The International DORIS Service (IDS) - Recent Developments in Preparation for ITRF2013

The International DORIS Service (IDS) was created in 2003 under the umbrella of the International Association of Geodesy (IAG) to foster scientific research related to the French DORIS tracking system and to deliver scientific products, mostly related to the International Earth rotation and Reference systems Service (IERS). We first present some general background related to the DORIS system (current and planned satellites, current tracking network and expected evolution) and to the general IDS organization (from Data Centers, Analysis Centers and Combination Center). Then, we discuss some of the steps recently taken to prepare the IDS submission to ITRF2013 (combined weekly time series based on individual solutions from several Analysis Centers). In particular, recent results obtained from the Analysis Centers and the Combination Center show that improvements can still be made when updating physical models of some DORIS satellites, such as Envisat, Cryosat-2 or Jason-2. The DORIS contribution to ITRF2013 should also benefit from the larger number of ground observations collected by the last generation of DGXX receivers (first instrument being onboard Jason-2 satellite). In particular for polar motion, sub-millarcsecond accuracy seems now to be achievable. Weekly station positioning internal consistency also seems to be improved with a larger DORIS constellation

Earth rotation monitoring, UT1 determination and prediction

International audienceMonitoring the Earth's rotation angle is essential in various domains linked to reference systems such as space navigation, precise orbit determinations of artificial Earth satellites including the Global Navigation Satellite Systems (GNSS), positional astronomy and for geophysical studies on time scales ranging from a few hours to decades

IAU Working Group for Numerical Standards of Fundamental Astronomy (NSFA): Past Efforts and Future Endeavors

International audienceIn 2006, the International Astronomical Union (IAU) General Assembly (GA) established the Working Group (WG) for Numerical Standards of Fundamental Astronomy (NSFA). The NSFA WG Current Best Estimates (CBEs) were adopted at the 2009 IAU GA in Resolution B2 as the IAU (2009) System of Astronomical Constants. The IAU 2012 Resolution on the re-definition of the au was proposed by the NSFA WG. Since then, the WG has concentrated on establishing the process for maintaining the CBEs in an effort to provide a service for the IAU. The NSFA web presence documents both the IAU (2009) System of Astronomical Constants and the CBEs. All old pages of the CBEs are archived in order to document history of the CBEs. The CBE policy documents the procedures established for proposal, discussion, and voting for the adoption of new CBEs. The talk reviews the efforts of the WG and provides insight into future efforts

IAU Working Group for Numerical Standards of Fundamental Astronomy (NSFA): Past Efforts and Future Endeavors

International audienceIn 2006, the International Astronomical Union (IAU) General Assembly (GA) established the Working Group (WG) for Numerical Standards of Fundamental Astronomy (NSFA). The NSFA WG Current Best Estimates (CBEs) were adopted at the 2009 IAU GA in Resolution B2 as the IAU (2009) System of Astronomical Constants. The IAU 2012 Resolution on the re-definition of the au was proposed by the NSFA WG. Since then, the WG has concentrated on establishing the process for maintaining the CBEs in an effort to provide a service for the IAU. The NSFA web presence documents both the IAU (2009) System of Astronomical Constants and the CBEs. All old pages of the CBEs are archived in order to document history of the CBEs. The CBE policy documents the procedures established for proposal, discussion, and voting for the adoption of new CBEs. The talk reviews the efforts of the WG and provides insight into future efforts

The IVS data input to ITRF2014

2015ivs..data....1N - GFZ Data Services, Helmoltz Centre, Potsdam, GermanyVery Long Baseline Interferometry (VLBI) is a primary space-geodetic technique for determining precise coordinates on the Earth, for monitoring the variable Earth rotation and orientation with highest precision, and for deriving many other parameters of the Earth system. The International VLBI Service for Geodesy and Astrometry (IVS, http://ivscc.gsfc.nasa.gov/) is a service of the International Association of Geodesy (IAG) and the International Astronomical Union (IAU). The datasets published here are the results of individual Very Long Baseline Interferometry (VLBI) sessions in the form of normal equations in SINEX 2.0 format (http://www.iers.org/IERS/EN/Organization/AnalysisCoordinator/SinexFormat/sinex.html, the SINEX 2.0 description is attached as pdf) provided by IVS as the input for the next release of the International Terrestrial Reference System (ITRF): ITRF2014. This is a new version of the ITRF2008 release (Bockmann et al., 2009). For each session/ file, the normal equation systems contain elements for the coordinate components of all stations having participated in the respective session as well as for the Earth orientation parameters (x-pole, y-pole, UT1 and its time derivatives plus offset to the IAU2006 precession-nutation components dX, dY (https://www.iau.org/static/resolutions/IAU2006_Resol1.pdf). The terrestrial part is free of datum. The data sets are the result of a weighted combination of the input of several IVS Analysis Centers. The IVS contribution for ITRF2014 is described in Bachmann et al (2015), Schuh and Behrend (2012) provide a general overview on the VLBI method, details on the internal data handling can be found at Behrend (2013)