Geosynchronous Satellites

An example of satellites in a geosynchronous orbit over North America is the Sirius constellation. Their 2325 MHz signals have been received in the UK - Image credit Sirius XM Holdings Inc.

An example of satellites in a geosynchronous orbit over North America is the Sirius constellation. Their 2325 MHz signals have been received in the UK – Image credit Sirius XM Holdings Inc.

Wikipedia describesgeosynchronous orbit (GSO) as an orbit around the Earth with an orbital period of one sidereal day, intentionally matching the Earth’s sidereal rotation period (approximately 23 hours 56 minutes and 4 seconds).

The synchronization of rotation and orbital period means that, for an observer on the surface of the Earth, an object in geosynchronous orbit returns to exactly the same position in the sky after a period of one sidereal day. Over the course of a day, the object’s position in the sky traces out a path, typically in the form of an analemma, whose precise characteristics depend on the orbit’s inclination and eccentricity.

Examples of satellites in geosynchronous orbits are the Sirius constellation and the National Oceanic and Atmospheric Administration’s (NOAA) GOES-11, GOES-13, MSG-2, Meteosat-7 and MTSAT-2. Geostationary is a special case of a geosynchronous orbit, see below.

AMSAT-NA announced in late April 2015 that, if all goes according to plan, an Amateur Radio payload will go into space on a geosynchronous satellite planned for launch in 2017.

The ARRL report that AMSAT-NA has accepted the opportunity to be a “hosted payload” on a spacecraft that Millennium Space Systems (MSS) of El Segundo, California, is under contract to design, launch, and operate for the US government. The satellite’s potential footprint could extend over the US from the Mid-Pacific to Africa.

The amateur radio payload will comprise a Software Defined Transponder capable of supporting many different modes, including analog SSB. The uplink will be in the 5830-5840 MHz band and the downlink in 10450-10500 MHz. The Amateur Radio payload must be delivered for testing and integration by spring 2016.

AMSAT-NA Vice President-Engineering Jerry Buxton, N0JY,  explained that the geosynchronous footprint will not be absolutely fixed; some variation may require some up/down movement of the user’s dish at certain times — although not continuously. He said AMSAT-NA is working on this issue in terms of what to recommend for ground stations, but that even in the worst case, a user with a fixed antenna would still be able to enjoy several hours of access each day.

Further information on the North American geosynchronous satellite

Geostationary Orbit

A special case of geosynchronous orbit is the Geostationary Earth Orbit (GEO) which is a circular geosynchronous orbit at zero inclination (that is, directly above the equator). A satellite in a geostationary orbit appears stationary, always at the same point in the sky, to ground observers. This means the ground station antennas do not have to move, but can be pointed permanently at the fixed location in the sky where the satellite appears.

Es'hail-2 coverage area

Es’hail 2 coverage area

Qatar’s Es’hail 2 geostationary satellite will carry amateur radio transponders that could link amateurs from Brazil to India. The satellite is expected to launch by the end of 2016 and will be positioned at 25.5 degrees East.

Es’hail 2 will carry two “Phase 4” amateur radio transponders operating in the 2400 MHz and 10450 MHz bands. A 250 kHz bandwidth linear transponder intended for conventional analogue operations and an 8 MHz bandwidth transponder for experimental digital modulation schemes and DVB amateur television.

Linear transponder
 2400.050 -  2400.300 MHz Uplink
10489.550 - 10489.800 MHz Downlink
Wideband digital transponder
 2401.500 -  2409.500 MHz Uplink
10491.000 - 10499.000 MHz Downlink

Further information on the Es’hail 2 satellite

What Is a Geosynchronous Orbit?
NASA Three classes of orbit
AMSAT-NA Opportunity for Rideshare to Geosynchronous Orbit