Mars Global Surveyor
Mars global surveyor.jpg
Artist's conception of Mars Global Surveyor
Mission typeMars orbiter
OperatorNASA / JPL
COSPAR ID1996-062A Edit this at Wikidata
SATCAT no.24648Edit this on Wikidata
Mission duration26 years, 3 months and 17 days (in orbit)
Spacecraft properties
Launch mass1,030.5 kg (2,272 lb)[1]
Power980 watts
Start of mission
Launch date7 November 1996, 17:00 (1996-11-07UTC17Z) UTC
RocketDelta II 7925
Launch siteCape Canaveral LC-17A
ContractorBoeing IDS
End of mission
Last contact2 November 2006 (2006-11-03) 16 years ago
Decay date2050 (planned)
Orbital parameters
Reference systemAreocentric
Semi-major axis3,769 km (2,342 mi)[2]
Periareion altitude372.8 km (231.6 mi)[2]
Apoareion altitude436.5 km (271.2 mi)[2]
Inclination92.9 degrees[2]
Period1.95 hours[2]
Epoch10 December 2004
Mars orbiter
Orbital insertion11 September 1997, 01:17 UTC
MSD 43972 16:29 AMT
Mars Global Surveyor - patch transparent.png

Mars Global Surveyor (MGS) was an American robotic space probe developed by NASA's Jet Propulsion Laboratory and launched November 1996. MGS was a global mapping mission that examined the entire planet, from the ionosphere down through the atmosphere to the surface.[3] As part of the larger Mars Exploration Program, Mars Global Surveyor performed atmospheric monitoring for sister orbiters during aerobraking, and helped Mars rovers and lander missions by identifying potential landing sites and relaying surface telemetry.[3]

It completed its primary mission in January 2001 and was in its third extended mission phase when, on 2 November 2006, the spacecraft failed to respond to messages and commands. A faint signal was detected three days later which indicated that it had gone into safe mode. Attempts to recontact the spacecraft and resolve the problem failed, and NASA officially ended the mission in January 2007.[4] MGS remains in a stable near-polar circular orbit at about 450 km altitude and, as of 1996, was expected to crash onto the surface of the planet in 2050. [5]


Mars Global Surveyor achieved the following science objectives during its primary mission:[6]

  1. Characterize the surface features and geological processes on Mars.
  2. Determine the composition, distribution and physical properties of surface minerals, rocks and ice.
  3. Determine the global topography, planet shape, and gravitational field.
  4. Establish the nature of the magnetic field and map the crustal remnant field.
  5. Monitor global weather and the thermal structure of the atmosphere.
  6. Study interactions between Mars' surface and the atmosphere by monitoring surface features, polar caps that expand and recede, the polar energy balance, and dust and clouds as they migrate over a seasonal cycle.

Mars Global Surveyor also achieved the following goals of its extended mission:[6]

  1. Continued weather monitoring to form a continuous set of observations with NASA's Mars Reconnaissance Orbiter, which reached Mars in March 2006.
  2. Imaging of possible landing sites for the 2007 Phoenix spacecraft, and the 2011 Curiosity rover.
  3. Observation and analysis of key sites of scientific interest, such as sedimentary-rock outcrop sites.
  4. Continued monitoring of changes on the surface due to wind and ice.

Mission timeline

The Mars rover Spirit's landing site and tracks taken by MGS
The Mars rover Spirit's landing site and tracks taken by MGS
The Mars Odyssey spacecraft image taken by Mars Global Surveyor
The Mars Odyssey spacecraft image taken by Mars Global Surveyor
Mars Express Seen by Mars Global Surveyor
Mars Express Seen by Mars Global Surveyor

Loss of contact

On 2 November 2006, NASA lost contact with the spacecraft after commanding it to adjust its solar panels. Several days passed before a faint signal was received indicating that the spacecraft had entered safe mode and was awaiting further instructions.[4]

On 21 and 22 November 2006, MGS failed to relay communications to the Opportunity rover on the surface of Mars. In response to this complication, Mars Exploration Program manager Fuk Li stated, "Realistically, we have run through the most likely possibilities for re-establishing communication, and we are facing the likelihood that the amazing flow of scientific observations from Mars Global Surveyor is over."[9]

On 13 April 2007, NASA announced the loss of the spacecraft was caused by a flaw in a parameter update to the spacecraft's system software.[4] The spacecraft was designed to hold two identical copies of the system software for redundancy and error checking. Subsequent updates to the software encountered a human error when two independent operators updated separate copies with differing parameters. This was followed by a corrective update that unknowingly included a memory fault which resulted in the loss of the spacecraft.

Originally, the spacecraft was intended to observe Mars for 1 Martian year (approximately 2 Earth years). However, based on the vast amount of valuable science data returned, NASA extended the mission three times. MGS remains in a stable near-polar circular orbit at about 450 km altitude, and was expected to crash onto the surface of the planet at some point after about 2047 at the time of its original launch, having by then spent fifty years orbiting the red planet. This is to prevent contamination of the Martian surface with any germs that may be stuck to the spacecraft.[5]

Spacecraft overview

The spacecraft, fabricated at the Lockheed Martin Astronautics plant in Denver, is a rectangular-shaped box with wing-like projections (solar panels) extending from opposite sides. When fully loaded with propellant at the time of launch, the spacecraft weighed 1,030.5 kg (2,272 lb). Most of its mass lies in the box-shaped module occupying the center portion of the spacecraft. This center module is made of two smaller rectangular modules stacked on top of each other, one of which is called the equipment module and holds the spacecraft's electronics, science instruments, and the 1750A mission computer. The other module, called the propulsion module, houses its rocket engines and propellant tanks. The Mars Global Surveyor mission cost about $154 million to develop and build and $65 million to launch. Mission operations and data analysis cost approximately $20 million/year.[10]

Scientific instruments

The Mars Orbiter Camera

Five scientific instruments flew aboard MGS:[11]

High resolution topographic map of Mars based on the Mars Global Surveyor laser altimeter research led by Maria Zuber and David Smith. North is at the top. Notable features include the Tharsis volcanoes in the west (including Olympus Mons), Valles Marineris to the east of Tharsis, and Hellas basin in the southern hemisphere.
High resolution topographic map of Mars based on the Mars Global Surveyor laser altimeter research led by Maria Zuber and David Smith. North is at the top. Notable features include the Tharsis volcanoes in the west (including Olympus Mons), Valles Marineris to the east of Tharsis, and Hellas basin in the southern hemisphere.

First complete test of aerobraking

The spacecraft was launched from a smaller Delta II rocket, necessitating restrictions in spacecraft weight. In order to achieve the near-circular orbit required for the mission while conserving propellant, the team designed a series of aerobraking maneuvers. Aerobraking had been successfully attempted by the Magellan mission at Venus, but the first complete test of the new procedure was to be carried out by MGS.[15]

Initially, MGS was placed in a highly elliptical orbit that took 45 hours to complete. The orbit had a periapsis of 262 km (163 mi) above the northern hemisphere, and an apoapsis of 54,026 km (33,570 mi) above the southern hemisphere. This would be subsequently be adjusted into its circular science orbit.[11]

After orbital insertion, MGS performed a series of orbit changes to lower the periapsis of its orbit into the upper fringes of the Martian atmosphere at an altitude of about 110 km (68 mi).[16] During every atmospheric pass, the spacecraft slowed down because of atmospheric resistance. This slowing caused the spacecraft to lose altitude on its next pass through the orbit's apoapsis. MGS had planned to use this aerobraking technique over a period of four months to lower the high point of its orbit from 54,000 km (33,554 mi) to altitudes near 450 km (280 mi).

About one month into the mission, it was discovered that air pressure from the planet's atmosphere caused one of the spacecraft's two solar panels to bend backwards. The panel in question had incurred a small amount of damage shortly after launch, the extent of which did not become apparent until subjected to atmospheric forces. MGS had to be raised out of the atmosphere to prevent further damage to the solar panel and a new mission plan had to be developed.[11]

From May to November 1998, aerobraking was temporarily suspended to allow the orbit to drift into the proper position with respect to the Sun and enable optimal use of the solar panels. Although data collection during aerobraking was not in the original mission plan, all science instruments remained functional and acquired vast amounts of data during this "unexpected bonus period of observation".[11] The team was able to evaluate more information about the atmosphere over a range of times rather than the anticipated fixed times of 0200 and 1400, as well as collect data during three close encounters with Phobos.[17]

Finally, from November 1998 to March 1999, aerobraking resumed and shrank the high point of the orbit down to 450 km (280 mi). At this altitude, MGS circled Mars once every two hours. Aerobraking was scheduled to terminate at the same time the orbit drifted into its proper position with respect to the Sun. In the desired orientation for mapping operations, the spacecraft always crossed the day-side equator at 14:00 (local Mars time) moving from south to north. This geometry was selected to enhance the total quality of the science return.[16]

Mission results


The spacecraft circled Mars once every 117.65 minutes at an average altitude of 378 km (235 mi). The nearly polar orbit (inclination = 93°) which is almost perfectly circular, moved from the south pole to the north pole in just under an hour. The altitude was chosen to make the orbit Sun-synchronous, so that all images that were taken by the spacecraft of the same surface features on different dates were taken under identical lighting conditions. After each orbit, the spacecraft viewed the planet 28.62° to the west because Mars had rotated underneath it. In effect, it was always 14:00 for MGS as it moved from one time zone to the next exactly as fast as the Sun. After seven sols and 88 orbits, the spacecraft would approximately retrace its previous path, with an offset of 59 km to the east. This ensured eventual full coverage of the entire surface.[11]

In its extended mission, MGS did much more than study the planet directly beneath it. It commonly performed rolls and pitches to acquire images off its nadir track. The roll maneuvers, called ROTOs (Roll Only Targeting Opportunities), rolled the spacecraft left or right from its ground track to shoot images as much as 30° from nadir. It was possible for a pitch maneuver to be added to compensate for the relative motion between the spacecraft and the planet. This was called a CPROTO (Compensation Pitch Roll Targeting Opportunity), and allowed for some very high resolution imaging by the onboard MOC (Mars Orbiting Camera).[18]

In addition to this, MGS could shoot pictures of other orbiting bodies, such as other spacecraft and the moons of Mars. In 1998 it imaged what was later called the Phobos monolith, found in MOC Image 55103.[19]

The Phobos monolith (right of center) as taken by MGS (MOC Image 55103) in 1998
The Phobos monolith (right of center) as taken by MGS (MOC Image 55103) in 1998

After analyzing hundreds of high-resolution pictures of the Martian surface taken by the spacecraft, a team of researchers found that weathering and winds on the planet create landforms, especially sand dunes, remarkably similar to those in some deserts on Earth.[20]

Other discoveries from this mission are:

The Lense–Thirring test

Main article: Frame-dragging

Data from MGS have been used to perform a test of the general relativistic Lense–Thirring precession which consists of a small precession of the orbital plane of a test particle moving around a central, rotating mass such as a planet. The interpretation of these results has been debated.[30][31]

Further evidence for water on Mars

Main article: Water on Mars

Hundreds of gullies were discovered that were formed from liquid water, possibly in recent times.[32][33][34]

A few channels on Mars displayed inner channels that suggest sustained fluid flows. The most well-known is the one in Nanedi Valles. Another was found in Nirgal Vallis.[28]

Inner channel on floor of Nanedi Valles that suggests that water flowed for a fairly long period.  Image from Lunae Palus quadrangle
Inner channel on floor of Nanedi Valles that suggests that water flowed for a fairly long period. Image from Lunae Palus quadrangle

On 6 December 2006 NASA released photos of two craters in Terra Sirenum and Centauri Montes which appear to show the presence of flowing water on Mars at some point between 1999 and 2001. The pictures were produced by Mars Global Surveyor and are quite possibly the spacecraft's final contribution to our knowledge of Mars and the question of whether water exists on the planet.[35]

Evidence of possible recent water flow
Evidence of possible recent water flow

Other pictures

See also


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