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Satellite orbital parameters and outline satellite communication principles
Published in L. Tetley, D. Calcutt, Understanding GMDSS, 2012
The main disadvantage of the GEO orbit is that its altitude is very large and a considerable amount of thrust is necessary to lift a payload into orbit. In practice, an easterly rocket launch is used in order to take advantage of the earth’s velocity and a point as close to the equator as possible is used as the launch site. Earth velocity is greatest at the equator. The satellite is first launched into a highly elliptical orbit whose point of apogee (the furthest point from the earth surface) is equal to the altitude required for a geostationary orbit. When the satellite reaches its point of apogee, an ‘apogee motor’ is fired to cause the satellite to be pushed into the new orbit.
Satellites
Published in Mohammad Razani, Commercial Space Technologies and Applications, 2018
Some of the less commonly used orbits are as follows: Polar Orbit (PO)This orbit refers to spacecraft at near-polar inclination and an altitude of 700–800 km. The satellite passes over the equator and each latitude on the Earth’s surface at the same local time each day, meaning that the satellite is overhead at essentially the same time throughout all seasons of the year. This feature enables collection of data at regular intervals and consistent times, which is especially useful for making long-term comparisons.Highly Elliptical Orbits (HEOs)These orbits are characterized by a relatively low altitude perigee and an extremely high-altitude apogee. These extremely elongated orbits have the advantage of long dwell times at a point in the sky; visibility near apogee can exceed 12 hours. These elliptical orbits are useful for communications satellites.Geo Transfer Orbit (GTO)This is an elliptical orbit of the Earth, with the perigee in LEO and the apogee in GEO. This orbit is generally a transfer path after launch to LEO by launch vehicles carrying a payload to GEO.
Satellite delivery of high-accuracy GNSS precise point positioning service: an overview for Australia
Published in Journal of Spatial Science, 2019
A HEO orbit is elliptical with low-altitude perigee and a high-altitude apogee. This means that a HEO satellite moves slower when it is further away from the Earth. The HEO satellite has the advantage of spending about two-thirds of its orbital period near apogee. The visibility of the satellite in apogee can exceed 12 h, thereby providing coverage over its operational area for an extended period of the time.