Locals help study water from space
Australian water-sensing technology is now in orbit.
Satellite technology that can measure freshwater reserves from space - developed in Australia – is central to NASA's Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, which launched last month.
Physicist Daniel Shaddock from the Australian National University says it was “a little bit surreal” to see 15 years of his work onboard the rocket.
“So many years of your life working on something — it was hard to believe it was actually happening and finally launching,” he said.
“It was very exciting when it finally went up and nothing blew up. And the most exciting part is still yet to come.”
Professor Shaddock helped create a retroreflector that uses lasers to measure water reserves from space with incredible accuracy.
“It measures something that's really important; the presence of water — whether that's frozen form or liquid form — across the entire globe at once. And that's something you can only do from space,” he said.
“Any large body of water will generate gravity and that gravity can be picked up by GRACE.”
GRACE can peer beneath the Earth's surface – where a third of all freshwater lies - to weigh the hidden groundwater reserves.
GRACE can detect tiny changes in gravity caused by large masses of water which cause a pair of satellites to speed up or slow down.
Professor Shaddock's laser can plot those changes in speed.
“In the case of the Laser Ranging Interferometer, we can pick up changes in the separation of the spacecraft by ten nanometres. That's ten billionths of a metre — about the diameter of a virus.”
Now that it is up in orbit, the system requires two laser beams from two separate satellites travelling at thousands of kilometres per hour to link with each other from over two hundred kilometres apart.
“Once the laser links have been acquired I'll certainly rest a little easier — that's really the biggest challenge facing GRACE,” Professor Shaddock said.
“If that doesn't work we won't get any data back, and if it does work, I'm much more confident that we'll get some really valuable insights.”
Australian National University water expert, Albert Van Dijk, said the GRACE mission has already given disturbing insights into freshwater loss.
In populated, arid parts of the world, huge amounts of water is being pumped out up to the surface.
“What GRACE is telling us is that a lot of that groundwater is not being replenished,” Professor Van Dijk said.
“We're actually mining groundwater and the magnitude of that is actually quite impressive.
“The direct consequence is the groundwater table goes lower and lower and farmers have to deepen their wells.”
GRACE has also shown groundwater in the Murray-Darling Basin region has not recovered from the Millennium Drought, which ended in 2011.
Freshwater is disappearing from Greenland and West Antarctica too as GRACE shows Earth’s ice caps melting.
“GRACE is giving us solid numbers about how much ice is disappearing, how much is ending up in the oceans and also how it's changing our water cycle and our water resources,” Professor Van Dijk said.
“We can see a lot of the impacts of climate change that was predicted decades ago; we can see them now.
“It's been incredibly useful in terms of seeing how climate change is rolling out.”