What ICE Really Does During An Exposure

  The exact sequence of events during a CCD camera exposure is laid out below.

• Prompt the observer for task parameters.
• Update the filter and focus parameters to be passed to the (telescope) server.
• Prompt the observer for the image title and retrieve hidden parameters.
• Construct the name for the output image.
  • abort if it already exists
  • print a message otherwise
• Open a connection to the detector server.
  • pass info back and forth to the controller
  • retrieve the detcap information
  • complain about the head ID if it does not match
  • check the error status
• Update the scan table parameters to be passed to the instrument server (if appropriate).
• Open a connection to the instrument server (usually "test").
  • pass info back and forth,
  • check the error status
• Open a connection to the telescope server.
  • pass info back and forth (e.g. image header info)
  • check the error status, but ignore any error if this is not an object exposure
• If no errors have been reported by the servers:
  • do whatever the instrument does before the exposure, e.g., position the scan table if appropriate
  • check the error status
• If no errors have been reported by the servers (including the telescope):
  • do whatever the telescope does before the exposure, e.g., position the focus and filter if appropriate
  • check the error status
• If no errors have been reported by the servers:
  • assign a unique RECID to the exposure
  • preallocate disk space if appropriate; the observe task aborts if the disk fills up
  • write out the exposure status line
  • prepare the chip
  • if no new detector error, start the exposure; the count down loop is entered if the exposure is longer than a few seconds
  • if exposure is not aborted, read out the chip:
    • open the output image (or reopen if preallocated)
    • write the header. Most keywords were filled in previously get a few (e.g., filter) from the servers now that were set after the bulk of the header info was retrieved
    • print ``reading out..." message
    • initiate ccd data transfer
    • complain if there is a problem
    • close the output image
    • rename the hidden image if preallocated
    • complain if the disk would fill up
• Close the detector, instrument and telescope servers.
• Null out the motor control parameters for the filter, focus, and scan table.
• If no errors were reported by the servers and the exposure was not aborted:
  • If not a test image, pass the image name to the archive queue.
  • Execute the postprocessing command:
    • sync the disks
    • beep the terminal
    • display the image
    • log the exposure (if loginit was run)

That's all folks!