ANSI-C program: pre_rc_JERS.c
NAME
pre_rc_JERS - Prefilter and
range compression of JERS-1 raw data including RFI
suppression.
SYNOPSIS
pre_rc_JERS
<SAR_par> <PROC_par> <psd> <raw_data>
<rc_data> [prefilt_dec] [kaiser] [filt_lm]
| <SAR_par> | (input) MSP SAR sensor parameter file |
| <PROC_par> | (input) MSP processing parameter file |
| <rspec> | (input) range spectra data file for RFI suppression |
| <signal_data> | (input) uncompressed raw SAR signal data filename |
| <rc_data> | (output) range compressed data filename |
| [prefilt_dec] | prefilter decimation factor (enter - for default from PROC_par) |
| [kaiser] | range chirp Kaiser window parameter beta (default=2.120, -30 dB sidelobes) |
| [filt_lm] | filter length multiplier (default FIR_lm=8) FIR_length = FIR_lm *prefilt_dec + 1 |
DESCRIPTION
pre_rc_JERS is similar to pre_rcbut also includes the capability to
suppress radio frequency interference (RFI). For JERS-1
there is also functionality to track the receiver gain and to
apply the inverse of the Sensitivity Time Control (STC) function.
PALSAR does not change the receiver gain along-track nor
does it apply an STC function. The along-track gain variations of
JERS-1 are related to the receiver automatic gain control
(AGC) that adjusts the gain for optimum SNR in the digitized
samples. RFI suppression uses the range spectra contained
in the file *.psd (calculated using rspec_JERS) to notch the range reference
function spectrum, thereby suppressing narrow-band interference
that often occurs in L-Band data.
This program has the option to perform decimation in azimuth (prefiltering) by applying a bandpass filter followed by subsampling. This is useful for survey mode processing to generate a "quicklook". Any integer decimation factor can be used because. The filter is implemented with as an FIR filter in the time-domain. The number of taps in the finite impulse response filter determines how closely the azimuth filter approximates an ideal response. Since the Doppler centroid varies in the cross-track direction, somewhat better results may be obtained by range compressing the entire data set followed by applying the azimuth bandpass filter and decimation rather than filtering prior to range compression. The program prefilt performs this function on the range compressed data set.
Notice: Updates for the number of range samples, number of offset lines, number of lines to process, and the swath extension parameter values must occur before running program rspec_JERS. If these values change, run rspec_JERS prior to pre_rc_JERS.
SEE ALSO
Users Guide, typedef_MSP.h, rspec_JERS Sensor
parameter file, MSP Processing
Parameter File, prefilt .