For the first time, CSIRO and US scientists are using the moon to check and
calibrate sensors on board weather satellites.

The ‘moon tuned’ sensors are expected to provide a wealth of improved
information about climate change and air pollution.

“The moon is the perfect object to point the satellite sensors at in order
to check them,” says Dr Ian Grant from CSIRO Atmospheric Research.

“The moon’s surface is bare and unchanging and there is no air between it
and the satellite.”

In the past, scientists have calibrated satellite sensors by checking their
views of uniform targets on Earth, such as deserts or clouds. However,
the atmosphere gets in the way and vegetation and rainfall can alter the
appearance of deserts.

“We are doing lunar calibrations with the imager on the Japanese
Geostationary Meteorological Satellite. This is the imager that gives us
the pictures of clouds over Australia that we see on TV weather reports,”
says Dr Grant.

Although the moon’s surface is unchanging, the brightness of any point on
the moon changes with the direction of sunlight and the direction from
which the satellite looks.

The US Geological Survey accurately maps the moon’s brightness from its
lunar observatory in Arizona. The satellite imager is calibrated at times
when its view of the moon matches the view angle of instruments at the
observatory.

“In future, we’ll be able to check the imager from a range of viewing
angles,” says Dr Grant.

Additionally, the newly calibrated satellite sensor will be able to more
accurately monitor smoke plumes from large fires that are prevalent in the
tropics. Climate scientists are especially interested in the way in which
such smoke can affect global warming.

Dr Grant presented this breakthrough in satellite imager calibration at a
recent international remote sensing conference in Australia. He collaborated
on the research with a team led by Dr Hugh Kieffer from the US Geological
Survey.

There are currently eight geostationary meteorological satellites in orbit,
and the lunar technique could be used in future to calibrate all of them.
This will make their data more consistent and accurate, and so better able
to monitor global climate and smoke plumes.

More information from:

Dr Ian Grant

03-9239 4668 (w)

ian.grant@dar.csiro.au

Paul Holper

03 9239 4661 (w)

0407 394 661 (m)

paul.holper@dar.csiro.au

IMAGE CAPTION:
[http://www.csiro.au/page.asp?type=imageDef&id=mooncal_color_lg (63KB)]
An image of the moon above the northern hemisphere, taken from the GMS-5
satellite. Image courtesy of the Bureau of Meteorology.

Contacts:

Mr Paul Holper

CSIRO Atmospheric Research

Private Bag No.1

ASPENDALE VIC 3195

Australia

Phone: +61 3 9239 4661

Fax: +61 3 9239 4444

Email: Paul.Holper@dar.csiro.au

Mr Nick Goldie

Journalist

CSIRO National Awareness

PO Box 225

Dickson ACT 2602

Phone:+61 2 6276 6478

Fax:+61 2 6276 6821

Mobile: +61 0417 299 586

Email: Nick.Goldie@nap.csiro.au