Salt Lake Helps Test "Sky Eye"

The team, from CSIRO's Earth Observation Centre, went to Lake Frome, about 500 kilometres north of Adelaide in South Australia. Their goal was to make sure that NASA's latest satellite is working properly.

"A salt lake is a difficult place to work. It's incredibly hot, the surface is boggy and it is very easy to get lost because there are no landmarks - just a blindingly white, flat surface for as far as the eye can see," says Susan Campbell, one of the team members.

NASA's 'EO-1' satellite, launched in November, contains the "Hyperion" imaging equipment. Hyperion is the first of its kind in space and it measures much more detailed information about the earth's surface than previous satellite instruments. These two factors mean that it needs to be carefully tested.

"Hyperion is unique because it records the brightness of the earth in 220 different spectral bands, or 'colours'. Other earth observation satellites typically detect a maximum of only seven spectral bands," says Dr David Jupp from the CSIRO Office of Space Science & Applications (COSSA), who is coordinating the Australian effort on the satellite.

"Previously, instruments like this have only been used on the ground or in aircraft. To have one working more than 700 km out in space is both exciting and a challenge," he says.

"Hyperion needs to be carefully calibrated or tested, to make sure that it is seeing from space what we would see from the ground."

"One of the best ways to test the satellite is to have it look at a very white surface, such as Lake Frome, because it is one of the brightest spots on the Australian continent and it is very uniform," he says.

"Each day, with a backpack full of instruments, we rode across the salt on balloon-tyred motorbikes to the centre of the lake," says Ms Campbell.

"The bikes were the only things that wouldn't break through the salty crust and get stuck in the black mud below!"

"We measured the exact brightness of the salt in the same 220 bands used by Hyperion. As well, instruments on the shore measured the amounts of water vapour and dust in the atmosphere and balloon soundings measured the atmosphere above the lake."

"With the results, we can check that the Hyperion readings are correct and we will be able to subtract the effect of the atmosphere," she says.

With temperatures regularly over 46°C, a critical part of working on the lake was getting to the right location and not getting lost. Ms Campbell tackled that task using Global Positioning System (GPS) equipment.

"Each day when I led the team out onto the lake and the shoreline disappeared in the heat haze, I knew that I had to be on the ball," she says.

"The area of salt crust being measured was big - 30 by 20 kilometres. I had to get my workmates to the exact measurement sites and, most importantly, I had to get them back to our shore camp by nightfall. I could not have done that without the GPS, which is an amazing piece of technology."

When Hyperion flashed over Lake Frome on December 20, the team was pleased that all had gone well.

Over the next year, the instrument will be tested at other extreme landscapes - like the darkness of the deep waters of Lake Argyle in Western Australia.

The Australian effort is headed by Dr Jupp and involves scientists from CSIRO and the Australian Centre for Remote Sensing (ACRES). It is one of ten teams chosen to work on Hyperion data with NASA and US instrument makers, TRW Inc.

Australian scientists are developing applications of the Hyperion data to geology, the environment and surveying. They will analyse the data to learn more about our rainforests, crops, forests and water bodies.

"Once we've analysed the Lake Frome results, we'll be able to better interpret the data from Hyperion - over Australia or anywhere on the globe," says Dr Jupp.

"By interpreting the Hyperion data, we will gain a better understanding of our resources and environment and how to manage them both."

The Australian team will communicate the Lake Frome results to NASA and TRW and the cooperative effort will continue throughout the mission. Australia will play a lead role in the southern hemisphere acquisitions.

Images of the team and the dramatic Lake Frome are available from http://www.cmis.csiro.au/mediapics.htm

More information on the project:http://www.eoc.csiro.au/hswww/

Hyperion website: http://eo1.gsfc.nasa.gov/Technology/Hyperion.html