NATIONAL REPORT OF THE FEDERAL REPUBLIC OF ... - IAG Office

VLBI
Space Geodetic Techniques (VLBI, LLR, SLR, DORIS)
The activities of the research groups in the field of geodetic
and astrometric VLBI in Germany are being coordinated
within the "Forschungsgruppe Satellitengeodäsie" (Research
Group Satellite Geodesy – FGS). Since the inauguration
of the International VLBI Service for Geodesy and
Astrometry (IVS) on February 11, 1999, all groups have
become members and are making significant contributions
to this international body (IVS 1999). The VLBI observatories
of Wettzell (Bavarian Forest), O'Higgins (Antarctic
peninsula) and TIGO (Conception, Chile) are imbedded in
the global observing activities and produce a large number
of observations in different global and regional network
configurations. The data is mostly correlated at the MPIfR-
BKG-Correlator which is jointly operated by the Bundesamt
für Kartographie und Geodäsie (BKG), the Max-Planck-
Institut für Radioastronomie (MPIfR) and the Institute of
Geodesy and Geoinformation of the University of Bonn
(IGGB). The Deutsches Geodätisches Forschungsinstitut
(DGFI) as well as BKG and IGGB maintain IVS Analysis
Centers for various research activities in the field of geodetic
and astrometric VLBI. At BKG (branch Leipzig) one
of the three global IVS Data Centers is responsible for
storing all VLBI observational data and IVS products to
allow easy access by all users. In the period reported here,
Germany was represented in the IVS Directing Board by
two members, WOLFGANG SCHLÜTER (Chairman) and AXEL
NOTHNAGEL (IVS Analysis Coordinator). The IVS Analysis
Coordinator's office is hosted by the Institute of Geodesy
and Geoinformation of the University of Bonn (IGGB).
Here, the official IVS Earth orientation parameter products
are generated from a rigorous combination of input series
produced by the IVS Analysis Centers (NOTHNAGEL and
STEINFORTH 2002). The results and more information are
available at the IVS home page http://ivscc.gsfc.nasa.gov
with a link to the IVS Analysis Coordinator's page.
BKG and FESG (Forschungseinrichtung Satellitengeodäsie
der TU München) on behalf of the FGS continued their
strong support for the VLBI community by operating the
20m VLBI facilities at the Fundamentalstation Wettzell,
the VLBI module of TIGO at Concepcion/Chile and the
9m VLBI facilities of the German Antarctic Receiving
Station (GARS) O’Higgins. All three telescopes have been
heavily involved in the regular activities of the International
VLBI Service (IVS). Wettzell and TIGO were employed
in the weekly IVS observing programs all over the year(s),
while GARS-O’Higgins was involved campaign-wise, as
A. NOTHNAGEL 1
1 Axel Nothnagel, Institute of Geodesy and Geoinformation of the University of Bonn, Nussallee 17, D-53115 Bonn, Germany,
Tel. +49 - 228 - 733574, email nothnagel@uni-bonn.de
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no continuous tracking could be implemented yet
(SCHLÜTER et al. 1999a, SCHLÜTER et al. 1999b).
Space technique co-location by means of GNSS
For about ten globally distributed ESA tracking sites colocation
ties for GPS sensors (IGS stations) and radio
telescope antennae (for other space techniques like VLBI,
SLR) were determined by means of GPS, total station and
levelling measurements. Co-location ties are finally derived
within ITRF at the mm accuracy level. A new algebraic
approach for the indirect method to determine radio telescope
antenna reference point and rotation axis parameters
was developed (LEINEN et al., 2007). The VLBI telescopes
at Wettzell, O'Higgins and Concepcion are co-located with
GPS stations of the IGS and the ties are routinely checked
by local ground surveys.
SLR
In Germany Satellite Laser Ranging was and still is carried
out by the GeoForschungszentrum (GFZ) at its station
Potsdam (Potsdam-3) and by the Bundesamt für Kartographie
und Geodäsie (BKG) on behalf of the Forschungsgruppe
Satellitengeodäsie (FGS) at the Fundamental Station
Wettzell employing WLRS (Wettzell Laser Ranging
System). In Concepcion/Chile the SLR module of the
Transportable Integrated Geodetic Observatory (TIGO-
SLR) is operated by BKG in close collaboration with a
Chilean consortium led by the University of Concepcion.
The station Potsdam and Wettzell are network stations of
EUROLAS. Potsdam, Wettzell and Concepcion are network
stations of the International Laser Ranging Service (ILRS).
All stations observed routinely with high efficiency with
respect to the number of passes tracked per year and with
respect to the quality. The TIGO SLR module was faced
with some hardware problems of the Titan Sapphire Laser.
Now, the laser is replaced by a Titan Sapphire Laser which
has a repetition rate of 100 Hz. After the replacement in
2006, TIGO SLR now provides observations in two colours,
infrared (850 nm) and blue (425 nm) as expected in the
number of passes observed and in quality.
A new Laser Ranging System was designed for the Fundamental
Station Wettzell, the so-called Satellite Observing
System Wettzell (SOS_W), which will take over routine
observations of satellites in a highly automated mode, continuously
24 h/day all over the year. The laser of SOS_W
will have a repetition rate of 1 kHz and will allow laser
ranging with two colours (infrared and blue) for troposphere