program would be signed with thirteen countries in 1985, including the European Space Agency member states, Canada , and Japan . Despite its status as the first international space program,

14036-416: Was launched in 1963 and involved a network of eleven Explorer satellites designed to collect data on space radiation in support of the Apollo program . The IMP program was a major step forward in spacecraft electronics design, as it was the first space program to use integrated circuit (IC) chips and MOSFETs (MOS transistors). The IMP-A ( Explorer 18 ) in 1963 was the first spacecraft to use IC chips, and

14157-497: Was launched in 1990 on STS-31 from the Discovery and could view galaxies 15 billion light years away. A major defect in the telescope's mirror could have crippled the program, had NASA not used computer enhancement to compensate for the imperfection and launched five Space Shuttle servicing flights to replace the damaged components. The Compton Gamma Ray Observatory was launched from the Atlantis on STS-37 in 1991, discovering

14278-544: Was managed by its principal investigator , with oversight by the GSFC Explorer Project. The Explorer program Office at Goddard Space Flight Center, provides management of the many operational scientific exploration missions that are characterized by relatively moderate costs and small to medium-sized missions that are capable of being built, tested, and launched in a short time interval compared to larger observatories like NASA's Great Observatories . Excluding

14399-617: Was replaced by the Juno II in 1959. With the establishment of NASA in 1958, the Explorer program was transferred to NASA from the U.S. Army . NASA continued to use the name for an ongoing series of relatively small space missions, typically an artificial satellite with a specific science focus. Explorer 6 in 1959 was the first scientific satellite under the project direction of NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland . The Interplanetary Monitoring Platform (IMP)

14520-406: Was the first to report radioastronomical observations of the Sun at 160 MHz. The fast development of radioastronomy revealed new peculiarities of the solar activity like storms and bursts related to the flares. Today, ground-based radiotelescopes observe the Sun from c. 15 MHz up to 400 GHz. Because the Earth's atmosphere absorbs much of the electromagnetic radiation emitted by

14641-467: Was the main, if not the only, source of information about solar flares. Other passband filters are also used. During World War II , on February 25 and 26, 1942, British radar operators observed radiation that Stanley Hey interpreted as solar emission. Their discovery did not go public until the end of the conflict. The same year, Southworth also observed the Sun in radio, but as with Hey, his observations were only known after 1945. In 1943, Grote Reber

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