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The International Laser Ranging Service (ILRS) was established in September 1998 as a service within the IAG to support programs in geodetic, geophysical, and lunar research activities and to provide data products to the International Earth Rotation and Reference Systems Service (IERS) in support of its prime objectives. The ILRS develops the standards and specifications necessary for product consistency and the priorities and tracking strategies required to maximize network efficiency. This network consists of more than forty SLR stations, routinely tracking nearly thirty retroreflector-equipped satellites and the Moon in support of user needs. The Service collects, merges, analyzes, archives and distributes satellite and lunar laser ranging data to satisfy a variety of scientific, engineering, and operational needs and encourages the application of new technologies to enhance the quality, quantity, and cost effectiveness of its data products. The ILRS works with the global network to improve station performance, new satellite missions in the design and building of retroreflector targets to maximize data quality and quantity, and science programs to optimize scientific data yield. The ILRS Central Bureau maintains a comprehensive web site (http://ilrs.gsfc.nasa.gov) as the primary vehicle for the distribution of information within the ILRS community. During the last few years, the ILRS has addressed very important challenges: (1) Data from the network stations are now submitted hourly and made available immediately through the data centers, (2) Tracking on low orbit satellites has been significantly improved through the sub-daily issuance of predictions, drag functions, and the real-time exchange of time biases, (3) Analysis products are now submitted in SINEX format for compatibility with the other space geodesy techniques, (4) The Analysis Working Group is now generating an operational station position and Earth Orientation Parameter (EOP) product, and (5) SLR has significantly increased its participation in the International Terrestrial Reference Frame (ITRF) activity. [ABSTRACT FROM AUTHOR]

Properly designed and structured ground-based geodetic networks materialize the reference systems to support sub-mm global change measurements over space, time and evolving technologies. Over this past year, the Ground Networks and Communications Working Group (GN&C WG) has been organized under the Global Geodetic Observing System (GGOS) to work with the IAG measurement services (the IGS, ILRS, IVS, IDS and IGFS) to develop a strategy for building, integrating, and maintaining the fundamental network of instruments and supporting infrastructure in a sustainable way to satisfy the long-term (10-20 year) requirements identified by the GGOS Science Council. Activities of this Working Group include the investigation of the status quo and the development of a plan for full network integration to support improvements in terrestrial reference frame establishment and maintenance, Earth orientation and gravity field monitoring, precision orbit determination, and other geodetic and gravimetric applications required for the long-term observation of global change. This integration process includes the development of a network of fundamental stations with as many co-located techniques as possible, with precisely determined intersystem vectors. This network would exploit the strengths of each technique and minimize the weaknesses where possible. [ABSTRACT FROM AUTHOR]

The combination of space-geodetic techniques is considered as an important tool for improving the accuracy and consistency of the resulting geodetic products. For GNSS satellites, tracking data is regularly collected by both the microwave and the SLR observation technique. In this study, we investigate the impact of combined analysis of microwave and SLR observations on precise orbit determination of GNSS satellites. Combined orbits are generated for the two GPS satellites equipped with Laser retroreflector arrays and for three GLONASS satellites that are currently observed by the 1LRS network. The combination is done at the observation level, implying that all parameters common to both techniques are derived from both observation types. Several experimental orbits are determined using different observation weights. As the well-known 5 cm-bias between SLR measurements and GPS microwave orbits is unexplained, SLR range biases as well as satellite retroreflector offsets are estimated in addition to the orbital parameters. The different orbit solutions are then compared in order to determine whether and to which extent the SLR measurements influence a microwave orbit primarily derived from microwave observations. [ABSTRACT FROM AUTHOR]