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Logs
5.1.5
ISMREDOBS Reduced phase and amplitude measurements
This log outputs the 60 second reduced and detrended phase and amplitude measurements. The
following data is included in this log to aid in ionospheric scintillation monitoring:
1.
Phase. The raw phase measurements are first detrended with a 6th order Butterworth high-pass
filter (with a user specified cutoff frequency). Then, for every minute on the minute, the statistics
of the residuals (of the previous 3,000 detrended phase measurements) are computed over periods
of 1 second, 3 seconds, 10 seconds, 30 seconds and 60 seconds. Thus for every 60 seconds, 5
values (1-sec, 3-sec, 10-sec, 30-sec and 60 second phase sigmas) are logged along with the time
tag (in week number and time of week).
2.
Amplitude. The raw amplitude measurements are detrended (by normalization), either with a 6th
order Butterworth low-pass filter output (with a user specified cutoff frequency) or with the
measurement average over the 60 second interval (if the user specified cutoff frequency is 0). The
latter method is the default method if no cutoff frequency is specified. Then, the total S
includes S
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second interval as the phase parameters. The receiver also computes the correction to the total S
which is the effect of ambient noise, based upon the average of the raw 1 Hz C/N
same 60 second intervals.
3.
Code/Carrier Divergence. The receiver also collects raw code/carrier divergence (difference
between code and carrier measurement) every second. The average and standard deviation of the
code/carrier divergence are then computed every minute on the minute. These values are
indicative of multi-path (and noise) activity and can be used to distinguish between S
multi-path (and noise) and S
scintillation.
4.
Lock Time. The lock time indicates how long the receiver has been locked to the carrier phase on
the signal. Since the phase detrending high-pass filter has to be reinitialized whenever lock is lost,
all phase parameters (sigmas) should be discarded for any lock time less than 180-240 seconds
(for a 0.1 Hz bandwidth) to allow the detrending filter to settle. For other bandwidths, this time
may vary inverse proportionally to the bandwidth. For the S
discard data for any lock time value less than 60 seconds. S
than 60 seconds since the power measurements are non coherent measurements that do not
require phase lock. However, on rare occasions, total signal lock could have been lost, so the use
of S
for lock time less than 60 seconds should be used with caution. However, in those cases, the
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code/carrier divergence measurements could be used to discard the data.
Structure:
Recommended Input:
GPStation-6 User Manual Rev 2
due to the effects of ambient noise (and multi-path), is computed over the same 60
due to scintillation, since there is no code/carrier divergence due to
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LOG ISMREDOBSB ONNEW
0
parameters, it suffices to only
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may also be valid for Lock Time less
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Message ID: 1393
Log Type:Asynch
, which
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,
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values over the
due to
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