Mon. Jan 17th, 2022

Geoscience Australia has participated in a global campaign to compare data from the Landsat 8 and 9 satellites during a rare underflyer.

The Landsat 9 satellite was launched by NASA on September 28, 2021 to deliver the next generation of Earth observation from space (EOS).

But a unique event in the life of the satellite took place between 13 and 17 November.

When the Landsat 9 was maneuvered to reach operating altitude, its orbit overlapped with the older Landsat 8 satellite.

Geoscience Australia’s National Earth and Marine Observations Branch Head Maree Wilson said this “underflow” provided a rare opportunity for scientists to compare the performance of sensors on the sister satellites as they passed over the same area almost simultaneously.

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Locations where field work was performed during the Landsat 8 – Landsat 9 underflying event. The notches depicted by Landsat 8 are shown in red, while the notches depicted by Landsat 9 are shown in blue.

“This was our only opportunity to confirm that both the Landsat 8 and 9 satellites see the world in the same way,” Ms Wilson said.

“When Landsat 9 reaches its operational orbit, the orbits of the two satellites will be shifted by 8 days, meaning this was the only chance we had to image the same shard of Australia with both satellites at the same time.

“It is important that we know that the Landsat satellites take similar measurements, as our ability to monitor the whole country and how it changes depends on having a long, growing and consistent record of data from Landsat satellites.

“We use Landsat data to track changes in the landscape, identify water bodies and monitor coastal erosion. Ensuring these data are accurate is crucial to the health and well-being of all Australians.”

As part of a global mission led by the United States Geological Survey, Geoscience Australia coordinated field surveys at several locations around Australia in collaboration with the Queensland Department of Environment and Science, University of Queensland, New South Wales Department of Planning, Industry and Environment, CSIRO, University of Western Australia and FrontierSI.

Man takes aim

Geoscience Australia Spectral Data Quality Officer Eric Hay in the Paroo-Darling State Conservation area near the Darling River on November 15, 2021, measuring under Landsat 8/9 underfly

The exercise spanned five locations – Perth, Western Australia; Cunnamulla Queensland; Wilcannia, New South Wales; Narromine, New South Wales; and Lake Hume, New South Wales – to increase the chance of clear skies during the flyover.

Scientists used spectrometers – instruments that measure the intensity of reflected light at many wavelengths – to replicate pixels in data acquired by Landsat 8- and 9-satellites when the slits – or the areas of the earth’s surface mapped by the satellites – overlapped.

“This nationwide collaboration is a great example of how members of the Australian Earth Observation Society are helping to instill confidence in the latest Landsat mission,” said Mrs Wilson.

“While it may take some time for Geoscience Australia to receive all satellite data, initial comparisons of the latest Landsat 8 data over the field sites give us a high degree of confidence in the field data collection.”

This campaign is just one way Geoscience Australia helps with the efficient use of data from the Landsat program.

Group of people standing in a field and taking measurements

Geoscience Australia’s Guy Byrne, Eric Hay and Medhavy Thankappan with Tony Gill of the NSW Department of Planning, Industry and Environment conducting field measurements in Narromine, NSW on 17 November 2021

Geoscience Australia’s satellite earth station at Alice Springs is also one of five stations globally that make up the United States Geological Survey’s Landsat Ground Network and now provide regular satellite support.

Geoscience Australia’s Digital Earth Australia program also makes Landsat data freely available through products such as DEA Coastlines.

“This calibration work will enable Geoscience Australia to continue to provide the government, businesses and industry with this high quality satellite data,” said Mrs Wilson.

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