Galileo: ESA Operations Centre contributes valuable expertise
In addition to mission control expertise, ESA's Space Operations Centre is working diligently to ensure the Galileo system will be reliable and fully functional for innovative navigation applications.
Galileo, a global satellite navigation system, is being developed through a joint initiative of ESA and the European Union. Once in routine operation, Galileo will provide an unprecedented level of navigational accuracy and is expected to enable numerous new commercial applications (see links at right).
With decades of experience in complex spacecraft operations, teams at ESA's Space Operations Centre (ESOC) are already providing valuable and in some cases unique expertise for the Galileo System Testbed, the future in-orbit validation (IOV) phase and the establishment of a global geo reference frame.
IOV will start with the 28 December 2005 launch of GIOVE-A, the first of two test satellites initially aimed at securing Galileo frequency requests, validating new technologies and characterising the medium Earth orbit (MEO) environment. By end-2008, the second part of IOV will begin with the launch of four more Galileo satellites, marking the start of significant ESOC contributions.
Major LEOP commitment for IOV
ESOC, together with France's space organisation CNES, will assume key mission control responsibilities for the 2008 IOV activities, including flight control during the critical, 1-month-long launch and early orbit phase (LEOP) period for two of the four satellites; CNES will control the other two.
This is a significant contribution to getting Galileo off the ground and will be a major commitment for ESOC in view of the Galileo satellites' new MEO orbital profile and spacecraft bus.
'Network of Centres' shares expertise, resources across Europe
Furthermore, the cooperation with CNES is a major step in the evolution of Europe's 'Network of Centres' (NoC), a cooperative grouping of mission control facilities including ESA and space centres in France, Germany, Spain, UK and Italy. The NoC concept aims to share expertise, facilities and resources and avoid duplication, thus strengthening Europe's overall space operations capability.
More than just an administrative grouping, NoC cooperation will entail the future integration of procedures, mission control systems and communications networks and is a significant activity that will support Galileo and other key missions.
"LEOP cooperation during IOV is the first major Galileo activity involving CNES and ESOC and is a remarkable example of technical cooperation," says Dr Uwe Feucht, a flight dynamics specialist at ESOC and one of the planners helping develop the Galileo project within ESA.
ESOC is already actively cooperating with other NoC partners. In 2005, ESOC started using the Weilheim ground station operated by DLR, the German Aerospace Centre, to help track SMART-1 and, in 2006, an ESA ground tracking station will reciprocally support the German TerraSAR-X mission.
Galileo sees early ESOC involvement
ESOC has been involved with Galileo since early days, contributing technical studies, accumulated knowledge and advice on Galileo constellation operations. Moreover, ESOC scientists are already contributing valuable expertise related to the fundamental science behind the navigation services to be provided by Galileo.
In the first of two major areas of ongoing support, ESOC has established a Service Level Agreement with the Galileo project at ESA's Space Research and Technology Centre (ESTEC), in Noordwijk, the Netherlands, to provide consulting and developmental services. The focus of this work is on the preliminary design of the Galileo Mission System (GMS), the core navigation system that will take signals from the 30 Galileo satellites, combine them with data from up to 40 ground stations and produce the final, highly accurate and time-corrected navigation data to end users. Work is also being undertaken on the Galileo Control System (GCS), which will ultimately control the satellites.
Part of this includes defining the reference frame that the system will use, similar to the familiar latitude and longitude reference frame used by generations of cartographers for map making.
"It's important that the signals generated by the GMS be delivered using a well-defined and very accurate reference frame," says Prof. John Dow, head of ESOC's Navigation Office and one of the world's leading experts in GPS science.
"It's not good if the system issues position information based on very accurate Galileo satellite signals, but the frame against which those positions are measured is uncertain," he adds.
ESOC is also providing third-party support as a contractor to the Galileo Joint Undertaking, the organisation established by the European Commission and ESA to manage the development phase of the Galileo Programme.
ESOC supports Galileo System Testbed
In 2006, ESOC will continue this work as one of only two centres of networking expertise supporting the Galileo System Testbed (GSTB), version 2 (the other is the GeoForschungsZentrum, in Potsdam, Germany).
GSTB-V2 hardware and software will allow engineers to validate Galileo-specific control algorithms, such as clock adjustments, and procedures for predicting individual satellite orbits, before the full system goes into operation. GSTB-V2 will include a test satellite and will allow critical technologies to be tested in MEO.
ESOC will deliver, install and operate specialised GPS signal receivers and antennas at seven ground stations worldwide, including five that are part of ESA's ESTRACK tracking station network, which is controlled from ESOC.
In addition, ESOC and a grouping of five other European technology centres are developing the Galileo Geodetic Service Provision Prototype, a framework system that will help ensure that Galileo's fundamental navigational services are accurate and well-referenced. One practical outcome of this work will be the highly accurate determination of the location of the network of ground support stations that will be built as part of Galileo.
"We'll need to know the ground station locations to plus or minus 3 centimetres for the Galileo system to provide end-user positions accurate to within a few metres," says Prof. Dow.
To support ongoing navigation science and engineering developmental work, ESOC recently established a new Navigation Facility (NF) as part of the centre's Navigation Office. When formally inaugurated, the NF will host test systems and workstations and significantly boost ESOC's ability to contribute to Galileo and other navigation projects.
"It's absolutely necessary for ESOC to have this facility," says Dr Feucht, adding: "ESOC is working on creating the framework for future third-party application development for Galileo. This has tremendous commercial importance."
