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Around 40km offshore from Burnie is the location of what is known
as a satellite altimetry cross-over site - a site where the
ascending and descending ground paths of the ocean-measuring
altimeter satellites cross and therefore, a site where multiple
measurements of the sea surface height are made by the altimeters.
This site has been used previously by researchers at the University
of Tasmania as the only southern hemisphere calibration site for
satellite altimetry missions [Watson et al, 2006].
We chose this location to test the accuracy and performance of
a mobile SLR system and a 5-month observing field campaign was
undertaken from December 2007 to April 2008. Concurrently with the
SLR observations, the following measurements were made:
- GPS observations at a site co-located with the mobile SLR instrument;
- tide gauge observations of relative sea level at the nearby harbour;
- GPS buoy observations to estimate directly the ocean surface offshore
at the altimeter cross-over location;
- ocean bottom pressure measurements, using infrastructure provided
by the IMOS capability area.
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Map showing altimeter ground tracks and the
locations of the tide gauge, SLR and GPS sites in the Burnie region.
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The French Transportable Laser Ranging System
The French Transportable Laser Ranging System (FTLRS) is ....
Under a collaborative arrangement with French scientists, the
instrument was sent to Burnie, Tasmania, for a 5-month period
to observe directly the distance from the ground to a number of
satellites as they passed overhead. Details of the FTLRS can
be found here.
RSES took part in the field observation for the Australian-French joint campaign of Jason-1 calibration and validation, operating the French Transportable Laser Ranging System (FTLRS) on a daily basis from early Dec 2007 to mid April in Burnie, Tasmania.
The City of Burnie is located right under the trajectory of Jason-1’s 88th descending pass and is one of the best calibration sites in the southern hemisphere.
About 3km away in the east from the Burnie Port, a continuous operating GPS reference station is located at the Round Hill Light House. This station is remotely operated by the Geoscience Australia based in Canberra, sampling at every 30 second. Upon requests, the MicroZ GPS receiver can be switched to observe at 1Hz rate for kinematic operations such as GPS buoy deployment.
The SLR site was built some kilometres away from the Burnie tidal gauge, in the campus of the Burnie TAFE. A precise spirit levelling was carried out to connect the SLR mark to the Tasmania State Controls and therefore the tidal gauge. The FTLRS was set up on the SLR site in Dec, 2007, for details of the station and the instrument, see http://ilrs.gsfc.nasa.gov/stations/sitelist/BURF_general.html. A Leica 500 GPS receiver system was collocated at the Burnie SLR site, observing and logging twice a minute through out the campaign. The receiver can be pre-programmed to have observation sessions at 1Hz rate.
The FTLRS performed well in Burnie in the campaign, which can be evidenced from the Global Performance Report Card evaluated and published by the ILRS http://ilrs.gsfc.nasa.gov/stations/site_info/global_report_cards/perf_2008q1_wLLR.html.
During the campaign, RSES helped to carry out 4 GPS buoy deployments when Jason-1 passed overhead. Each time, two GPS buoy systems were deployed to a selected site in Bass Strait where a mooring system is located in the water (Watson et al, 2003), and three GPS receivers were set up to operate in Stanley, Rocky Cape, and Table Cape respectively. This, together with the two GPS receivers at the FTLRS station and Round Hill, formed a robust control network which is capable to accurately determine the time series of the geodetic heights of the GPS buoys.
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The FTLRS in operation at Burnie.
Photo: C. Kidd
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