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AuScope Geospatial at RSES

Geospatial at RSES

Publications

Introduction

In November 2006, the Australian Federal Government announced $15.8M in funding for geospatial research infrastructure through the National Collaborative Research Infrastructure Strategy (NCRIS) as part of the AuScope capability area. In addition, significant co-investment was forthcoming from universities and State/Territory and Federal government departments. The national geospatial infrastructure to be acquired includes absolute and tidal gravimeters, radio telescopes to be used for geodetic Very Long Baseline Interferometry (VLBI), a continent-wide network of continuously operating Global Navigation Satellite System (GNSS) receivers, Satellite Laser Ranging (SLR) instruments, as well as the associated operating costs for all these components. Funding is provided until the end of June 2011.

RSES is involved directly in the gravity and satellite laser ranging components of AuScope Geospatial, receiving funding for both infrastructure acquisition and operating costs.



Satellite Laser Ranging

Satellite Laser Ranging (SLR) is a space-geodetic technique that allows us to measure the distance between a ground-based laser and satellites orbiting the Earth. The general principle is that short pulses of laser light are fired from the lasers, reflect off special reflectors fitted to the satellites and return to the ground laser. By measuring the time it takes the light to travel to and from the satellite, the distance between the ground laser and the satellite can be calculated.

SLR is used to estimate the orbits of many satellites including satellites equipped with altimeters that measure, for example, the height of the Earth's oceans and polar ice sheets. It is therefore of great importance to estimate as accurately as possible the orbits of these satellites.

The satellite laser ranging (SLR) component of AuScope Geospatial encompasses two components: the upgrade of the existing SLR facility at Mt Stromlo to a system with more power, and the testing of a mobile SLR system. RSES played a significant role in the latter component, using AuScope funding to employ a SLR observer/analyst as well as contributing to the field deployment costs.

The Burnie field campaign

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.

Map showing altimeter ground tracks and the locations of the tide gauge, SLR and GPS sites in the Burnie region.

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.


The FTLRS in operation at Burnie. Photo: C. Kidd

Results

The SLR observations taken by the FTLRS at Burnie are currently being analysed at RSES using the GINS software [Biancale et al. ????].

Jason, we need to populate this with information about the SLR analysis already done by Francis etc at Grasse, as well as perhaps links to their site(s)?



Gravity

Precise measurement of gravity contributes to the analysis of the time dependent variation of the gravity field near the surface of earth and the study of global change processes.

The NCRIS funding for gravity provides for:

  • The purchase of a precision absolute gravimeter
  • The purchase of one or more precision relative gravimeters
  • The establishment of a building at Mount Stromlo for gravimeter calibrations and intercomparisons
  • The operation of these instruments and the existing Super Conducting gravimeter at Mount Stromlo through to July 2011.

The fieldwork program is being organised through RSES in close collaboration with Nick Dando from Geoscience Australia. It incorporates a regular observation program at a network of short-term observations at fundamental absolute gravity sites throughout Australia as well as longer-term (ie 3-6 month) deployments of the tide meter(s) at specific sites) deployments of the tide meter(s) at specific sites


The FG5 absolute gravimeter operating at Mt Stromlo

Absolute Gravity

A Micro-g LaCoste FG5 absolute gravimeter was purchased and delivered to the ANU in March 2008.

Micro-g LaCoste provided 4 days of training in the setup and operation of the FG5 gravimeter at the ANU during April. Familiarization with the instrument continued with measurements being made at the Mount Stromlo absolute gravity station in the basement of the Commonwealth Solar Observatory building.

Measurements have been completed at existing absolute gravity stations located at the Mount Stromlo Seismic facility vault, National Measurement Institute in Sydney, the University of Western Sydney Werrington, and the Canberra Deep Space Communications Complex at Tidbinbilla near Canberra.

An observation program is being developed to repeat observations at existing absolute gravity sites within Australia. As additional sites are developed by AUScope they will be included in the observation program.

The gravity data from these observations will be processed producing a precise set of time series values for each site.

Relative Gravity

A precise superconducting gravimeter has been in operation since 1997 in the basement of the Commonwealth Solar Observatory building at Mount Stromlo (see details here). The installation has been a collaborative project between the Geodynamics group in the Research School of Earth Sciences and the Japanese National Astronomical Observatory, Mizusawa. Ownership and full operating responsibility for this instrument has now been transferred to the ANU.

This is the most precise instrument available for measuring changes in the Earth.s gravity field. It is essentially a laboratory instrument and not well suited for relocation to other measurement sites. Its prime purpose is to study tidal deformation of the Earth and the structure of the Earth.s interior from measurements over extended periods of time.

A Micro-g Lacoste gPhone portable earth tide relative gravimeter was purchased and delivered to the ANU in June 2008. This instrument has been operating adjacent to the Mount Stromlo superconducting gravimeter since delivery. Familiarization and validation measurements are being carried before deployment to the first remote measurement site late in 2008. The purpose of this instrument is for the study of earth and ocean loading tides at the instrument measurement sites.


Geospatial Publications

The following publications involving RSES staff have utilised the AuScope Geospatial infrastructure:

1

The University Component of the AuScope Geospatial Team, 2008. New geodetic infrastructure for Australia, J. Spatial Sci. , in press

 


Student Research Projects @ RSES

In the Drop down menus below choose the Degree type you are looking to complete then a subject type and if you know of a supervisor
you wish to study under select the supervisors name then click on the search button and the relevant projects will be displayed.
If you do not make any selections all available projects will be displayed.

Degree Type ? Subject?Supervisor?
Note: These projects are an indication of the topics available, you should contact your prospective supervisor asap to discuss the details of the project.
Mass variations estimated from GRACE
project image
Supervisor:Tregoning, Paul
Subject keywords: Geodesy/GPS, Mathematical Geophysics, Physics, Geophysics, Computational
Degree types: Honours, M.Sc, PhD, PhB,
The Gravity Recovery and Climate Experiment (GRACE) space gravity mission provides a means of estimating changes in mass on the Earth, including hydrological processes, oceanic variations and melting of polar ice sheets. The raw measurements are actually changes in the distance (accurate to 1/10 of the width of a human hair) between two satellites orbiting at 450 km altitude and separated by ~200 km. To achieve this, we must first compute the orbit of the two satellites, taking into account gravitational effects of the Sun, Moon, ocean tides, atmospheric variations to then be able to identify the signal of the temporal changes in the Earth's gravity field. The figure shows the accumulation of mass( i.e. water) on the east coast of Australia during the 2011 January floods as estimated by GRACE.

The student will be involved in developing software and background models to derive more accurate estimates of the Earth's gravity field. They will then use the estimates to study geophysical processes on Earth.

Monitoring groundwater changes in Australia
project image
Supervisor:Tregoning, Paul
Subject keywords: Sea level change/Climate change, Geodesy/GPS, Mathematical Geophysics, Geophysics, Computational GRC
Degree types: Honours, M.Sc, PhB
Water is a critical resource for Australia. We can't begin to manage properly what we don't monitor; therefore, monitoring the changes in water resources at local- and basin-scales is becoming increasingly important. The Gravity Recovery and Climate Experiment (GRACE) satellite gravity mission enables the possibility to measure basin-scale mass changes at monthly intervals, yet such capability is not being exploited to monitor Australia\'s water systems. Considerable research is required to determine the accuracy of the technique in the Australian environment where drainage basins are relatively small. This would involve the analysis and comparison of different international GRACE solutions and simulations for the Australian region to assess the achievable accuracy. The student would conduct an interesting scientific study that should lead to unique results pertinent to water resources in the Australian region.
Climate Change and the Melting of Polar Ice Caps
project image
Supervisor:Tregoning, Paul
Subject keywords: Geodesy/GPS,Sea level change/Climate change,Mathematical Geophysics,Physics,Computational,Fieldwork, GRC,
Degree types: PhD,
Global warming is causing increased melting in polar regions. How do we know this? Because we can measure changes in mass balance (or the amount of ice that has melted) using space-geodetic techniques that detect variations in the Earth's gravity field and changes in ice height.
How fast are Antarctica and Greenland melting and how is such melting contributing to rising sea level?
There is the opportunity to study all aspects of the effects and ramifications of climate change, from measuring sea level variations using satellite altimetry and tide gauges, measuring with GPS the rebound of the Earth's crust caused by the melting of past ice sheets, monitoring mass balance changes through GRACE observations of gravity changes and/or assimilating all these observations to develop new models of past and present ice sheets for Greenland, Antarctica and North America. This exciting area of research has direct implications for understanding the present-day effects of climate change.
Sensing water vapour in the atmosphere using GPS
project image
Supervisor:Tregoning, Paul
Subject keywords: Geodesy/GPS,Sea level change/Climate change,Climate Dynamics,Physics,Geophysics,Computational,Analytical,
Degree types: Honours,M.Sc,PhD,PhB,
Signals transmitted from satellites orbiting the Earth are delayed as they pass through the troposphere of the Earth. This is measurable by GPS and so it is possible to measure how much water vapour is actually in the atmosphere using GPS. This is a new area of research that will involve the student learning about high-accuracy GPS analysis and modelling of the atmospheric effects. The map to the right shows the precipitable water vapour over the USA as estimated from GPS observations. Assimilating this information into weather forecasting and climate studies has not yet been attempted in Australia.

Contact the supervisor directly for more information.

Combining Very Long Baseline Interferometry and GPS in Australia
project image
Supervisor:Tregoning, Paul
Subject keywords: Geodesy/GPS,Mathematical Geophysics,Physics,Computational,Fieldwork,GRC,
Degree types: PhD,
Very Long Baseline Interferometry (VLBI) involves observing radio sources with astronomy telescopes, from which very accurate estimates of distances between telescopes and estimates of Earth rotation can be made. Recently, a software program was developed at Swinburne University (Victoria) to correlate astronomic VLBI observations - which is a very significant improvement over convential correlation and provides Australian researchers with considerable independence. This PhD program will involve continuing the development of the software correlator so that it can be applied to geodetic VLBI observations as well. Once this can be done, exciting new opportunities will become available - such as observing GPS satellites using VLBI instruments, analysing for the first time the data from the new VLBI installations in Western Australia and the Northern Territory (to be commissioned in 2008). The student will be involved in developing and enhancing software, analysing VLBI data and integrating the VLBI observations to GPS satellites into existing geodetic software packages. The student will be supervised jointly by Steven Tingay (Swinburn) and Paul Tregoning (ANU).

We don't know yet what new results such research is going to uncover ...... come and find out!

Tectonic deformation of Papua New Guinea
project image
Supervisor:Tregoning, Paul
Subject keywords: Geodesy/GPS,Tectonics/Earth Deformation/faults,Mathematical Geophysics,Geophysics,Computational,Analytical,Fieldwork,
Degree types: Honours,M.Sc,PhD,PhB,
Papua New Guinea is one of the most active tectonic regions of the world, with every possible type of plate boundary, dozens of active faults and several major earthquakes occurring every year. Measurement of ground movement from GPS observationscan tell us about deformation, strain caused by locked faults etc. Estimating earthquake locations can identify faults and explain the observed deformations. There are numerous research projects available using earthquakes and/or geodetic data to study how the Earth moves in Papua New Guinea.

Contact the supervisor directly for more information.