Tongariro ash plume seen in moonlight satellite image

18:32, Nov 21 2012
Tongariro eruption low light satellite image
ERUPTION BY MOONLIGHT: The ash plume can be seen in this low-light satellite image.

The ash cloud from Tongariro's midnight eruption this week was caught on camera by a special low-light imaging satellite just an hour after it began.

Nasa released the picture today showing the ash plume at 12.55am on August 7.

It says the image was acquired by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the new Suomi National Polar-Orbiting satellite.

It has a "day-night band" that can detect volcanic ash plumes lit by moonlight alone.

Nasa says the detection of volcanic plumes is useful because ash can endanger airplanes in flight.

"It is interesting to note that the ash downwind was lofted fairly high," said William Straka of the Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin.

The first appearance of the ash plume occurred far downwind of Tongariro in thermal imagery because ash was lofted high enough to produce a strong thermal contrast in the atmosphere.