Australia in Space Magazine, Oct 2022
By Shane Keating
Pioneering ocean-sensing satellite to benefit Australia’s Blue Economy
Australia’s $80B “Blue Economy” will receive a boost later this year from a pioneering new US-French ocean-sensing satellite.
The $1.5B Surface Water and Ocean Topography (SWOT) mission will carry a ground-breaking new radar altimeter that will map sea-surface elevation and ocean currents at 10 times the resolution of present-day instruments. This increase in resolving power – analogous to jumping from the earliest days of television to HDTV – will unveil ocean currents that are critical for coastal and maritime industries.
“Today, satellite altimetry measures sea level variations and ocean currents, but even with multiple satellites in flight, we can only construct maps of the larger features”, says Australian researcher Rosemary Morrow, who is leading the oceanography component of the mission. “SWOT aims to provide global observations of the smaller-scale currents — it’s a missing link”.
Essential satellite data
Satellite remote sensing data is crucial to ensure Australia’s economic prosperity, maritime safety, climate resilience, and national security.
Marine industries such as offshore oil and gas, fisheries, tourism, and shipping support 340,000 FTE jobs nationally and are forecast to grow to $100B/yr by 2025. These industries rely on satellite geospatial data to drive accurate and timely ocean forecasts for decision-making and risk assessment.
The workhorse of ocean remote sensing is satellite altimetry, which has provided continuous global measurements of sea-surface height (SSH) for the past 25 years. These data are routinely used by meteorological agencies around the world for ocean forecasting and form part of the “backbone” of essential satellite data for global numerical weather prediction and ocean forecasts.
In Australia, altimetry data are used by the Bureau of Meteorology’s operational forecast model, Bluelink, which supports search-and-rescue and safety-of-navigation services and delivers geospatial information in support of Defence, marine conservation activities, and fisheries management.
A Grand Challenge for ocean remote sensing
Once it becomes operational, the SWOT mission will provide the first 2D maps of the ocean surface at horizontal scales of 1-10 km. This regime of ocean dynamics — called the submesoscale — is found ubiquitously throughout the upper ocean and plays a central role in ocean circulation, climate, and marine ecology.
Submesoscale ocean currents interact strongly with the atmosphere and can couple with weather systems. “SWOT will help us to observe and understand this coupling, important for both ocean and meteorological prediction”, says Dr Morrow, who completed her PhD in Physical Oceanography at Sydney University and is now an oceanographer at the Laboratory of Space Geophysical and Oceanographic Studies (LEGOS) in France. “In Australia, our land of droughts and floods, it is important to understand how these ocean interactions can impact on our regional weather.”
Submesoscale currents also critically impact Australia’s Blue Economy, including coastal industries, fisheries, offshore oil and gas, and marine safety. Kilometre-scale ocean turbulence disperse ocean-borne material, such as marine pollutants like plastics, radioactive plumes, and debris from the MH370 disaster, over large distances. Surface convergence and downwelling near submesoscale fronts concentrate harmful algal blooms and oil from the 2009 Montara Wellhead Platform and the 2010 Deepwater Horizon spill.
Merging observations with ocean models (“data assimilation”) — a key component of ocean forecasting efforts — presents additional practical challenges: submesoscale dynamics are complex, rapidly evolving, and difficult to predict. As a result, monitoring submesoscale ocean currents is “a Grand Challenge for ocean remote sensing”, in the words of NASA oceanographer Dr. Lee-Leung Fu, Lead Scientist for the SWOT Mission.
Australia invests in SWOT
Australian researchers are making important contributions to the SWOT mission.
“Australia has always been a strong international contributor to our scientific understanding of ocean sea level, ocean currents and their variations”, says Dr Morrow. “Australian scientists are contributing ground-breaking studies to calibrate the SWOT instrument, to undertake important field work to validate the satellite’s observations of surface currents, to develop innovation mapping schemes to combine the data with models, and to ingest the data in our ocean prediction schemes.”
The Australian government is providing essential support for SWOT through enhancements to Australia’s observing infrastructure. These include the Integrated Marine Observing System (IMOS) altimeter subfacility in the Bass Strait — the only southern hemisphere calibration stream for the SWOT mission — as well as an IMOS mooring in the Southern Ocean and the Yongala National Reference Station in the Great Barrier Reef.
The broader Australian marine sciences community is also contributing to this trail-blazing mission through the Australian SWOT (AUSWOT) working group, which I established in early 2019. Our working group is actively engaged in leadership roles within the international SWOT Science Team and BOM’s Bluelink ocean forecasting system, ensuring that the outcomes of this research will benefit the broader international oceanographic community.
AUSWOT will leverage Australia’s investment in the SWOT mission by building the “intellectual infrastructure” required to ensure that the economic benefits of the SWOT mission flow through to Australian marine industries. This intellectual infrastructure will include new domestic capacity in wide-swath altimetric observations, data assimilation and forecasting of ocean submesoscales, downstream data products for end-users in fisheries management, marine safety, defence, and oil and gas, and training skilled professionals for the rapidly growing Earth Observation sector, which is projected to generate 15,000 jobs in Australia by 2025.
SWOT is a path-finding mission — the first of its kind, but by no means the last. Several future satellite missions utilizing wide-swath altimetry are currently being planned for launch in the next decade, including by the US, European, and Chinese space agencies. The intellectual infrastructure developed by the AUSWOT project will have a legacy well beyond the planned lifetime of the SWOT satellite itself.
A once-in-a-generation opportunity for Australian marine science
The SWOT mission will provide a once-in-a-generation opportunity to advance our understanding of upper ocean dynamics in Australia’s marine environment.
The RV Investigator, Australia’s national flagship for blue water ocean research, will conduct two dedicated field campaigns to support the SWOT mission in 2023. These campaigns are part of an unprecedented global effort to gather essential in situ measurements under the SWOT ground track to assist with calibration and validation and fine-scale ocean process studies.
The voyages, led by Prof Moninya Roughan (UNSW Sydney) and Dr Benoit Legresy (CSIRO), will study eddy interactions and fine-scale dynamics in the Tasman Sea and Southern Ocean using the Investigator’s suite of world-class scientific equipment and instrumentation. Prof Roughan will lead the Tasman Sea campaign, which aims to understand eddy-eddy interactions and frontal processes in the mesoscale eddy field of the East Australian Current. Dr Legresy is lead-CI of the Southern Ocean campaign, which will target a standing meander of the Antarctic Circumpolar Current south of Tasmania.
For the first 90 days of its mission, SWOT will operate in a “fast sampling mode”, revisiting specific locations around the globe once per day and offering a glimpse of ocean dynamics at high spatial and temporal resolution. With the world’s third largest exclusive economic zone, Australia has a lion’s share of potential field sites of high oceanographic and economic significance in the footprint of the fast-sampling orbit.
Australian researchers will participate in a global series of field campaigns in regions covered by SWOT’s unique fast-sampling phase. Preliminary science data from SWOT will be made available to these groups to carry out studies of fine-scale ocean processes that have never been possible before. The AUSWOT working group has identified several high-priority target sites for synergistic research activities during SWOT’s initial fast-sampling phase, including the Great Barrier Reef, the Tasman Sea, and the Northwest Shelf.
Preparing for launch
Engineers at NASA’s Jet Propulsion Laboratory in California, USA and Thales Alenia Space facility in Toulouse, France have spent almost a decade designing, building, and assembling this complex mission. The satellite has now passed its final round of tests and is scheduled for launch aboard a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California on December 5, 2022.
For Dr Morrow and the rest of the SWOT team, it is a thrilling and anxious time. “We are all so excited now to get the satellite launched”, she says. “I admit I’ll be a little stressed when it is on the launchpad. I’ll be so relieved when our first data comes through!”