Mariner 9

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Mariner 9
The Mariner 9 spacecraft
Mission typeMars orbiter
OperatorNASA / JPL
COSPAR ID1971-051A Edit this at Wikidata
SATCAT no.5261
Mission duration1 year, 4 months and 26 days[1]
Spacecraft properties
ManufacturerJet Propulsion Laboratory
Launch mass997.9 kilograms (2,200 lb) [2]
Dry mass558.8 kilograms (1,232 lb)
Power500 watts
Start of mission
Launch dateMay 30, 1971, 22:23:04 (1971-05-30UTC22:23:04Z) UTC
RocketAtlas SLV-3C Centaur-D
Launch siteCape Canaveral
End of mission
DeactivatedOctober 27, 1972 (1972-10-28)
Decay dateAround October 2022
Orbital parameters
Reference systemAreocentric
Periareion altitude1,650 km (1,030 mi)
Apoareion altitude16,860 km (10,480 mi)
Inclination64.4 degrees
Period11.9 hours / 719.47 minutes
Epoch29 December 1971, 19:00:00 UTC[3]
Mars orbiter
Orbital insertionNovember 14, 1971, 00:42:00 UTC

Mariner 9 (Mariner Mars '71 / Mariner-I) was a robotic spacecraft that contributed greatly to the exploration of Mars and was part of the NASA Mariner program. Mariner 9 was launched toward Mars on May 30, 1971,[3][4] from LC-36B at Cape Canaveral Air Force Station, Florida, and reached the planet on November 14 of the same year,[3][4] becoming the first spacecraft to orbit another planet[3] – only narrowly beating the Soviet probes Mars 2 (launched May 19) and Mars 3 (launched May 28), which both arrived at Mars only weeks later.

After the occurrence of dust storms on the planet for several months following its arrival, the orbiter managed to send back clear pictures of the surface. Mariner 9 successfully returned 7,329 images over the course of its mission, which concluded in October 1972.[5]


Mariner 9 launch

Mariner 9 was designed to continue the atmospheric studies begun by Mariner 6 and 7, and to map over 70% of the Martian surface from the lowest altitude (1,500 kilometers (930 mi)) and at the highest resolutions (from 1 kilometer to 100 meters (1,100 to 110 yards) per pixel) of any Mars mission up to that point. An infrared radiometer was included to detect heat sources in search of evidence of volcanic activity. It was to study temporal changes in the Martian atmosphere and surface. Mars' two moons were also to be analyzed. Mariner 9 more than met its objectives.

Under original plans, a dual mission was to be flown like Mariners 6–7, however the launch failure of Mariner 8[6] ruined this scheme and forced NASA planners to fall back on a simpler one-probe mission. NASA still held out hope that another Mariner probe and Atlas-Centaur could be readied before the 1971 Mars launch window closed. A few logistical problems emerged, including the lack of an available Centaur payload shroud of the correct configuration for the Mariner probes, however there was a shroud in NASA's inventory which could be modified. Convair also had an available Centaur stage on hand and could have an Atlas readied in time, but the idea was ultimately abandoned for lack of funding.

Mariner 9 was mated to Atlas-Centaur AC-23 on May 9 with investigation into Mariner 8's failure ongoing. The malfunction was traced to a problem in the Centaur's pitch control servoamplifier and because it was not clear if the spacecraft itself had been responsible, RFI testing was conducted on Mariner 9 to ensure the probe was not releasing interference that could cause problems with the Centaur's electronics. All testing came back negative and on May 22, a tested and verified rate gyro package arrived from Convair and was installed in the Centaur.

Liftoff took place on May 30 at 22:23:04 UT.[7] All launch vehicle systems performed normally and the Mariner separated from the Centaur at 13 minutes and 18 seconds after launch.


  1. Ultraviolet Spectrometer (UVS)
  2. Infrared Interferometer Spectrometer (IRIS)
  3. Celestial Mechanics (not a separate instrument; it relied upon tracking measurements including range, range rate, and Doppler)
  4. S-Band Occultation (not a separate instrument; experiment observed the attenuation of the communication signal as the orbiting satellite passed out of view)
  5. Infrared Radiometer (IRR)
  6. Visual Imaging System – in a lower orbit, half that of Mariner 6 and Mariner 7 flyby missions, and with a vastly improved imaging system, Mariner 9 achieved a resolution of 98 metres (320 ft) per pixel, whereas previous Martian probes had achieved only approximately 790 metres (2,600 ft) per pixel.[8]

Spacecraft and subsystems[edit]

The power for the spacecraft was provided by a total of 14,742 solar cells, being distributed between 4 solar panels, which in total resulted in 7.7 meters of solar panels being present in the spacecraft. The solar panels produced a 500 watts in the orbit of Mars, the energy was stored in a 20 amp-hr nickel-cadmium battery.[3]

Propulsion was provided by the RS-2101a engine, which could produce 1340 N thrust, and in total could have 5 restarts. The engine was fueled by monomethyl hydrazine and nitrogen tetroxide. For atittude control, the spacecraft contained 2 sets of 6 nitrogen jets on the tip of the solar panels. Attitude knowledge was provided by a Sun sensor, a Canopus star tracker, gyroscopes, an inertial reference unit, and an accelerometer. The thermal control was achieved by the use of louvers on the eight sides of the frame and thermal blankets.[3]


Mariner 9 view of the Noctis Labyrinthus "labyrinth" at the western end of Valles Marineris.

Mariner 9 was the first spacecraft to orbit another planet. It carried an instrument payload similar to Mariners 6 and 7, but because of the need for a larger propulsion system to control the spacecraft in Martian orbit, it weighed more than Mariners 6 and 7 combined (Mariner 6 and Mariner 7 weighed 413 kilograms while Mariner 9 weighed 997.9 kilograms).[9][10] When Mariner 9 arrived at Mars on November 14, 1971, planetary scientists were surprised to find the atmosphere was thick with "a planet-wide robe of dust, the largest storm ever observed."[3] The surface was totally obscured. Mariner 9's computer was thus reprogrammed from Earth to delay imaging of the surface for a couple of months until the dust settled. The main surface imaging did not get underway until mid-January 1972. However, surface-obscured images did contribute to the collection of Mars science, including understanding of the existence of several huge high-altitude volcanoes of the Tharsis Bulge that gradually became visible as the dust storm abated. This unexpected situation made a strong case for the desirability of studying a planet from orbit rather than merely flying past.[8] It also highlighted the importance of flexible mission software. The Soviet Union's Mars 2 and Mars 3 probes, which arrived during the same dust storm, were unable to adapt to the unexpected conditions, which severely limited the amount of data that they were able to collect.

After 349 days in orbit, Mariner 9 had transmitted 7,329 images, covering 85% of Mars' surface, whereas previous flyby missions had returned less than one thousand images covering only a small portion of the planetary surface.[11] The images revealed river beds, craters, massive extinct volcanoes (such as Olympus Mons, the largest known volcano in the Solar System; Mariner 9 led directly to its reclassification from Nix Olympica), canyons (including the Valles Marineris, a system of canyons over about 4,020 kilometres (2,500 mi) long), evidence of wind and water erosion and deposition, weather fronts, fogs, and more.[12] Mars' small moons, Phobos and Deimos, were also photographed.[13][14]

The findings from the Mariner 9 mission underpinned the later Viking program.[8]

The enormous Valles Marineris canyon system is named after Mariner 9 in honor of its achievements.[8]

After depleting its supply of attitude control gas, the spacecraft was turned off on October 27, 1972.[8]


A schematic of Mariner 8/9, showing the major components and features

The ultraviolet spectrometer (UVS) aboard Mariner 9 was constructed by the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder, Colorado.[15] The ultraviolet spectrometer team was led by Professor Charles Barth.

The Infrared Interferometer Spectrometer (IRIS) team was led by Dr. Rudolf A. Hanel from NASA Goddard Spaceflight Center (GSFC).[16] The IRIS instrument was built by Texas Instruments, Dallas, Texas.

The Infrared Radiometer (IRR) team was led by Professor Gerald Neugebauer from the California Institute of Technology (Caltech).[17]

Error-correction codes achievements[edit]

To control for errors in the reception of the grayscale image data sent by Mariner 9 (caused by a low signal-to-noise ratio), the data had to be encoded before transmission using a so-called forward error-correcting code (FEC). Without FEC, noise would have made up roughly a quarter of a received image, while the FEC encoded the data in a redundant way which allowed for the reconstruction of most of the sent image data at reception.

Since the flown hardware was constrained with regards to weight, power consumption, storage, and computing power, some considerations had to be put into choosing an FEC, and it was decided to use a Hadamard code for Mariner 9. Each image pixel was represented as a six-bit binary value, which had 64 possible grayscale levels. Because of limitations of the transmitter, the maximum useful data length was about 30 bits. Instead of using a repetition code, a [32, 6, 16] Hadamard code was used, which is also a 1st-order Reed-Muller code. Errors of up to seven bits per each 32-bit word could be corrected using this scheme.[18][19] Compared to a five-repetition code, the error correcting properties of this Hadamard code were much better, yet its data rate was comparable. The efficient decoding algorithm was an important factor in the decision to use this code. The circuitry used was called the "Green Machine", which employed the fast Fourier transform, increasing the decoding speed by a factor of three.[20]

Present location[edit]

As of February 2022, Mariner 9's location is unknown; it is either still in orbit, or has already burned up in the Martian atmosphere or crashed into the surface of Mars.

NASA has provided multiple dates for when Mariner 9 could enter the Martian atmosphere. In 2011, NASA predicted that Mariner 9 would burn up or crash into Mars around 2022.[21] However, a 2018 revision to the Mariner 9 mission page by NASA expected Mariner 9 would crash into Mars "sometime around 2020".[22] At the time of the mission, Mariner 9 was left in an orbit that would not decay for at least 50 years, which placed the earliest date of atmospheric entry to October 2022.[3] By August 2023, it is likely that Mariner 9 entered the Martian atmosphere and either burned up or impacted the surface.

See also[edit]


  1. ^ "Mariner 9". NASA's Solar System Exploration website. Retrieved September 28, 2023.
  2. ^ "Mariner 9". NASA's Solar System Exploration website. Retrieved November 30, 2022.
  3. ^ a b c d e f g h "Mariner 9: Trajectory Information". National Space Science Data Center. Retrieved December 28, 2011.Public Domain This article incorporates text from this source, which is in the public domain.
  4. ^ a b "Mariner Mars 1971 Project Final Report" (PDF). NASA Technical Reports Server. Archived (PDF) from the original on 2022-10-09. Retrieved December 28, 2011.
  5. ^ "NASA Programs & Missions Historical Log". Archived from the original on 2014-11-13. Retrieved 2011-12-12.
  6. ^ "Mariner 8 (Mariner H) - Mars Missions - NASA Jet Propulsion Laboratory". NASA Jet Propulsion Laboratory (JPL). Retrieved 2023-12-20.
  7. ^ "In Depth | Mariner 09". NASA Solar System Exploration. Retrieved 2022-03-08.
  8. ^ a b c d e Pyle, Rod (2012). Destination Mars. Prometheus Books. pp. 73–78. ISBN 978-1-61614-589-7. It was the first spacecraft to enter orbit around another world. ... [It] continues to orbit Mars to this day, sailing around the planet deaf and dumb in the cold darkness.
  9. ^ "Missions - Mariner 6 & 7". Retrieved 2023-12-20.
  10. ^ "Mariner 9 - NASA Science". Retrieved 2023-12-20.
  11. ^
  12. ^ "Mariner 9: First Spacecraft to Orbit Mars". 8 November 2018.
  13. ^ Mars Exploration Program: Mariner 8 & 9
  14. ^ Hartmann, W. O. Raper. 1974. The New Mars. The Discoveries of Mariner 9. With the Cooperation of the Mariner 9 Science Experiment Team. Prepared for the NASA Office of Space Science.
  15. ^ "Ultraviolet Spectrometer (UVS)". Retrieved 2024-02-23.
  16. ^ "Infrared Interferometer Spectrometer (IRIS)". Retrieved 2024-02-23.
  17. ^ "Infrared Radiometer (IRR)". Retrieved 2024-02-23.
  18. ^ [1] 64 Shades of Martian Grey – Computerphile
  19. ^ [2] Reed-Muller Code (64 Shades of Grey pt2) – Computerphile
  20. ^ [3] Archived 2013-09-27 at the Wayback Machine Combinatorics in Space The Mariner 9 Telemetry System
  21. ^ "This Month in NASA History: Mariner 9 | APPEL Knowledge Services". Retrieved 2022-02-21.
  22. ^ "In Depth | Mariner 09". NASA Solar System Exploration. Retrieved 2022-02-21.

External links[edit]