French Advances in Science & Technology: Issue #336 “A SPOT in the Sky”

The earth is increasingly ringed with spots as the CNES’s (National Space
Agency) latest earth photographing satellite, SPOT 5, was successfully
launched last week and placed in sun-synchronous orbit along with the three
of its predecessors still active (Spot 3 ceased activity in 1996 after three
years of service). But instead of seeing spots, earthlings will be seen by
them, as Number Five is the latest step in the ESA’s commitment to keeping
the planet under observation.

Although the equipment on board Spot 5 permits
greatly increased performance and resolution–it’s High Resolution
Stereoscopic (HRS) camera will permit 3D images of a swathe of the globe’s
surface 80×100 miles with a resolution of 2.5 meters in black-and-white and
10m in color-signals from predecessor Spots (particularly 2 and 4) will
continue to be treated by Spot project tracking systems. Even at lower
resolutions, the Spot network taken all together can now provide
photographic coverage of any place on the earth within 24 hours instead of
having to wait typically several weeks before an observation satellite
covers the same ground twice.

Spot 5 plays a large part in this new and
useful capacity (e.g. tracking the development of floods or volcanic
eruptions) because of its wide peripheral vision; although only repeating
its orbit every 26 days, it will be able to photograph any point on earth
every 4 or 5 days. While Spot 5’s resolution is still not as sharp as the
best US effort, the satellite Ikonos, the sterescopic capacity of recording
topographical information as well as information from the other three
instruments on board ensure a leading role to the Spot project in the
competitive market for satellite photographs, such as its specialized eye
trained to analyze vegetation coverage. Also, geographic institutes around
the world, most of whom find Ikonos images too expensive, may well be able
to use Spot’s topographical views which cover 100 times more area. (China
has already signed with Spot Images to help it produce for the first time
cartographic coverage of its entire territory at a scale of 1/50,000.)

The
next step for the CNES will be its Pleiades series of radar-equipped
satellites able to see through clouds. Meanwhile early transmissions from
Spot 5 are up to expectations, as the first image beamed back last week was
a view of the city of Athens. (Le Figaro, May 3, p12, Fabrice NodŽ-Langlois;
France in Space #’s 205,6)