The first satellite-relayed images from Envisat have
been received, via the Artemis data-relay spacecraft in
geostationary orbit, at ESA’s data processing centre at
ESRIN, near Rome.

The images represent twin triumphs for the European
Space Agency. “For the Envisat Earth observation mission,
bringing Artemis online to relay Earth imagery and
scientific measurements means that more data can be
acquired and downloaded and the process of delivering
Earth observation data to end users will be much faster.
This is very good news” said José Achache, Director of
Earth Observation.

For Artemis, the Advanced Relay Technology Mission, the
image transmission caps a historic, 18-month recovery
operation that brought the spacecraft to its assigned
geostationary orbit after a July 2001 launch that left
Artemis stranded in an orbit far lower than intended.
Despite the lack of sufficient conventional propellant
to raise the spacecraft’s orbit, ESA engineers used
Artemis’ groundbreaking ion propulsion system, combined
with innovative operations of its chemical thrusters,
and succeeded in raising the satellite to its nominal
geostationary position at 21.5 degrees East.

“This recovery mission was a real demonstration of
experimental technology” said Claudio Mastracci,
Director of Applications, “I am pleased Artemis is
now able to support the whole space community”.

“The purpose of the Artemis mission is to qualify new
space communication technologies in orbit and to offer
new communication services,” said Gotthard Oppenhäuser,
ESA’s Artemis Mission Manager, “Via the data relay
system, users can receive their data in real time
while maintaining full security.”

Artemis carries payloads supporting land mobile
communications, navigation systems and data relay
systems. The spacecraft operates at S-band (2 GHz),
Ka-band (26 GHz) and optical frequencies. Artemis
and Envisat communicate at Ka-band frequencies.

Setting up the operational data relay system in the
Ka-band between Artemis and Envisat is a first for
Europe. The system proves the space qualifications of
new technologies and operational procedures, along
with demonstrating the complex software used in both
the ground and space segments. It also shows the
usefulness of data relay payloads.

Once testing of the inter-satellite link is completed,
Envisat will transmit about half of its sensor data
through Artemis straight to the Envisat data
processing centre at ESRIN, starting at the end of
April. Data from various instruments will continue to
be downloaded to the Envisat ground station and data
processing centre in Kiruna, Sweden, but the addition
of the data relay satellite offers several important
new capabilities to the Envisat data network.

The Kiruna ground station can ‘see’ the satellite for
about 10 minutes of Envisat’s 100-minute orbit, and
for 10 daily orbits. Because of its orbital position
above Envisat, Artemis can remain in contact with
Envisat on almost all its 14 daily orbits, and for
longer periods.

Shifting a large portion of Envisat’s downloads to
Artemis for relay to ESRIN will ease the workload at
Kiruna and thus reduce the time taken in processing
information from Envisat’s sensors to within three
hours of the initial data acquisition. The use of
Artemis will also enable ESA to increase the amount
of data acquired by Envisat anywhere in the world,
particularly in the case of the Advanced Synthetic
Aperture Radar (ASAR) instrument, increase the
flexibility of the mission’s ground segment, and
provide a back-up in the event of a problem with
the onboard recorders, which will improve mission
reliability.

“Artemis will be a great help to us in improving our
services to Envisat users,” said Henri Laur, ESA’s
Mission Manager for Envisat. “It will reduce the
delivery time for Envisat data and remove some
processing delays.”

Envisat recently marked its first year in orbit.
Launched on 28 February 2002 from Europe’s spaceport
in French Guiana, it is the largest and most capable
Earth observation satellite ever built. Its suite of
10 sensors is designed to provide a comprehensive
view of the Earth’s oceans, land, atmosphere and ice
caps.

The optical data relay system will be used between
Artemis and the French Earth observation satellite,
SPOT 4, starting in April. In 2005 the Automatic
Transfer Vehicle will start using a regular data
relay service and in 2006 (to be confirmed) Columbus,
the European element of the International Space
Station, will establish data relay links to Artemis
for nearly five hours a day.

For further information, please contact:

Gotthard Oppenhaüser
ESA’s Artemis Mission Manager
Tel: +31.71.565.3168

Henri Laur
ESA’s Envisat Mission Manager
+39.06.9418.0557

ESA Media Relations Service
Tel: +33(0)1.53.69.7155
Fax: +33(0)1.53.69.7690