AIDJEX Bulletin #40 - Polar Science Center - University of Washington

model ice motion in the statistical filter, We do not believe that our
methods of data reduction provide the greatest accuracy? but they are
expedient and they meet our needs.
ACKNOWLEDGMENTS
We gratefully acknowledge our introduction to the Navy Navigation
Satellite System by the NavSat community, and the efforts of the employees
of the Satellite Positioning Corporation, who built the positioning systems.
Logistic support was provided by the Naval Arctic Research Laboratory and
by the Distant Early Warning System in Alaska. We are indebted to the men
and women who operated and maintained the equipment for one year on the
Arctic Ocean. The work was funded by the National Science Foundation? the
Office of Naval Research, and the Bedford Institute of Oceanography.
APPENDIX A
DOPPLER COllNTING CORRECTIONS
The desired Doppler count is the integral of the Doppler frequency over
the interval (tl, t2).
of timing marks transmitted by the satellite at known times (T, T+T).
tice the Doppler count is not measured exactly.
The counting logic requires
some time to recognize the timing marks during which time several full Doppler
cycle marks may have passed.
1.2 msec, with jitter of the order 50 usec.
interval over which the Doppler measurement was made will generally be lagged
with respect to the desired interval and of different length.
An additional
random error of 0-1 Doppler count at the beginning and end of each interval
exists because the counting logic recognizes only zero crossings of the
Doppler signal.
follows.
This interval is defined by the arrival at the antenna
In our hardware? delays were estimated to be
In prac-
Figure 11 illustrates that the
A corrected Doppler count B was constructed from the measured value D as
The Doppler count can be interpreted as an area under the curve of
Doppler frequency versus time (Fig. 11).
Therefore,
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