Europe's New MetOp
Weather Satellite Reaches Polar Orbit
(19 October 2006) For 28 years, Europe
has been operating its famous Meteosat weather satellites in geostationary
orbit. Today, they were joined by the first of a brand new generation of
meteorological satellites.
MetOp is designed to provide a closer
view of the atmosphere from low earth orbit, delivering data that will improve
global weather prediction and enhance our understanding of climate
change.
The first of three satellites developed under a joint programme
being carried out by the European Space Agency and the European Meteorological
Satellite Organisation (Eumetsat), MetOp-A was successfully launched from
Baikonur, Kazakhstan by a Russian Soyuz 2/Fregat rocket operated by the
Euro-Russian company Starsem.
The Soyuz 2 launcher, on its first
operational mission, lifted off at 18:28 CEST (16:28 UT) with the 4093kg
spacecraft encapsulated in a new 4.1m diameter payload fairing, similar in
shape and size to that of Ariane 4. The newest member of the nearly 50-year old
Semyorka family of boosters, Soyuz 2 is due to be launched from French Guiana
from 2008 onwards.
Some 69 minutes after launch, the Fregat upper stage
released the first MetOp satellite into a circular orbit at an altitude of 837
km over the Kerguelen archipelago in the South Indian Ocean. With a slightly
retrograde 98.7° inclination, this orbit will enable MetOp-A to circle the
globe from pole to pole while always crossing the equator at the same local
time, i.e. 9:30 am. Known as 'sun-synchronous', this type of orbit allows
revisits to almost each point of the Earth's surface under similar solar
illumination conditions on an approximately daily basis.
The satellite
is now under the control of ESA's European Space Operations Centre (ESOC) in
Darmstadt, Germany, and has deployed its solar array. Over the coming days, it
will undergo the first technical check-outs of its systems and will deploy its
antennas. Handover to Eumetsat is expected on 22 October for full satellite
commissioning and routine operations.
MetOp-A will form the space
segment of the Eumetsat Polar System (EPS), designed to collect atmospheric and
environmental data to complement the hemispheric survey conducted from
geostationary orbit by the Meteosat system. EPS will be operated in
co-ordination with the US Polar Operational Environmental Satellite (POES)
system managed by the National Oceanic and Atmospheric Administration. While
NOAA satellites are deployed in an 'afternoon' orbit (i.e. crossing the equator
in the afternoon, local time), Europe's MetOp will take up service in a
'morning' orbit.
The most complete atmospheric probe
ever
To fulfil its ambitious mission, MetOp-A incorporates a
comprehensive remote-sensing payload consisting of a set of new-generation
European instruments, plus a set of 'heritage' instruments provided by the
United States similar to those flown on current NOAA
satellites.
Supplied by the French space agency CNES, the Infrared
Atmospheric Sounding Interferometer (IASI) will take measurements in more than
8,000 channels to provide temperature and water vapour profiles with
unprecedented accuracy to feed numerical weather-prediction models. Its
soundings will be complemented by measurements from the US heritage instruments
and the Microwave Humidity Sounder (MHS), a five-channel radiometer developed
for Eumetsat but also planned to fly on future NOAA satellites.
Jointly
developed by ESA and Eumetsat, the second-generation Global Ozone Monitoring
Experiment (GOME-2) is an improved version of a scanning spectrometer already
flown on ERS-2 which is designed to probe the atmosphere for profiles of ozone
concentrations as well as other trace gases.
Another ESA/Eumetsat
instrument with a strong ERS programme legacy is the Advanced Scatterometer
(ASCAT). This enhanced C-band radar will measure the speed and direction of
winds over the surface of the oceans, also to feed numerical weather prediction
models, but in addition providing useful information on ice, snow and soil
moisture.
One new instrument developed by ESA and Eumetsat is the GNSS
Receiver for Atmospheric Sounding (GRAS), which will use occultation of
satellite navigation signals through the atmospheric limb to derive atmospheric
temperature and humidity profiles.
NOAA-supplied instruments include:
the third-generation Advanced Very High Resolution Radiometer (AVHRR-3) to
acquire global imagery of cloud cover as well as of ocean and land surfaces;
two 15-channel Advanced Microwave Sounding Units (AMSU/A) to scan atmospheric
temperature profiles; and the fourth-generation High Resolution Infrared
Radiation Sounder (HIRS), a 20-channel equivalent of the IASI interferometer
which will support validation of data collected by the European instrument and
serve as a back-up afterwards.
In addition, MetOp-A carries an advanced
Argos data collection system supplied by CNES to locate and communicate with
automated stations, whether fixed or mobile; two search & rescue payloads
respectively provided by the Canadian Space Agency and CNES to support the
international Cospas-Sarsat network by picking up and retransmitting distress
signals; and a US-supplied Space Environment Monitor (SEM-2), a spectrometer to
survey the charged particle flux in space.
A major boost to weather
forecasting
Approved back in 1992, MetOp is a meteorological
operational satellite programme like Meteosat. ESA's contribution to its
inception is being managed through the Earth Watch component of its Living
Planet programme. ESA is in charge of the satellite's development and
procurement. In that capacity, it funded most of the first flight model
manufacturing. Eumetsat is in charge of the operational system and is funding
the development of the ground segment and follow-on satellites, the launchers
and operations.
Three flight models have been ordered from an industrial
team led by EADS Astrium. The spacecraft, integrated in Toulouse, France, are
based on a bus derived from ESA's Envisat and France's Spot 5 satellites and
incorporate advanced equipment to ensure flexible operations, with more than 36
hours' autonomy and a 24 Gbit data storage capability.
MetOp satellites
will circle the planet some 14 times a day, gathering data that they will
download to the EPS Command & Data Acquisition (CDA) ground station located
in the Svalbard archipelago, North of Norway. Due to its high latitude
(78°N), the CDA station will be visible to MetOp on each of its orbits, as
the satellite flies over the Arctic. Once collected, MetOp data will be
transmitted to Eumetsat's facilities in Darmstadt for processing and
distribution. In addition, some real-time Polar System data will be broadcast
directly to regional meteorological organisations whenever the satellite comes
into visibility in terms of their receiving stations.
Thanks to its
advanced payload and broadcast capacity, MetOp will be able to detect and
report the early development of localised severe weather conditions, such as
violent thunderstorms, which cannot be observed from geostationary orbit. The
satellite will thus make it possible to issue weather alerts at much earlier
notice than at present.
"I congratulate our friends and partners from
Eumetsat, NOAA, CNES, Starsem, the European space industry and the
international meteorological community on this successful launch", said ESA
Director General Jean-Jacques Dordain." Like the two generations of Meteosat,
this programme is more than a success story for international co-operation; it
is the perfect illustration of what priceless benefits space can bring to all
citizens. The harvest of data expected from MetOp-A and its follow-on
satellites will provide a new dimension to our knowledge of the Earth's
atmosphere and climate. Not only will these data lead to tremendous
improvements in the accuracy of weather forecasting in Europe and world-wide;
they will also enable the science community to develop more complex models of
our planet's climate in order to better understand ongoing global change and
steer international environmental policies accordingly."
(source:
ESA)