Geoscience Reference
In-Depth Information
integrated measurement devices, Transportable Integrated Geodetic Observatory
(TIGO), which includes various measurement methods such as SLR, VLBI, GPS,
and PRARE, and instruments like gravimeters, seismometers, meteorological
instruments, and so on. The SLR system in Wettzell uses the most advanced
diode-laser-pumped Ti sapphire laser and is able to undertake dual-wavelength
ranging. The Matera station recently installed a highly advanced SLR system with a
telescope aperture of 1.5 m and the same ranging accuracy as that of NASA.
WPLTN
The West Pacific SLR Network (WPLTN) was set up in 1994. Its members include
China, Japan, Australia, Russia, and Saudi Arabia, with 15 stations altogether.
There are two stations in Australia. One was the Orroral station of the Australian
Surveying and Land Information Group (AUSLIG), located in Canberra and
opened in the 1970s. Both its quantity and quality of observations ranked within
the world's top five. It was closed in November 1998 and replaced by a new SLR
system made by Electro Optic Systems (EOS) for AUSLIG. This new system was
installed in Mount Stromlo, not far from the former station. It uses the advanced
continuously diode-laser-pumped mode-locked oscillator from the Nd:YAG laser
and a regenerative amplifier with pulse width of 25 ps. Their numbers of observa-
tions, ranging accuracy, and system stability currently all rank within the world's
top three. It has been experimenting with unmanned automatic observation and has
yielded initial results unprecedented in the world. The equipment in Yarragadee in
the west of Australia is MOBLAS 5 of NASA, which has been turned over to
AUSLIG. The weather conditions at this station are quite good so its number of
observations is often among the world's top two.
The four SLR systems in Keystone, Japan, belong to the Communications
Research Laboratory (CRL) and were made by EOS in Australia. They specialize
in monitoring crustal deformation around Tokyo. The whole set of systems was
highly advanced when it was put into use in 1996-1997. In 1999 it had realized a
relatively stable ranging during the day with an accuracy of 1-1.5 cm. Unfortu-
nately, these four stations no longer run normally due to lack of funds. The
Simosato station of the Hydrographic Office of Japan is an old one that is still
making regular observations.
Russia has more SLR stations, two of which are Komsomolsk and Maidanak
(now belonging to Uzbekistan) and often participate in international cooperation.
Their single ranging accuracy is about 4-6 cm. The number of observations per
station per year is around 400-600 laps. In addition, two or three new stations have
been successfully developed. With good performance, they will be used for regular
observations.
The Chinese SLR Network comprises five fixed and two mobile stations (the
equipment of some stations is shown in Fig. 3.21 ).
During 1971-1972, the North China Research Institute of Electro-optics
(NCRIEO, in collaboration with Beijing Observatory) and Shanghai Observatory
(working together with Shanghai Institute of Optics and Fine Machines) undertook
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