The ESA/EUMETSAT Metop satellites, Europe’s first operational meteorological satellites in polar orbit, will carry a GPS Receiver for Atmospheric Sounding (GRAS). This instrument will deliver data from which atmospheric temperature, pressure and humidity profiles, based on the radio occultations of the GPS signals, may be derived.

The GRAS Ground Support Network (GSN), implemented and to be operated by the Navigation Support Office at ESOC, will provide support data to the MetOp ground segment at EUMETSAT, to process the sounding data into near-realtime atmospheric products, and to perform MetOp precise orbit determination. It will provide, among others, precise GPS orbits and ground and satellite clock offsets, with stringent requirements on availability and timeliness.

The first Metop launch is expected in June 2006, when the GSN system will become operational.

This project presents an example of the application of the know-how and experience accumulated over many years of active participation in the IGS.

Formosat3 / COSMIC is a joint Taiwan - US mission for weather, climate, space weather, and geodetic research. The COSMIC mission was successfully launched into a circular ~ 500 km low-Earth orbit (LEO) from Vandenberg Air Force Base, California, at 0140 UTC on 15 April 2006. Six identical microsatellites, each carrying an advanced GPS radio occultation receiver and two other ionospheric instruments, were deployed successfully about 20 minutes after launch. The satellites and payloads are now going through check-out and testing. After the check-out period operational processing of the data from the constellation will begin. One of the main goals of COSMIC is to demonstrate the value of radio occultation data for operational weather forecasting. To achieve this goal near-real time processing is required to deliver atmospheric profiles as quickly as possible to operational weather centers world-wide. Satellite data will be dumped from LEO once every 100-minute orbit. These data will be received within a few minutes of the orbit-to-ground dump at the COSMIC Data Analysis and Archive Center (CDAAC) and at the Taiwan Analysis Center for COSMIC (TACC). There they are processed together with ground-based fiducial data, IGS orbit products, predicted weather models, and the 50-Hz GPS data bits. This presentation will provide a status update of the mission, discuss the data analysis plans with emphasis on the importance of real-time data and IGS products, describe how the data and products will be made available to the community, and present some early mission example results.

Since the boom in mobile telecommunications allows Internet access for anyone anywhere at any time, this medium has also become an alternative method for transmitting GNSS data streams. Since 3 years the IGS (International GNSS Service) Real-Time Working Group exploits the options offered by the World Wide Web to disseminate raw observation data of a subset of stations of the IGS network as well as ephemeris and surface meteorological data. This observation data can be used for a real time integrity monitoring of the GNSS-Broadcast orbits as well as for the IGS predicted orbits (Ultra Rapid Orbits). These satellite ephemeris demonstrate significantly higher accuracy (~10 cm) than the broadcast orbits (~ 2m), but carry the risk of individual, recurring outliers. This poster highlights the functionality of a software-tool for integrity monitoring. The program “RTR- Control” has been developed at the Institute of Geodesy and Geophysics, TU-Vienna, supported by the IGS Real-Time Working Group. The input data for the Program are code pseudoranges measured at any permanent station in the global RTIGS network (received via RTIGS- datastream) and theoretical pseudoranges calculated on the basis of precise, predicted satellite orbits (“RTR- control” automatically loads the most recent IGU- orbits). This information can be used for the diagnose of incorrectly predicted satellite- orbits and clocks as well as for the detection of multi-path distorted pseudoranges. Operated in processing facilities of RTK station networks “RTR- Control” prevents that observation data of mismodeled satellites is further used for the calculation of range-corrections which are passed to the RTK users within the network. Thus the user group interested in a rigorous integrity monitoring comprises on the one hand IGS itself to qualify the issued orbital data and on and the other hand authorities and companies operating such Real Time GNSS station networks.

ESOC has been operating most of the stations of the ESA/ESOC GPS tracking network in real time mode since 2003. So far, GPS measurements have been streamed from the remote sites to ESOC using internally developed tools and protocols. Data from some of the stations have been shared with the IGS Real Time Network since 2004. ESOC has been also involved in the development of a system for Real Time Navigation (RETINA). This is based on a sequential filter for the real time processing of the GPS and GLONASS observations and includes specially designed and built infrastructure elements for streaming the data and archiving and retrieving data and results.

In 2006 the IGS UDPrelay software has been installed at ESOC to get data from the IGS network and also to deliver the complete ESA/ESOC network to the IGS Real Time Working Group. An assessment of the strategy and results of the developed applications is made using the data from different sources including the current IGS Real Time Network.