Mariner 9

At the end of 1968, NASA decided to launch in 1971 two identical automatic interplanetary stations “Mariner” into orbit around Mars.

The main tasks of flights

1. Large-scale topographic and thermophysical studies.
2. The study of seasonal changes in the atmosphere and surface of Mars.
3. Conducting other long-term dynamic observations.

It was assumed that the duration of research using two artificial satellites of Mars will be at least 90 days.

Scientific tasks are divided into the study of the invariable properties of the surface and the study of the changing properties of the surface and atmosphere. It is not possible to optimally carry out scientific tasks using a single orbit of the artificial satellite of Mars. Therefore, it was decided to use one AMS (Mariner-9) to study unchanging properties, and another (Mariner-8) to study changing properties, with each AMS supposed to be put into a special orbit.

To study the invariable properties, a 12-hour orbit synchronous with the rotation of the Earth was chosen. Such an orbit makes it possible to fill the on-board tape recorder twice daily with information from television cameras and transmit this information to a tracking station in Goldstone for 8–9 hours every day. Since the rotation period of Mars is 24 hours 37 minutes, for each revolution of the Mariner in orbit, the viewing zone shifts by 9-10 degrees in longitude. A full revolution in longitude will be completed in 18-20 days. In 90 days, the AMS route will cover a significant part of Mars between −90 and +40 degrees of latitude, and the television system will complete the survey of the surface of the indicated region, and a continuous image with a low resolution and uniformly distributed sections with high resolution will be obtained. The inclination of the orbit should be in the range from 60 to 80 degrees. The southern polar region is within sight, and the zone from −90 to +40 degrees in latitude can be photographed in 90 days.

To study the changing properties, an orbit with a period of 32.8 hours equal to 4/3 of the rotation period of Mars was chosen. Such an orbit allows one to repeatedly observe the same surface area between 0 and −30 degrees latitude under the same lighting and viewing conditions. This period provides a consistent view of the surface of Mars with a shift of 120 degrees in longitude. Thus, multiple measurements of changing parameters are carried out for three given longitudes. In addition, the high altitude in some parts of the orbit allows you to view and photograph almost the entire planet on one frame of a wide-angle television camera. The inclination of the orbit - approximately 50 degrees - provides an overview of the surface area from 0 to −30 degrees in latitude with each passage of the apocenter. The height of the apocenter allows you to observe the southern polar region.

It was assumed that data on the chemical composition, density, pressure and temperature of the atmosphere, as well as information on the composition, temperature and surface topography, would be collected. It was planned to explore about 70 percent of the planet’s surface.

Scientific research

1. Television studies using the modified television system of spacecraft Mariner-69 ( Mariner-6 and Mariner-7 ).
2. Infrared radiometric studies using an infrared radiometer used at the Mariner-69.
3. Infrared spectroscopic studies using a modified infrared spectrometer originally developed for the Nimbus meteorological satellite.
4. Ultraviolet spectroscopic studies using the advanced Mariner-69 spacecraft ultraviolet spectrometer.
5. The study of eclipses by Mars of Mariner radio signals in the S-band.
6. Researches in the field of celestial mechanics, similar to those carried out on Mariner-69 spacecraft ^[1] .

Mariner-9 was intended to continue the study of Mars, begun by the Mariner-4 station, continued by the Mariner-6 and Mariner-7 stations, and was able to map more than 70% of the Martian surface from a shorter distance (1500 kilometers) and with a higher resolution (from 1 km per pixel to 100 m per pixel) than any previous spacecraft. To find possible foci of volcanic activity, an infrared radiometer is included in the scientific equipment of the station.

Also, the study program was planned to study two natural satellites of Mars - Phobos and Deimos .

The body of the spacecraft has the shape of an octahedron, made of aluminum , magnesium and fiberglass. The case is leaky. Four solar panels generated about 800 watts of electricity in low Earth orbit and 500 watts near Mars. Electricity was accumulated in nickel-cadmium storage batteries (20 Ah ). The spacecraft was oriented along three axes with an accuracy of 0.25 degrees using 12 shunting engines using compressed gas.

The propulsion system was designed as a single unit. The unit included a rocket engine, fuel tanks, cylinders for compressed gas, pipelines, valves and a power structure for mounting the engine and pipelines. The rocket engine had a thrust of 1335 Newtons. The engine combustion chamber is made of beryllium, the nozzle is made of cobalt alloy. The mass of the engine is 7.2 kg. Nitrogen tetraoxide and monomethylhydrazine were used as fuel components. All spacecraft maneuvers were performed using this single propulsion system, the duration of which could vary. To transfer Mariner-9 from the flight path to the orbit of the artificial satellite Mars, a very large change in speed is required (engine operating time 860 seconds), and for corrections small and very accurate pulses are required (engine operation time 4-13 seconds). The flight program provided for two corrections of the flight path to Mars, the transition to the orbit of an artificial satellite and at least two corrections of the orbit of the satellite of Mars ^[2] .

Scientific instruments are placed on a biaxial scanning platform. The platform directs instruments to predetermined sections of the surface of Mars. On the scanning platform were infrared and ultraviolet spectrometers , an infrared radiometer, and also two television cameras (high and low resolution).

The mass of the interplanetary station at launch was 997.9 kg . About 438 kg accounted for the fuel necessary for correcting the flight path to Mars, entering the orbit of an artificial satellite, and correcting this orbit. Thus, the mass of the device in orbit of the artificial satellite of Mars was about 560 kg. Of these, 63.1 kg accounted for scientific instruments.

Structurally, Mariner-9 is identical to Mariner-8 , which was lost during an emergency start.

Mariner-9 was launched on May 30, 1971 at 22:23:00 UTC from the Cosmodrome at Cape Canaveral with the Atlas D booster rocket with the Centaurus booster block.

On June 5, 1971, the flight path was corrected.

September 22, 1971 in the land of Noah - a bright area in the southern hemisphere - a powerful dust storm has begun. By September 29, it spanned two hundred degrees in longitude from Avzonia to Tavmasia , and on September 30 it closed the southern polar cap . This dust storm made it difficult to study the surface of Mars from the satellites Mariner-9, Mars-2 and Mars-3 . Only around January 10, 1972, the dust storm ceased, Mars took its usual form, and Mariner-9 began to send clear images of its surface to Earth .

On November 14, 1971 at 00:18 UTC, the engine was turned on to brake the automatic interplanetary station. The engine worked for 915.6 seconds, reduced the AMS speed by 1600 m / s, and Mariner-9 entered the orbit of the artificial Mars satellite with parameters of 1398 x 17916 km, an inclination of 64.3 °, and a rotation period of 12 hours 34 minutes 1 second ^[3] .

On November 16, 1971, the first orbit correction was performed. Correction was carried out to change the circulation period so that the AMS underwent periapsis when the Goldstone tracking station was at its zenith. After correction, the treatment period was 11 hours 58 minutes 14 seconds, periapsis - 1387 km.

On December 30, 1971, a second orbit correction was performed. After the second orbit correction, the circulation period was 11 hours 59 minutes 28 seconds, periapsis - 1650 km. The periapsis was increased to allow mapping of 70% of the surface by obtaining overlapping images for the remaining time, when the distance to the Earth is such that high-speed data transmission is possible.

On February 11, 1972, NASA reported that Mariner 9 completed its flight program ^[3] .

Mariner-9 was turned off on October 27, 1972 after it ran out of compressed gas for the orientation system.

When Mariner-9 entered the orbit of the satellite of Mars, the surface of the planet was covered by a dense veil of dust storm. Surveying for mapping purposes has been delayed. There was an opportunity to devote more time to shooting the satellites of Mars , Phobos and Deimos . In November and December 1971, about 40 photographs were taken (subsequently about 70 more). Mapping of the surface of Mars began in mid-January 1972.

Over 349 days of operation in the near-Martian orbit, the spacecraft transmitted a total of 7329 images, covering about 85% of the planet’s surface with a resolution of 1 to 2 km (2% of the surface was photographed with a resolution of 100 to 300 meters). The pictures show the channels of dried rivers, craters, huge volcanic formations (such as Mount Olympus - the largest of the volcanoes found in the Solar System ), canyons (including the Mariner valleys - a giant canyon system with a length of over 4000 kilometers, named after the scientific achievements of the Mariner station 9), signs of wind and water erosion and displacement, weather fronts, fog and many more interesting details.

Mariner-9 has successfully completed a study of the invariable surface properties - thermophysical measurements and mapping.

Using an infrared spectrometer, several areas were found where the surface pressure exceeds 6.1 millibars. In these areas, liquid water may exist. In addition to the greatly lowered Hellas region, extensive regions have been found in the Argyre region, in the west of Margarites Sinus and in the Isidas Regio region, where the pressure also exceeds 6.1 mbar during the southern summer.

In addition, he performed a study of 27 surface areas with details that change over time (seasonal changes). Such research is actually part of the scientific program of the lost Mariner-8.

The data obtained by Mariner-9, became the basis for planning future AMS flights to the Red Planet. Images of the surface of Mars along with the results of radio astronomy research were used to select the landing sites of the descent vehicles of the Viking-1 and Viking-2 automatic interplanetary stations. The choice of landing sites was completed in June – July 1976, when images from the Viking-1 orbital vehicle were taken into account ^[4] .

• Mariner-8 - a spacecraft from the Mariner series. The design is identical to the Marine-9.
• Mariner-4 - an automatic interplanetary station. Exploration of Mars from the flight path.
• Mariner-6 - an automatic interplanetary station. Exploration of Mars from the flight path.
• Mariner-7 - an automatic interplanetary station. Exploration of Mars from the flight path.
• Mariner (KA) - automatic interplanetary stations of the Mariner series
• Exploration of Mars - A review of exploration of Mars by classical methods of astronomy and using spacecraft.

• Mariner 9 ( inaccessible link) . Solar System Exploration . NASA - Mariner 9 on the NASA website. Date of treatment May 2, 2019. Archived February 11, 2012.
• Mariner 9 . Details ( inaccessible link) . Solar System Exploration . NASA - Mariner 9 on the NASA website. Date of treatment May 2, 2019. Archived January 22, 2012.
• Pictures taken by Mariner-9 on NASA
• Pictures of Mars obtained by Mariner-9, on the NASA website
• Forty years ago, Mariner 9 became the first artificial satellite of Mars - This Month in NASA History: Mariner 9, November 29, 2011-Vol. 4, Issue 9 on the NASA website
• Solar System Research at NASA