FedSat

Payload Experiments

GPS Receiver
The GPS, Global Positioning System, is an American network of satellites which transmit radio signals containing time and orbit-position codes. GPS receivers decode the signals, and by comparing signals of up to 4 satellites with known positions, they can derive their own locations by triangulation. The system serves many scientific and civilian applications.

FedSat's dual-frequency GPS receiver was supplied under a collaborative agreement between NASA and CSIRO.

On-board satellite GPS receivers allow accurate measurement of the satellite's position. This information will support the CRCSS study into methods of precisely determining satellite orbits. This includes metre-level accuracy for satellite operations control; centimetre-level accuracy for mission-data processing; and position determination using multiple antennas.

The Precise Orbit Determination study includes a section on GPS multipath errors. On the ground, reflections of the GPS signal from the landscape give conflicting information to the GPS receiver, causing errors in position-calculation. Investigating the multipath errors on FedSat's simple shape will help establish principles for studying the more complex reflections on the ground. This will help eliminate multipath as a source of GPS position errors.

The FedSat GPS receiver also supports space-science studies of the ionosphere, an electrically-charged layer of the atmosphere. GPS satellites are much higher than FedSat's orbit, so FedSat can detect GPS signals that have travelled through the ionosphere. Interpretation of the GPS signals can illustrate the dynamics of that region. By taking GPS slices of the ionosphere, it's possible to build up a 3D moving picture of the ionosphere. The CRCSS is the only organisation studying the little-known southern region of the ionosphere in this way.

Finally, the GPS receiver provides timing data for other FedSat payloads.

NewMag

The NewMag magnetometer is a very sensitive and rapid-sampling device for measuring the strength of the Earth's magnetic field. Earth is like a big bar magnet, with magnetic field lines emerging from the poles and far out into space. FedSat's polar orbit crosses all these lines, so NewMag can effectively gain a window into the whole magnetosphere region. NewMag can also measure vibrations simultaneously with ground- based magnetometers, so investigating the dynamics of the magnetosphere (changes in it shape due to variations in the Sun), and study magnetospheric wave-propagation.

Earlier research has shown this is a complex region, with variations in the solar wind having a huge effect on the magnetosphere and space weather. This can also affect ground infrastructure. The CRCSS study will help provide early warning systems against solar- magnetic events and space weather events, which damage satellites.

NewMag is mounted away from the main satellite on a 2.5 m extendable boom, similar to the one used on South Africa's UNSAT satellite. The boom was manufactured by Stellenbosch University, and its purpose is to avoid magnetic interference from the satellite itself.

The CRCSS and University of California, Los Angeles USA, built NewMag to the CRCSS design.

High performance computing experiment
The FedSat high performance computing payload is the world's first use of reconfigurable computing technology in space. Reconfigurable computers permit change of their physical circuits via software control; new physical circuits can be installed into a reconfigurable computer module by remote command. For spacecraft, this technology means that satellites can be rewired without having to retrieve them.

The FedSat payload established the principles of working with these devices in space, including their susceptibility to radiation. This study is of great interest to the international community, and the CRCSS hopes to build in our experience with FedSat in order to be able to build better, more reliable satellite equipment in the future.

NASA and Johns Hopkins University, USA, collaborated with the CRCSS on the research involved in the payload.
Reconfigurable computing could open up new realms of spacecraft adaptability, including re-use of old spacecraft.

Ka-band transponder
The FedSat Ka-band transponder is designed to handle the new experimental high- frequency and high-capacity Ka part of the radio spectrum. The transponder processes signals to and from the ground in the frequency band. The transponder incorporates novel CRCSS-designed Gallium Arsenide monolithic microwave circuits. FedSat is the first microsatellite capable of operating in the Ka band. This ability is due to the superior efficiency of the on-board equipment and the ground station, in Sydney.

The FedSat Ka-band transponder communicates with the CRCSS-designed Ka-band ground station. Together they will lead to new Australian-developed remote area communications applications. The CRCSS will use FedSat and its ground station to study a range of Ka-related issues.

The Ka-band system has been built entirely by the CRCSS.

Baseband processor
The baseband processor provides on-board computer processing of the Ka- and UHF- band payloads. It was designed and built by the CRCSS, to operate as a low power single modem with flexible operation. It will also provide the channel for satellite operations commands.

Students will use the FedSat baseband processor to study and develop a variety of telecommunications protocols, including ground-satellite links and inter-satellite links.

UHF communications payload
The Ultra High Frequency band payload incorporates a new type of packet data service for Low Earth Orbiting satellites to obtain environmental data and for store-and-forward messaging services.
For example, ocean buoys may transmit their data using this means to orbiting satellites, which are retransmitted back to the lab for analysis.

This payload will facilitate high speed transmission via a special multiple access scheme and error-control techniques.
The payload was fully designed and built by the CRCSS. Clones of the CRCSS system will be flown on South Korean and Singaporean satellites over the next few years.

CD ROM
FedSat carries a compact disc mounted on the side, containing the audio messages members of the Australian public recorded to go into space from March to August 2000. The disc also contains a copy of the song From Little Things, Big Things Grow, by Paul Kelly, with kind permission of the writers (Kev Carmody/Paul Kelly) and publishers (Larrikin Music, Mushroom Records).

The CD will orbit Earth as long as FedSat does, about a century, so the recorded messages are a time capsule about life in Australia in 2000.

The FedSat compact disc is made of nickel and is a mastering disk similar to those used to manufacture the normal commercial CDs. The CD is titled "Leap of Faith" and represents the CRCSS' aspirations for a more active space presence by Australians in the future. It is Australia's first long-term cultural artefact in space.