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Everyone knows that NASA studies space; fewer people know that NASA also studies Earth. Since the agency’s creation almost 50 years ago, NASA has been a world leader in space-based studies of our home planet. Our mission has always been to explore, to discover, and to understand the world in which we live from the unique vantage point of space, and to share our newly gained perspectives with the public. That spirit of sharing remains true today as NASA operates 18 of the most advanced Earth-observing satellites ever built, helping scientists make some of the most detailed observations ever made of our world. | Scroll to the bottom of the page for links to Blue Marble Next Generation imagery. Monthly global images shows changes over time on the Earth’s surface, with links to high-resolution images. | ||
 In celebration of the deployment of its Earth Observing System, NASA is pleased to share the newest in its series of stunning Earth images, affectionately named the “Blue Marble.” This new Earth imagery enhances the Blue Marble legacy by providing a detailed look at an entire year in the life of our planet. In sharing these Blue Marble images, NASA hopes the public will join with the agency in its continuing exploration of our world from the unique perspective of space. To learn more about the development of NASA’s imagery of the Earth as a whole, read the History of the Blue Marble. EnhancementsBlue Marble: Next Generation offers greater spatial detail of the surface and spans a longer data collection period than the original. The original Blue Marble was a composite of four months of MODIS observations with a spatial resolution (level of detail) of 1 square kilometer per pixel. Blue Marble: Next Generation offers a year’s worth of monthly composites at a spatial resolution of 500 meters. These monthly images reveal seasonal changes to the land surface: the green-up and dying-back of vegetation in temperate regions such as North America and Europe, dry and wet seasons in the tropics, and advancing and retreating Northern Hemisphere snow cover. From a computer processing standpoint, the major improvement is the development of a new technique for allowing the computer to automatically recognize and remove cloud-contaminated or otherwise bad data—a process that was previously done manually. | The Blue Marble: Next Generation is a series of images that show the color of the Earth’s surface for each month of 2004 at very high resolution (500 meters/pixel) at a global scale. This image shows South America from September 2004. (NASA image courtesy Reto Stöckli and Robert Simmon)
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Blue Marble: Next Generation improves the techniques for turning satellite data into digital images. Among the key improvements is greater detail in areas that usually appear very dark to the satellite (because a large amount of sunlight is being absorbed), for example in dense tropical forests. The ability to create a digital image that provides great detail in darker regions without “washing out” brighter regions, like glaciers, snow-covered areas, and deserts is one of the great challenges of visualizing satellite data. The new version also improves image clarity, and gives highly reflective land surfaces, such as salt flats, a more realistic appearance. | Monthly imagery shows seasonable variability, like the change in Alpine snow-cover from January to July. (NASA images by Reto Stöckli)
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 LimitationsThose who intend to use the Blue Marble: Next Generation in their own publications or projects should be aware of areas that still require improvement. Areas of open water still show some “noise.” In tropical lowlands, cloud cover during the rainy season can be so extensive that obtaining a cloud-free view of every pixel of the area for a given month may not be possible. Deep oceans are not included in the source data; the creator of the Blue Marble uses a uniform blue color for deep ocean regions, and this value has not been completely blended with observations of shallow water in coastal areas. The lack of blending may, in some cases, make the transition between shallow coastal water and deep ocean appear unnatural. Finally, the data do not completely distinguish between snow and cloud cover in areas with short-term snow cover (less than three or four months). This problem may be resolved in the future through the use of a more sophisticated snow mask. Data AccessFull-resolution, subsetted, and reduced-resolution files are available on the Blue Marble Next Generation collection on NASA’s Visible Earth. Monthly global images provides web-resolution copies of each of the monthly maps, along with links to 8km/pixel and 2km/pixel JPEGs, and full-resolution torrents. 500 meter/pixel images are available either via BitTorrent (see monthly global images page for links to torrent files) or from one of our mirror sites:
Sample 500 meter/pixel images.
CreditsBlue Marble: Next Generation was produced by Reto Stöckli, NASA Earth Observatory (NASA Goddard Space Flight Center). See The Blue Marble Next Generation—A true color Earth dataset including seasonal dynamics from MODIS (880 kB PDF) for acknowledgments. Anyone using or republishing Blue Marble: Next Generation please credit “NASA’s Earth Observatory.”
| Improvements to the data-processing algorithms resulted in relatively noise-free images with few artifacts. Dry salt flats, such as the Etosha Pan in Namibia, rendered as water in the original Blue Marble, but are now accurately colored. (NASA images by Reto Stöckli.)
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Sunday, August 2, 2009
Blue Marble Next Generation
Moon
Main
![The familiar near side of Earth’s Moon, photographed on December 7, 1992, by the Galileo spacecraft … [Credits : Photo NASA/JPL/Caltech (NASA photo # PIA00405)]](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_sI3-HQ0Ru8QzyUOa9GarHH1vgZrZryX0m4hD1ejR8EWdudM82ffpme7w7YW9KPQu-e3uGDMcXZOcS15SSy52JzCD1rOTc36k48TyHGB5EhrCnFxrO4dhmtDr-QcjLq2BD-Y8Oh259k=s0-d "The familiar near side of Earth’s Moon, photographed on December 7, 1992, by the Galileo spacecraft … [Credits : Photo NASA/JPL/Caltech (NASA photo # PIA00405)]")
![View of the Moon never seen from Earth, predominantly the heavily cratered far side, photographed … [Credits : F.J. Doyle/National Space Science Data Center]](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_vLkfuRvTV5tlFT2CrX510knyle0sKp9qsdf7bRQjxHE5zXfWrH5df62ynALHjNpKDWYIBMIwx736dVlE0BrU_Xyg6aRvZhMddAdMdlEa62zyoXaKsIxU9MMLNoHghswSWMqPqNyhP6=s0-d "View of the Moon never seen from Earth, predominantly the heavily cratered far side, photographed … [Credits : F.J. Doyle/National Space Science Data Center]")
Centuries of observation and scientific investigation have been centred on the nature and origin of the Moon. Early studies of the Moon’s motion and position allowed the prediction of tides and led to the development of calendars. The Moon was the first new world on which humans set foot; the information brought back from those expeditions, together with that collected by automated spacecraft and remote-sensing observations, has led to a knowledge of the Moon that surpasses that of any other cosmic body except Earth itself. Although many questions remain about its composition, structure, and history, it has become clear that the Moon holds keys to understanding the origin of Earth and the solar system. Moreover, given its nearness to Earth, its rich potential as a source of materials and energy, and its qualifications as a laboratory for planetary science and a place to learn how to live and work in space for extended times, the Moon remains a prime location for humankind’s first settlements beyond Earth orbit.
| Properties of the Moon and the Earth-Moon system | |||
| Moon | Earth | approximate ratio (Moon to Earth) | |
| mean distance from Earth (orbital radius) | 384,400 km | -- | -- |
| period of orbit around Earth (sidereal period of revolution) | 27.3217 Earth days | -- | -- |
| inclination of equator to ecliptic plane (Earth’s orbital plane) | 1.53° | 23.45° | -- |
| inclination of equator to body’s own orbital plane (obliquity to orbit) | 6.68° | 23.45° | -- |
| inclination of orbit to Earth’s Equator | 18.28°-28.58° | -- | -- |
| eccentricity of orbit around Earth | 0.0549 | -- | -- |
| recession rate from Earth | 3.8 cm/year | -- | -- |
| rotation period | synchronous with orbital period | 23.9345 hr | -- |
| equatorial radius | 1,738 km | 6,378 km | 1:4 |
| surface area | 37,900,000 km2 | 510,066,000 km2 (land area, 148,000,000 km2) | 1:14 |
| mass | 0.0735 × 1024 kg | 5.976 × 1024 kg | 1:81 |
| mean density | 3.34 g/cm3 | 5.52 g/cm3 | 1:1.7 |
| mean surface gravity | 162 cm/sec2 | 980 cm/sec2 | 1:6 |
| escape velocity | 2.38 km/sec | 11.2 km/sec | 1:5 |
| mean surface temperature | day, 380 K (224 °F, 107 °C); night, 120 K (-244 °F, -153 °C) | 288 K (59 °F, 15 °C) | -- |
| temperature extremes | 396 K (253 °F, 123 °C) to 40 K (-388 °F, -233 °C) | 331 K (136 °F, 58 °C) to 184 K (-128 °F, -89 °C) | -- |
| surface pressure | 3 × 10-15 bar | 1 bar | 1:300 trillion |
| atmospheric molecular density | day, 104 molecules/cm3; night, 2 × 105 molecules/cm3 | 2.5 × 1019 molecules/cm3 (at standard temperature and pressure) | about 1:100 trillion |
| average heat flow | 29 mW/m2 | 63 mW/m2 | 1:2.2 |
Distinctive features
The Moon is a spherical rocky body, probably with a small metallic core, revolving around Earth in a slightly eccentric orbit at a mean distance of about 384,000 km (238,600 miles). Its equatorial radius is 1,738 km (1,080 miles), and its shape is slightly flattened in a such a way that it bulges a little in the direction of Earth. Its mass distribution is not uniform—the centre of mass is displaced about 2 km (1.2 miles) toward Earth relative to the centre of the lunar sphere, and it also has surface mass concentrations, called mascons for short, that cause the Moon’s gravitational field to increase over local areas. The Moon has no global magnetic field like that of Earth, but some of its surface rocks have remanent magnetism, which indicates one or more periods of magnetic activity in the past. The Moon presently has very slight seismic activity and little heat flow from the interior, indications that most internal activity ceased long ago.
Scientists now believe that more than four billion years ago the Moon was subject to violent heating—probably from its formation—which resulted in its differentiation, or chemical separation, into a less dense crust and a more dense underlying mantle. This was followed hundreds of millions of years later by a second episode of heating—this time from internal radioactivity—which resulted in volcanic outpourings of lava. The Moon’s mean density is 3.34 grams per cubic cm, close to that of Earth’s mantle. Because of the Moon’s small size and mass, its surface gravity is only about one-sixth of the planet’s; it retains so little atmosphere that the molecules of any gases present on the surface move without collision. In the absence of an atmospheric shield to protect the surface from bombardment, countless bodies ranging in size from asteroids to tiny particles have struck and cratered the Moon. This has formed a debris layer, or regolith, consisting of rock fragments of all sizes down to the finest dust. In the ancient past the largest impacts made great basins, some of which were later partly filled by the enormous lava floods. These great dark plains, called maria (singular mare [Latin: “sea”]), are clearly visible to the naked eye from Earth. The dark maria and the lighter highlands, whose unchanging patterns many people recognize as the “man in the moon,” constitute the two main kinds of lunar territory. The mascons are regions where particularly dense lavas rose up from the mantle and flooded into basins. Lunar mountains, located mostly along the rims of ancient basins, are tall but not steep or sharp-peaked, because all lunar landforms have been eroded by the unending rain of impacts. For additional orbital and physical data, see the table.
Satellite sensor maps global atmospheric ammonia emissions
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Using radiation measurements obtained by the MetOp satellite, scientists have produced the first complete map of global ammonia emissions – a pollutant of key environmental concern. The map, based on observations throughout 2008, shows inaccuracies in current ammonia inventories and identifies new hotspots.
Ammonia emissions contribute to a host of environmental problems, including soil acidification, reductions in biodiversity and the formation of atmospheric particulate matter, which has been linked to human health problems such as asthma. Yet despite its importance, many uncertainties remain about its global distribution.
Mapping ammonia is difficult, in part, because once emitted it only remains in the atmosphere for a short period. While in the atmosphere, however, it reacts with acid pollutants, such as nitric acid and sulfuric acid, to produce ammonium aerosol, which is believed to influence climate.
Lieven Clarisse and Pierre Coheur from the University of Bruxelles, Cathy Clerbaux from the French Scientific Research Centre (CNRS) and colleagues developed a methodology to be used with MetOp’s Infrared Atmospheric Sounding Interferometer (IASI) sensor that could isolate the signature of ammonia.
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Ammonia concentrations over Italy |
Most of the hotspots appeared over agricultural regions in Europe, North America and Asia, as expected. However, the measurements taken from space over agricultural valleys, such as Italy’s Po Valley, Uzbekistan’s Fergana Valley and the US’s Snake River Valley in Idaho, were higher than the current inventories. The scientists also identified some sources in Central Asia that had not been included in current inventories.
Areas with biomass burning also had high ammonia emissions. For instance, increased ammonia concentrations were found over regions, such as Africa, Asia and South America, that had experienced a large number of fires.
Atmospheric ammonia is being increasingly recognised as a key pollutant that contributes to several environmental problems. In 1999 the UN Economic Commission for Europe (UNECE) set stringent reduction targets for ammonia to be obtained by 2010. However, reducing ammonia emissions has proved uncertain.
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MetOp in orbit |
MetOp, launched in 2006, is the first of three meteorological satellites developed under a joint programme being carried out by ESA and the European Meteorological Satellite Organisation (EUMESAT). The IASI sensor was developed by CNES (the French space agency) in cooperation with EUMETSAT.
These new results, published online in Nature Geoscience in June, were obtained as part of a scientific project in response to a Research Announcement of Opportunity for MetOp, organised jointly by ESA and EUMETSAT. The support to scientific research by ongoing ESA programmes is important for developing and testing innovative methods with data from operational missions.satellite
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Any small body that orbits a larger one. Natural satellites that orbit planets are called moons. The first artificial satellite, Sputnik 1, was launched into orbit around the Earth by the USSR in 1957. Artificial satellites can transmit data from one place on Earth to another, or from space to Earth. Satellite applications include science, communications, weather forecasting, and military use.
Space probes have been sent to natural satellites including the Earth's Moon, Mars's Deimos, and the moons of the giant planets Jupiter, Saturn, Uranus and Neptune.
At any time, there are several thousand artificial satellites orbiting the Earth, including active satellites, satellites that have ended their working lives, and discarded sections of rockets. The brightest artificial satellites can be seen by the naked eye. Artificial satellites eventually re-enter the Earth's atmosphere. Usually they burn up by friction, but sometimes debris falls to the Earth's surface, as with Skylab and Salyut 7.
Hundreds of millions of pieces of space junk, ranging from particles a millimetre across up to disabled satellites, are careering around the Earth. The US Space Command catalogues the larger items to make sure they are not mistaken for enemy missiles; currently about 10,000 items are listed.
Launch and mission
The control system of the Sputnik Rocket was tuned to provide an orbit with the following parameters: perigee height - 223 km (139 mi), apogee height - 1,450 km (900 mi), orbital period - 101.5 min.[39] A rocket trajectory with these parameters was calculated earlier by Georgi Grechko,[40] after completing the calculations over several nights on the USSR Academy of Sciences's mainframe computer.[20]
The Sputnik Rocket was launched at 19:28:34 UTC, on 4 October 1957, from Site No.1 at NIIP-5.[41] Processing of the information, obtained from the "Tral" system showed[20] that the side boosters separated 116.38 seconds into the flight and the second stage engine was shut-down 294.6 seconds into the flight.[39] At this moment the second stage with PS-1 attached had a height of 223 km (139 mi) above Earth's surface, a velocity of 7,780 m/s (25,500 ft/s) and velocity vector inclination to the local horizon was 0 degrees 24 minutes. This motion resulted in an orbit with initial parameters: perigee height - 223 km, apogee height - 950 km (590 mi), initial orbital period - 96.2 minutes.[39]
After 314.5 seconds PS-1 separated from the second stage[39] and at the same moment at the small "Finnish house" of IP-1 station Junior Engineer-Lieutenant V.G.Borisov heard the "Beep-beep-beep" signals from the radio receiver R-250. Reception lasted for two minutes, while PS-1 was above the horizon. There were many people in the house, both military and civil, and they were probably the first to celebrate the event.[20][42] After 325.44 seconds a corner reflector on the second stage was opened, that also allowed measurement of its orbit parameters - like the working "Tral" system did.[29]
The designers, engineers and technicians who developed the rocket and satellite watched the launch from the range.[43] After the launch they ran to the mobile radio station to listen to signals from the satellite.[43] They waited about 90 minutes to ensure that the satellite had made one orbit and was transmitting, before Korolyov called Khrushchev.[44] The downlink telemetry included data on temperatures inside and on the surface of the sphere.
On the first orbit the Telegraph Agency of the Soviet Union (TASS) transmitted: "As result of great, intense work of scientific institutes and design bureaus the first artificial Earth satellite has been built".[45] The Sputnik 1 rocket booster (second stage of the rocket) also reached Earth orbit and was visible from the ground at night as a first magnitude object following the satellite. Korolyov had intentionally requested reflective panels placed on the booster in order to make it so visible.[44] The satellite itself, a small but highly polished sphere, was barely visible at sixth magnitude, and thus more difficult to follow optically. Ahead of Sputnik 1 flew the third object - the payload fairing, 80 cm (31 in)-long cone, i.e. a little bit bigger than the satellite.
Observational complex
The measurement complex at the proving ground for monitoring launch vehicle parameters from its start onward was completed prior to the first R-7 rocket test launches in December 1956. It consisted of six static stations: IP-1 through IP-6, with IP-1 situated at a distance of 1 km (0.62 mi) from the launch pad.[20] The main monitoring devices of these stations were telemetry and trajectory measurement stations, "Tral," developed by OKB MEI. They received and monitored data from the "Tral" system transponders mounted on the R-7 rocket;[23] an on-board system that provided precise telemetric data about Sputnik's launch vehicle. The data was useful even after the satellite's separation from the second stage of the rocket; Sputnik's location was calculated from the data on the second stage's location (which followed Sputnik at a known distance) using nomograms developed by P.E. Elyasberg.[24]
An additional observational complex, established to track the satellite after its separation from the rocket, was completed by a group led by Colonel Yu.A.Mozzhorin in accordance with the General Staff directive of 8 May 1957. It was called the Command-Measurement Complex and consisted of the coordination center in NII-4 by the Ministry of Defence of the USSR (at Bolshevo) and seven ground tracking stations, situated along the line of the satellite's ground track. They were: NIP-1 (at Tyuratam station, Kazakh SSR, situated not far from IP-1), NIP-2 (at Makat station, Guryev Oblast), NIP-3 (at Sary-Shagan station, Dzhezkazgan Oblast), NIP-4 (at Yeniseysk), NIP-5 (at village Iskup, Krasnoyarsk Krai), NIP-6 (at Yelizovo) and NIP-7 (at Klyuchi).[20][25] The complex had a communication channel with the launch pad. Stations were equipped with radar, optical instruments, and communication means. PS-1 was not designed to be controlled, it could only be observed. Data from stations were transmitted by telegraphs into NII-4 where ballistics specialists calculated orbital parameters. The complex became an early prototype of the Soviet Mission Control Center[26]
Launch vehicle preparation and launch site selection
The first launch of an R-7 rocket (8K71 No.5L) occurred on 15 May 1957. The flight was controlled until the 98th second, but a fire in a strap-on rocket led to an unintended crash 400 km from the site.[17] Three attempts to launch the second rocket (8K71 No.6) were made on 10-11 June, which failed due to a mistake made during the rocket's assembly.[18] The unsuccessful launch of the third R-7 rocket (8K71 No.7) took place on 12 July.[17] During the flight the rocket began to rotate about its longitudinal axis and its engines were automatically turned off. The packet of stages was destroyed 32.9 seconds into the flight. The stages fell 7 km (4.3 mi) from the site and exploded.[19]
The launch of the fourth rocket (8K71 No.8), on 21 August at 15:25 Moscow Time,[17] was successful. Its head part separated, reached the defined region, entered the atmosphere, and was destroyed at a height of 10 km (6.2 mi) due to thermodynamic overload after traveling 6,000 km. On 27 August TASS the USSR issued a statement on the launch of a long-distance multistage ICBM. The launch of the fifth R-7 rocket (8K71 No.9), on 7 September[17] was also successful, but the head part was also destroyed in the atmosphere,[19] and hence needed a long redesign to completely fit its military purpose. The rocket, however, was already suitable for scientific satellite launches and this "time-out" of the rocket's military exploitation was used to launch the PS-1 and PS-2 satellites.[20]
On 22 September a modified R-7 rocket, named Sputnik Rocket (Russian: ракета-носитель Спутник) and indexed as 8K71PS, with the satellite PS-1, arrived at the proving ground and preparations for the launch began.[21] As the R-7 was designed to carry the much heavier Object D, its adaptation to PS-1 reduced its initial mass from 280 to 272.83 short tons (250 to 250 metric tons) and its mass at launch was 267 short tons (242 metric tons); its length with PS-1 was 29.167 metres (95 ft 8.3 in) and the thrust was 3.90 MN (880,000 lbf)Satellite construction project
The history of the Sputnik 1 project dates back to 27 May 1954, when Sergei Korolev addressed Dmitry Ustinov, then Minister of Defense Industries, proposing the development of an Earth-orbiting artificial satellite. Korolev also forwarded Ustinov a report by Mikhail Tikhonravov with an overview of similar projects abroad.[5] Tikhonravov emphasized that an artificial satellite is an inevitable stage in the development of rocket equipment, after which interplanetary communication would become possible.[6] On 29 July 1955 the U.S. President Dwight Eisenhower announced, through his press secretary, that the United States would launch an artificial satellite during the International Geophysical Year (IGY).[7] A week later, on 8 August the Presidium of the Central Committee of the CPSU approved the idea of creating an artificial satellite.[8] On 30 August Vasily Ryabikov – the head of the State Commission on R-7 rocket test launches – held a meeting where Korolev presented calculation data for a spaceflight trajectory to the Moon. They decided to develop a three-stage version of the R-7 rocket for satellite launches.[9]
On 30 January 1956 the Council of Ministers of the USSR approved practical work on an artificial Earth-orbiting satellite. This satellite, named "Object D", was planned to be completed in 1957-58; it would have a mass of 1,000 to 1,400 kg (2,200 to 3,090 lb) and would carry 200 to 300 kg (440 to 660 lb) of scientific instruments.[10] The first test launch of "Object D" was scheduled for 1957.[6] According to that decision, work on the satellite was to be divided between institutions as follows:[11]
- USSR Academy of Sciences was responsible for the general scientific leadership and research instruments supply
- Ministry of Defense Industry and its main executor OKB-1 were assigned the task of creating the satellite as a special carrier for scientific research instruments
- Ministry of Radiotechnical Industry would develop the control system, radio/technical instruments and the telemetry system
- Ministry of Ship Building Industry would develop gyroscope devices
- Ministry of Machine Building would develop ground launching, refueling and transportation means
- Ministry of Defense was responsible for conducting launches
By July 1956 the draft was completed and the scientific tasks to be carried out by a satellite were defined. It included measuring the density of the atmosphere, its ion composition, corpuscular solar radiation, magnetic fields, cosmic rays, etc. Data, valuable in creating future satellites, were also to be collected. A ground observational complex was to be developed, that would collect information transmitted by the satellite, observe the satellite's orbit, and transmit commands to the satellite. Such a complex should include up to 15 measurement stations. Due to the limited time frame, they should have means designed for rocket R-7 observations. Observations were planned for only 7 to 10 days and orbit calculations were expected to be not quite accurate.[12]
Unfortunately, the complexity of the ambitious design and problems in following exact specifications meant that some parts of 'Object D', when delivered for assembly, simply did not fit with the others, causing costly delays. By the end of 1956 it became clear that plans for 'Object D' were not to be fulfilled in time due to difficulties creating scientific instruments and the low specific impulse produced by the completed R-7 engines (304 sec instead of the planned 309 to 310 sec). Consequently the government re-scheduled the launch for April 1958.[6] Object D would later fly as Sputnik 3.
Fearing the U.S. would launch a satellite before the USSR, OKB-1 suggested the creation and launch of a satellite in April-May 1957, before the IGY began in July 1957. The new satellite would be simple, light (100 kg or 220 lb), and easy to construct, forgoing the complex, heavy scientific equipment in favour of a simple radio transmitter. On 15 February 1957 the Council of Ministers of the USSR approved this, providing for launching the simplest version satellite, designated 'Object PS'.[13] This version also facilitated the satellite to be visually tracked by Earth-based observers while in orbit, and transmit tracking signals to ground-based receiving stations.[13] Launch of two satellites PS-1 and PS-2 with two R-7 rockets (8K71) was allowed, but only after one or two successful R-7 test launches.Sputnik 1
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| Major contractors | OKB-1, Soviet Ministry of Radiotechnical Industry |
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| Mission type | Atmospheric studies |
| Satellite of | Earth |
| Orbits | 1,440 |
| Launch date | 19:28:34, October 4, 1957 (UTC) (22:28:34 MSK) |
| Launch vehicle | Sputnik Rocket |
| Mission duration | 3 months |
| Orbital decay | 4 January 1958 |
| COSPAR ID | 1957-001B |
| Home page | NASA NSSDC Master Catalog |
| Mass | 83.6 kg (184.3 lb) |
| Orbital elements | |
| Semimajor axis | 6,955.2 km (4,321.8 mi) |
| Eccentricity | 0.05201 |
| Inclination | 65.1° |
| Orbital period | 96.2 minutes |
| Apoapsis | 7,310 km (4,540 mi) from centre, 939 km (583 mi) from surface |
| Periapsis | 6,586 km (4,092 mi) from centre, 215 km (134 mi) from surface |
Sputnik 1 (Russian: "Спутник-1" Russian pronunciation: [ˈsputnʲɪk], "Satellite-1", ПС-1 (PS-1, i.e. "Простейший Спутник-1", or Elementary Satellite-1)) was the first Earth-orbiting artificial satellite. It was launched into a low altitude elliptical orbit by the Soviet Union on 4 October 1957, and was the first in a series of satellites collectively known as the Sputnik program. The unanticipated announcement of Sputnik 1's success precipitated the Sputnik crisis in the United States and ignited the Space Race within the Cold War.
Apart from its value as a technological first, Sputnik also helped to identify the upper atmospheric layer's density, through measuring the satellite's orbital changes. It also provided data on radio-signal distribution in the ionosphere. Pressurized nitrogen, in the satellite's body, provided the first opportunity for meteoroid detection. If a meteoroid penetrated the satellite's outer hull, it would be detected by the temperature data sent back to Earth.
Sputnik-1 was launched during the International Geophysical Year from Site No.1, at the 5th Tyuratam range, in Kazakh SSR (now at the Baikonur Cosmodrome). The satellite traveled at 29,000 kilometres (18,000 mi) per hour, taking 96.2 minutes to complete an orbit, and emitted radio signals at 20.005 and 40.002 MHz[1] which were monitored by amateur radio operators throughout the world.[2] The signals continued for 22 days until the transmitter batteries ran out on 26 October 1957.[3] Sputnik 1 burned up on 4 January 1958 as it fell from orbit upon reentering Earth's atmosphere, after traveling about 60 million km (37 million miles) and spending 3 months in orbit.[4]
