Error Recovery

Occasionally, things will go wrong. Here is a brief list of some of the potential problems and some suggestions for how to escape from them without exercising the ultimate sanction of shutting down and reloading the system.

1. No light? Check: coudé 3 mirror cover open? coudé 4 mirror cover open? coudé 5 mirror cover open? east coudé hatch open? TV mirror position? slit filters or lamp filters inappropriate? UHRF ThAr in beam? shutter switched to correct control (CCD vs echelle)? hartmann masks open? UCLES collimator and grating covers open? configuration successful?

2. Mechanism movement fails or appears to `stick' -- try using the CANCEL command to cancel it and re-issue the original command; if this fails, your support staff might reboot the SYNTEL; then reload the D-task by typing `LOAD ECH_ICL:ECHELLE' (this may not be necessary but is probably a good idea)
3. System appears to hang -- try typing Ctrl-C, which should always return safely to the ICL prompt
4. You get a traceback from a task -- if you know which task it is, try `LOAD ECH_ICL: task', where task will be one of `ECHELLE' (the D-task), `UCLES_A' (the A-task monolith), `UCLES_C' (the C-task monolith) or `UCLES_CD' (the CD-task). It's sometimes hard to know which one has caused the problem. All the mechanism commands use only the D-task; USE, LIST, CENTRE and ISET are in the A-task monolith; PIXELS, OFFSETS, FOCPARS, ARGS, IMAGE, ICUR and ROTCEN are in the C-task monolith; DISPLAY, CONFIGURE, TRACKPA and VERTICAL are in the CD-task
5. Something that did work stops working -- perhaps the rotator tracking suddenly fails; try the same fix as in the previous item; if this fails, try Ctrl-C and repeat and/or try an explicit `KILLW task'
6. If none of this works, it's probably best to shutdown the system, either with the `SHUTDOWN' command or with a trusty Ctrl-Y. You really shouldn't need to log out; simply type `UCLES' at the DCL prompt. However, if the problems persist, try logging out and in again.
7. If an error message ``Failed to get Telescope Position" is reported, check the CAMAC ACCESS ARBITRATOR. If light 0 is on steadily instead of flashing, CAMAC has hung, so press SYSTEM INIT on module 22 of the system crate.
8. If the CCD readout does not complete, you might try RECOVER XMEM and RECOVER CCD from the CCD system, but probably the data are lost.