Lustrumboek 'The 5th Element"
Basically there are two possibilities to counteract the damping effect: first of all,
r6onan oli i ^ellite as low as possible. The lowest altitude, however, is limited
to ^UU-250 km or technical, financial, and safety reasons, and this is not sufficient
to meet the goals given in fiaure 3. The second possibility is indicated in figure 5
I he top panel shows the information content of the second radial derivative of
the potential at 250 km altitude. Obviously, this quantity has much more power
in the short wavelengths compared to the first derivative (bottom panel of figure
5), which is of course due to the differentiation. Derivatives of the potential are
provided by differencing techniques. For instance, second derivatives of the
potential can be derived from acceleration differences between two proof masses
over very short distances (some decimeters). This is called 'differential
accelerometry'. In general, the term 'gravity gradiometry' is used to indicate the
measurement of second order potential derivatives. These quantities are much
more sensitive to the fine structures of the gravitational field, and this sensitivity
increases with decreasing distance between the proof masses.
Gravity gradient at 250km altitude
SO 120 180 240
Longitude
109 S"2
Gravity anomalies at 250km altitude
Figure 5: The attenuation effect counteracted
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