Gravity Field Explorer

ESA's gravity mission GOCE

The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) is dedicated to measuring the Earth's gravity field and modelling the geoid with extremely high accuracy and spatial resolution. It is the first Earth Explorer Core mission to be developed as part of ESA's Living Planet Programme and is scheduled for launch in 2007.

Mission objectives

To determine the gravity-field anomalies with an accuracy of 1 mGal (where 1 mGal = 10^-5 m/s^2).
To determine the geoid with an accuracy of 1-2 cm.
To achieve the above at a spatial resolution better than 100 km.

Mission elements

Single rigid octagonal spacecraft of approximately 5 m long and 1 m in diameter with fixed solar wings and no moving parts.
Gradiometer -- 3 pairs of 3-axis, servo-controlled, capacitive accelerometers (each pair separated by a distance of 0.5 m).
12-channel GPS receiver with geodetic quality.
Laser retroreflector enabling tracking by ground-based lasers.

---

Closed Caption:

when we think you gravity
anything give it literally is the force
that keeps our feet on the ground
although it's invisible
it provides us with the sense that the
horizontal and vertical
most diverse take the Earth's constant
beloved gravity for granted
buddy have studied in detail gravity on
earth turns out to be more complex than
most people assume
gravity is not the same all over the
world and it supports that varies from
place to place on the surface of the
planet
depending on a number of different
factors and
firstly the distance between the center
of the earth and its surface is smaller
the polls than the equator this
flattening is due to the Earth's
rotation
making the beloved gravity slightly
stronger at the polls
secondly the service if the earth is not
even with high mountains and ocean
trenches causing the value of gravity
two very
thirdly the material composition inside
the earth
there is and matter is not evenly
distributed
love which perfect gravitational pull
even small changes in topography such as
my sheet movements
sea level changes volcanic eruptions and
the erection a blonde buildings
consistently a third local gravity field
all these factors taken together
Fulmer gravity feel that is very
different from the smooth globe we
traditionally think I'll
the other on
run to the sideline derail gravity had
not being measured accurately across the
world
what we had looked fragmented the world
map with the gravity field if uneven
quality
the go to a satellite due to be launched
in 2006
is the first eases satellites solely
dedicated to measuring the Earth's
gravity
and it will make uniform high accuracy
measurements have the gravity field
was rotating round the other two
critically low orbit hi to the only 250
kilometers
I'm during its 20-month mission go che
will build up a detailed and precise
picture of the Earth's gravitational
field
using an incredibly sensitive new
instrument called
McGrady a meter
ghosts been designed to fly alone
orbited 250 kilometers because the
gravitational signal is stronger closer
to the earth
however the remaining atmosphere at low
altitudes creates demanding environment
for the satellite
presents a real challenge for its design
in order to ensure that the effect of
the remaining atmosphere
it's a kept to the bare minimum this
satellite configuration
it's a quite a unique one to peter is a
is shaped which is quite slim
so is fine me too long in only one meter
well for the you meet him in actually
the cross-section he's ok Dagenham
plus we have in nineteen engine we
cheese compensating contracting effect
on the atmospheric
unlike other missions were various
independent instruments are carried on
board the space craft
ghost is unique in that instrumentation
actually forms part of the structure
the satellite goes is a very unique
satellite is to
Ferrari of gravity missions we have farm
in contrast to previous cover two
missions we have
6 accelerometers the instrument the
Great Yarmouth to resist known
is comprised of three there's
accelerometers
oriented in that the along track flight
direction at the satellite in the across
truck
flight direction and in the radial
direction
which points from the center of the
earth outwards what this gives us access
to is gradients in the gravity field
oceanography is an important signs for
understanding
driving forces behind our global climate
and go check will allow oceanographers
to greatly improve what they call the
deal lead
this is a global height reference
surface
which the North would take if the oceans
will motionless
the G like provides the reference
against which scientists compare the
oceans motions
which are the circulation batons a
surface waters and deep occurrence
which play such an important role our
climate
another benefit if the coach a mission
will be an improved knowledge of the
activity and dynamics of the Earth's
interior
because gravity is directly related to
the distribution
mass within the earth and improved
gravity field map will provide a greater
insight into the process is
that create earthquakes and volcanoes
and
their location hazards associated with
plate motions such as earthquakes have
an everyday impact on people's lives and
one thing that goes can do is provide
details of the gravitational field that
are a consequence of
the way in which the plates moving over
the top of one another
and using did the gravity information we
can provide
its detailed three-dimensional
information about
the earth's crust and its structure and
by having that
information we can improve models the
way in which
the plate motions actually work and in
reality
the should be should give us better
understanding that we can use in the
predicted trends for
particularly volcanic areas and and
places where
people suffering from earthquakes on a
regular basis only the future will tell
to what degree the value of the
information gathered from the Gooch a
mission
will contribute to the will scientific
knowledge that influences the future of
the planet