(Lightning), a series of Soviet-built artificial earth satellites. The series consists of two types (Molniia 1 and Molniia 2), which are used for relaying television programs and for longdistance radio communications by telephone, telegraph, and phototelegraph. The satellites are part of the Orbit long-distance radio space communications system. Satellites of the Molniia 1 type have been used systematically since 1965; they have onboard relay transmitters operating in the decimeter wavelength band (frequencies of 800 to 1000 megahertz). Launches of satellites of the Molniia 2 type began in 1971, in accordance with a program for further development of satellite communications systems. They have on-board relay transmitters operating in the centimeter wavelength band.

The Molniia satellites travel along elliptic highly eccentric synchronous orbits with an apogee above the northern hemisphere. The apogee is about 40,000 km, the perigee is 460–630 km, the inclination relative to the plane of the equator is 62.8° -65.5°, and the orbital period is about 12 hours. Such orbits provide for reception of satellite transmissions for periods of 8–10 hours per day for points in the USSR or other countries in the northern hemisphere. A system consisting of three satellites in such orbits is capable of maintaining communications around the clock.

After launch, a Molniia satellite is first inserted into a low satellite orbit together with the last stage of its booster rocket. The rocket motor of the last booster stage is then fired, imparting to the satellite the additional velocity needed to insert it into its final orbit. The Molniia 1 satellite is about 4.4 m long; the diameter of its shell is 1.4 m, and the spread of the panels of the solar batteries is 8.6 m. Most of the apparatus and equipment is located in a vacuum-tight housing. An attitude-control system continuously orients the solar batteries toward the sun and one of the highly directional parabolic antennas toward the earth. An orbital correction system serves to adjust the satellite’s path relative to points on earth and to change the communications schedule.

The power supply of the Molniia satellites consists of solar batteries arranged in six flat panels, which open after separation from the booster rocket. Thermal regulation is provided by an active system with a liquid heat-transfer loop and external radiators. Measurement of orbital parameters, radio reception of instructions transmitted from earth, and transmission of telemetry data for monitoring the operation of on-board systems are handled by an integrated complex of radio aids. Control of transmitting schedules may be automatic (according to instructions from the on-board timing logical unit), or it may be provided by signals transmitted directly through a radio command line.

The on-board equipment provides simultaneous relaying of television programs and the accompanying sound or multichannel telephony with the possibility of secondary multiplexing of channels by voice telegraphy and phototelegraphy. Relay transmission is done through a highly directional parabolic antenna (to provide reserve capacity, there are two such antennas). The high output power of the transmitter (up to 40 watts) and the directivity of the on-board antennas make possible the use at earth stations of very simple antennas (with diameters of 12–15 m) and of parametric amplifiers, the simplest kind of low-noise receiver.

The first Molniia 1 satellite was launched Apr. 23, 1965. The launch of the second Molniia 1 satellite on Oct. 14, 1965, began experimental operation of long-distance two-way television and telephone-telegraph communications. The third Molniia 1 satellite was launched Apr. 25, 1966. This satellite was used not only for communications and television broadcasting within the USSR but also for an exchange of television programs between the USSR and France, arranged within the framework of international cooperation; the plan included color transmissions using the SECAM system. In May 1966, the on-board apparatus of the Molniia 1 satellite began transmitting images of earth taken from altitudes of 30,000 m and higher with the purpose of obtaining data on the global distribution of the cloud cover. In 1967 a color television image of earth as viewed from outer space was obtained. By Jan. 1, 1974, 34 artificial earth satellites of the Molniia type had been launched. They provided regular communications and television broadcasting in the USSR and other countries.