February 3, 2000. Copyright 2000. Graphic News. All rights reserved.

SHUTTLE ENDEAVOUR TO MAP THE EARTH

LONDON, February 3, Graphic News: THE FIRST Shuttle flight of the new century Ð the Shuttle Radar Topography Mission Ð will deploy an innovative imaging radar to produce three dimensional maps of Earth, 30 times as precise as the best global maps in use today.

The topographical maps will be made during the 11-day flight by measuring the differences between two radar signals bounced off the planetÕs surface and received at slightly different locations.

Two types of radar will be used. A ÒC-bandÓ synthetic aperture radar (SAR) will map a 139-mile (225km) swath of the EarthÕs surface and an ÒX-bandÓ radar will generate high-resolution images, just 30 miles (50km) wide per orbit. 

The 14.5-ton (11,800kg) radar system will orbit 145 miles (233 kilometres) above Earth, with two radar antennas mounted in the Shuttle payload bay and two extended on a $142 million, 197-foot (60-metre) mast so that the radar readings will be sufficiently offset.

The carbon fibre mast Ð the longest fixed structure ever to fly in space Ð is expected to whip about like a fishing rod whenever Endeavour fires its engines, so the astronauts have developed a special manoeuvre they call Òfly-castingÓ to help stabilise the mast.

The challenge will be to keep everything running 24 hours a day, with the crew split into two shifts, so that no part of the planet is missed as they pass over it.

"We need to do 159 consecutive orbits," said Kevin Kregel, commander of the six-astronaut crew, now set to launch on February 11. ÒWe can get just about everything, every land mass on Earth between the two arctic circles.Ó The resulting topographic map will cover 72-80 percent of the Earth.

Topographic maps show the heights of hills and mountains and the depths of valleys and gorges. At high resolutions, they even measure trees and buildings.

ÒThere are global maps, but theyÕre not at the resolutions weÕre going to get from this flight,Ó said Janice Voss, payload commander in charge of the radar, preparing for her fifth space flight. ÒWe donÕt have a map of the entire Earth made from one set of data.Ó

Although ultra-high resolution topographic maps of small areas exist, world maps are pieced together from different readings. The best set of world maps are based on measurements taken once every 1,100 yards (1 kilometre), EndeavourÕs crew will take measurements every 30 yards (30 metres.)

The STS-99 mission is a joint project between NASA and the super-secret National Imagery and Mapping Agency (NIMA), provider of maps and spy-satellite images to the U.S. military and intelligence services. 

Other collaborators include the German Aerospace Centre (Deutsches Zentrum fur Luft- und Raumfart) and the Italian Space Agency, which provided the experimental X-band SAR system.

But many scientists may never see the high-resolution 30-yard (30-metre) maps because NIMA plans to release only the U.S. portion, retaining the rest of the maps for potential military applications.

Instead, a 90-yard (90-metre) resolution map of the world will be released, with scientists applying on a case-by-case basis for access to the better maps.

The international crew aboard Endeavour includes Mamoru Mohri of the Japanese space agency, NASDA, and Gerhard Thiele, a German astronaut with the European Space Agency.

/ENDS

Sources: NASA, JPL, Reuters, Aviation Week