The gestation period was ten years, and the preparations were intense. Now
the waiting is nearly over, and the European Space Agency’s ambitious new
Earth-observing satellite Envisat is en route for Kourou in French Guiana
where engineers will prepare the satellite for its launch this autumn.

The journey began at 10:15 CET on Monday when the 2-billion Euro satellite
and its police escort left the European Space Research and Technology Centre
(ESTEC) in Noordwijk, The Netherlands for Amsterdam’s International Airport.
Here Envisat was loaded on to an Antonov 124, the only transport aircraft
large enough. Two 747s and the transport ship Toucan are additionally
carrying nearly 400 tonnes of testing and support equipment to the launch

The satellite is pivotal in ESA’s strategy for Earth observation. From its
vantage point of an 800-kilometre-high orbit over the Earth’s poles, the
satellite will, for the next five years, monitor environmentally crucial
processes as diverse as changes in ocean circulation, the ice caps, land
use and atmospheric pollution.

Its instruments are either new developments or major improvements of those
that flew on ERS-1 and -2, the Agency’s groundbreaking Earth observation
satellites of the 1990s. Besides contributing to a broad range of science
and application, Envisat’s multiple instruments will play a crucial part
in helping to implement an initiative global monitoring for environment
and security proposed last year by ESA, the European Commission and the
French Space Agency.

Envisat’s roots

Envisat has its roots in a time in the late 1980s when the philosophy within
space agencies around the world was to develop large multi-purpose missions.
At the time satellite and launcher technology were less sophisticated and
flexible than they are today, economies of scale underpinned much thinking
about technological development in general and the thinking was that a broad
range of applications were needed to justify any space project.

Since then space technology has moved on, and there is increasing emphasis
worldwide on small, flexible missions that can be developed quickly and
cheaply. “Certainly Envisat’s size and multiple missions make it risky, and
we are now moving to a new logic and era that will see the launch of small
satellites with specific missions,” says Claudio Mastracci, ESA’s director
of space applications, “but Envisat is a miracle of engineering and it will
provide invaluable data for environmental monitoring.”

One of the satellite’s strengths, he argues, is that it could provide data
for 7 to 10 years (design life is five years, but both ERS-1 and ERS-2 have
significantly exceeded their design life), which would allow continuity of
observation over slowly changing environmental phenomenon.

Testing time

For the moment, though, it is not Earth-observing strategy that is at the
forefront of the minds of the Envisat team, but the welfare of the satellite
that has captured their professional attention for the past decade. Earlier
this year, the satellite was fully assembled to permit a final test of every
instrument, antenna, microprocessor and line of software.

Vibration testing exposed the satellite to forces equivalent to those from
an earthquake of 7.5 on the Richter scale, and acoustic tests battered the
satellite with the volume of 156 rock concerts. For a month, the satellite
sat in massive chamber from which all the air was sucked, exposing the
spacecraft to the hard vacuum and extreme temperatures of space. During
that time, software engineers tested the thousands of lines of code that
will control the satellite’s operations and instruments.

In separate radio frequency tests, all the antennas were operated
simultaneously to ensure their transmission patterns did not overlap
in unforeseen ways. Each instrument was switched on to check that its
electromagnetic field did not impinge on the operation of nearby

Mission controllers at the European Space Operations Centre in Darmstadt,
Germany established telephone links to the satellite in ESTEC and practised
controlling the satellite and its instruments. And at the European Space
Research Institute (ESRIN) in Frascati, Italy staff are preparing for the
deluge of data — a minimum of one CD-Rom per minute … every minute!

Every test indication was that Envisat will withstand the rigours of its
launch aboard an Ariane-5 rocket and is ready for its task in orbit.

With the testing complete, engineers disassembled Envisat into two sections
small enough for shipping. After arrival in Kourou in the early hours of
16 May, it will be allowed to sit for a day so that the air temperature
inside the shipping cases equalises with that in French Guiana. Then
engineers will open the cases to begin assembly of the satellite, make
final tests and integrate Envisat with the Ariane-5 for launch. The coming
months will see the culmination of 10 arduous years of complex engineering,
and Envisat will be ready to begin its task. “I am,” says Mastracci,
“very proud of the teams at ESTEC and ESRIN and of the scientists and
industrialists around the Agency’s Member States [Canada is an associate
member] who have worked on Envisat and are preparing to exploit its data.”

Related News

* Envisat’s last weeks on European soil

* Envisat: only a few months to go

* Europe’s satellites track changes

Related Links

* Envisat homepage

* Earth Observation Homepage


[Image 1:]
Loading Envisat onto the Antonov at Amsterdam Schiphol Airport, en route for
the launch site in Kourou, French Guiana, 14 May 2001.

[Image 2:]
Envisat convoy negotiates the first roundabout after leaving ESA’s testing
facilities at ESTEC in Noordwijk (NL), 14 May 2001, en route for Schiphol
airport, from where it is is transported to Kourou, French Guiana aboard
an Antonov 124.

[Image 3:]
Envisat undergoing rigourous testing at ESA’s test falicities at ESTEC,
Noordwijk, NL.

[Image 4:]
Envisat at ESTEC.

[Image 5:]
Envisat leaving the test facility at ESTEC,14 May 2001, en route for
Schiphol and its flight to French Guiana aboard an Antonov 124.