Mars 4

The main structural element to which the units are attached, including the propulsion system, solar panels, parabolic pointed and unidirectional antennas, radiators of the cold and hot loops of the thermal management system and the instrument part, is the fuel tank unit of the propulsion system.

An important difference between the M-73C and M-73P modifications is the placement of scientific equipment on the orbital vehicle: in the satellite version, the scientific equipment is installed in the upper part of the tank unit, in the variant with the descent device, on a conical transition element connecting the instrument compartment and the tank unit.

For the expedition vehicles of 1973, KTDU is modified. Instead of the 11D425.000 main engine, 11D425A is installed, the thrust of which in the low-thrust mode is 1105 kg (specific impulse - 293 seconds), and in the high-thrust mode - 1926 kg (specific impulse - 315 seconds). The tank unit has been replaced with a new one - of large dimensions and volume due to the cylindrical insert, while also increased consumable fuel tanks are used. Additional helium cylinders for boosting fuel tanks were installed. Otherwise, the orbital vehicles of the M-73 series, with the exception of the layout and composition of the on-board equipment, repeated the M-71 series.

Mass

The total mass of the Mars-4 spacecraft was 4000 kg, including the dry weight of the span - 2187 kg. The mass of the scientific equipment of the orbital apparatus (with FTU) is 117.8 kg. The corrective propulsion system of the Mars-4 spacecraft is filled with 1,692.47 kg of fuel: 590.47 kg of fuel and 1,102.0 kg of oxidizer. The supply of nitrogen for gas engines of the orientation system is 82.1 kg.

Technological novelty of the project

For the first time in the practice of Russian cosmonautics, four automatic spacecraft simultaneously participated in one interplanetary expedition. In preparation for the expedition, the modernization of the ground experimental and test bases and the command-measuring ground complex, begun for the M-71 series vehicles, was continued. ^[1] So, to check and clarify thermal calculations, special vacuum units equipped with simulators of solar radiation have been created. An analogue of automatic spacecraft passed in them the full scope of complex thermal vacuum tests, the task of which was to test the ability of the temperature control system to maintain the temperature regime within specified limits at all stages of operation. ^[one]

• Creation of a long-term artificial satellite Mars, operating in near-planet space, receiving and transmitting information to the Earth from the AMS landing on the Martian surface of the M-73P spacecraft;
• Ensuring the second inclusion of AMS in the work a day after landing;
• The implementation of the scientific program, which in many respects coincides with the program carried out by the M-73P flying vehicles:

• Getting color photographs of certain areas of the surface of Mars;
• Studying the distribution of water vapor over the planet’s disk;
• Determination of gas composition and density of the atmosphere;
• The study of the relief by the distribution of CO2, determining the distribution of gas concentration in the atmosphere, the brightness temperature of the planet and the atmosphere;
• Determination of dielectric constant, polarization and surface temperature of the planet;
• Measurements of the magnetic field along the flight path and near the planet;
• Measurement of electron and proton fluxes on the flight path and near the planet;
• Studies of the infrared spectrum of the planet in the region of 1.5 - 5.5 microns (in particular, for the search for organic compounds);
• Polarimetric studies of the planet to determine the structure of the surface;
• Investigations of the spectra of the self-emission of the atmosphere of Mars
• Registration of cosmic radiation and radiation belts of the planet.

All spacecraft of the M-73 series have successfully passed the entire cycle of ground tests. Launches of these automatic spacecraft in accordance with the Soviet program for the study of outer space and planets of the solar system were carried out in July - August 1973 ^[1]

To launch the spacecraft of the M-73 series, a four-stage Proton-K launch vehicle with a launch weight of 690 tons was used.

The relative position of the Earth and Mars in 1973 required that the spacecraft’s flight speed be higher — by 250-300 m / s (900 - 1080 km / h) more than in 1971. The restrictions on the total mass the payload brought to the interplanetary trajectory, led to the need for the use of the so-called double-launch flight scheme. According to her, the tasks of delivering a descent vehicle and creating an artificial satellite of Mars are performed by two different vehicles. Given the need for their joint work at a certain stage of the expedition (with the functioning of the AMS on the Martian surface), the future satellite of Mars starts earlier than the second spacecraft. The difference in their flight patterns is significant only at the final stages.

Each of these vehicles is duplicated, so four spacecraft take part in the expedition: Mars-4 , Mars-5 , Mars-6 and Mars-7 . The sites of launching onto interplanetary trajectories and the subsequent flight up to the approach to Mars are identical for all the vehicles both with each other and with the corresponding flight stages in 1971.

Flight Control

To work with the spacecraft of the M-73 series, the Pluton ground-based radio complex located at NIP-16 near Yevpatoriya was used. When receiving information from spacecraft at long distances, to increase the potential of the radio link, the summation of signals from two ADU 1000 antennas (K2 and K3) and one KTNA-200 antenna (K-6) was used. The issuance of commands is carried out through antennas ADU 1000 (K1) and P 400P (K8) on the second site of NIP-16. Both antennas are equipped with Harpoon-4 decimetric transmitters capable of radiating power up to 200 kW. ^[1] From the point of view of the spacecraft’s session control, some changes have been made to the logic of the onboard systems functioning: for the M-73P vehicles, the standard 6T session is designed to slow down and enter the orbit of the Mars satellite.

The Mars-4 spacecraft (M-73C No. 52) was launched from the left launcher of the platform No. 81 of the Baikonur Cosmodrome on July 21, 1973 at 22.30 minutes 59.2 seconds with the Proton-K launch vehicle. With the help of three stages of the Proton-K launch vehicle and the first inclusion of the remote control of the spacecraft’s upper stage, it was launched into an intermediate satellite orbit with an altitude of 174x162 km. The second inclusion of the booster block remote control after ~ 1 hour 20 minutes of a passive flight, the spacecraft was transferred to the flight path to Mars. At 23 hours 49 minutes 28.4 seconds, the spacecraft separated from the upper stage. 204 days after the launch, on February 10, 1974, the spacecraft flew at a distance of 1844 km from the surface of Mars. 27 minutes before this moment, single-line optical-mechanical scanners — telephotometers — were used to capture panoramas of two regions of the Martian surface (in the orange and red-infrared ranges). Two minutes before the pericenter of the target hyperbola, a photographic television device with a short-focus lens is turned on. One 12-frame cycle of the Mars survey from the flight path at ranges of 1900/2100 km on a scale of 1: 5,000,000 was carried out. The pictures were of good quality. Due to the malfunction of the FTU with a telephoto lens, detected 5 days before the flight, during the flight this photo-television device did not turn on. In addition, after the spacecraft’s passage, it turned out to be in radio shadow from the planet for some time, which made it possible to carry out two-frequency radio illumination of the Martian atmosphere. During the flight of the Mars-4 spacecraft along the Earth – Mars route, ion-electron spectrometers were used to measure the energy of solar wind particles, particle composition, temperature and velocity of individual components of the solar plasma, as well as measure the parameters of interplanetary magnetic fields.

Scientific Results

The Mars-4 spacecraft took photographs of Mars from the flight path. On photographs of the planet’s surface, which are of very high quality, details up to 100 m in size can be distinguished. This makes photography one of the main means of studying the planet. With his help, using color filters by synthesizing negatives, color images of a number of sections of the surface of Mars are obtained. Color images are also of high quality and are suitable for geological-morphological and photometric studies.

Using a two-channel ultraviolet photometer with a high spatial resolution, we obtained photometric profiles of the atmosphere near the planet's limb in the spectral range 2600–2800 A, inaccessible to ground-based observations.

Technical Results

The flight program of the Mars-4 station has not been completed.

• Mars-5 is a Soviet automatic interplanetary station from the M-73 series.
• Mars-6 is a Soviet automatic interplanetary station from the M-73 series.
• Mars-7 is a Soviet automatic interplanetary station from the M-73 series.
• List of spacecraft with x-ray and gamma detectors on board

• AMC series M-73 on the website of the NGO named after Lavochkina (unopened) (inaccessible link) . Date of treatment August 20, 2012. Archived July 23, 2015.
• VG Perminov The Difficult Road to Mars AMC Developer Memories Mars and Venus
• TSB Yearbook 1975
• Mars 4 at NASA
• Mars-4 on NASA's Solar System Exploration (unopened) (inaccessible link) . Archived January 4, 2014.