ISEE-3/ICE Telemetry demodulator and decoder
Copyright Phil Karn, KA9Q, 8 June 2014
May be used under the terms of the GNU Public License 2.0 (GPL)


This is a snapshot of my ISEE-3/ICE telemetry decoder. It is now broken into three modules that you run
in a UNIX pipeline like this:

./pmdemod input_file | ./symdemod | ./decode

The input_file is expected to be a series of 16-bit signed integer samples in little-endian format. The I
channel is expected first. If Q is first, use the -f (flip) flag to invert the spectrum.

Each program writes its status to stderr so you can see what it's doing while its output is redirected.

Only Manchester (>= 512 bps) is supported at present. Low speed modes on 1024Hz subcarrier coming soon.
Only the 512 bps rate has been tested.

pmdemod - reads raw receiver file, tracks carrier, writes baseband PM samples (doubles) on stdout

-S starting carrier frequency estimate, Hz
-W +/- Frequency search range while locked, Hz (searches entire passband when unlocked)
-D Doppler chirp rate, Hz/s
-t C/N0 lock threshold, dB; default 21 dB
-q Quiet mode
-b carrier tracking FFT bin size, Hz; default 1 Hz
-f flip I & Q samples (invert spectrum)
-r Sample rate, Hz; default: 250000

symdemod - reads output of pmdemod on stdin, writes demodulated, 8-bit (offset-128) soft decisions on stdout
-c Symbol rate, Hz; default 1024
-r Sample rate, Hz; default 250000
-q quiet mode

vdecode - Reads output of symdemod on stdin, writes Viterbi-decoded bits on stdout ('0'/'1')
-p Start with opposite decoder symbol phase (also flips automatically based on encoded sync observations)
-i Status update interval, bits; default 1024
-d Viterbi decode delay, bits; default 200
-q quiet mode

framer - reads output of vdecode on stdin, detects frame sync, writes decoded telemetry frames in hex on stdout
-r bitrate, Hz; default 512 (only for time estimation)

The old programs icedemod, icesync and bitsync are included for reference but are not built by default.