Quick Dips

Space Mystery Solved

Scientists studying satellite data have solved a small mystery. Staff at Landcare Research in Wellington were curious about bright spots appearing on images of Marlborough obtained from an experimental Japanese radar satellite. From 600 kilometres above the Earth its sensors were picking up something unusual.

A check of maps and visual satellite images of the same area, followed by a field trip, showed the bright spots were coming from the region's vineyards. Dr Stephen McNeill says wires supporting the vines were giving the strange results.

"We found most of the lines of grapes were planted north-south, parallel to the flight path of the satellite. The direction and spacing of the wires meant that these were picked up by the radar."

Staff first noticed the bright features on images from the Russian radar satellite Almaz, but the poor quality of the image meant that they were unsure of their significance. Members of the remote sensing team have been testing the images from the new JERS satellite and comparing them with visual images and what is on the ground. This radar satellite gives a better indication of the texture and wetness of the terrain, says McNeill.

"We are getting a different kind of data from the radar satellite because it is able to see through the vegetation and clouds to give us an idea of the roughness of the land. Most other satellites provide optical images."

McNeill says the image was taken in mid-winter when there was little foliage present.

"We can't tell a cabernet from a riesling from space, only whether the planter of the vineyard was preoccupied with north, south, east or west."

He believes scientists now have a better understanding of how human artifacts, such as roads, rail lines, windbreaks and power lines, affect radar imagery.

"Radar imagery has been largely experimental in the past, but we are seeing the beginnings of satellites that will give us regular data for environmental monitoring, with the advantage of viewing the Earth at night and through clouds."