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Mariner Program

Mariner program

The Mariner program was a series of unmanned interplanetary probes designed to investigate Mars, Venus and Mercury. The program included a number of firsts, including the first planetary flyby, the first planetary orbiter, and the first gravity assist. Of the ten vehicles in the Mariner series, seven were successful and three were lost. The planned Mariner 11 and 12 vehicles evolved into Voyager 1 and Voyager 2 of the Voyager program.

Mariners 1 and 2

Mariner 1, intended to fly by Venus, failed shortly after launch. Mariner 2 was built as a backup to Mariner 1. It was launched on August 27, 1962, sending it on a 3½-month flight to Venus. The mission was a success and Mariner 2 became the first spacecraft to fly by another planet.
- Mission: Venus flyby
- Mass: 203 kg (446 lb)
- Sensors: microwave and infrared radiometers, cosmic dust, solar plasma and high-energy radiation, magnetic fields

Mariners 3 and 4

Mariner 3 and Mariner 4 were Mars flyby missions. Mariner 3 was lost when the launch vehicle's nose fairing failed to jettison. Its sister ship, Mariner 4, launched on November 28, 1964, the first successful flyby of the planet Mars and gave the first glimpse of Mars at close range.
- Mission: Mars flyby
- Mass: 261 kg (575 lb)
- Sensors: camera with digital tape recorder (about 20 pictures), cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics

Mariner 5

The Mariner 5 spacecraft was launched to Venus on June 14, 1967 and arrived in the vicinity of the planet in October 1967. It carried a complement of experiments to probe Venus' atmosphere with radio waves, scan its brightness in ultraviolet light, and sample the solar particles and magnetic field fluctuations above the planet.
- Mission: Venus flyby
- Mass: 245 kg (540 lb)
- Sensors: ultraviolet photometer, cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics

Mariners 6 and 7

Mariners 6 and 7 were identical teammates in a two-spacecraft mission to Mars. Mariner 6 was launched on February 24, 1969, followed by Mariner 7 on March 27, 1969. They flew over the equator and southern hemisphere of the planet Mars.
- Mission: Mars flybys
- Mass 413 kg (908 lb)
- Sensors: wide- and narrow-angle cameras with digital tape recorder, infrared spectrometer and radiometer, ultraviolet spectrometer, radio occultation and celestial mechanics.

Mariners 8 and 9

Mariner 8 and Mariner 9 were identical sister craft designed to map the Martian surface simultaneously, but Mariner 8 was lost in a launch vehicle failure. Its identical sister craft, Mariner 9, was launched in May 1971 and became the first artificial satellite of Mars. It entered Martian orbit in November 1971 and began photographing the surface and analyzing the atmosphere with its infrared and ultraviolet instruments.
- Mission: orbit Mars
- Mass 998 kg (2,200 lb)
- Sensors: wide- and narrow-angle cameras with digital tape recorder, infrared spectrometer and radiometer, ultraviolet spectrometer, radio occultation and celestial mechanics

Mariner 10

The Mariner 10 spacecraft launched on November 3, 1973 and was the first to use a gravity assist trajectory, accelerating as it entered the gravitational influence of Venus, then being flung by the planet's gravity onto a slightly different course to reach Mercury. It was also the first spacecraft to encounter two planets at close range, and the first (and so far only) spacecraft to photograph Mercury in closeup.
- Mission: Venus and Mercury flybys
- Mass: 433 kg (952 lb)
- Sensors: twin narrow-angle cameras with digital tape recorder, ultraviolet spectrometer, infrared radiometer, solar plasma, charged particles, magnetic fields, radio occultation and celestial mechanics Category:Mars missions Category:Mercury spacecraft Category:Venus spacecraft Category:NASA programs ja:マリナー計画

Mars

Mars, the fourth planet from the Sun in our solar system, is named after the Roman god of war Mars (Ares in Greek mythology), because of its apparent red color. This feature also earned it the nickname "The Red Planet". Mars has two moons, Phobos and Deimos, which are small and oddly-shaped, possibly being captured asteroids. The prefix areo- refers to Mars in the same way geo- refers to Earth—for example, areology versus geology. (However, areology is also used to refer to the study of Mars as a whole rather than just the geological processes of the planet.) The astronomical symbol for Mars is a circle with an arrow pointing northeast (Unicode: ♂). This symbol is a stylized representation of the shield and spear of the god Mars, and in biology it is used as a sign for the male sex. The Chinese, Korean, Japanese, and Vietnamese cultures refer to the planet as the fire star, 火星, a naming based on the ancient Chinese mythological cycle of Five Elements.

Mythology

Mars has been obvious to skygazers since prehistoric times. It was known by the Egyptians as "Her Deschel" or "the Red One." Among the Babylonians Mars was known as "Nergal" or "the Star of Death." The Romans were the ones to give Mars its modern name, after their god of war.

Physical characteristics

The red, fiery appearance of Mars is caused by iron oxide (rust) on its surface. Mars has only a quarter the surface area of the Earth and only one-tenth the mass, though its surface area is approximately equal to that of the Earth's dry land because Mars lacks oceans. The solar day (or sol) on Mars is very close to Earth's day: 24 hours, 39 minutes, and 35.244 seconds.

Atmosphere

Mars' atmosphere is thin: the air pressure on the surface is only 750 pascals, about 0.75% of the average on Earth. However, the scale height of the atmosphere is about 11 km, somewhat higher than Earth's 6 km. The atmosphere on Mars is 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water. The atmosphere quite dusty, giving the Martian sky a tawny color when seen from the surface; data from the Mars Exploration Rovers indicates the suspended dust particles are roughly 1.5 microns across. In 2003, methane was apparently discovered in the atmosphere by Earth-based telescopes and possibly confirmed in March 2004 by the Mars Express Orbiter; present measurements state an average methane concentration of about 11±4 ppb by volume (see reference). The thin atmosphere cannot hold heat and is the cause of the lower temperatures on Mars. The maximum temperature is roughly 20℃ (68℉). The presence of methane on Mars would be very intriguing, since as an unstable gas it indicates that there must be (or have been within the last few hundred years) a source of the gas on the planet. Volcanic activity, comet impacts, and the existence of life in the form of microorganisms such as methanogens are among possible but as yet unproven sources. The methane appears to occur in patches, which suggests that it is being rapidly broken down before it has time to become uniformly distributed in the atmosphere, and so it is presumably also continually being released to the atmosphere. Plans are now being made to look for other companion gases that may suggest which sources are most likely; in the Earth's oceans biological methane production tends to be accompanied by ethane, while volcanic methane is accompanied by sulfur dioxide. Other aspects of the Martian atmosphere vary significantly. In the winter months when the poles are in continual darkness, the surface gets so cold that as much as 25% of the entire atmosphere condenses out into meters thick slabs of CO₂ ice (dry ice). When the poles are again exposed to sunlight the CO₂ ice sublimates, creating enormous winds that sweep off the poles as fast as 250 mph. These seasonal actions transport large amounts of dust and water vapor giving rise to Earth-like frost and large cirrus clouds. These clouds of water-ice were photographed by the Opportunity rover in 2004.[http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20041213a/merb_sol290_clouds-B313R1_br.jpg] Recently, evidence has been discovered suggesting that Mars may be warming in the short term[http://news.bbc.co.uk/2/hi/science/nature/4266474.stm]; however, it is now cooler than it was in the 1970s.[http://catdynamics.blogspot.com/2005/09/climate-science-mars-and-politics.html]

Geology

Opportunity The surface of Mars is thought to be primarily composed of basalt, based upon the Martian meteorite collection and orbital observations. There is some evidence that some portion of the Martian surface might be more silica-rich than typical basalt, perhaps similar to andesitic rocks on Earth, though these observations may also be explained by silica glass. Much of the surface is deeply covered by dust as fine as talcum powder. Observations of the magnetic fields on Mars by the Mars Global Surveyor spacecraft have revealed that parts of the planet's crust has been magnetized. This magnetization has been compared to alternating bands found on the ocean floors of Earth. One interesting theory, published in 1999 and reexamined in October 2005 in a publication by the same group, is that these bands could be evidence of the past operation of plate tectonics on Mars. However, this has yet to be proven [http://photojournal.jpl.nasa.gov/catalog/PIA02008] or widely accepted and remains an area of active research. plate tectonics Amongst the findings from the Opportunity rover is the presence of hematite on Mars in the form of small spheres on the Meridiani Planum. The spheres are only a few millimeters in diameter and are believed to have formed as rock deposits under watery conditions billions of years ago. Other minerals have also been found containing forms of sulfur, iron or bromine such as jarosite. This and other evidence led a group of 50 scientists to conclude in the December 9, 2004 edition of the journal Science that "Liquid water was once intermittently present at the Martian surface at Meridiani, and at times it saturated the subsurface. Because liquid water is a key prerequisite for life, we infer conditions at Meridiani may have been habitable for some period of time in Martian history". On the opposite side of the planet the mineral goethite, which (unlike hematite) forms only in the presence of water, along with other evidence of water, has also been found by the Spirit rover in the "Columbia Hills". In 1996, researchers studying a meteorite (ALH84001) believed to have originated from Mars reported features which they attributed to microfossils left by life on Mars. As of 2005, this interpretation remains controversial with no consensus having emerged.
Topography
As of 2005 As of 2005 The dichotomy of Martian topography is striking: northern plains flattened by lava flows contrast with the southern highlands, pitted and cratered by ancient impacts. The surface of Mars as seen from Earth is consequently divided into two kinds of areas, with differing albedo. The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian 'continents' and given names like Arabia Terra (land of Arabia) or Amazonis Planitia (Amazonian plain). The dark features were thought to be seas, hence their names Mare Erythraeum, Mare Sirenum and Aurorae Sinus. The largest dark feature seen from Earth is Syrtis Major. Syrtis Major Mars has polar ice caps that contain frozen water and carbon dioxide that change with the Martian seasons — the carbon dioxide ice sublimates in summer it uncovers an underlying surface of layered water ice and dust. The polar carbon dioxide "hood" then forms again in winter. The supposedly-extinct shield volcano, Olympus Mons (Mount Olympus), is at 26 km the highest mountain in the solar system. It is in a vast upland region called Tharsis, which contains several large volcanos. See list of mountains on Mars. Mars also has the solar system's largest canyon system, Valles Marineris or the Mariner Valley, which is 4000 km long and 7 km deep. Mars is also scarred by a number of impact craters. The largest of these is the Hellas impact basin, covered with light red sand. See list of craters on Mars. The difference between Mars' highest and lowest points is nearly 31 km (from the top of Olympus Mons at an altitude of 26 km to the bottom of the Hellas impact basin at an altitude of 4 km below the datum). In comparison, the difference between Earth's highest and lowest points (Mount Everest and the Mariana Trench) is only 19.7 km. Combined with the planets' different radii, this means Mars is nearly three times "rougher" than Earth. The International Astronomical Union's Working Group for Planetary System Nomenclature is responsible for naming Martian surface features. Other notes: Zero elevation: Since Mars has no oceans and hence no 'sea level', a zero-elevation surface or mean gravity surface must be selected. The datum for Mars is defined by the fourth-degree and fourth-order spherical harmonic gravity field, with the zero altitude defined by the 610.5 Pa (6.105 mbar) atmospheric pressure surface (approximately 0.6% of Earth's) at a temperature of 273.16 K. This pressure and temperature correspond to the triple point of water. Zero meridian: Mars' equator is defined by its rotation, but the location of its Prime Meridian was specified, as was Earth's, by choice of an arbitrary point which was accepted by later observers. The German astronomers Wilhelm Beer and Johann Heinrich Mädler selected a small circular feature as a reference point when they produced the first systematic chart of Mars features in 1830-32. In 1877, their choice was adopted as the prime meridian by the Italian astronomer Giovanni Schiaparelli when he began work on his notable maps of Mars. After the spacecraft Mariner 9 provided extensive imagery of Mars in 1972, a small crater (later called Airy-0), located in the Sinus Meridiani ('Middle Bay' or 'Meridian Bay') along the line of Beer and Mädler, was chosen by Merton Davies of the RAND Corporation to provide a more precise definition of 0.0° longitude when he established a planetographic control point network. RAND Corporation
Canals
Mars has an important place in human imagination due to the belief by some that life existed on Mars. These beliefs are due mainly to observations by many in the 19th century popularized by Percival Lowell and Giovanni Schiaparelli. Schiaparelli called these observed features canali, meaning channels in Italian. This was popularly mistranslated as 'canals', and the myth of the Martian canals began. They were apparently artificial linear features on the surface that were asserted to be canals, and due to seasonal changes in the brightness of some areas that were thought to be caused by vegetation growth. This gave rise to many stories concerning Martians. The linear features are now known to be mostly non-existent or, in some cases, dry ancient watercourses. The color changes have been ascribed to dust storms.
Ice lakes
many stories On 29 July 2005, the BBC reported that a visible ice lake had been discovered in a crater in the north polar region of Mars[http://news.bbc.co.uk/1/hi/sci/tech/4727847.stm]. Images of the crater, taken by the High Resolution Stereo Camera on board the European Space Agency's Mars Express spacecraft, clearly show a broad sheet of ice in the bottom of an unnamed crater located on Vastitas Borealis, a broad plain that covers much of Mars' far northern latitudes, at approximately 70.5° North and 103° East. The crater is 35 km (23 mi) wide and about 2 km (1.2 mi) deep. The BBC report however, appears to have either intentionally sensationalized or unintentionally mis-interpreted the original HRSC/Mars Express feature[http://www.esa.int/SPECIALS/Mars_Express/SEMGKA808BE_0.html], which makes no claim or insinuation that this is a "lake". Like many thousands of other places on Mars, this ice sheet is a thin layer of frost that has condensed onto dark, cold sand dunes (about 200 m high) making their way across the bottom of the crater. The only thing remarkable about this feature is that it is far enough north to maintain at least some frost throughout the year.
The moons of Mars
Mars has two tiny natural moons, Phobos and Deimos, which orbit very close to the planet and are thought to be captured asteroids.
The exploration of Mars
asteroid Dozens of spacecraft, including orbiters, landers, and rovers, have been sent to Mars by the Soviet Union, the United States, Europe, and Japan to study the planet's surface, climate, and geography. Roughly two-thirds of all spacecraft destined for Mars have failed in one manner or another before completing or even beginning their missions. Part of this high failure rate can be ascribed to technical problems, but enough have either failed or lost communications for no apparent reason that some researchers half-jokingly speak of an Earth-Mars "Bermuda Triangle" or of a Great Galactic Ghoul which subsists on a diet of Mars probes, or of a Mars Curse. Among the most successful missions are the Mars probe program, the Mariner and Viking programs, Mars Global Surveyor, Mars Pathfinder, and Mars Odyssey. Global Surveyor has taken pictures of gullies and debris flow features that suggest there may be current sources of liquid water, similar to an aquifer, at or near the surface of the planet. Another possible origin proposed for these gully features is transient melting of surface water snow, frost, or ice. Mars Odyssey determined that there are significant deposits of water ice in the upper meter or so of Mars' regolith within 30° of the north and south pole. In 2003, the ESA launched the Mars Express craft consisting of the Mars Express Orbiter and the lander Beagle 2. Attempts to contact the Beagle 2 failed and it was declared lost in early February 2004. Beagle 2 Also in 2003, NASA launched the twin Mars Exploration Rovers named Spirit (MER-A) and Opportunity (MER-B). Both missions landed successfully in January 2004 and have met or exceeded all their targets; while a 90-day nominal mission was planned, as of February 2005, their missions have been extended twice and they continue to return science, although some mechanical faults have occurred. Among the most significant science return has been evidence of liquid water some time in the past at both landing sites. In addition, dust devils imaged from ground-level have been detected moving across the surface of Mars by Spirit (MER-A). (See picture below). Dust devils were first imaged on Mars from the surface by Mars Pathfinder. Mars Pathfinder
Nomenclature

Early nomenclature
Although better remembered for mapping the Moon starting in 1830, Johann Heinrich Mädler and Wilhelm Beer were the first "areographers". They started off by establishing once and for all that most of the surface features were permanent, and pinned down Mars' rotation period. In 1840, Mädler combined ten years of observations and drew the first map of Mars ever made. Rather than giving names to the various markings they mapped, Beer and Mädler simply designated them with letters; Meridian Bay (Sinus Meridiani) was thus feature "a". Over the next twenty years or so, as instruments improved and the number of observers also increased, various Martian features acquired a hodge-podge of names. To give a couple of examples, Solis Lacus was known as the "Oculus" (the Eye), and Syrtis Major was usually known as the "Hourglass Sea" or the "Scorpion". In 1858, it was also dubbed the "Atlantic Canale" by the Jesuit astronomer Angelo Secchi. Secchi commented that it "seems to play the role of the Atlantic which, on Earth, separates the Old Continent from the New" —this was the first time the fateful canale, which in Italian can mean either "channel" or "canal", had been applied to Mars. In 1867, Richard Anthony Proctor drew up a map of Mars based, somewhat crudely, on the Rev. William Rutter Dawes' earlier drawings of 1865, then the best ones available. Proctor explained his system of nomenclature by saying, "I have applied to the different features the names of those observers who have studied the physical peculiarities presented by Mars." Here are some of his names, paired with those later proposed by Schiaparelli:
- Kaiser Sea = Syrtis Major1865
- Lockyer Land = Hellas
- Main Sea = Lacus Moeris
- Herschel II Strait = Sinus Sabaeus
- Dawes Continent = Aeria and Arabia
- De La Rue Ocean = Mare Erythraeum
- Lockyer Sea = Solis Lacus
- Dawes Sea = Tithonius Lacus
- Madler Continent = Chryse, Ophir, Tharsis
- Maraldi Sea = Mares Sirenum and Cimmerium
- Secchi Continent = Memnonia
- Hooke Sea = Mare Tyrrhenum
- Cassini Land = Ausonia
- Herschel I Continent = Zephyria, Aeolis, Aethiopis
- Hind Land = Libya Proctor's nomenclature has often been criticized, mainly because so many of his names honored English astronomers, but also because he used many names more than once. In particular, Dawes appeared no fewer than six times (Dawes Ocean, Dawes Continent, Dawes Sea, Dawes Strait, Dawes Isle, and Dawes Forked Bay). Even so, Proctor's names are not without charm, and for all their shortcomings they were a foundation on which later astronomers would improve.
Modern nomenclature
Today, features on Mars derive from a number of sources. Large albedo features retain many of the older names, but are often updated to reflect new knowledge of the nature of the features. For example 'Nix Olympica' (the snows of Olympus) has become 'Olympus Mons' (Mount Olympus). Large Martian craters are named after important scientists and science fiction writers; smaller ones are named after towns and villages on Earth.
Observation of Mars
Earth passes Mars every 780 days (or two years plus seven weeks and one day) at a distance of about 80,000,000 km. However, this varies because the orbits are elliptical. To a naked-eye observer, Mars usually shows a distinct yellow, orange or reddish colour, and varies in brightness more than any other planet as seen from Earth over the course of its orbit, due to the fact that when furthest away from the Earth it is more than seven times as far from the latter as when it is closest (and can be lost in the Sun's glare for months at a time when least favourably positioned). At its most favourable times — which occur twice every 32 years, alternately at 15 and 17-year intervals, and always between late July and late September — Mars shows a wealth of surface detail to a telescope. Especially noticeable, even at low magnification, are the polar ice caps. polar ice cap On August 27, 2003, at 9:51:13 UT, Mars made its closest approach to Earth in nearly 60,000 years: 55,758,006 km (approximately 35 million miles) without Light-time correction. This close approach came about because Mars was one day from opposition and about three days from its perihelion, making Mars particularly easy to see from Earth. The last time it came so close is estimated to have been on September 12, 57,617 BC. Detailed analysis of the solar system's gravitational landscape forecasts an even closer approach in 2287. However, to keep this in perspective, this record approach was only an imperceptibly tiny fraction less than other recent close approaches that occur four times every 284 years. For instance, the minimum distance on August 22 1924 was 0.37284 AU, compared to 0.37271 AU on August 27 2003, and the minimum distance on August 24 2208 will be 0.37278 AU. A transit of the Earth as seen from Mars will occur on November 10, 2084. At that time the Sun, the Earth and Mars will be exactly in a line. There are also transits of Mercury and transits of Venus, and the moon Deimos is of sufficiently small angular diameter that its partial "eclipses" of the Sun are best considered transits (see Transit of Deimos from Mars). The only occultation of Mars by Venus to be observed was that of October 3, 1590, seen by M. Möstlin at Heidelberg. Heidelberg
Appearance

Martian meteorites
:Main article: Martian meteorites A handful of objects are known that are surely meteorites and may be of Martian origin. Two of them may show signs of ancient bacterial activity. On August 6, 1996 NASA announced that analysis of the ALH 84001 meteorite thought to have come from Mars, shows some features that may be fossils of single-celled organisms, although this idea is controversial. In Solar System Research (March 2004, vol 38, page 97) it was suggested that the unique Kaidun meteorite, recovered from Yemen, may have originated on the Martian moon of Phobos. On April 14, 2004, NASA revealed that a rock known as "Bounce", studied by the Mars Exploration Rover Opportunity, was similar in composition to the meteorite EETA79001-B, discovered in Antarctica in 1979. The rock may have been ejected from the same crater as the meteorite, or from another crater in the same area of the Martian surface.
Life on Mars
Evidence exists that the planet once was significantly more habitable than today, but the question whether living organisms ever actually existed there is an open one. Some researchers think that a certain rock which is believed to have originated on Mars - specifically, meteorite ALH84001 - does contain evidence of past biologic activity, but no consensus about these claims has been achieved so far and recent research indicates that the rock, since its creation several billion years ago, has never been exposed to temperatures for extended periods of time that would allow for liquid water. The Viking probes carried experiments designed to detect microorganisms in Martian soil at their respective landing sites, and had some positive results, later denied by many scientists, resulting in ongoing controversy. Also, present biologic activity is one of the explanations that have been suggested for the presence of traces of methane within the Martian atmosphere, but other explanations not involving life are generally considered more likely. If colonization is going to happen, Mars seems a likely choice due to its rather hospitable conditions (compared with other planets, it is most like Earth).
The Mars flag
colonization In early 2000, a proposed Mars flag flew aboard the space shuttle Discovery. Designed by NASA engineer and Flashline Mars Arctic Research Station task force leader Pascal Lee and carried aboard by astronaut John Mace Grunsfeld, the flag consists of three vertical bars (red, green, and blue), symbolizing the transformation of Mars from a barren planet (red) to one bearing sustainable life (green), and finally to a fully terraformed planet with open bodies of water. This design was suggested by the Kim Stanley Robinson sci-fi trilogy Red Mars, Green Mars, and Blue Mars. While other designs have been proposed, the republican tricolor has been adopted by the Mars Society as its own official banner. In a statement released after the launch of the mission, the Society said that the flag "has now been honored by a vessel of the leading spacefaring nation on Earth," and added that "(i)t is fitting that this action occurred when it did: at the dawning of a new millenium."
Mars in fiction
The depiction of Mars in fiction has been stimulated its dramatic red color and by early scientific speculations that its surface conditions might be capable of supporting life. Until the arrival of planetary probes, the traditional view of Mars derived from the astronomers Percival Lowell and Giovanni Schiaparelli, whose observation of supposedly linear features on the planet created the myth of canals on Mars. For many years, a standard notion of the planet as a drying, cooling, dying world with ancient civilizations constructing irrigation works. Thus originated a large number of science fiction scenarios, the best known of which is H. G. Wells' The War of the Worlds, in which Martians seek to escape their dying planet by invading Earth. After the Mariner and Viking spacecraft had returned pictures of Mars as it really is, an apparently lifeless and canal-less world, these ideas about Mars had to be abandoned and a vogue for accurate, realist depictions of human colonies on Mars developed, the best known of which may be Kim Stanley Robinson's Mars trilogy. However, pseudo-scientific speculations about the Face on Mars and other enigmatic landmarks spotted by space probes have meant that ancient civilizations continue to be a popular theme in science fiction, especially in film. Another popular theme, particularly among American writers, is the Martian colony that fights for independence from Earth. This is a major plot element in the novels of Greg Bear and Kim Stanley Robinson, as well as the movie Total Recall (based on a novel by Philip K. Dick) and the television series Babylon 5. Many video games also use this element, such as Red Faction.
See also

- Areography
- Astrobiology
- Astronomy on Mars
- Colonization of Mars
- Darian calendar
- Face on Mars photo article
- Timekeeping on Mars
- Exploration of Mars
- List of artificial objects on Mars
- List of craters on Mars
- List of mountains on Mars
- Martian meteorite
- Mars photos
- Mars in fiction
- Extraterrestrial life
- Terraforming
- Mars Direct
- Mars in astrology
- Ares
- Tyr
- Richard C. Hoagland
References

- William Sheehan, [http://www.uapress.arizona.edu/onlinebks/mars/contents.htm The Planet Mars: A History of Observation and Discovery], The University of Arizona Press, Tucson, 1996
- Vladimir A. Krasnopolsky, Jean-Pierre Maillard, Tobias C. Owen, [http://www.google.ca/url?sa=U&start=1&q=http://www.cosis.net/abstracts/EGU04/06169/EGU04-A-06169.pdf&e=912 Detection of methane in the Martian atmosphere: evidence for life?], Icarus, 172 (2), 537-547. [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2004Sci...306.1753L&db_key=AST&data_type=HTML&format=&high=439c7b95b425777 Lemmon et al., "Atmospheric Imaging Results from the Mars Exploration Rovers: Spirit and Opportunity"]
External links

- [http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html NASA's Mars fact sheet]
- [http://www.nineplanets.org/mars.html Nine Planets Mars page]
- [http://www.marsnews.com MarsNews.com - News and info site]
- [http://www.student.oulu.fi/~jkorteni/space/mars/surface/ Introduction to Martian topography, with Hubble Space Telescope photos]
- [http://www.geoinf.fu-berlin.de/mex/ FU Berlin: HRSC (camera) experiment at Mars Express] (eng. & ger.; press releases and high resolution images)
- [http://www.giss.nasa.gov/tools/mars24/help/notes.html Technical Notes about Time on Mars]
- [http://history.nasa.gov/SP-4212/on-mars.html On Mars: Exploration of the Red Planet 1958-1978] from the NASA History Office.
- [http://flagspot.net/flags/mars.html The Mars Society flag]
- [http://www.vias.org/spacetrip/mars_globalview.html A Trip Into Space] Photos and descriptions of Mars
- [http://www.cato.org/pubs/wtpapers/980815paper.html Martian Law - a CATO white paper]
- [http://www.marsunearthed.com/ Mars Unearthed] - Comparisons of terrains between Earth and Mars
- [http://www.ibiblio.org//e-notes/VRML/Globe/Globe.htm 3D VRML Mars globe]
- [http://www.enterprisemission.com/ Enterprise Mission: Richard C. Hoagland's Homepage]
Water on Mars

- [http://news.bbc.co.uk/1/hi/sci/tech/4727847.stm Highly visible ice lake found on Mars - BBC]
- Dr. Tony Phillips: [http://science.nasa.gov/headlines/y2000/ast29jun_1m.htm "Making a Splash on Mars"], Science@NASA article, June 29, 2000. Phillips describes the Martian "gullies" and explains the conditions under which liquid water can exist on the surface of Mars.
- [http://news.bbc.co.uk/hi/english/sci/tech/newsid_2009000/2009318.stm BBC News story on subsurface ice deposits on Mars]
- [http://news.bbc.co.uk/1/hi/sci/tech/3426539.stm BBC News update on Mars Express' findings of polar water ice and water-eroded features on the surface]
- [http://www.nasa.gov/vision/universe/solarsystem/opportunity_water.html Mars Rover Scientists Wring Water Story from Rocks] This image taken by Mars Rover Opportunity shows microscopic rock forms indicating past signs of water. Courtesy: NASA
- [http://news.bbc.co.uk/1/hi/sci/tech/4285119.stm BBC News Mars pictures reveal frozen sea]
Mars exploration

- [http://www.transhumanist.com/volume4/space.htm The Political Economy of Very Large Space Projects (Journal Of Evolution and Technology)]
- [http://www.exploremarsnow.org/ exploreMarsnow] Interactive Mars base simulation. Winner of 2003 Webby Award for Science.
- [http://marsrovers.jpl.nasa.gov/home/index.html NASA Mars Exploration Rover Home Page]
- [http://dualmoments.com/marsrovers/index.html Be on Mars] Anaglyphs from the Mars Rovers (3D)
- als:Mars (Planet) ko:화성 ms:Marikh ja:火星 simple:Mars (planet) th:ดาวอังคาร

Gravitational slingshot

Image:StillJupiter.jpg Image:MovingJupiter.jpg

In orbital mechanics and aerospace engineering, a gravitational slingshot is the use of the motion of a planet to alter the path and speed of an interplanetary spacecraft. It is a commonly used maneuver for visiting the outer planets, which would otherwise be prohibitively expensive, if not impossible, to reach with current technologies. A slingshot maneuver around a planet changes a spacecraft's velocity relative to the Sun, even though it preserves the spacecraft's speed relative to the planet (as it must do, according to the law of conservation of energy). To a first approximation, from a large distance, the spacecraft appears to have bounced off the planet.

Explanation

Consider a spacecraft on a trajectory that will take it close to a planet, say Jupiter. As the spacecraft approaches the planet, Jupiter's gravity will pull on the spacecraft, speeding it up. After passing the planet, the gravity will continue pulling on the spacecraft, slowing it down. The net effect on the speed is zero, although the direction may have changed in the process. So where is the slingshot? The key is to remember that the planets are not standing still, they are moving in their orbits around the Sun. Thus while the speed of the spacecraft has remained the same as measured with reference to Jupiter, the initial and final speeds may be quite different as measured in the Sun's frame of reference. Depending on the direction of the outbound leg of the trajectory, the spacecraft can gain a significant fraction of the orbital speed of the planet. In the case of Jupiter, this is over 13 km/s. A slingshot may be simulated by rolling a steel ball past a magnet in one hand that is then moved away. Because both masses must not cross paths, the acceleration is oblique to the field and thus is similar to a sail vehicle tacking to work against the force.

Background

It is important to understand how spacecraft move from planet to planet. Taking Mars as an example destination, the simplest way to solve this problem is to use a Hohmann transfer orbit, an elliptical orbit with the Earth at perihelion and Mars at aphelion. If launched at the proper moment, the spacecraft will arrive at the aphelion just as Mars is passing by. These types of transfers are commonly used, e.g., for moving between orbits over the Earth, Earth-Moon and Earth-Mars transfers. A Hohmann transfer to the outer planets requires long times and considerable delta V (the velocity adjustments that consume rocket propellant). This is where the slingshot finds its most common applications. Instead of the Hohmann trajectory directly to, say Saturn, the spacecraft is instead sent in a path that is aimed only as far as, say, Jupiter, and the slingshot is then used to accelerate the spacecraft on towards Saturn. This way, the planet lends the spacecraft additional angular momentum, allowing it to reach Saturn using little or no fuel on top of that required to reach Jupiter. Also, during the spacecraft's close approach to Jupiter, the effectiveness of the rocket's propellant is magnified, such that small thrusts near Jupiter produce large changes in the spacecraft's eventual velocity. Such missions require careful timing, making the launch window a crucial part of the mission. A Hohmann transfer to Saturn would require a total of 15.7 km/s delta V (disregarding Earth's and Saturn's own gravity wells, and disregarding aerobraking) which is not within the capabilities of our current spacecraft boosters. A trip using multiple gravitational assists may take longer, but will use considerably less delta V, allowing a much larger spacecraft to be sent. Such a strategy was used on the Cassini probe, which passed by Venus twice, then Earth, and finally Jupiter on the way to Saturn. The 6.7-year transit is slightly longer than the six years needed for a Hohmann transfer, but cut the total amount of delta V needed to about 2 km/s, so that the large and heavy Cassini was able to reach Saturn even with the small boosters available. center center. The speed above is instantaneous distance in kilometers per second. The time and date is Orbiter UTC, which is from 1997-Oct-16 00:00:01 to 2008-Jul-07 00:00:00, notably there is one leap second during this period. Note also that the minimum velocity achieved during Saturnian orbit is more or less equal to Saturn's own orbital velocity, which is the ~5km/s velocity which Cassini matched to enter orbit.]] Another example is Ulysses, the ESA spacecraft which studied the polar regions of the Sun. All the planets orbit roughly in a plane aligned with the equator of the Sun; to move to an orbit passing over the poles of the Sun, the spacecraft would have to change its 30 km/s of the Earth's orbit to another trajectory at right angles to the plane of the Earth's orbit, a task impossible with current spacecraft propulsion systems. Instead the craft was sent towards Jupiter, aimed to arrive at a point in space just "in front" and "below" the planet. As it passed the planet, the probe 'fell' through Jupiter's gravity field, borrowing a minute amount of momentum from the planet; after it had passed Jupiter, the velocity change had bent the probe's trajectory up out of the plane of the planetary orbits, placing it in an orbit that passed over the poles of the Sun, rendering that region visible to the probe. This manoeuvre required only enough fuel to send Ulysses to a point near Jupiter, which is well within current technologies.

Powered slingshots

A well-established way to get more energy from a slingshot is to fire a rocket engine near the periapsis to increase the spacecraft's speed. Although a given rocket burn will provide the same change in velocity (delta-v) regardless of when it occurs, the resulting change in kinetic energy is proportional to the velocity at the time of the burn. Therefore, to maximize the effect of the burn, gaining the most kinetic energy for the propellant expended, the burn must occur at the moment when the velocity is at its maximum, which occurs at periapsis. From an energy conservation standpoint, the extra energy comes from the propellant being "left behind" in the planet's gravity well. If the ship travels at velocity

v

at the start of a burn that changes the velocity by

\Delta v

, then the change in specific orbital energy (SOE) is: :

v \Delta v + \frac

Once the space craft is far from the planet again, the SOE is entirely kinetic, since gravitational potential energy tends to zero. Therefore, the larger the

v

at the time of the burn, the greater the final kinetic energy, and the higher the final velocity. For example, a Hohmann transfer orbit from Earth to Jupiter brings a spacecraft into a hyperbolic flyby of Jupiter with a periapsis velocity of 60 km/s, and a final velocity (asymptotic residual velocity) of 5.6 km/s, which is 10.7 times slower. That means a burn that adds one joule of kinetic energy when far from Jupiter would add 10.7 joules at periapsis. Every 1 m/s gained at periapsis adds

\sqrt = 3.3

m/s to the spacecraft's final velocity. Thus, Jupiter's immense gravitational field has tripled the effectiveness of the space craft's propellant. See also specific energy change of rockets: :

\Delta \epsilon =  \int v\, d (\Delta v)

where

\epsilon

is the specific energy of the rocket (potential plus kinetic energy) and

\Delta v

is a separate variable, not just the change in

v

Limits to slingshot use

The main practical limit to the use of a slingshot is the size of the available masses in the mission. Another limit is caused by the atmosphere of the available planet. The closer the craft can get, the more boost it gets, because gravity falls with the square of distance. If a craft gets too far into the atmosphere, the energy lost to friction can exceed that gained from the planet. Interplanetary slingshots using the Sun itself are impossible because the Sun is at rest with respect to its own frame of reference and is therefore incapable of donating any angular momentum. However, thrusting when near the Sun has the same effect as the powered slingshot described above. This has the potential to magnify a spacecraft's thrusting power enormously, but is limited by the spacecraft's ability to resist the heat. An interstellar slingshot using the Sun is conceivable, involving for example an object coming from elsewhere in our galaxy and slingshotting around the Sun to boost its galactic travel. The energy and angular momentum would then come from the Sun's orbit around the Milky Way. The time scales involved for such an operation are considerably beyond current human capabilities, however. There's also another, theoretical limit based on general relativity. If a spacecraft gets close to the Schwarzschild radius of a black hole (the ultimate gravity well), space becomes so curved that slingshot orbits require more energy to escape than the energy that could be added by the black hole's motion. Also, a spinning mass produces frame-dragging. A spinning black hole actually is surrounded by a region of space, called the ergosphere, within which standing still (with respect to the black hole's spin) is impossible, as space itself slips in the same direction as the black hole's spin at the speed of light. Suffice it to say that there is a subtle relativistic effect (the Lense-Thirring effect) which can transfer angular momentum between any spinning mass and a passing object.
See also

- Delta-v budget
- Pioneer 11
- Voyager 1
- Voyager 2
- MESSENGER
- Michael Minovitch
External links

- [http://www.dur.ac.uk/bob.johnson/SL/ Slingshot effect]
- [http://www.esa.int/esaCP/SEMXLE0P4HD_index_0.html Animation of Cassini Huygens gravitational sling shot]
- [http://www.mathpages.com/home/kmath114.htm Gravitational Slingshot Theory]
- [http://saturn.jpl.nasa.gov/mission/gravity-assist-primer.cfm A Quick Gravity Assist Primer] Category:Spacecraft propulsion Category:Celestial mechanics ja:スイングバイ

Mariner 12

The Voyager 2 spacecraft was launched in 1977. It is identical to its sister Voyager program craft, Voyager 1, but Voyager 2 followed a somewhat different trajectory during its Saturn encounter, bypassing a close encounter with Titan to take advantage of a gravitational slingshot to travel on to Uranus and Neptune. It thus became the first and so far only probe to visit those two planets and the first spacecraft to make the Grand Tour of Jupiter, Saturn, Uranus and Neptune. This was possible only due to a rare geometric arrangement of those four planets that only occurs once every 175 years [http://voyager.jpl.nasa.gov/science/planetary.html]. For details on the Voyager instrument packages, see the separate article on the Voyager program. Voyager program

Mission planning and launch

Voyager 2 was originally planned to be Mariner 12, part of the Mariner program. Voyager 2 was launched on August 20, 1977, from Cape Canaveral, Florida aboard a Titan III-E Centaur rocket. Ground crews became engrossed in a launch problem with Voyager 1 and forgot to send an important activation code to Voyager 2. This caused the probe to shut down its main high-gain antenna. Fortunately, ground crews were able to establish contact through the craft's low-gain antenna and reactivate it.

Jupiter

The closest approach to Jupiter occurred on July 9, 1979.

Saturn

1979The closest approach to Saturn occurred on August 25, 1981. While behind Saturn (as viewed from Earth), Voyager 2 probed Saturn's upper atmosphere with its radar, to measure temperature and density profiles. Voyager 2 found that at the highest levels (70 millibars or 7.0 kilopascals) Saturn's temperature was 70 kelvins, while at the deepest levels measured (1200 millibars or 120 kilopascals) the temperature increased to 143 kelvins. The North pole was found to be 10 kelvins cooler, although this may be seasonal (see also Saturn Oppositions). After the Saturn fly-by, the camera platform on Voyager 2 locked up briefly, putting plans to officially extend the mission to Uranus and Neptune in jeopardy. Fortunately, the mission team were able to fix the problem, and the probe was given the go-ahead to examine Uranus.

Uranus

NeptuneThe closest approach to Uranus occurred on January 24, 1986. Voyager 2 discovered 10 previously unknown moons; studied the planet's unique atmosphere, caused by its axial tilt of 97.77°; and examined its ring system.

Neptune

ring systemThe closest approach to Neptune occurred on August 25, 1989. Since this was the last major planet Voyager 2 could visit, it was decided to make a close flyby of the moon Triton, regardless of the consequences to the trajectory, as with Voyager 1s encounter with Saturn and its moon Titan. This was a wise decision, as Triton turned out to have a fascinating surface. The probe also discovered the Great Dark Spot, which has since disappeared, according to Hubble Space Telescope observations.

Escaping the solar system
Since its planetary mission is over, Voyager 2 is now described as working on an Interspace Mission, which NASA is using to find out what the solar system is like beyond the heliosphere. As of January 11, 2005, Voyager 2 is at a distance of 75.4 AU and is escaping the solar system at a speed of about 3.3 AU per year (ca. 15.6 km/s). Although it has not yet escaped the solar system, it is believed to be on the verge of doing so. Voyager 2 is expected to keep on transmitting into the 2030s.
Current Voyager 2 data processing and operations
There were 41.1 hours of DSN scheduled support for Voyager 2 of which 22.5 hours were large aperture coverage. There were no real-time or scheduled support changes or significant outages during the period. Science instrument performance was nominal for all activities during this period. One frame of GS-4 data was recorded this week. The EDR backlog is 2 days. Voyager 2 command operations consisted of the uplink of seven bracketed command loss timer resets sent on five-minute centers using 1.0 Hz steps on 03/16 [DOY 075/0342z]. The spacecraft received two of the seven commands sent. This information is available from: http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm
Voyager 2 in fiction and popular culture
:This section contains specific references to Voyager 2. For other references to the Voyagers, see Voyager in fiction and popular culture in the Voyager program article.
- The motion picture Starman portrayed Voyager 2 as having been located by an alien intelligence who subsequently sent one of their own race to investigate intelligent life on Earth.
- In the episode "Parasites Lost" of the animated show Futurama, Leela scrubs the remains of Voyager 2 off the windscreen of her spaceship while refuelling at an interplanetary service station.
See also

- Voyager program for more information about this spacecraft.
External links

- [http://voyager.jpl.nasa.gov NASA Voyager website]
- [http://voyager.jpl.nasa.gov/spacecraft/spacecraftlife.html Voyager Spacecraft Lifetime]
- [http://www.heavens-above.com/solar-escape.asp Spacecraft Escaping the Solar System] - current positions and diagrams
- [http://voyager.jpl.nasa.gov/mission/weekly-reports/ Mission state]
References
Category:Voyager program Category:Jupiter spacecraft Category:Saturn spacecraft Category:Uranus spacecraft Category:Neptune spacecraft ko:보이저 2호

Voyager 2

Mission planning and launch

Jupiter

The closest approach to Jupiter occurred on July 9, 1979.

Saturn

Uranus

Neptune

Voyager program

:Voyager is also the name of a planned series of unmanned probes to Mars, cancelled in 1968. The Voyager program consisted of a pair of unmanned scientific probes, Voyager 1 and Voyager 2, launched in 1977. They were sent to study Jupiter and Saturn, using an advantageous planetary alignment of the late 1970s. However, the mission planners always had in the back of their minds a continued mission, and Voyager 2 also examined Uranus and Neptune. They were originally conceived as part of the Mariner program, being Mariner 11 and Mariner 12 respectively. The original program name was Mariner Jupiter-Saturn. It was later given the more appealing and romantic name "Voyager". Voyager was actually a scaled back version of the Grand Tour program of the late 1960s and early 1970s to send a pair of probes to fly by all the outer planets (scaled back because of budget cuts). In the end, they fulfilled all the Grand Tour flyby objectives save Pluto despite not being officially designed for such a long duration mission. Both missions revealed large amounts of information about the gas giants of the solar system. In addition, the spacecraft have been used to place limits on the existence of a hypothetical post-Plutonian Planet X. In the 1990s Voyager 1 overtook the slower travelling Pioneer 10 to become the most distant human made artifact in space - a record it will keep for at least several more decades (and since they are traveling in opposite directions, Voyager 1 and Pioneer 10 are also the most widely separated human made objects). Pioneer 10 Periodic contact has been maintained with both probes to monitor conditions in the outer expanses of the solar system. The crafts' radioactive power sources are still producing electrical energy, fuelling hopes of locating our solar system's heliopause. In late 2003, Voyager 1 began sending data that seemed to indicate it had crossed the termination shock, but interpretations of this data were in dispute. It is now believed that the termination shock was crossed in December, 2004, with the heliopause an unknown distance ahead. Due to budget shifts prompted by President Bush's Vision for Space Exploration, it seems the probes may be deactivated and abandoned [http://news.bbc.co.uk/1/hi/sci/tech/4338245.stm] as early as October 2005, before they observe the heliopause, disappointing many scientists. These probes were built at JPL funded by NASA. Attached to each of them is a copy of the Voyager Golden Record.

Voyager spacecraft design and instrumentation

The identical Voyager spacecraft are three-axis stabilized systems that use celestial or gyro referenced attitude control to maintain pointing of the High Gain Antennas toward Earth. The prime mission science payload consisted of 10 instruments (11 investigations including radio science). Only five investigator teams are still supported, though data is collected for two additional instruments. The Flight Data Subsystem (FDS) and a single eight-track digital tape recorder (DTR) provide the data handling functions. The FDS configures each instrument and controls instrument operations. It also collects engineering and science data and formats the data for transmission. The DTR is used to record high-rate Plasma Wave Subsystem (PWS) data. Data is played back every six months. The Imaging Science Subsystem, made up of a wide angle and a narrow angle camera, is a modified version of the slow scan vidicon camera designs that were used in the earlier Mariner flights. The Imaging Science Subsystem Narrow Angle Camera consists of two television-type cameras, each with 8 filters in a commandable Filter Wheel mounted in front of the vidicons. One has a low resolution 200 mm wide-angle lens with an aperture of f/3, while the other uses a higher resolution 1500 mm narrow-angle f/8.5 lens. Unlike the other onboard instruments, operation of the cameras is not autonomous, but is controlled by an imaging parameter table residing in one of the spacecraft computers, the Flight Data Subsystem (FDS). The computer command subsystem (CCS) provides sequencing and control functions. The CCS contains fixed routines such as command decoding and fault detection and corrective routines, antenna pointing information, and spacecraft sequencing information. The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft orientation, maintains the pointing of the High Gain Antenna towards Earth, controls attitude maneuvers, and positions the scan platform. Uplink communications is via S band (16-bit/s command rate) while an X band transmitter provides downlink telemetry at 160 bit/s normally and 1.4 kbit/s for playback of high-rate plasma wave data. All data is transmitted from and received at the spacecraft via the 3.7-meter high-gain antenna (HGA). Electrical power is supplied by three radioisotope thermoelectric generators (RTGs). The current power levels are about 315 W for each spacecraft. As the electrical power decreases, power loads on the spacecraft must be deactivated in order to avoid exceeding its remaining power supply. As loads are turned off, some spacecraft capabilities are eliminated. To date, the entire Voyager 2 and Voyager 1 scan platform, including all of the platform instruments, has been powered down. The ultraviolet spectrometer (UVS)[http://voyager.jpl.nasa.gov/spacecraft/instruments_uvs.html] on Voyager 1 was on until 2003, when it too was deactivated. Gyro operations will end in 2010 for Voyager 2 and 2011 for Voyager 1. Gyro operations are used to rotate the probe 360 degrees 6 times a year. This is used to measure the magnetic field of the spacecraft, which is then subtracted from the magnetometer science data. The two Voyager spacecraft continue to operate, with some loss in subsystem redundancy, but retain the capability of returning science data from a full complement of VIM science instruments. Both spacecraft also have adequate electrical power and attitude control propellant to continue operating until around 2020 when the available electrical power will no longer support science instrument operation. At this time science data return and spacecraft operations will cease. The radioisotope thermoelectric generators are powered by plutonium, and provided approximately 470 W of 30-volt DC when the spacecraft was launched. Plutonium-238 decays with a radioactive half-life of approximately 85 years, so RTGs using it lose a factor of

1 - \sqrt[85]

of their power output per year, approximately 0.81%. 23 years after launch, such an RTG would produce only 470 W × 0.9919²³ ~= 390 W — or roughly 83% — of the initial power. However, the bi-metallic thermocouples used to convert thermal energy into electrical energy degrade as well; at the beginning of 2001, the power generated by Voyager 1 and Voyager 2 had dropped to 315 W and to 319 W respectively, about 80% of the power output at launch. Both of these power levels represent better performance than the pre-launch predictions, which included a conservative degradation model for the thermocouples.

Golden Record

2001 Voyager 1 carries with it a golden record (Voyager Golden Record) that contains pictures and sounds of Earth, along with symbolic directions for playing the record and data detailing the location of Earth. The record is intended as a combination time capsule and interstellar message to any civilization, alien or far-future human, that recovers Voyager 1. The contents of this record were selected by a committee chaired by Carl Sagan.
Voyager in fiction and popular culture
:The section Voyager 2 in fiction and popular culture in the Voyager 2 article contains specific references to Voyager 2 in pop culture. Star Trek: The Motion Picture has as its premise an alien intelligence, V'ger which turns out to be the fictional Voyager 6. It is able to show character Mr. Spock its history through holographic recordings, analogous to the Voyager Golden Disk, and is on a journey back to earth to bond with its creator. In the television series Star Trek: Voyager the starship the crew travels on is named for the Voyager space probes. In the "Life Line" episode of that series, Dr. Lewis Zimmerman wrongfully mentions Voyager as Pioneer. This is an attempt at humor since both the Pioneer 10 and Pioneer 11 space probes shared the same fate as the Voyager 1 and Voyager 2 space probes. The Pathfinder project in the same episode probably references NASA's Pathfinder project. In the animated television series Beast Wars: Transformers, the Predacon leader Megatron travels back in time and uses data encoded on Voyager 1's golden disk as a guide to altering Earth's history. "Code of Hero", "The Agenda: Part 2"
See also

- Voyager 1 for mission details
- Voyager 2 for mission details
External links

- [http://voyager.jpl.nasa.gov NASA Voyager website] - Main source of information.
- [http://voyager.jpl.nasa.gov/spacecraft/spacecraftlife.html Voyager Spacecraft Lifetime]
- [http://www.heavens-above.com/solar-escape.asp Spacecraft Escaping the Solar System] - current positions and diagrams
- [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840027171_1984027171.pdf Voyager 1 and 2 atlas of six Saturnian satellites (PDF format) 1984]
- [http://voyager.jpl.nasa.gov/mission/weekly-reports/ Mission state] Category:Jupiter Category:Saturn Category:Uranus Category:Neptune
- Category:Space exploration Category:NASA programs ja:ボイジャー

Mariner 2

Mariner 2, a space probe to Venus, was the first successful spacecraft in the NASA Mariner program. The Mariner 1 and 2 spacecraft were simplified versions of the Block I spacecraft of the Ranger program. The Mariner probe consisted of a 100 cm diameter hexagonal bus, to which solar panels, instrument booms, and antennae were attached. The scientific instruments onboard the Mariner spacecraft were two radiometers (microwave and infrared) mounted on a tilting platform, a micrometeorite sensor, a solar plasma sensor, a charged particle sensor, and a magnetometer. These instruments were designed to measure the temperature distribution on the surface of Venus, as well as making basic measurements of Venus' atmopshere. Due to the planet's thick cloud cover, no cameras were included in the Mariner units. The Atlas-Agena rocket carrying Mariner 1 veered off-course during its launch on July 22, 1962, and the spacecraft was destroyed. A month later, the identical Mariner 2 spacecraft was launched successfully on August 27, 1962, sending it on a 3½-month flight to Venus. On the way it measured for the first time the solar wind, a constant stream of charged particles flowing outwards from the Sun. It also measured interplanetary dust, which turned out to be more scarce than predicted. In addition, Mariner 2 detected high-energy charged particles coming from the Sun, including several brief solar flares, as well as cosmic rays from outside the Solar system. As it flew by Venus on December 14, 1962, Mariner 2 scanned the planet with its pair of radiometers, revealing that Venus has cool clouds and an extremely hot surface. The spacecraft is now defunct in a heliocentric orbit.

Detailed Description

The Mariner 2 spacecraft was the second of a series of spacecraft used for planetary exploration in the flyby, or nonlanding, mode and the first spacecraft to successfully encounter another planet. Mariner 2 was a backup for the Mariner 1 mission which failed shortly after launch to Venus. The objective of the Mariner 2 mission was to fly by Venus and return data on the planet's atmosphere, magnetic field, charged particle environment, and mass. It also made measurements of the interplanetary medium during its cruise to Venus and after the flyby.

Spacecraft and Subsystems

Mariner 2 consisted of a hexagonal base, 1.04 meters across and 0.36 meters thick, which contained six magnesium chassis housing the electronics for the science experiments, communications, data encoding, computing, timing, and attitude control, and the power control, battery, and battery charger, as well as the attitude control gas bottles and the rocket engine. On top of the base was a tall pyramid-shaped mast on which the science experiments were mounted which brought the total height of the spacecraft to 3.66 meters. Attached to either side of the base were rectangular solar panel wings with a total span of 5.05 meters and width of 0.76 meters. Attached by an arm to one side of the base and extending below the spacecraft was a large directional dish antenna. The Mariner 2 power system consisted of the two solar cell wings, one 183 cm by 76 cm and the other 152 cm by 76 cm (with a 31 cm dacron extension (a solar sail) to balance the solar pressure on the panels) which powered the craft directly or recharged a 1000 Watt-hour sealed silver-zinc cell battery, which was used before the panels were deployed, when the panels were not illuminated by the Sun, and when loads were heavy. A power-switching and booster regulator device controlled the power flow. Communications consisted of a 3 Watt transmitter capable of continuous telemetry operation, the large high gain directional dish antenna, a cylindrical omnidirectional antenna at the top of the instrument mast, and two command antennas, one on the end of either solar panel, which received instructions for midcourse maneuvers and other functions. Propulsion for midcourse maneuvers was supplied by a monopropellant (anhydrous hydrazine) 225 N retro-rocket. The hydrazine was ignited using nitrogen tetroxide and aluminum oxide pellets, and thrust direction was controlled by four jet vanes situated below the thrust chamber. Attitude control with a 1 degree pointing error was maintained by a system of nitrogen gas jets. The Sun and Earth were used as references for attitude stabilization. Overall timing and control was performed by a digital Central Computer and Sequencer. Thermal control was achieved through the use of passive reflecting and absorbing surfaces, thermal shields, and movable louvers. The scientific experiments were mounted on the instrument mast and base. A magnetometer was attached to the top of the mast below the omnidirectional antenna. Particle detectors were mounted halfway up the mast, along with the cosmic ray detector. A cosmic dust detector and solar plasma spectrometer detector were attached to the top edges of the spacecraft base. A microwave radiometer and an infrared radiometer and the radiometer reference horns were rigidly mounted to a 48 cm diameter parabolic radiometer antenna mounted near the bottom of the mast. All instruments were operated throughout the cruise and encounter modes except the radiometers, which were only used in the immediate vicinity of Venus.

Mission Profile

After launch and termination of the Agena first burn, the Agena-Mariner was in a 118 km altitude Earth parking orbit. The Agena second burn some 980 seconds later followed by Agena-Mariner separation injected the Mariner 2 spacecraft into a geocentric escape hyperbola at 26 minutes 3 seconds after lift-off. Solar panel extension was completed about 44 minutes after launch. On 29 August 1962 cruise science experiments were turned on. The midcourse maneuver was initiated at 22:49:00 UT on 4 September and completed at 2:45:25 UT 5 September. On 8 September at 17:50 UT the spacecraft suddenly lost its attitude control, which was restored by the gyroscopes 3 minutes later. The cause was unknown but may have been a collision with a small object. On October 31 the output from one solar panel deteriorated abruptly, and the science cruise instruments were turned off. A week later the panel resumed normal function and instruments were turned back on. The panel permanently failed on 15 November, but Mariner 2 was close enough to the Sun that one panel could supply adequate power. On December 14 the radiometers were turned on. Mariner 2 approached Venus from 30 degrees above the dark side of the planet, and passed below the planet at its closest distance of 34,773 km at 19:59:28 UT 14 December 1962. After encounter, cruise mode resumed. Spacecraft perihelion occurred on 27 December at a distance of 105,464,560 km. The last transmission from Mariner 2 was received on 3 January 1963 at 07:00 UT. Mariner 2 remains in heliocentric orbit.

Scientific Results

Scientific discoveries made by Mariner 2 included a slow retrograde rotation rate for Venus, hot surface temperatures and high surface pressures, a predominantly carbon dioxide atmosphere, continuous cloud cover with a top altitude of about 60 km, and no detectable magnetic field. It was also shown that in interplanetary space the solar wind streams continuously and the cosmic dust density is much lower than the near-Earth region. Improved estimates of Venus' mass and the value of the astronomical unit were made. Total research, development, launch, and support costs for the Mariner series of spacecraft (Mariners 1 through 10) was approximately $554 million.

External links

- [http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Venus&MCode=Mariner_02 NASA-Jet Propulsion Laboratory Guide to Mariner 2]
- [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660005413_1966005413.pdf Mariner-Venus 1962 Final project report - NASA (PDF)]
- [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650072055_1965072055.pdf Mariner 1 and 2. tracking information memorandum - Jun 1962 (PDF)] Category:Venus spacecraft Category:Mariner program

1962

1962 (MCMLXII) was a common year starting on Monday (link will take you to calendar). In Chinese Zodiac, the "year" of the Ox ended on February 4, 1962 and the "year" of the Tiger began on February 5, 1962.

Events

January

- January 1 - Western Samoa becomes independent from New Zealand
- January 3 - Pope John XXIII excommunicates Fidel Castro
- January 4 - New York City introduces a train that operates without a crew on-board
- January 5 - The first record by The Beatles is released by Deutsche Grammophon
- January 8 - Leonardo da Vinci's Mona Lisa is exhibited in the United States for the first time (National Gallery of Art in Washington, DC)
- January 9 - Trade pact between Cuba and the Soviet Union
- January 10 - Avalanche on Nevado Huascarán in Peru; 4000 deaths
- January 11 - Volcano erupts in the Peruvian Andes and causes an avalanche that buries 3000
- January 12 - Indonesian army confirms that it has began operations in West Irian
- January 13 - Albania allies itself with the People's Republic of China
- January 16 - Military coup in the Dominican Republic
- January 19 - Counter-coup in the Dominican Republic - old government returns except for the new president Rafael Bonnely
- January 22 - The Organization of American States (OAS) suspends Cuba's membership
- January 24 - East German goverment readopts conscription
- January 24 - OAS bomb in French foreign ministry
- January 26 - Mafioso Lucky Luciano dies at the Naples Airport
- January 26 - Ranger 3 is launched to study the moon. The space probe later missed the moon by 22,000 miles
- January 27 - Soviet government changes all place names honoring Molotov, Kaganovich and Georgi Malenkov
- January 30 - Two of the high-wire "Flying Wallendas" are killed when their famous seven-person pyramid collapsed during a performance in Detroit, Michigan

February

- February 2 - For the first time in 400 years Neptune and Pluto align
- February 3 - US announces its trade embargo with Cuba
- February 4 - The Sunday Times becomes the first paper to print a colour supplement
- February 4 - Latin American Gnostic master Samael Aun Weor declares the advent of the New Age of Aquarius
- February 5 - French President Charles De Gaulle calls for allowing Algeria to be an independent nation
- February 7 - The United States Government bans all US-related Cuban imports and exports
- February 9 - Taiwan Stock Exchange Corporation opens
- February 10 - February 10 - Captured American spy pilot Francis Gary Powers is exchanged for captured Soviet spy Rudolf Abel in Berlin
- February 12 - Six members of the Committee of 100 of the Campaign for Nuclear Disarmament are found guilty of a breach of the Official Secrets Act
- February 14 - First Lady Jacqueline Kennedy takes television viewers on a tour of the White House
- February 15 - Urho Kekkonen re-elected president of Finland
- February 16/February 17 - Heavy storm flood on Germany's North Sea coast, mainly around Hamburg, more than 300 people die, thousands losing their homes
- February 17 - Flooding in North Sea coasts
- February 20 - Mercury program: While aboard Friendship 7, John Glenn orbits the Earth three times in 4 hours, 55 minutes becoming the first American to orbit the Earth
- February 23 - 12 European countries form European Space Agency

March-April

- March 1 - An American Airlines Boeing 707 crashes on takeoff at New York International Airport after its rudder separates from the tail, with loss of all life on board
- March 2 - Military coup in Burma
- March 8-12 - In Geneva, France and Algerian FLN begin negotiations
- March 15 - Katangan prime minister Moise Tshombe begins negotiations to rejoin Congo
- March 19 - Armistice begins in Algeria
- March 18 - France and Algeria sign an agreement in Evian ending the Algerian War. See Évian Accords.
- March 19 - Armistice in Algeria - however, Organisation de l'armée secrète continues its terrorist attacks against Algerians
- March 23 - Scandinavian States of Nordic Council sign Helsinki Convention on Nordic Co-operation
- March 24 - OAS leader Edmond Jouahud arrested in Oran
- March 26 - France shortens the term for military service from 26 months to 18
- April 3 - Nehru elected de facto prime minister of India
- April 4 - James Hanratty is hanged in Bedford Gaol for A6 murder - many believe he was innocent
- April 6 - Belgium reforms diplomatic relations with Congo
- April 7 - Author Milovan Djilas arrested in Yugoslavia
- April 8 - In France, the Évian Accords are adopted in a referendum with a majority of 90%.
- April 10 - In Los Angeles, the first game is played at Dodger Stadium.
- April 13 - OAS leader Edmond Jouhaud sentenced to death in France
- April 14 - Cuban military tribunal convicts 1179 Bay of Pigs attackers
- April 18 - Commonweath Immigration Bill in the United Kingdom removes free immigration from the citizens of member states of the British Commonwealth
- April 20 - OAS leader Raoul Salan arrested in Algiers
- April 26 - The Ranger 4 spacecraft crashes into the Moon

May-June

- May 2 - OAS bomb explodes in Algeria - this and other attacks kill 110 and injure 147
- May 31 - Adolf Eichmann hanged in Israel
- May 5 - 12 East Germans escape via a tunnel under the Berlin Wall
- May 14 - Juan Carlos marries the Greek Princess Sophia in Athens
- May 14 - Milovan Djilas, former vice-president of Yugoslavia, is given further sentence for publishing Conversations with Stalin
- May 23 - Drilling for new