Any old earth-observing satellite could have recorded a very high tension
area over the Ariane launch site in French Guyana last Thursday night as
Arianespace’s Ariane 5 heavy-lift launcher put Envisat, the European Space
Agency’s 8-ton multi-instrument platform, into orbit, while a lot of breath
was held.

First of all, the future of the Ariane program after a spotty
history of heavy-load launching was at stake; secondly, the ESA had a huge
number of eggs in one $2-billion-basket in what will likely prove to be the
last of the big cluster platforms; not to mention the hundreds of scientists
and laboratories who had 10-15 years invested in the instruments and
projects waiting to be borne aloft.

In a big boost for European space, and
very likely a small one for the champagne market, Envisat was placed in
orbit with eye-popping precision, arriving without a glitch onto a
sun-synchronous orbit about 20 meters from the planned path, and with so
little maneuvering necessary that its unspent fuel reserve may mean a
much-extended life.

Envisat is an ambitious program of earth observation to
be carried out by 10 on-board instruments, and fina?ӝ/ by 14 European
nations. As explained by the ESA’s Director of Earth Observation, JosŽ
Achache (also chair of the international Committee on Earth Observing
Satellites-CEOS), Envisat will be focusing its sharp eyes on three large
areas: the atmosphere, the oceans and polar caps, and land.

Four of its
instruments will keep Envisat’s data as accurate as possible by providing
constant data on its position and speed, one of which–the altimeter–will
also provide data on ocean level and even the topography of the ocean floor.
Three will concentrate on tracking not only the concentrations but also
precise locations of a number of atmospheric components and pollutants,
including greenhouse gases, ozone, aerosols of all origins, industrial
pollution, and even the effects on the atmosphere of forest fires, dust
storms, and volcanic eruptions.

One of these, GOMOS, is designed to provide
ozone-concentration data by star occultation, whereby the spectra from
bright stars will be analyzed as Envisat orbits the earth and light from the
stars passes through the atmosphere at the horizon, thus identifying the
chemical makeup of that patch of atmosphere.

An ocean-gazing spectrometer
will pick up changes in ocean color due to algae proliferation, while a
radiometer reading several wavelengths of light is designed to provide a
detailed map of ocean temperature (and will even be able to detect a forest
fire getting started). Polar ice will also be under close surveillance, as
will icebergs, and even dishonest tankers illegally rinsing their tanks at

Radar on board this global-scale Big Brother will also detect slight
changes in the land levels, such as Venice slipping a few millimeters into
the sea or Djakarta sinking slightly as water tables are over-solicited.
Achache promised that a very liberal policy of access will be observed,
predicting that probably a 100,000 scientists worldwide will benefit from
Envisat data. He says the ESA is ready for data demand, as a result of
having invested in considerable crunching power in anticipation of the huge
flow of data Envisat will be beaming down.

First though, a several month
period of synchronization and calibration is required to ensure reliability.
Meanwhile, European space, at national as well as multilateral levels, is
tending to the preparation of the next generation of earth observers which
will be small, specialized satellites requiring much less breath to be held
at launch time and presumably adding years to launch directors’ lifespans.

(Le Monde, February 27, p28, Pierre BarthŽlŽmy; LibŽration, March 2, p18-19,
Sylvestre Huet; Le Figaro, March 2, p11, Fabrice NodŽ-Langlois)