Astrium to build two new research
satellites for NASA
29 November 2012
Astrium, has been commissioned to build two
new research satellites for NASA’s Jet Propulsion Laboratory JPL
(Pasadena, California). The agreement was signed today in
Friedrichshafen, Germany. For a minimum of five years from August 2017,
the Gravity Recovery and Climate Experiment Follow-On (Grace FO) mission
will continue the extremely accurate measurement data collection of the
first twin Grace satellites, which have been in orbit since 17 March,
2002.
Astrium’s Grace satellites have been making a
hugely important contribution to global climate research since 2002.
Based on their observations of changes in the Earth’s gravity field over
time, geoscientists are gaining new insights into the dynamic processes
in the planet’s interior, into deep and surface currents in the oceans,
and into variations in the extent of ice coverage at the poles, in
Greenland and over mountain ranges. The original Grace mission allowed
scientists for the first time to identify which masses of water, ice and
solid material are moving; Grace is even able to provide long-term
observation of water table levels around the world.
Each of the Grace FO satellites measures
approximately 3 x 2 x 0.8 metres and weighs around 580 kg. Like their
predecessors, they will be placed in a polar orbit at an altitude of
some 500 kilometres and follow each other 220 km apart. As they fly, the
two satellites constantly and extremely precisely determine the distance
between them, which varies under the influence of the Earth’s gravity;
this fluctuating distance provides the data for continued measurement of
our planet’s gravity field.
The measurements taken by the Grace FO
satellites will be exceptionally accurate because their positions will
be minutely ascertained using on-board GPS (Global Positioning System)
receivers, while a satellite-to-satellite microwave link will enable the
exact distance between them to be calculated to within a few thousandths
of a millimetre. In contrast to the original Grace mission, the distance
between the new satellites will also be measured using lasers – a
technological experiment in preparation for future generations of
gravity-research satellites.
Throughout the five-year mission, these
measurements will be used to generate an updated model of the Earth’s
gravitational field every 30 days. In addition, every day each satellite
will create up to 200 profiles of temperature distribution and water
vapour content in the atmosphere and ionosphere.
With this new two-satellite contract, Astrium
in Friedrichshafen is building on the success of its unique series of
small satellites. Numerous important scientific missions, such as Champ,
GOCE and Swarm, have been based on Astrium’s satellite platform. The
Grace satellites, launched in 2002, have now been successfully carrying
out their mission for double their nominal five-year service lifetime.
Moreover, they were delivered to NASA on time and on budget.
