Data from various sources can be combined in a manner assigned to minimize the
mean-squared error in the resulting estimate. This estimate of isobaric surface height,
together with the output of a hypsometer, can provide the required altitude data for
gravimeter compensation.
The nature of the signal processing and filtering problem is, in most cases, such
that post-flight data processing is possible. This allows the design of a filter free of the
usual readability constraints. The noise present in the gravimeter output before filtering
is mostly due to aerodynamic, wind, and turbulence loading of the airframe. These
interfering forces result in aircraft accelerative that are partially counteracted by the
autopilot system.
Low-frequency prizoelectric gravimeter. This gravimeter (sensor) has an
accuracy of 1 mGal. The sensitive element of PG (Fig. 1) consists of a piezoelectric
element (PE) 5, which operates on the compression-stretching deformation, insulators
7 at the ends of PE and inertial mass (IM) 6. A sensitive element is elastically attached
to the basis 8 by a screw 10 with purpose to increase reliability and durability of the
structure. Due to cable 11 PG is connected to an operational amplifier. Piezoelectric
element 5 is a multi-layer structure (piezoelectric packet) consisting of layers of
crystalline lithium niobate.
Figure 1. Structure of PG: 1 –PE; 2 – insulators; 3 – IM;
4 – basis; 5 – hermetic enclosure; 6 – screw; 7 – inlet cable
The principle of operation and design features of this gravimeter is shown in [9-
12].
Paper [1, 17] presents analytical expressions of useful signal spectral densities
(ω) and vertical aircraft acceleration (ω) and their characteristics (Fig. 2).
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