The second stratum of the Russian space based communications system consists of 16 Molniya-class spacecraft in highly elliptical, inclined (63 degrees) semi-synchronous orbits. With initial perigees between 450 and 600 km fixed deep in the Southern Hemisphere and apogees near 40,000 km in the Northern Hemisphere. Molniya satellites are synchronized with the Earth's rotation, making two complete revolutions each day (orbital period of 718 minutes). The laws of orbital mechanics dictate that the spacecraft orbital velocity is greatly reduced near apogee, allowing broad visibility of the Northern Hemisphere for periods up to eight hours at a time. By carefully spacing 3-4 Molniya spacecraft, continuous communications can be maintained. This type of orbit was pioneered by the USSR and is particularly suited to high latitude regions which are difficult or impossible to service with geostationary satellites.
The first prototype Molniya satellite was launched in 1964 and to date more than 150 have been deployed. Primarily produced by the Applied Mechanics NPO in Krasnoyarsk, Molniya satellites weigh approximately 1.6 metric tons at launch and stand 4.4 m tall with a base diameter of 1.4 m. Electrical energy is provided by six windmill-type solar panels producing up to 1 kW of power. A liquid propellant attitude control and orbital correction system maintains spacecraft stability and performs orbital maneuvers, although the latter usage is rarely needed. Sun and Earth sensors are used to determine proper spacecraft attitude and antenna pointing.
The 16 operational Molniya satellites are divided into two types and four distinct groups. Eight Molniya 1 satellites are divided into two constellations of four vehicles each. Both constellations consist of four orbital planes spaced 90 degrees apart, but the ascending node of one constellation is shifted 90 degrees from the other, i.e., the Eastern Hemisphere ascending nodes are approximately 65 degrees and 155 degrees E, respectively. Although the system supports the Russian Orbita Television network, a principal function is to service government and military communications traffic via a single 40 W. 1.0/0.8 GHz transponder. Since Molniya 1-75 in 1989, all Molniya 1 spacecraft have been launched from the Plesetsk Cosmodome by the Molniya booster.
Half of the Molniya 1 constellation was replenished during 1993-1994. In 1993 Molniya's 1-85, 1-86, and 1-87 replaced Molniya's 1-78, 1-81, and 1-77, respectively. The sole Molniya 1 launch of 1994, Molniya 188, relieved Molniya 1-82 of its duties. At the end of 1994, these four new spacecraft were working with Molniya's 1-79, 1-80, 1-83, and 184. The oldest spacecraft in the constellation, Molniya 1-79, had just turned four years old in November, 1994. All currently operational Molniya 1 spacecraft are of the Molniya 1T class which was introduced in the 1970's.
The first Molniya 3 spacecraft appeared in 1974, primarily to support civil communications (domestic and international), with a slightly enhanced electrical power system and a communications payload of three 6/4 GHz transponders with power outputs of 40 W or 80 W. Although the launch requirements are the same for Molniya 1 and Molnlya 3 and although Molniya 1 satellites have been launched from either Plesetsk or Baikonur, Molniya 3 spacecraft have only originated from Plesetsk. Until 1983 the Molniya 3 constellation consisted of only four satellites which were essentially co-located with four Molniya 1 satellites. When the Molniya 3 system was expanded to eight vehicles in 1983-1985, the new additions inaugurated the 155 degrees E ascending node geometry. After the restructuring of the Molniya 1 constellations in 1991, the Molniya 1 and Molniya 3 systems are essentially the same from a deployment perspective and to some extent provide an inherent backup capability.
On the average Molniya 3 spacecraft are replaced slightly less frequently than their Molniya 1 cousins, representing an apparent longer operational life by 5-6 months. Two Molniya 3 spacecraft were launched in 1993, Molniya 3-44 and Molniya 3-45, to replace Molniya's 3-41 and 3-37, respectively. Like the Molniya 1 constellation, the Molniya 3 network received only one new number in 1994: Molniya 3-46 to replace Molniya 3-40. Thus, at the end of 1994 the Molniya 3 constellation consisted of these three new spacecraft as well as five older spacecraft (Molniya's 3-36, 3-38, 3-39, 3-42, and 3-43). The oldest spacecraft was five years old.
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