ESA's Most Advanced
Navigation Satellite Launched Tonight
(27 April 2008) A further step towards the deployment of Europe's Galileo global navigation satellite system was taken tonight, with the successful launch of ESA's second Galileo In-Orbit Validation Element (GIOVE-B) satellite, carrying the most accurate atomic clock ever flown into space.
The Soyuz-Fregat launch vehicle carrying GIOVE-B, the second of ESA's two Galileo In-Orbit Validation Element demonstrators for the Galileo global navigation satellite system, lifts off from launch complex at the Baikonour spaceport, Kazakhstan, on April 27, 2008. (courtesy: ESA - S. Corvaja)
The GIOVE-B satellite was lofted into a
medium altitude orbit around the earth by a Soyuz/Fregat rocket departing from
the Baikonur cosmodrome in Kazakhstan by launch operator Starsem. Lift-off
occurred at 04:16 local time on 27 April (00:16 Central European Summer Time).
The Fregat upper stage performed a series of manoeuvres to reach a circular
orbit at an altitude of about 23 200 km, inclined at 56 degrees to the Equator,
before safely delivering the satellite into orbit some 3 hours and 45 minutes
later. The two solar panels that generate electricity to power the spacecraft
deployed correctly and were fully operational by 05:28 CEST.
This 500 kg
satellite was built by a European industrial team led by Astrium GmbH, with
Thales Alenia Space performing integration and testing in Rome. Two years after
the highly successful GIOVE-A mission, this latest satellite will continue the
demonstration of critical technologies for the navigation payload of future
operational Galileo satellites.
Three high-accuracy space clocks
aboard
Like its predecessor, GIOVE-B carries two redundant
small-size rubidium atomic clocks, each with a stability of 10 nanoseconds per
day. But it also features an even more accurate payload: the Passive Hydrogen
Maser (PHM), with stability better than 1 nanosecond per day. The first of its
kind ever to be launched into space, this is now the most stable clock
operating in earth orbit. Two PHMs will be used as primary clocks onboard
operational Galileo satellites, with two rubidium clocks serving as
back-up.
GIOVE-B also incorporates a radiation-monitoring payload to
characterise the space environment at the altitude of the Galileo
constellation, as well as a laser retroreflector for high-accuracy laser
ranging.
Signal generation units will provide representative Galileo
signals on three separate frequencies broadcast via an L-band phase array
antenna designed to entirely cover the visible earth below the
satellite.
The satellite is now under the control of Telespazio's
spacecraft operations centre in Fucino, Italy, and in-orbit checking-out of the
satellite has begun.
Final demonstration before Galileo
In
addition to its technology-demonstration mission, GIOVE-B will also take over
GIOVE-A's mission to secure the Galileo frequencies, as that first Galileo
demonstration satellite launched in December 2005 is now approaching the end of
its operational life.
Beyond GIOVE-B, the next step in the Galileo
programme will be the launch of four operational satellites, to validate the
basic Galileo space and related ground segment, by 2010. Once that In-Orbit
Validation (IOV) phase is completed, the remaining satellites will be launched
and deployed to reach the Full Operational Capability (FOC), a constellation of
30 identical satellites.
"With the successful launch of GIOVE-B, we are
about to complete the demonstration phase for Galileo", said ESA Director
General Jean Jacques Dordain in Fucino while congratulating the ESA and
industrial teams. "The strong co-operation between ESA and the European
Commission has been instrumental in making progress in a difficult environment
over the past few years; and, even with that being so, Galileo has already
materialised, with two satellites now in orbit, significant headway made on the
next four (already in the construction phase) and a fully qualified EGNOS
service (*) - all this designed to serve citizens in Europe and all around the
globe. ESA will begin shortly the procurement process for the overall
constellation beyond IOV under EC responsibility."
Galileo will be
Europe's very own global navigation satellite system, providing a highly
accurate, guaranteed global positioning service under civil control. It will be
interoperable with the US Global Positioning System (GPS) and Russia's GLONASS,
the two other global satellite navigation systems. Galileo will deliver
real-time positioning accuracy down to the metre range with unrivalled
integrity.
Numerous applications are planned for Galileo, including
positioning and derived value-added services for transport by road, rail, air
and sea, fisheries and agriculture, oil-prospecting, civil protection,
building, public works and telecommunications.
(*) European
Geostationary Navigation Overlay Service. EGNOS is a joint programme being
carried out by the European Space Agency, the European Commission and
Eurocontrol. It comprises a network of more than forty elements all over Europe
that collect, record, correct and improve data from the US Global Positioning
System. The modified signals are then relayed via geostationary satellites to
user terminals, offering positional accuracy better than two metres, compared
with 15 to 20 metres for GPS alone. In addition, EGNOS provides a guarantee of
signal quality that GPS does not.
(source: ESA)
