Molniya-type orbit
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Molniya-type orbit. Image credit: Alaska Aerospace
Development Corp. |
A very elliptical, 12-hour orbit, with a high apogee
in the northern hemisphere and a relatively low perigee
in the southern hemisphere. Soviet Molniyas were
the first to be placed in such paths. Since satellites in Molniya-type orbits
move very slowly at apogee, they appear to hover for hours at a time over
northern latitudes enabling them to relay for long periods in these locations.
In addition, they can see two-thirds of the globe during a complete circuit
– much more than a satellite in geosynchronous
orbit. The disadvantage is that the sending/receiving dish on the ground
must track the satellite, whereas for a geosynchronous satellite a fixed
dish can be used. Various American military satellites, including those
in the SDS (Satellite Data System) series, have
been placed in Molniya-type orbits to spy on the Soviet Union and neighboring
territories.
Related category
• CELESTIAL
MECHANICS
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