Mars pathfinder

The Mars Pathfinder (total weight 895 kg and dimensions 1.5 × 2.65 m) was launched on December 4, 1996 by NASA using the Delta-2 launch vehicle one month after the launch of the Mars Global Surveyor . The landing of the device on the surface of Mars took place on July 4, 1997 in the Valley of Ares , in the region of the Plain of Chrys (Chryse Planitia).

The descent vehicle entered the atmosphere at a speed of over 7.5 km / s ^[6] , while the thermal insulation protection prevented it from overheating during braking in the atmosphere. The front screen for two minutes extinguished the speed of up to 400 m / s. Then a parachute with a diameter of 12.7 m was opened. Approximately 8 seconds before the impact on the surface, the brake engines started up and depreciation balloons inflated. The device reached the surface of Mars at a speed of 25 m / s (90 km / h) and bounced off it several times to a complete stop.

Due to a malfunction at the station of the Telecommunication Network , it was not possible to separate the rover that day. In addition, there was an instability of communication between the Martian station and the rover, which could be eliminated only by 17:00 the next day ^[5] .

On July 5, the Sojourner rover rode out of the Martian station and on July 6 began scientific experiments (in particular, the study of the nearest stone). On July 6, a circular panorama shot by the camera of the Martian station was also transmitted. Subsequently, the rover studied several more stones, and the station measured wind parameters, temperature and took pictures.

On September 27, 1997, the last communication session with the Martian station took place (a signal containing no data was received until October 7, and attempts to establish communication with it were made until March 1998). On March 10, 1998, the Mars Pathfinder program was declared completed. The Martian station worked on the planet’s surface for 3 months, much more than the estimated time (according to plan - from a week to a month).

According to researchers, the failure occurred due to a battery that failed due to a large number of discharge / charge cycles. The battery was used to heat the station's electronics to a level slightly above the expected night temperature of Mars. After a battery failure, low temperatures led to the failure of critical systems, and, ultimately, loss of connection.

Martian Station

The Martian station (see diagram ) is equipped with three solar panels with a total area of ​​2.8 m², providing a power of 35 W on a sunny day. In addition to them, the station was also equipped with batteries.

The Martian station had a camera (IMP) located on a retractable mast up to 1.8 m high. The camera is equipped with two optical inputs (for receiving stereo images) and filters with 12 color shades (exposure through different filters after combination makes it possible to obtain color images). The ASI / MET meteocomplex was installed at the station with sensors for measuring wind speed and direction, atmospheric pressure and temperature, as well as magnets for extracting magnetic particles from the ground up to 0.1 mm in size.

The Martian station was equipped with high and low gain antennas (on some days there wasn’t enough electricity for the main high gain antenna to work and data was transmitted through the low gain antenna at a speed of 40-150 bit / s; the main antenna allowed communication at speeds above 8 Kbps ) The work of the station was controlled by a RAD6000 computer with a 32-bit processor and 128 MB of memory. Onboard, the VxWorks operating system ^{[7] was used} .

Rover Sojourner

The mass of the rover (see diagram ) was, together with all the equipment, about 15.5 kg, the weight during operation on the surface of Mars was 10.6 kg; dimensions - 0.65 × 0.48 × 0.3 m. Sojourner uses 11 3.2 W DC motors RE016DC, created by Maxon Motor . Six engines rotate the wheels, one for each wheel, 4 set the direction of movement and the latter raises and lowers the spectrometer. Engines can tolerate temperatures up to −100 ° C ^[8] .

The rover was equipped with six wheels with a diameter of 13 cm, each of which is able to rotate independently. The device can tilt 45 ° without turning over and overcome obstacles up to 20 cm high.

Sojourner was powered by a solar panel with gallium arsenide elements. Battery area 0.2 m², manufacturer Tecstar Inc. ". Battery power was enough to operate the device for several hours a day, even in cloudy weather. In addition, the rover had three radioisotope elements with several grams of plutonium-238 to maintain the required temperature in the electronic unit.

The rover maintained communication with the Earth through the Martian station. The rover was equipped with three cameras - a front stereo system and a rear single camera. The apparatus also had a spectrometer for studying the chemical composition of rocks. Sojourner was controlled using an 8-bit Intel 80C85 processor operating at a frequency of 100 kHz , the amount of RAM was 512 kB , and there was also a solid-state flash drive with a capacity of 176 kB. Worked without an operating system .

Having received several images of the sky at various positions of the star, scientists were able to determine that the radius of the particles in the composition of the pink haze is about 1 micrometer. Judging by the color, the soil is rich in iron hydroxide , which speaks in favor of the theory of a warm, humid climate in the past. Pathfinder carried several magnets on board to evaluate the magnetic component of Martian dust. In the end, all but one magnet was covered in dust. Since the weakest magnet did not collect any particles of soil on itself, it was concluded that the air dust does not contain pure magnetite (magnetic iron ore) or oxymagnetites . Probably, dust settling was provoked by iron oxide (Fe ₂ O ₃ ). Later, using simpler tools, the Spirit rover discovered that only the presence of magnetite can explain the magnetic properties of the dust and soil of Mars.

Daily tracking of Doppler shift and less frequent measurement of the distance between the spacecraft and the space communications stations during communication sessions made it possible to determine the position of the Martian station and the direction of the axis of rotation of Mars. The data obtained, taking into account the information previously obtained by the Viking descent vehicles, allowed three times to improve the definition of the precession constant of Mars. A certain degree of precession is consistent with the hypothesis that the non-hydrostatic component of the pole moment of inertia is caused by the existence of the enormous volcanic plateau of Tharsis . It is calculated that the radius of the metallic core of Mars is from 1300 to 2000 km. ^[9]

In total, 16.5 thousand camera images of the Martian station and 550 camera images of the rover were transmitted, 15 rock analyzes were carried out. Scientific results have further supported the hypothesis that Mars was once more “wet and warm.”

Sojourner exploring stones

The rover began to explore the first stone on the thirdsol . The stone was called " Barnacle Bill " ( born Barnacle Bill ) . The composition was studied using an alpha-proton X-ray spectrometer (APXS) for 10 hours. All elements were discovered with the exception of hydrogen , which is less than 0.1% of the mass of stone or soil. “Barnacle Bill” turned out to be similar in composition to terrestrial andesites , which confirms the great volcanic activity of Mars in the past.

The next object for research was the stone, called " Yoga ." The stone resembled the head of a bear, so it was named after the hero of the animated films of the bear Yogi Bear (born Yogi Bear). Analysis using APXS showed that the stone is a piece of basalt rock, more primitive in elemental composition than Barnacle Bill. The shape and surface structure of "Yoga" make it possible to assume that it is brought by streams of water.

Then scientists attracted with its whitish coloration the stone “Scooby-Doo” (Scubee-Doo), a rover was sent to it to check if the stone is covered with sedimentary crust. On the 18th sol, the results of the Scooby-Doo measurements were successfully taken, and on the 21st sol the analysis of data on the composition of the stone was completed. It turned out that it is similar in composition to the soil of the planting area, but has a higher content of calcium and silicon compared to previously studied stones ^[10] .

On the next stone, the Moe, several marks were found on its surface showing wind erosion .

In an area called the Rock Garden, Sojourner collided with crescent-shaped dunes similar to terrestrial ones.

• The cost of the program was relatively low - $ 265 million.
• The rover is named after the female fighter against Negro slavery Sojourner Truth .
• Alpha emitter for alpha-particle spectrometer (APXS) - analysis of the chemical composition of rocks and soils, made at the Russian Research Institute of Atomic Reactors (NIIAR); ^{[four] [11]}

• Ares Valley

• Page on NASA website . Date of treatment May 7, 2012. Archived May 18, 2012.
• Mars Pathfinder NASA / JPL Website
• Super-Resolution Stereo Pairs of "Twin Peaks"
• Mars Pathfinder Mission Profile (unopened) (link not available) . Archived on September 29, 2010. by NASA's Solar System Exploration
• Ted Stryk's Mars Pathfinder page (unopened) (link not available) . Archived on October 5, 2007.
• “A Crawl On Mars” - Ted Stryk's Sojourner rover page (unopened) (link not available) . Archived on October 5, 2007.
• NASA Office of Space Science
• JPL - Mars Exploration Rover Mission
• Authoritative Account of MPF Reset Issue - discussion of the software problems on the Pathfinder spacecraft
• A Little Rock on Mars - children's story about the Pathfinder landing
• Sojourner rover replica (fr.) - description and images of a full scale functional replica of the Sojourner rover
• Pathfinder landing site as seen from orbit by Mars Reconnaissance Orbiter
• Paper model ( source )