Molniya Orbit
Overview
A Molniya orbit is a type of highly elliptical orbit with an inclination of 63.4 degrees, an argument of perigee of −90 degrees and an orbital period of one half of a sidereal day. Molniya orbits are named after a series of Soviet/Russian Molniya communications satellites which have been using this type of orbit since the mid-1960s.
Characteristics
A Molniya orbit is designed to provide a high latitude ground station with long periods of visibility. It has a high inclination and high eccentricity which results in an orbit that is highly elliptical. The orbit is arranged so that the satellite spends the great majority of its time over a particular area of the Earth, the so-called apogee dwell.
History
The first satellite to use a Molniya orbit was the Molniya 1-01 launched by the Soviet Union on April 23, 1965. The success of this launch and subsequent missions validated the concept of using such an orbit for high-latitude communications, a strategy later adopted by other countries.
Applications
Molniya orbits have been used for various types of applications including communication, navigation, and reconnaissance. The long dwell time at high latitudes makes these orbits useful for providing communication services to high latitude countries which may not be effectively covered by geostationary satellites.
Advantages and Disadvantages
While the Molniya orbit offers certain advantages such as high latitude coverage and long dwell times, it also has certain disadvantages. These include the need for ground stations to track the satellite across the sky and the fact that the satellite spends a significant part of its orbit outside the Earth's geopotentiel well, which exposes it to various space weather phenomena.