Editor's note: This page is no longer being updated, but will be preserved as a record.
'Payload' was originally a seafaring term for revenue-producing cargo on a ship. In space terms it refers to those elements of the spacecraft specifically dedicated to producing mission data and then relaying that data back to Earth.
Microwave radio signals serve as the backbone of communication between space systems and the ground. Whether on an active or passive basis, radio signals also function as a remote sensing tool for scientific observation and environmental monitoring on space science and Earth observation missions. And space-based radio navigation signals returned back to Earth form the basis of increasingly indispensable sat-nav systems.
Payload Systems deals with not only the specific radio technologies and systems aboard a spacecraft tasked with delivering mission objectives, but also the supporting ground equipment and telecommunication systems through which spacecraft payloads are controlled and results communicated to mission control.
On the spacecraft side this incorporates the definition and design of scientific and remote sensing instruments operating on the radio spectrum up to microwave or millimetre-wave frequencies as well as dedicated communication payloads, such as those flown on telecommunication satellites.
It also includes devices capable of transmitting, receiving or utilising radio signals from current and future navigation systems – the current GPS and GLONASS satellite constellations, Europe's land-based EGNOS overlay signal and the forthcoming Galileo satellite navigation system.
In terms of the Earth-based 'ground segment', Payload Systems covers all aspects of telemetry, tracking and telecommand (TT&C), including signal coding and modulation and radio frequency equipment and subsystems.
Whether they be space science, Earth observation or telecom satellites, our space-based infrastructure is constantly growing more sophisticated and expected to handle and communicate ever larger amounts of data.
New technologies and techniques are required to respond to this steady increase in data rates, with signal coding and modulation for more efficient use of the spectrum and transponders and amplifiers establishing reliable radio links across thousands of kilometres of space.
Specialised expertise is also required in support of the design and evaluation of new types of microwave and millimetre-wave-based science and Earth observation instruments such as synthetic aperture radar (SAR), radar altimeters and radiometers. Specialised analysis tools and software are also developed in order to evaluate their performance.
Most of all, the availability of space-based radio navigation is well on its way to revolutionising terrestrial transportation and related aspects of everyday life. When Europe's Galileo satellite navigation system is completed in the next decade it will enable numerous life-critical applications such as air traffic control, so its accuracy and reliability need to be assured.
Payload Systems involves the technical development of new generations of specialised radio-based instrumentation and communication systems, as well as the industrial development of new technologies and subsystems.
On the instrument side that implies new types of payload capable of increased performance while reducing cost, employing radio signals to return data about various important aspects of the Earth environment, from surface characteristics to atmospheric patterns.
Examples of 'active' radio sensors include synthetic aperture radar (SAR), which fires a radar beam down to Earth and records signal bounce back while 'passive' sensors include radiometers which detect microwaves radiating out from Earth's surface or atmosphere.
The innovations involved on the signal side include novel algorithms for signal coding, modulation and processing as well as the design of telecom system architectures and methodologies, plus networking techniques related to radio resource and network management. Security techniques for telecom networking is also important – covering means of assuring secure end-to-end communications – and the physical equipment required, including user terminals.
Another crucial area of activity is radio navigation systems, where work includes the development of ground receivers, the positioning and accuracy algorithms that underpin them and, increasingly, ways of integrating them with other telecommunication systems to further increase their reliability and utility.
And onboard receivers should not be overlooked: an increasing number of satellites already employ radio navigation systems as a tool for highly-accurate positioning. This application will only become more important once formation flying satellite constellations begin to enter service.
Future enabling technologies for radio frequency systems include more compact but higher power radio frequency systems, measurement and calibration systems and also enhanced accuracy time and frequency technologies such as more stable atomic clocks – among the most likely components to fail in current spacecraft.
The work of Payload Systems includes the definition and analysis of new technologies and new architectural concepts for future Telecom, Navigation and Earth observing payloads.
This includes the ESA-fostered Alphabus class of telecommunication satellites with enhanced onboard power and data handling. Payload Systems also has responsibility for the design and deployment of ESA's EGNOS and Galileo satellite navigation systems.
The availability of onboard radio navigation receivers has influenced the design of multiple missions, such as the GOCE and LISA Pathfinder spacecraft which both require extremely accurate positioning control. That is equally true of the forthcoming Proba-3 mission, a two-satellite technology demonstrator designed to establish the concept of highly-controllable formation flying in space.
Payload Systems also enables science instruments such as the radio-based CONSERT and MIRO sensors aboard the Rosetta mission, designed to return information about cometary surfaces and surrounding dust, and the radiometer-based Planck mission, mapping variations in the Cosmic Microwave Background to a greater accuracy than ever before.
In addition Payload Systems has supported the development of novel Earth observing instruments for future missions including the radiometer measuring both soil moisture on land and salinity levels in the ocean on the SMOS mission, the atmospheric radar and radiometer flown aboard EarthCARE and the next-generation SAR instrument destined for the Sentinel-1 radar satellite.
Abonnez-vous à notre newsletter pour recevoir les dernières actualités, les mises à jour des missions et des informations exclusives directement dans votre boîte de réception. Soyez parmi les premiers informés de nos prochains projets et avancées.
