NSIGUI trouble shooting

The nsQueryEngine.tcl script assumes that ftp and telnet are in the path - make sure those are available.

From time to time JPL horizons changes the telnet interface used to get non-sidereal object ephemerides. When this happens, the script nsQueryEngine.tcl must be modified. nsQueryEngine.tcl is in both the IRTC installation (/lbt/irtc/current/bin/), and the TCS installation (/lbt/tcs/current/) (it is used by the NSIGUI, the irc, and the IIF.).

The script tries to detect many failure conditions, but if the telnet question/response is broken, it often returns error "Invalid number of arguments" after about 17 seconds. It may also send messages like this to stderr:

can't read "ftpName": no such variable
    while executing
"send "get $ftpName $localFile\r""
    invoked from within
"expect "ftp> " {send "get $ftpName $localFile\r"}"
    (file "/lbt/irtc/current/bin/nsQueryEngine.tcl" line 356)

The problem is ftpName has not been set because the preceding question/response is broken.

The nsQueryEngine.tcl script uses expect to manage the telnet and ftp sessions needed to communicate with JPL Horizons. If the session question/response is changed by Horizons, the tcl script must be changed to match. Probably the best way is to manually open a telnet session to Horizons following the script, and see what has changed. Then fix the script.

Another way is to look at the script logfile. The script makes a logfile (/lbt/ephemeris/) named <object>.log. Examining the logfile together with the script can show you where the changes are. This allows one error to be fixed at a time. For example, if an additional question is being asked by Horizons, following the logfile and the script will show where the new question is. Change the script for the new question, and run it again. Now the script will answer the new question, but the following question(s) may be handled incorrectly. Fix the script and repeat.

On at least one occasion JPL Horizons changed the output format of the ephemeris, which caused errors in the PCS when it read the file. Figuring out what to do required an understanding of the PCS with regard to what it expects to find in the ephemeris file.

-- %USERSIG{ChrisBiddick - 2017-06-30}%