Ten years on the radar: How Australian infrastructure is supporting space agencies around the world
A 1.5 m radar corner reflector of the Queensland Corner Reflector Array (QCRA) installed near Cecil Plains, in the Darling Downs region of south-east Queensland. Image: Geoscience Australia AuScope edited
Over ten years ago, a curious network of triangular aluminium structures was erected across the quiet paddocks of Queensland’s Darling Downs region. Scattered amongst grazing livestock, these radar corner reflectors sit idly, without using power, collecting data or transmitting signals. But despite their seemingly simple design, these metal structures play a critical role in Earth observation, helping to calibrate radar satellites for leading international space agencies like the European Space Agency (ESA), the Japanese Aerospace Exploration Agency (JAXA), and NASA. This is the story of the Queensland Corner Reflector Array (QCRA) and how an early investment by AuScope blossomed into a significant Australian contribution to global Earth science.
Precision from the ground up
Every time a radar satellite orbits overhead, it sends pulses of microwave energy down to Earth; signals that sweep through space, beyond the clouds and storms, toward the ground below. These satellites can map and monitor the Earth at extremely high resolutions, providing valuable information for navigation, resource exploration, and disaster response. But despite their widespread use, there’s one thing radar satellites can’t do on their own: know exactly where on Earth they’re looking.
Radar satellites rely on precise calibration from the ground to ensure their images are accurate and trustworthy. To do this, they must be anchored to the real world using a known geospatial reference – the corner reflector array.
“One of the real challenges with any satellite imaging is making sure that the image sits in the right place on the ground. Using targets like these reflectors, it's possible to measure the accuracy of the image alignment on the ground. So, if they’re metres out, or centimetres out, users can take action to force the images back into place.”
– Dr Matt Garthwaite, SAR Capability and Cal/Val Facilities Lead, CSIRO Centre for Earth Observation
Dr Matt Garthwaite worked in the National Geodesy team at Geoscience Australia when the QCRA was implemented. He said each corner reflector acts like a passive ‘mirror,’ designed to reflect radar signals directly back to the satellite that sent them. This makes the radar signal from the reflector very bright compared to the surrounding landscape.
“When a radar satellite pings down a radar to Earth, usually only some of the radar energy will reflect from the ground back in the direction of the radar satellite. But when that radar hits one of these reflectors, it bounces off the 3 triangular plates and nearly all the radar energy goes back directly towards the satellite from whence it came.”
– Dr Matt Garthwaite, SAR Capability and Cal/Val Facilities Lead, CSIRO Centre for Earth Observation
Supported by a $1 million investment from AuScope over a decade ago, the QCRA was installed in 2014 as part of the Australian Geophysical Observing System (AGOS) program. The QCRA was initially deployed to help monitor vertical ground motion using radar satellites for groundwater monitoring and coal seam gas development in the Surat Basin. Now, it is one of the many pieces of critical infrastructure through which the legacy of the AGOS program lives on.
A global asset for Earth observation
While the corner reflectors haven’t moved in over a decade, the impact they’ve made has stretched across continents. Today, over 15 international space agencies and commercial space companies, including ESA, JAXA and NASA, use this Australian infrastructure to calibrate and validate their satellite radar systems.
“The unique thing here is that no one has ever built a network of these corner reflectors at such a scale – with 40 high quality targets spread across a 130 by 130 kilometre area, there’s nothing quite like it in the world. AuScope’s significant investment means that other space agencies around the globe can leverage this unique infrastructure.”
– Dr Matthew Adams, Director Global Data Interoperability and Integrity Satellite Land Imaging Collection Branch, Space Division, Geoscience Australia
The European Space Agency, in particular, regularly uses the QCRA to calibrate its Sentinel-1 satellites, which helps provide freely available imagery used worldwide for environmental monitoring, disaster response, and more.
“The European Space Agency has actively contributed to the characterisation of QCRA for cal/val purposes. It is now fully integrated in the routine performance and calibration assessment of the Sentinel-1 mission. The QCRA is unique in the world by the number of targets and by the large area covered. It has helped the Agency to further refine the Sentinel-1’s performance over the last decade and hopefully for the next to come.”
– Dr Nuno Miranda, Sentinel-1 Mission Manager, European Space Agency
SARCalNet (SAR Calibration Network - https://www.sarcalnet.org/), an initiative of the Committee on Earth Observation Satellites (CEOS) Working Group on Calibration and Validation (WGCV), is a global network of calibration infrastructure to support current and future SAR missions. Geoscience Australia is currently working to get the QCRA embedded as part of SARCalNet, strengthening Australia’s contribution to international satellite calibration and ensuring consistent, reliable data for a range of applications. Medhavy Thankappan, Senior Advisor, Earth Observation at Geoscience Australia, Vice-Chair of CEOS-WGCV, and member of the initial design and development team for the QCRA, noted:
“The unique configuration and long-term stability over the last ten years, has made the QCRA a benchmark for Synthetic Aperture Radar (SAR) mission calibration and validation. Its inclusion in SARCalNet will be a significant milestone and ensure that Australia continues to play a leading role in delivering trusted, high-quality SAR satellite observations to the global community.”
– Medhavy Thankappan, Senior Advisor, Earth Observation at Geoscience Australia and Vice-Chair of CEOS-WGCV
The strategic investment that keeps giving
The return on AuScope’s early investment in the QCRA has been exponential. Dr Lisa Hall, Director of Geodesy at Geoscience Australia, said that she views AuScope as being at the start of the value chain.
“Today, the QCRA is recognised as a globally significant asset,” says Dr Lisa Hall, Director of National Geodesy at Geoscience Australia. “But it was AuScope’s early investment that made it possible. That foresight didn’t just support a project – it enabled an entire value chain that’s now delivering impact on the international stage.”
– Dr Lisa Hall, Director of Geodesy, Geoscience Australia
The QCRA is just one part of a much larger story. Over the past 25+ years, AuScope has played a catalytic role in Australia’s national geospatial capabilities, providing the seed funding that enables agencies like Geoscience Australia to scale operations into world-class infrastructure.
As the global demand for accurate, open satellite data continues to grow, so too will the value of this Australian infrastructure. With new partnerships on the horizon, the QCRA shows us that, sometimes, the most important infrastructure doesn’t always sit in labs or launch pads, but quietly in the open plains.
Key People and Organisations
Dr Matt Garthwaite, SAR Capability and Cal/Val Facilities Lead, CSIRO Centre for Earth Observation
Dr Lisa Hall, Director of Geodesy, Geoscience Australia
Dr Matthew Adams, Director, Global Data Interoperability and Integrity Satellite Land Imaging Collection Branch, Space Division, Geoscience Australia
Medhavy Thankappan, Senior Advisor, Earth Observation, Geoscience Australia, Vice Chair, CEOS Working Group on Calibration and Validation
Contact Information
For media enquiries, please contact media@ga.gov.au or 1800 882 035.
Provide contact details for project researchers who may have further inquiries.
Case Study
The NCRIS-enabled Queensland Corner Reflector Array, installed in Queensland’s Darling Downs region in 2014, has become a trusted calibration site for Earth observation satellites around the world.
Authors
Author: Dr Cintya Dharmayanti, Scientell
Further information
