The satellite configuration is dictated by mission Requirements (minimization of air drag forces and torques) and engineering constraints (the available volume under the launch vehicle fairing, with no deployable parts; passive aerodynamic stability).
The satellite body has the shape of an octagonal prism, About 5.3 m long and with a transversal cross section of 1.1 m2. Seven main platforms , called floors, horizontal in the launch configuration, divide the volume inside the spacecraft body into compartments.
It is fundamental that the position of the Gradiometer is such that its center is as much as possible close to the Spacecraft CoM, to minimize the angular accelerations produced on the sensors by the lateral drag forces. This explains the mounting of the EGG in the central part of the SC body.
The in-orbit attitude of the Spacecraft is such that the body has a Sun facing hot side and a shadowed cold side that is almost invariable during the mission. That characteristic is exploited to mount on the shadowed side a radiator used to keep a stable thermal environment to the Gradiometer. The SST receiver electronic and the transponder are distributed on the sixth floor and the second floor respectively.
The star trackers are mounted as close as possible to the Gradiometer to reduce misalignment during mission operation. The micro-propulsion was originally justified by the need to guarantee the linear acceleration control along the Y and Z Axes of the S/C and for the pointing control. Their presence was also concurring to the angular acceleration control about the Gradiometer sensor axis and to the Gradiometer Calibration.
The development of the micro-propulsion thrusters has been
pursued via a pre-verification program, suite for determining the
best candidate between cold gas and FEEP technology. In July 2003,
the use of micro-propulsion was abandoned because the development
maturity was no longer in line with the need of the GOCE program.
The control strategy of the spacecraft has been then revisited and
redefined, by maximizing the use of already present capability and
minimizing the impacts of cost and schedule. A simpler calibration
system “Gradiometer Calibration Device” (GCD) has been
added to the GOCE on board functions for allowing the performance
of the in flight calibration of the Gradiometer.
The xenon tank is placed at the satellite's lower end close to
the ion thrusters for short xenon lines. The solar array consists
of six panels, 2 wings self-supporting and 4 body panels mounted
directly to the S/C body, with necessary thermal isolation
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