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NEAR Shoemaker
Artist's conception of the NEAR Shoemaker spacecraft
Artist's conception of the NEAR Shoemaker spacecraft
Organization NASA
Mission type Flyby, Orbiter
Flyby of 253 Mathilde on June 27, 1997
Satellite of Eros
Orbital insertion date 14 February 2000 at 15:33 UT (10:33 AM EST)
Launch date 1996-02-17 at 20:43:27 UTC
Launch vehicle Delta 7925-8
NSSDC ID 1996-008A
Webpage Official NEAR Mission Site (Johns Hopkins Applied Physics Laboratory)
Mass 487 kg
Power 1800 W
Orbital elements
Apoapsis 200 km (inicial)
Near Earth Asteroid Eros as seen from the NEAR spacecraft.
Near Earth Asteroid Eros as seen from the NEAR spacecraft. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program TemplateInfobox Planet. --> 253 Mathilde (məˈtɪldə is a main belt Asteroid that Events 1358 - Republic of Dubrovnik is founded 1709 - Peter the Great defeats Charles XII of Sweden Year 1997 ( MCMXCVII) was a Common year starting on Wednesday (link will display full 1997 Gregorian calendar TemplateInfobox Planet. --> 433 Eros (ˈɪərɒs irr'-os) is the first discovered Near-Earth asteroid Events 842 - Charles the Bald and Louis the German swear the Oaths of Strasbourg in the French and German 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Year 1996 ( MCMXCVI) was a Leap year starting on Monday (link will display full 1996 Gregorian calendar) Events 1500 - Battle of Hemmingstedt. 1600 - Philosopher Giordano Bruno is burned alive at Campo de' Fiori The International Designator (or NSSDC ID) is an international naming convention for Satellites It consists of the launch year a 3-digit incrementing launch number The elements of an orbit are the parameters needed to specify that Orbit uniquely given a model of two point-masses obeying the Newtonian laws of motion and the In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from

The Near Earth Asteroid Rendezvous - Shoemaker (NEAR Shoemaker), renamed after its launch in honor of planetary scientist Eugene M. Shoemaker, is a robotic space probe designed to study the near-Earth asteroid Eros from close orbit over a period of a year. Eugene Merle Shoemaker (or Gene Shoemaker ( April 28, 1928  &ndash July 18, 1997) was one of the founders of the fields of Planetary A robotic spacecraft is a Spacecraft with no humans on board that is usually under Telerobotic control A space probe is a scientific Space exploration mission in which a Robotic spacecraft leaves the Gravity well of Earth and approaches the Near-Earth asteroids (NEAs are Asteroids whose Orbits are close to Earth 's orbit Asteroids, sometimes called Minor planets or planetoids', are bodies—primarily of the inner Solar System —that are smaller than planets but TemplateInfobox Planet. --> 433 Eros (ˈɪərɒs irr'-os) is the first discovered Near-Earth asteroid The primary scientific objective of NEAR was to return data on the bulk properties, composition, mineralogy, morphology, internal mass distribution and magnetic field of Eros. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges Secondary objectives include studies of regolith properties, interactions with the solar wind, possible current activity as indicated by dust or gas, and the asteroid spin state. Regolith ( Greek: "blanket rock" is a layer of loose Heterogeneous material covering solid rock. The solar wind is a Stream of charged particles&mdasha plasma &mdashthat are ejected from the upper atmosphere of the Sun. This data will be used to help understand the characteristics of asteroids in general, their relationship to meteorites and comets, and the conditions in the early solar system. Asteroids, sometimes called Minor planets or planetoids', are bodies—primarily of the inner Solar System —that are smaller than planets but A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — To accomplish these goals, the spacecraft was equipped with an X-ray/gamma ray spectrometer, a near-infrared imaging spectrograph, a multi-spectral camera fitted with a CCD imaging detector, a laser rangefinder, and a magnetometer. X-ray spectroscopy is a gathering name for several spectroscopic techniques for determining the electronic structure of materials by using X-ray excitation A Gamma-Ray Spectrometer, or (GRS is an instrument for measuring the distribution (or Spectrum —see figure) of the intensity of gamma radiation versus the energy A charge-coupled device ( CCD) is an analog Shift register, that enables the transportation of analog signals (electric charges through successive stages (capacitors A magnetometer is a scientific instrument used to measure the strength and/or direction of the Magnetic field in the vicinity of the instrument A radio science experiment was also performed using the NEAR tracking system to estimate the gravity field of the asteroid. Gravitation is a natural Phenomenon by which objects with Mass attract one another The total mass of the instruments was 56 kg, and they required 81 W power.

Contents

Mission profile

Summary

The primary goal of the mission was to study the near Earth asteroid 433 Eros from orbit for approximately one year. Year 1996 ( MCMXCVI) was a Leap year starting on Monday (link will display full 1996 Gregorian calendar) Events 1500 - Battle of Hemmingstedt. 1600 - Philosopher Giordano Bruno is burned alive at Campo de' Fiori TemplateInfobox Planet. --> 433 Eros (ˈɪərɒs irr'-os) is the first discovered Near-Earth asteroid Eros is an S-type asteroid approximately 13 × 13 × 33 km in size, the second largest near-Earth asteroid. S-type asteroids are of a silicaceous ( stony) composition hence the name Initially the orbit was circular with a radius of 200 km. The radius of the orbit was brought down in stages to a 50 × 50 km orbit on 30 April 2000 and decreased to 35 × 35 km on July 14, 2000. Events 313 - Roman emperor Licinius unifies the entire Eastern Roman Empire under his rule 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Events 1223 - Louis VIII becomes King of France upon the death of his father Philip II of France. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. The orbit was raised over succeeding months to a 200 × 200 km orbit and then slowly decreased and altered to a 35 × 35 km retrograde orbit on December 13, 2000. Events 1294 - Saint Celestine V abdicates the papacy after only five months Celestine hoped to return to his previous life 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. The mission ended with a touchdown in the "saddle" region of Eros on February 12, 2001. Events 1429 - English Forces under Sir John Fastolf defend a supply convoy carrying rations to the army besieging Orleans from attack by the Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar.

Some scientists claim that the ultimate goal of the mission was to link Eros, an asteroidal body, to meteorites recovered on Earth. With sufficient data on chemical composition, a causal link could be established between Eros and other S-type asteroids, and those meteorites believed to be pieces of S-type asteroids (perhaps Eros itself). Once this connection is established, meteorite material can be studied with large, complex, and evolving equipment, and the results extrapolated to bodies in space. NEAR-Shoemaker did not prove or disprove this link to the satisfaction of scientists. However, it is undeniable that NEAR data advanced the field of asteroidal studies tremendously.

Launch of the NEAR spacecraft, February 1996.
Launch of the NEAR spacecraft, February 1996. Year 1996 ( MCMXCVI) was a Leap year starting on Monday (link will display full 1996 Gregorian calendar)

The journey to Eros

After launch on a Delta 7925-8 (a Delta II Lite launch vehicle with nine strap-on solid-rocket boosters and a Star 48 (PAM-D) third stage) and exit from Earth orbit, NEAR entered the first part of its cruise phase. It spent most of this phase in a minimal activity "hibernation" state, which ended a few days before the flyby of the 61 km diameter asteroid 253 Mathilde on June 27, 1997. TemplateInfobox Planet. --> 253 Mathilde (məˈtɪldə is a main belt Asteroid that Events 1358 - Republic of Dubrovnik is founded 1709 - Peter the Great defeats Charles XII of Sweden Year 1997 ( MCMXCVII) was a Common year starting on Wednesday (link will display full 1997 Gregorian calendar The spacecraft flew within 1200 km of Mathilde at 12:56 UT at 9. 93 km/s, returning imaging and other instrument data. On July 3, 1997 NEAR executed the first major deep space maneuver, a two-part burn of the main 450 N thruster. Events 324 - Battle of Adrianople Constantine I defeats Licinius, who flees to Byzantium. Year 1997 ( MCMXCVII) was a Common year starting on Wednesday (link will display full 1997 Gregorian calendar This decreased the velocity by 279 m/s and lowered perihelion from 0. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from 99 AU to 0. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the 95 AU. The Earth gravity assist swingby occurred on January 23, 1998 at 7:23 UT. In Orbital mechanics and Aerospace engineering, a gravitational slingshot, gravity assist or swing-by is the use of the relative movement and Events 393 - Roman Emperor Theodosius I proclaims his nine year old son Honorius co-emperor Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) The closest approach was 540 km, altering the orbital inclination from 0. 5 to 10. 2 degrees, and the aphelion distance from 2. In Celestial mechanics, an apsis, plural apsides (ˈæpsɨdɪːz is the point of greatest or least distance of the Elliptical orbit of an object from 17 to 1. 77 AU, nearly matching those of Eros. Instrumentation was active at this time.

Failure of first attempt at orbital insertion

The first of four scheduled rendezvous burns on December 20, 1998 at 22:00 UT aborted due to a software problem. Events 69 - Vespasian, formerly a general under Nero, enters Rome to claim the title of Emperor. Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) Contact was lost immediately after this and was not re-established for over 24 hours. The original mission plan called for these four burns to be followed by an orbit insertion burn on January 10, 1999, but the abort of the first burn and loss of communication made this impossible. Events 49 BC - Julius Caesar crosses the Rubicon, signaling the start of civil war. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) A new plan was put into effect in which NEAR flew by Eros on December 23, 1998 at 18:41:23 UT at a speed of 965 m/s and a distance of 3827 km from the center of mass of Eros. Events 962 - Byzantine-Arab Wars: Under the future Emperor Nicephorus Phocas, Byzantine troops stormed the city Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) Images of Eros were taken by the camera, data were collected by the near IR spectrograph, and radio tracking was performed during the flyby. A rendezvous maneuver was performed on January 3, 1999 involving a thruster burn to match NEAR's orbital speed to that of Eros. Events 1431 - Joan of Arc is handed over to the Bishop Pierre Cauchon. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) A hydrazine thruster burn took place on January 20 to fine-tune the trajectory. Hydrazine is a Chemical compound with the formula N2H4 It has an Ammonia -like odor and is derived from the same industrial chemistry Events 250 - Emperor Decius begins a widespread persecution of Christians in Rome. On August 12 a two minute thruster burn slowed the spacecraft velocity relative to Eros to 300 km/h. Events 1099 - First Crusade: Battle of Ascalon - Crusaders under the command of Godfrey of Bouillon defeat Fatimid

Orbital insertion

Trajectory graphic depicting the voyage of the NEAR spacecraft.
Trajectory graphic depicting the voyage of the NEAR spacecraft.

Orbital insertion around Eros occurred on 14 February 2000 at 15:33 UT (10:33 AM EST) after NEAR completed a 13 month heliocentric orbit which closely matched the orbit of Eros. Orbit insertion is a deceleration or acceleration maneuver performed by a Spacecraft designed to allow the spacecraft to be captured into Orbit around a Planet Events 842 - Charles the Bald and Louis the German swear the Oaths of Strasbourg in the French and German 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. A rendezvous maneuver was completed on February 3 at 17:00 UT, slowing the spacecraft from 19. Events 1112 - Ramon Berenguer III of Barcelona and Douce I of Provence marry uniting the fortunes of those two states 3 to 8. 1 m/s relative to Eros. Another maneuver took place on February 8 increasing the relative velocity slightly to 9. Events 421 - Constantius III becomes co- Emperor of the Western Roman Empire. 9 m/s. Searches for satellites of Eros took place on January 28, and 4 and 9 February, none were found. Events 1077 - Walk to Canossa: The Excommunication of Henry IV Holy Roman Emperor is lifted The scans were for scientific purposes and to mitigate any chances of collision with a satellite. NEAR went into a 321 x 366 km orbit around Eros on February 14. Events 842 - Charles the Bald and Louis the German swear the Oaths of Strasbourg in the French and German The orbit was slowly decreased to a 35 km circular polar orbit by July 14. Events 1223 - Louis VIII becomes King of France upon the death of his father Philip II of France. NEAR remained in this orbit for 10 days and then was backed out in stages to a 100 km circular orbit by September 5, 2000. Events 1590 - Alexander Farnese 's army forces Henry IV of France to raise the siege of Paris. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Maneuvers in mid-October led to a flyby of Eros within 5. 3 km of the surface at 07:00 UT on 26 October. Events 740 - An Earthquake strikes Constantinople, causing much damage and death

Orbits and landing

Eros asteroid from approximately 1,150 meters (area in image is roughly 54 meters wide [1]). This image was taken during NEAR's descent to the surface of the asteroid.
Eros asteroid from approximately 1,150 meters (area in image is roughly 54 meters wide [1]). This image was taken during NEAR's descent to the surface of the asteroid.

Following the flyby NEAR moved to a 200 km circular orbit and shifted the orbit from prograde near-polar to a retrograde near-equatorial orbit. Direct motion is the motion of a Planetary body in a direction similar to that of other bodies within its system and is sometimes called prograde motion. By December 13, 2000 the orbit was shifted back to a circular 35 km low orbit. Events 1294 - Saint Celestine V abdicates the papacy after only five months Celestine hoped to return to his previous life 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Starting on January 24, 2001 the spacecraft began a series of close passes (5 to 6 km) to the surface and on January 28 passed 2 to 3 km from the asteroid. Events 41 - Gaius Caesar (Caligula, known for his eccentricity and cruel Despotism, is Assassinated by his disgruntled Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Events 1077 - Walk to Canossa: The Excommunication of Henry IV Holy Roman Emperor is lifted The spacecraft then made a slow controlled descent to the surface of Eros ending with a touchdown just to the south of the saddle-shaped feature Himeros on February 12, 2001 at approximately 20:01 UT (3:01 p. Events 1429 - English Forces under Sir John Fastolf defend a supply convoy carrying rations to the army besieging Orleans from attack by the Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. m. EST). To the surprise of the controllers, the spacecraft was undamaged and operational after the landing at an estimated speed of 1. 5 to 1. 8 meters per second (thus becoming the first spacecraft to soft-land on an asteroid). After receiving an extension of antenna time on the Deep Space Network, the spacecraft's gamma-ray spectrometer was reprogrammed to collect data on Eros' composition from a vantage point about four inches from the surface where it was ten times more sensitive than when it was used in orbit. The Deep Space Network, or DSN, is an international network of communication facilities that supports Interplanetary Spacecraft missions and [2]

At 7 p. m. EST on February 28, 2001 the last data signals were received from NEAR Shoemaker before it was shut down. Events 202 BC - coronation ceremony of Liu Bang as Emperor Gaozu of Han takes place initiating four centuries of the Han Dynasty 's rule Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. A final attempt to communicate with the spacecraft on December 10, 2002 was unsuccessful. Events 1041 - Empress Zoe of Byzantium elevates her adoptive son to the throne of the Eastern Roman Empire as Michael V See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar. [3]

Spacecraft and subsystems

NEAR spacecraft inside its Delta II rocket.
NEAR spacecraft inside its Delta II rocket.

The spacecraft has the shape of an octagonal prism, approximately 1. 7 m on a side, with four fixed gallium arsenide solar panels in a windmill arrangement, a fixed 1. Gallium arsenide ( GaAs) is a compound of two elements Gallium and Arsenic. In the field of Photovoltaics, a photovoltaic module is a packaged interconnected assembly of photovoltaic cells also known as Solar cells An installation of 5 m X-band high-gain radio antenna with a magnetometer mounted on the antenna feed, and an X-ray solar monitor on one end (the forward deck), with the other instruments fixed on the opposite end (the aft deck). The X band is part of the Microwave region of the Electromagnetic spectrum. A magnetometer is a scientific instrument used to measure the strength and/or direction of the Magnetic field in the vicinity of the instrument Most electronics are mounted on the inside of the decks. The propulsion module is contained in the interior.

The craft is three-axis stabilized and uses a single bipropellant (hydrazine / nitrogen tetroxide) 450 newton (N) main thruster, and four 21 N and seven 3. A bipropellant rocket engine is a Rocket engine that uses two propellants (very often liquid propellants) which are kept separately prior to reacting to form a hot Hydrazine is a Chemical compound with the formula N2H4 It has an Ammonia -like odor and is derived from the same industrial chemistry Nitrogen tetroxide ( dinitrogen tetroxide or nitrogen peroxide) is the Chemical compound N2O4 The newton (symbol N) is the SI derived unit of Force, named after Isaac Newton in recognition of his work on Classical 5 N hydrazine thrusters for propulsion, for a total delta-V potential of 1450 m/s. In Astrodynamics, the term delta-v, literally "change in velocity" (see symbol delta) has a specific meaning it is a Scalar which takes Attitude control is achieved using the hydrazine thrusters and four reaction wheels. The propulsion system carries 209 kg of hydrazine and 109 kg of NTO oxidizer in two oxidizer and three fuel tanks.

Power is provided by four 1. 8 by 1. 2 meter gallium arsenide solar panels which can produce 400 watts at 2. The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. 2 AU (329,000,000 km), NEAR's maximum distance from the Sun, and 1800 W at one AU (150,000,000 km). The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the Power is stored in a nine ampere-hour, 22-cell rechargeable super nickel-cadmium battery. The nickel-cadmium battery (commonly abbreviated NiCd and ˈnɑɪˌkæd "nye-cad" is a type of Rechargeable battery using Nickel oxide hydroxide

Spacecraft guidance is achieved through the use of a sensor suite of five digital solar attitude detectors, an inertial measurement unit, (IMU) and a star tracker camera pointed opposite the instrument pointing direction. The IMU contains hemispherical resonator gyroscopes and accelerometers. A gyroscope is a device for measuring or maintaining orientation, based on the principles of Angular momentum. Four reaction wheels (arranged so that any three can provide complete three-axis control) are used for normal attitude control. A reaction wheel is a type of Flywheel used primarily by Spacecraft to change their Angular momentum without using fuel for Rockets or other reaction The thrusters are used to dump angular momentum from the reaction wheels, as well as for rapid slew and propulsive maneuvers. In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position Attitude control is to 0. 1 degree, line-of-sight pointing stability is within 50 microradians over one second, and post-processing attitude knowledge is to 50 microradians.

The command and data handling subsytem is composed of two redundant command and telemetry processors and solid state recorders, a power switching unit, and an interface to two redundant 1553 standard data buses for communications with other subsystems. MIL-STD-1553 is military standard published by the United States Department of Defense that defines the mechanical, Electrical and functional The solid state recorders are constructed from 16 Mbit IBM Luna-C DRAMs. International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology One recorder has 1. 1 gigabits of storage, the other has 0. A gigabit is a unit of information or computer storage abbreviated Gbit (or Gb) 67 gigabits.

The NEAR mission was the first launch of NASA's Discovery Program, a series of small-scale spacecraft designed to proceed from development to flight in under three years for a cost of less than $150 million. NASA 's Discovery Program is a series of lower-cost highly focused scientific space missions The construction, launch, and 30 day cost for this mission is estimated at $122 million.

References

External links

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