50 years since the launch of the "Mars-4, Mars-5" spacecrafts
50 years ago, on July 21 and July 25, 1973, respectively, the Mars-4 and Mars-5 spacecrafts developed at Lavochkin Association were launched by “Proton-K” launch vehicles from Baikonur Cosmodrome.
The spacecraft belonged to the “M-73” series, which consisted of two modifications:
– M-73S – vehicles designed to function as Mars satellites (“Mars-4”, rev. M-73S No. 52 and “Mars-5”, rev. M-73S No. 53);
– M-73P – vehicles designed for delivery to the near-planetary region and landing from the flyby trajectory to the surface of Mars of a research probe – an autonomous Martian station (“Mars-6”, rev. M-73P No. 50 and “Mars-7”, rev. M-73P No. 51).
The objectives of the Mars satellites (M-73S) were:
– creation of an artificial satellite of Mars functioning for a long time in near-planetary space, receiving and transmitting information from the AMSs landed on the Mars surface by the M-73P spacecraft to Earth;
– ensuring the second activation of the AMS a day after landing;
– execution of the scientific program, which in many respects coincides with the program executed by the M-73P flyby vehicles:
– obtaining color photographs of certain areas of the surface of Mars;
– studying the distribution of water vapor on the planet’s disk;
– determination of the gas composition and density of the atmosphere;
– study of relief by CO2 distribution, determination of gas concentration distribution in the atmosphere, brightness temperature of the planet and atmosphere;
– determination of dielectric permittivity, polarization and temperature of the planet surface;
– measurements of the magnetic field along the flight path and near the planet;
– measurements of electron and proton fluxes along the flight path and near the planet;
– research of the infrared spectrum of the planet in the region of 1.5 – 5.5 mkm (in particular, to search for organic compounds);
– polarimetric studies of the planet to determine the surface structure;
– studies of the intrinsic luminescence spectra of Mars’ atmosphere;
– registration of cosmic radiations and radiation belts of the planet.
“Mars-4” approached the planet 204 days after the launch, on February 10, 1974. During the flight three channels of the on-board computer failed to carry out the autonomous correction and put the spacecraft into the orbit of the ISM. As a result the station passed near the planet at a distance of 1844 km from its surface. Twenty-seven minutes before that moment, the single-line optical-mechanical scanners – telephotometers – were switched on, with the help of which panoramas of two regions of the surface of Mars (in the orange and red-infrared bands) were taken. Two minutes before the pericenter of the approach hyperbola, a photo-television device with a short-focus lens was switched on. One 12-frame cycle of imaging of Mars from the flyby trajectory at ranges of 1900/2100 km at a scale of 1:5000000 was carried out. The images were of good quality. Also, after the flyby the spacecraft was in the radio shadow from the planet for some time, which made it possible to conduct dual-frequency radio illumination of the Mars atmosphere.
During the “Mars-4” mission along the Earth-Mars route, measurements of solar wind particle energy, particle composition, temperature and velocity of individual solar plasma components, as well as measurements of interplanetary magnetic field parameters were made using ion and electron spectrometers. However, despite the data collected by the “Mars-4” spacecraft, the mission program was not fulfilled.
The goals and objectives of the “Mars-5” mission were similar to those of “Mars-4”. The flight plan of the “Mars-5” mission included three trajectory corrections, deceleration near Mars and exit to an elliptical orbit. “Mars-5” reached the vicinity of the planet on February 12, 1974, 202 days after the launch. At 6:45 p.m., the braking propulsion system was switched on to place the station into the orbit of the Mars satellite. All dynamic operations at the final stage of the flight were performed autonomously with the help of the onboard astronavigation system. As a result of the maneuver, the “Mars-5” station became an artificial satellite of the planet.
Immediately after entering orbit, depressurization of the instrument compartment of the orbiter, which contained electronic units of service systems and scientific equipment, was detected. Calculations showed that AMS “Mars-5” could work no more than three weeks. The last communication session was carried out on February 28, 1974.
Due to a significant reduction of the station’s period of operation in orbit, the “Mars-5” spacecraft mission program was not fulfilled in full. However, despite short period of active existence of the “Mars-5” spacecraft, the following observations and measurements were made during the interplanetary flight and from the ISM orbit with its help:
– during the Earth-Mars flight, measurements of solar wind particle energy, particle composition, temperature and velocity of individual components of the solar plasma were made using ion and electron spectrometers;
– two-frequency radio illumination of the Mars atmosphere was carried out, and estimates of the pressure in the lower atmosphere and the characteristics of the planet’s ionosphere were obtained;
– imaging of the surface of Mars using FTU (108 frames) and telephotometers (4 panoramas) was carried out;
– research of surface and ground properties by their radiation characteristics was carried out, gamma radiation spectra of Martian rocks were obtained;
– infrared radiometer was applied to measure the brightness temperatures of the ground along the satellite flight path;
– several hundred spectra in the range from 2 to 5 microns were obtained using an infrared spectrophotometer to determine the composition of the Mars soil and its structure;
– the water vapor content in the atmosphere of Mars was measured;
– the presence of ozone in the atmosphere of Mars was detected using a photometer;
– detailed data on the temperature of the planet’s upper atmosphere were obtained;
– measurements of interplanetary magnetic fields and the magnetic field of Mars were made.
Thus, despite the difficulties and problems faced during the mission, the “Mars 4” and “Mars 5” satellites were able to transmit new information about the planet and its surrounding space to Earth.