128-593: Neil Gehrels Swift Observatory , previously called the Swift Gamma-Ray Burst Explorer , is a NASA three-telescope space observatory for studying gamma-ray bursts (GRBs) and monitoring the afterglow in X-ray, and UV/visible light at the location of a burst. It was launched on 20 November 2004, aboard a Delta II launch vehicle . Headed by principal investigator Neil Gehrels until his death in February 2017,
256-628: A GRB, the UVOT is used to detect an optical afterglow. The UVOT provides a sub-arcsecond position and provides optical and ultra-violet photometry through lenticular filters and low resolution spectra (170–650 nm) through the use of its optical and UV grisms . The UVOT is also used to provide long-term follow-ups of GRB afterglow lightcurves. The UVOT is based on the XMM-Newton 's Optical Monitor (OM) instrument, with improved optics and upgraded onboard processing computers. On 9 November 2011, UVOT photographed
384-531: A coded aperture to locate the source. The software to locate the source is provided by the Los Alamos National Laboratory (LANL). The CdZnTe detector of 5,200 cm (810 sq in) area, consisting of 32,500 units of 4 × 4 × 2 mm (0.157 × 0.157 × 0.079 in), can pin-point the location of sources within 1.4 arcminutes. The energy range is 15-150 keV. UVOT (Ultraviolet/Optical Telescope) monitors
512-607: 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
640-521: A detector plane of 32,768 4 mm (0.16 in) Cadmium zinc telluride (CdZnTe) hard X-ray detector tiles; it is purpose-built for Swift. Energy range: 15–150 keV . The XRT can take images and perform spectral analysis of the GRB afterglow. This provides more precise location of the GRB, with a typical error circle of approximately 2 arcseconds radius. The XRT is also used to perform long-term monitoring of GRB afterglow light-curves for days to weeks after
768-423: A factor of 100. Therefore a new definition of the second is planned. Atomic clocks now set the length of a second and the time standard for the world. 12960276813 408986496 × 10 − 9 {\displaystyle {\frac {12960276813}{408986496}}\times 10^{-9}} of the tropical year for 1900 January 0 at 12 h ET. 11th CGPM 1960 Resolution 9 CIPM 1967
896-611: A formula describing a mean tropical year that decreased linearly over time. In 1956, the second was redefined in terms of a year relative to that epoch . The second was thus defined as "the fraction 1 ⁄ 31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time". This definition was adopted as part of the International System of Units in 1960. Even the best mechanical, electric motorized and quartz crystal-based clocks develop discrepancies from environmental conditions; far better for timekeeping
1024-522: A measure of radioactive decay, is measured in inverse seconds and higher powers of second are involved in derivatives of acceleration such as jerk . Though many derivative units for everyday things are reported in terms of larger units of time, not seconds, they are ultimately defined in terms of the SI second; this includes time expressed in hours and minutes, velocity of a car in kilometers per hour or miles per hour, kilowatt hours of electricity usage, and speed of
1152-518: A meter long; the fastest human sprinters run 10 meters in a second; an ocean wave in deep water travels about 23 meters in one second; sound travels about 343 meters in one second in air; light takes 1.3 seconds to reach Earth from the surface of the Moon, a distance of 384,400 kilometers. A second is directly part of other units, such as frequency measured in hertz ( inverse seconds or s ), speed in meters per second, and acceleration in meters per second squared. The metric system unit becquerel ,
1280-458: A microwave cavity. The fraction of excited atoms is then detected by laser beams. These clocks have 5 × 10 systematic uncertainty, which is equivalent to 50 picoseconds per day. A system of several fountains worldwide contribute to International Atomic Time. These caesium clocks also underpin optical frequency measurements. Optical clocks are based on forbidden optical transitions in ions or atoms. They have frequencies around 10 Hz , with
1408-629: 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
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#17329381655661536-523: A natural linewidth Δ f {\displaystyle \Delta f} of typically 1 Hz, so the Q-factor is about 10 , or even higher. They have better stabilities than microwave clocks, which means that they can facilitate evaluation of lower uncertainties. They also have better time resolution, which means the clock "ticks" faster. Optical clocks use either a single ion, or an optical lattice with 10 – 10 atoms. A definition based on
1664-570: 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
1792-628: 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
1920-508: A second was selected to correspond exactly to the length of the ephemeris second previously defined. Atomic clocks use such a frequency to measure seconds by counting cycles per second at that frequency. Radiation of this kind is one of the most stable and reproducible phenomena of nature. The current generation of atomic clocks is accurate to within one second in a few hundred million years. Since 1967, atomic clocks based on atoms other than caesium-133 have been developed with increased precision by
2048-474: A single day differs from the next by only a small amount; 15 minutes is a cumulative difference over a part of the year. The effect is due chiefly to the obliqueness of Earth's axis with respect to its orbit around the Sun. The difference between apparent solar time and mean time was recognized by astronomers since antiquity, but prior to the invention of accurate mechanical clocks in the mid-17th century, sundials were
2176-532: 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
2304-400: A turntable in rotations per minute. Moreover, most other SI base units are defined by their relationship to the second: the meter is defined by setting the speed of light (in vacuum) to be 299 792 458 m/s, exactly; definitions of the SI base units kilogram , ampere , kelvin , and candela also depend on the second. The only base unit whose definition does not depend on the second
2432-456: Is 604,800 seconds; a year (other than leap years ) is 31,536,000 seconds; and a ( Gregorian ) century averages 3,155,695,200 seconds; with all of the above excluding any possible leap seconds . In astronomy, a Julian year is precisely 31,557,600 seconds. Some common events in seconds are: a stone falls about 4.9 meters from rest in one second; a pendulum of length about one meter has a swing of one second, so pendulum clocks have pendulums about
2560-583: Is a 1-gigahertz microprocessor that has a cycle time of 1 nanosecond. Camera shutter speeds are often expressed in fractions of a second, such as 1 ⁄ 30 second or 1 ⁄ 1000 second. Sexagesimal divisions of the day from a calendar based on astronomical observation have existed since the third millennium BC, though they were not seconds as we know them today. Small divisions of time could not be measured back then, so such divisions were mathematically derived. The first timekeepers that could count seconds accurately were pendulum clocks invented in
2688-425: Is a multi- wavelength space observatory dedicated to the study of gamma-ray bursts . Its three instruments work together to observe GRBs and their afterglows in the gamma-ray , X-ray , ultraviolet , and optical wavebands. Based on continuous scans of the area of the sky with one of the instrument's monitors, Swift uses momentum wheels to autonomously slew into the direction of possible GRBs. The name "Swift"
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#17329381655662816-551: 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 ,
2944-659: Is an unsigned clock depicting Orpheus in the Fremersdorf collection, dated between 1560 and 1570. During the 3rd quarter of the 16th century, Taqi al-Din built a clock with marks every 1/5 minute. In 1579, Jost Bürgi built a clock for William of Hesse that marked seconds. In 1581, Tycho Brahe redesigned clocks that had displayed only minutes at his observatory so they also displayed seconds, even though those seconds were not accurate. In 1587, Tycho complained that his four clocks disagreed by plus or minus four seconds. In 1656, Dutch scientist Christiaan Huygens invented
3072-530: Is located at the University of Leicester . The Swift satellite bus was built by Spectrum Astro , which was later acquired by General Dynamics Advanced Information Systems , which was in turn acquired by Orbital Sciences Corporation (now Northrop Grumman Innovation Systems ). The BAT detects GRB events and computes its coordinates in the sky. It covers a large fraction of the sky (over one steradian fully coded, three steradians partially coded; by comparison,
3200-643: Is not a mission-related acronym, but rather a reference to the instrument's rapid slew capability, and the nimble swift (bird of the same name). All of Swift's discoveries are transmitted to the ground and those data are available to other observatories which join Swift in observing the GRBs. In the time between GRB events, Swift is available for other scientific investigations, and scientists from universities and other organizations can submit proposals for observations. The Swift Mission Operation Center (MOC), where commanding of
3328-412: Is the mole , and only two of the 22 named derived units, radian and steradian , do not depend on the second either. A set of atomic clocks throughout the world keeps time by consensus: the clocks "vote" on the correct time, and all voting clocks are steered to agree with the consensus, which is called International Atomic Time (TAI). TAI "ticks" atomic seconds. Civil time is defined to agree with
3456-413: Is the natural and exact "vibration" in an energized atom. The frequency of vibration (i.e., radiation) is very specific depending on the type of atom and how it is excited. Since 1967, the second has been defined as exactly "the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom". This length of
3584-407: The pars minuta secunda , "second small part", dividing again into sixty. Analog clocks and watches often have sixty tick marks on their faces, representing seconds (and minutes), and a "second hand" to mark the passage of time in seconds. Digital clocks and watches often have a two-digit seconds counter. SI prefixes are frequently combined with the word second to denote subdivisions of
3712-583: 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
3840-720: 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
3968-762: 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
Neil Gehrels Swift Observatory - Misplaced Pages Continue
4096-658: 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
4224-672: The Compton Gamma Ray Observatory . The Swift mission was launched with a nominal on-orbit lifetime of two years. Swift is a NASA MIDEX (medium-class Explorer) mission. It was the third to be launched, following IMAGE and WMAP . While originally designed for the study of gamma-ray bursts, Swift now functions as a general-purpose multi-wavelength observatory, particularly for the rapid followup and characterization of astrophysical transients of all types. As of 2020, Swift received 5.5 Target of Opportunity observing proposals per day, and observes ~70 targets per day, on average. Swift
4352-660: 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 ,
4480-753: 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
4608-676: 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
4736-411: The International System of Units (SI) is more precise: The second [...] is defined by taking the fixed numerical value of the caesium frequency, Δ ν Cs , the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz , which is equal to s . This current definition was adopted in 1967 when it became feasible to define
4864-742: 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
4992-634: 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
5120-543: 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
5248-551: The Pennsylvania State University (PSU), the Brera Astronomical Observatory , Italy, and the University of Leicester , United Kingdom. It has a detector of area 135 cm (20.9 sq in) consisting of 600 x 600 pixels, and covers the energy range of 0.2-10 keV. It can locate the afterglow source at an accuracy of four arcseconds. The Swift mission has four key scientific objectives: Swift
Neil Gehrels Swift Observatory - Misplaced Pages Continue
5376-527: The Rydberg constant would involve fixing the value to a certain value: R ∞ = m e e 4 8 ε 0 2 h 3 c = m e c α 2 2 h {\displaystyle R_{\infty }={\frac {m_{\text{e}}e^{4}}{8\varepsilon _{0}^{2}h^{3}c}}={\frac {m_{\text{e}}c\alpha ^{2}}{2h}}} . The Rydberg constant describes
5504-631: 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
5632-616: 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
5760-471: 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
5888-609: 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,
6016-602: 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
6144-405: 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
6272-454: The mean time , as opposed to the apparent time displayed by sundials . By that time, sexagesimal divisions of time were well established in Europe. The earliest clocks to display seconds appeared during the last half of the 16th century. The second became accurately measurable with the development of mechanical clocks. The earliest spring-driven timepiece with a second hand that marked seconds
6400-491: The sidereal year at that epoch by the IAU in 1952. This extrapolated timescale brings the observed positions of the celestial bodies into accord with Newtonian dynamical theories of their motion. In 1955, the tropical year , considered more fundamental than the sidereal year, was chosen by the IAU as the unit of time. The tropical year in the definition was not measured but calculated from
6528-400: The 14th century, had displays that divided the hour into halves, thirds, quarters and sometimes even 12 parts, but never by 60. In fact, the hour was not commonly divided in 60 minutes as it was not uniform in duration. It was not practical for timekeepers to consider minutes until the first mechanical clocks that displayed minutes appeared near the end of the 16th century. Mechanical clocks kept
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#17329381655666656-467: The 17th century. Starting in the 1950s, atomic clocks became better timekeepers than Earth's rotation, and they continue to set the standard today. A mechanical clock, which does not depend on measuring the relative rotational position of the Earth, keeps uniform time called mean time , within whatever accuracy is intrinsic to it. That means that every second, minute and every other division of time counted by
6784-468: 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
6912-690: 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
7040-424: The 2010s held the accuracy record: it gains or loses less than a second in 15 billion years, which is longer than the estimated age of the universe. Such a clock can measure a change in its elevation of as little as 2 cm by the change in its rate due to gravitational time dilation . There have only ever been three definitions of the second: as a fraction of the day, as a fraction of an extrapolated year, and as
7168-655: 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
7296-559: The Advancement of Science (BAAS) in 1862 stated that "All men of science are agreed to use the second of mean solar time as the unit of time." BAAS formally proposed the CGS system in 1874, although this system was gradually replaced over the next 70 years by MKS units. Both the CGS and MKS systems used the same second as their base unit of time. MKS was adopted internationally during the 1940s, defining
7424-450: 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
7552-448: 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
7680-410: 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
7808-478: 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
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#17329381655667936-426: 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
8064-439: 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
8192-448: 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
8320-402: 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
8448-404: 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
8576-427: 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
8704-409: 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
8832-507: 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
8960-422: 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
9088-404: 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
9216-418: 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
9344-505: 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,
9472-544: 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
9600-660: 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
9728-483: 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
9856-571: 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
9984-502: The Sun (a year) was much more stable than Earth's rotation. This led to proposals as early as 1950 to define the second as a fraction of a year. The Earth's motion was described in Newcomb's Tables of the Sun (1895), which provided a formula for estimating the motion of the Sun relative to the epoch 1900 based on astronomical observations made between 1750 and 1892. This resulted in adoption of an ephemeris time scale expressed in units of
10112-578: 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
10240-569: 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
10368-625: The XRT would be usable even without the TEC being operational. Additional testing on 16 December 2004 did not yield any further information as to the cause of the anomaly. On 17 December 2004 at 07:28:30 UTC, the Swift Burst Alert Telescope (BAT) triggered and located on board an apparent gamma-ray burst during launch and early operations. The spacecraft did not autonomously slew to the burst since normal operation had not yet begun, and autonomous slewing
10496-467: The afterglow in ultraviolet and visible light, and locates the source at an accuracy of one arcsecond. Its aperture is 30 cm (12 in), with an f-number equal to 12.7, and is backed by 2048 x 2048 photon counting CCD pixels . The source location accuracy is better than one arcsecond. XRT (X-Ray Telescope) aims at the source more accurately, and monitors the afterglow in X-rays. It was built jointly by
10624-450: The asteroid 2005 YU55 as the asteroid made a close flyby of the Earth . On 3 June 2013, UVOT unveiled a massive ultraviolet survey of the nearby Magellanic Clouds . In August 2017, UVOT imaged UV emissions from gravitational wave event GW170817 detected by LIGO & Virgo detectors. BAT (Burst Alert Telescope) is a gamma ray telescope, built by NASA's Goddard Space Flight Center, uses
10752-552: The atoms move very fast, causing Doppler shifts. The radiation needed to cool the hydrogen – 121.5 nm – is also difficult. Another hurdle involves improving the uncertainty in QED calculations, specifically the Lamb shift in the 1s-2s transition of the hydrogen atom. A redefinition must include improved optical clock reliability. TAI must be contributed to by optical clocks before the BIPM affirms
10880-402: The caesium atom used to realize the definition. In a laboratory sufficiently small to allow the effects of the non-uniformity of the gravitational field to be neglected when compared to the uncertainties of the realization of the second, the proper second is obtained after application of the special relativistic correction for the velocity of the atom in the laboratory. It is wrong to correct for
11008-473: The clock has the same duration as any other identical division of time. But a sundial , which measures the relative position of the Sun in the sky called apparent time , does not keep uniform time. The time kept by a sundial varies by time of year, meaning that seconds, minutes and every other division of time is a different duration at different times of the year. The time of day measured with mean time versus apparent time may differ by as much as 15 minutes, but
11136-691: The constellation Eridanus . On 10 January 2018, NASA announced that the Swift spacecraft had been renamed the Neil Gehrels Swift Observatory in honor of mission PI Neil Gehrels , who died in early 2017. Swift entered safe mode on March 15, 2024 (after the 2nd of 4 gyroscopes failed) and was not conducting science. A software patch for two-gyroscope mode was developed, uplinked and tested in April 2024, and Swift returned to nominal operations at that point. NASA The National Aeronautics and Space Administration ( NASA / ˈ n æ s ə / )
11264-457: The energy levels in a hydrogen atom with the nonrelativistic approximation E n ≈ − R ∞ c h n 2 {\displaystyle E_{n}\approx -{\frac {R_{\infty }ch}{n^{2}}}} . The only viable way to fix the Rydberg constant involves trapping and cooling hydrogen. This is difficult because it is very light and
11392-552: The event, depending on the brightness of the afterglow. The XRT uses a Wolter Type I X-ray telescope with 12 nested mirrors, focused onto a single MOS charge-coupled device (CCD) similar to those used by the XMM-Newton EPIC MOS cameras. On-board software allows fully automated observations, with the instrument selecting an appropriate observing mode for each object, based on its measured count rate. The telescope has an energy range of 0.2–10 keV. After Swift has slewed towards
11520-420: 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
11648-510: 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
11776-402: 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
11904-499: The first pendulum clock. It had a pendulum length of just under a meter, giving it a swing of one second, and an escapement that ticked every second. It was the first clock that could accurately keep time in seconds. By the 1730s, 80 years later, John Harrison 's maritime chronometers could keep time accurate to within one second in 100 days. In 1832, Gauss proposed using the second as the base unit of time in his millimeter–milligram–second system of units . The British Association for
12032-458: The footnote was added at the 86th (1997) meeting of the CIPM GCPM 1998 7th Edition SI Brochure A future re-definition of the second would be justified if these idealized conditions can be achieved much easier than with the current definition. The definition of the second should be understood as the definition of the unit of proper time: it applies in a small spatial domain that shares the motion of
12160-465: 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,
12288-452: The full sky solid angle is 4π or about 12.6 steradians). It locates the position of each event with an accuracy of 1 to 4 arcminutes within 15 seconds . This crude position is immediately relayed to the ground, and some wide-field, rapid-slew ground-based telescopes can catch the GRB with this information. The BAT uses a coded-aperture mask of 52,000 randomly placed 5 mm (0.20 in) lead tiles, 1 m (3 ft 3 in) above
12416-596: The hour like the modern second (= hour / 60×60 ). Sundials and water clocks were among the earliest timekeeping devices, and units of time were measured in degrees of arc. Conceptual units of time smaller than realisable on sundials were also used. There are references to "second" as part of a lunar month in the writings of natural philosophers of the Middle Ages, which were mathematical subdivisions that could not be measured mechanically. The earliest mechanical clocks, which appeared starting in
12544-451: 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
12672-408: The local gravitational field. The reference to an unperturbed atom is intended to make it clear that the definition of the SI second is based on an isolated caesium atom that is unperturbed by any external field, such as ambient black-body radiation. The second, so defined, is the unit of proper time in the sense of the general theory of relativity. To allow the provision of a coordinated time scale,
12800-504: 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
12928-431: The microwave frequency of a caesium atomic clock, which have each realized a sexagesimal division of the day from ancient astronomical calendars. Civilizations in the classic period and earlier created divisions of the calendar as well as arcs using a sexagesimal system of counting, so at that time the second was a sexagesimal subdivision of the day (ancient second = day / 60×60 ), not of
13056-447: The mission was developed in a joint partnership between Goddard Space Flight Center (GSFC) and an international consortium from the United States, United Kingdom, and Italy. The mission is operated by Pennsylvania State University as part of NASA's Medium Explorer program (MIDEX). The burst detection rate is 100 per year, with a sensitivity ~3 times fainter than the BATSE detector aboard
13184-609: 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
13312-437: The only reliable timepieces, and apparent solar time was the only generally accepted standard. Fractions of a second are usually denoted in decimal notation, for example 2.01 seconds, or two and one hundredth seconds. Multiples of seconds are usually expressed as minutes and seconds, or hours, minutes and seconds of clock time, separated by colons, such as 11:23:24, or 45:23 (the latter notation can give rise to ambiguity, because
13440-608: 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
13568-553: The realization of the second based on the Cs hyperfine transition frequency, but some can be reproduced with superior stability. SI Brochure 9 In 2022, the best realisation of the second is done with caesium primary standard clocks such as IT-CsF2, NIST-F2, NPL-CsF2, PTB-CSF2, SU–CsFO2 or SYRTE-FO2. These clocks work by laser-cooling a cloud of Cs atoms to a microkelvin in a magneto-optic trap. These cold atoms are then launched vertically by laser light. The atoms then undergo Ramsey excitation in
13696-421: The rotation of the Earth with respect to the Sun, and does not contain any leap seconds. UT1 always differs from UTC by less than a second. While they are not yet part of any timekeeping standard, optical lattice clocks with frequencies in the visible light spectrum now exist and are the most accurate timekeepers of all. A strontium clock with frequency 430 THz , in the red range of visible light, during
13824-409: The rotation of the Earth. The international standard for timekeeping is Coordinated Universal Time (UTC). This time scale "ticks" the same atomic seconds as TAI, but inserts or omits leap seconds as necessary to correct for variations in the rate of rotation of the Earth. A time scale in which the seconds are not exactly equal to atomic seconds is UT1, a form of universal time . UT1 is defined by
13952-403: The same notation is used to denote hours and minutes). It rarely makes sense to express longer periods of time like hours or days in seconds, because they are awkwardly large numbers. For the metric unit of second, there are decimal prefixes representing 10 to 10 seconds. Some common units of time in seconds are: a minute is 60 seconds; an hour is 3,600 seconds; a day is 86,400 seconds; a week
14080-740: The satellite is performed, is located in State College, Pennsylvania and operated by the Pennsylvania State University and industry subcontractors. The Swift main ground station is located at the Broglio Space Center near Malindi on the coast of eastern Kenya , and is operated by the Italian Space Agency (ASI). The Swift Science Data Center (SDC) and archive are located at the Goddard Space Flight Center outside Washington, D.C. The United Kingdom Swift Science Data Centre
14208-502: 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
14336-412: The second as 1 ⁄ 86,400 of a mean solar day. Sometime in the late 1940s, quartz crystal oscillator clocks with an operating frequency of ~100 kHz advanced to keep time with accuracy better than 1 part in 10 over an operating period of a day. It became apparent that a consensus of such clocks kept better time than the rotation of the Earth. Metrologists also knew that Earth's orbit around
14464-477: The second based on fundamental properties of nature with caesium clocks . Because the speed of Earth's rotation varies and is slowing ever so slightly , a leap second is added at irregular intervals to civil time to keep clocks in sync with Earth's rotation. "Minute" comes from the Latin pars minuta prima , meaning "first small part" i.e. first division of the hour - dividing into sixty, and "second" comes from
14592-404: The second: milliseconds (thousandths), microseconds (millionths), nanoseconds (billionths), and sometimes smaller units of a second. Multiples of seconds are usually counted in hours and minutes. Though SI prefixes may also be used to form multiples of the second such as kiloseconds (thousands of seconds), such units are rarely used in practice. An everyday experience with small fractions of a second
14720-641: 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
14848-552: 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
14976-424: The signals of different primary clocks in different locations are combined, which have to be corrected for relativistic caesium frequency shifts (see section 2.3.6). The CIPM has adopted various secondary representations of the second, based on a selected number of spectral lines of atoms, ions or molecules. The unperturbed frequencies of these lines can be determined with a relative uncertainty not lower than that of
15104-534: 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
15232-476: 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,
15360-579: 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
15488-433: The various projects, mission architectures and associated timelines relevant to lunar and Mars exploration and science. Second The second (symbol: s ) is a unit of time , historically defined as 1 ⁄ 86400 of a day – this factor derived from the division of the day first into 24 hours , then to 60 minutes and finally to 60 seconds each (24 × 60 × 60 = 86400). The current and formal definition in
15616-454: 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
15744-434: 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
15872-663: 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,
16000-467: 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,
16128-492: 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
16256-678: Was launched on 20 November 2004, at 17:16:01 UTC aboard a Delta II 7320-10C from Cape Canaveral Air Force Station and reached a near-perfect orbit of 585 × 604 km (364 × 375 mi) altitude , with an inclination of 20.60°. On 4 December 2004, an anomaly occurred during instrument activation when the Thermo-Electric Cooler (TEC) Power Supply for the X-Ray Telescope did not turn on as expected. The XRT Team at University of Leicester and Pennsylvania State University were able to determine on 8 December 2004 that
16384-655: Was not yet enabled. Swift had its first GRB trigger during a period when the autonomous slewing was enabled on 17 January 2005, at about 12:55 UTC. It pointed the XRT telescope to the on-board computed coordinates and observed a bright X-ray source in the field of view. On 1 February 2005, the mission team released the first light picture of the UVOT instrument and declared Swift operational. By May 2010, Swift had detected more than 500 GRBs. By October 2013, Swift had detected more than 800 GRBs. On 27 October 2015, Swift detected its 1,000th GRB, an event named GRB 151027B and located in
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