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The Earth completes half a rotation in twelve hours, so the apogees of successive Molniya orbits will alternate between one half of the northern hemisphere and the other. For the original Molniya orbit, the apogees were placed over Russia and North America, but by changing the right ascension of the ascending node this can be varied. [19]
Tundra and Molniya orbits are used to provide high-latitude users with higher elevation angles than a geostationary orbit.This is desirable as broadcasting to these latitudes from a geostationary orbit (above the Earth's equator) requires considerable power due to the low elevation angles, and the extra distance and atmospheric attenuation that comes with it.
A highly elliptical orbit (HEO) is an elliptic orbit with high eccentricity, usually referring to one around Earth.Examples of inclined HEO orbits include Molniya orbits, named after the Molniya Soviet communication satellites which used them, and Tundra orbits.
They had a lifespan of approximately 1.5 years, as their orbits were disrupted by perturbations, as well as deteriorating solar arrays and they had to be constantly replaced. [15] [11] [16] By the 1970s, the Molniya 1 series (and the upgrade Molniya 1T) was mostly used for military communications, with civilian communications moving to Molniya ...
"All geostationary orbits must be geosynchronous, but not all geosynchronous orbits are geostationary." [8] Tundra orbit: A synchronous but highly elliptic orbit with significant inclination (typically close to 63.4°) and orbital period of one sidereal day (23 hours, 56 minutes for the Earth).
If the argument of perigee is non-zero, however, the satellite will behave differently in the northern and southern hemispheres. The Molniya orbit, with an argument of perigee near −90°, is an example of such a case. In a Molniya orbit, apogee occurs at a high latitude (63°), and the orbit is highly eccentric (e = 0.72). This causes the ...
The US-K and US-KS satellites developed under the Oko program were the first generation of Soviet early warning satellites. 86 US-K satellites were placed in a Molniya orbit between 1972 and 2010 and 7 US-KS satellites, of a very similar design, were placed in geostationary orbit between 1975 and 1997, the system becoming operational in 1980.
Space debris at geostationary orbits typically has a lower collision speed than at low Earth orbit (LEO) since all GEO satellites orbit in the same plane, altitude and speed; however, the presence of satellites in eccentric orbits allows for collisions at up to 4 km/s (14,400 km/h; 8,900 mph). Although a collision is comparatively unlikely, GEO ...