SANSA Space Operations FAQ

If you require more information, please revert to the SANSA Space Operations Contact Information page to get hold of a Space Operations representative.

What does SANSA Space Operations do?

The TT&C group provides companies globally with space operations and applications, as well as applied research and development (R&D) and innovation in these areas. The group builds, maintains and hosts antennas and ground stations and supports satellite launches, as well as what happens to the satellites during their lifecycles and in emergencies.
The station at Hartebeesthoek also undertakes orbit transfers and testing, carrier monitoring and remote sensing reception and provides international clients with mission control services and the hosting of ground infrastructure.
Clients throughout Southern Africa benefit from a host of satellite technology services, such as project management; systems and radio frequency engineering; soil testing; civil and electrical, high-voltage alternating current works; procurement, import and logistics; installation and integration of antenna systems; acceptance testing and commissioning and developing procedures for operations and maintenance.

What is NASA?

America's National Aeronautics and Space Administration (NASA) coordinates the country's space exploration activities. We all know about NASA's many significant  deep space probes, including those to the Moon and Mars and currently its Space Shuttle programme that is helping to build the International Space Station. But NASA's pioneering work in space applications and communications satellites has also changed the way we view our home planet and contributed to many important scientific findings.

What is a geostationary orbit?

LEOA geostationary orbit is one in which a satellite orbits the Earth at exactly the same speed as the Earth turns, which positions it in the same spot directly above the Equator to provide uninterrupted coverage of a specific area on Earth.
Satellites move along three types of orbits. Low Earth Orbits(LEO) example: earth observation data, Medium Earth Orbits (MEO) example: navigation; and Geostationary Earth Orbits (GEO) example: communication satellites.

Space junk?

space junk
Space junk are human-made objects that orbit around Earth without any useful purpose because of equipment failure or having becoming obsolete. The objects range from spent rocket stages and defunct satellites to explosion and collision fragments. The orbits of these objects often overlap the trajectories of spacecraft and can therefore pose a potential collision risk.

A piece of 'space junk' - debris from outer space - was found on a farm in South Africa. The piece eventually arrived at Hartebeesthoek where its probable origins were investigated by members of the TT&C team. It can still be seen there today.

What is an apogee rocket?

The apogee is the remotest point of a satellite's non-circular (elliptical) orbit around the Earth. Such a satellite has variable altitude and orbital speed and the point of highest altitude is called apogee. The term also applies to the maximum distance between the satellite and the centre of the Earth, approximately 6,400 km. At apogee, a satellite travels more slowly than at any other point. It is the best time to access a satellite because it is accessible for a comparatively long time. If a directional antenna is used at a ground-based station, it is relatively easy to track the satellite because the position of the antenna does not have to be adjusted quickly or often.

What is an antenna?

A satellite antenna is a dish-shaped, parabolic device  designed to receive micro-waves from  communications satellites that transmit data or broadcasts, such as satellite

The parabolic shape reflects the signal to the focal point of the dish. A feed horn, mounted on a mast from the center of the dish or on tripod legs attached to the edge of the dish, conveys radio waves between the transmitter and/or receiver (transceiver) and the reflector.

Antennas serve as interfaces between uplinks (signals transmitted from Earth) and downlinks (signals transmitted to Earth) and the electronics inside the satellite.

The antennas at Hartebeesthoek have different dish sizes and slew rates and accommodate a number of frequency bands and tracking modes.

What is slew rate?

The slew rate of an antenna is its ability to respond to change. An amplifier with low slew rate will 'lag' in its response to instantaneous power requests, as the power curve cannot be met and the amplifier will not mimic the input curve correctly. If the slew rate is matched to the input it will provide an accurate response and therefore a realistic output. Simply put, in electronics, the slew rate is the maximum rate of change of a signal at any point in a circuit that helps to identify the maximum input frequency of an amplifier before the output becomes distorted. In mechanics, the slew rate is associated with the change in position over time of an object which orbits around the observer.

What is telemetry?

Telemetry is the transmission of radio signals, data, etc. automatically and at a distance, such as between a ground station and an artificial satellite to record information or operate guidance apparatus.

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