Observing with the Green Bank Telescope may be done interactively through a graphical control screen or may be run by a pre-planned observing table. The two types of observing run in parallel, and you can switch between them as the need requires. Parameter changes made by executing the table will automatically show up in the interactive display. The combination of tables and graphical screens will be referred to as "GBT Observe."
The main graphical control screen is designed so that everything essential to run an observing scan is presented to the observer. As you might imagine with a system as complex as the GBT, there are a lot more control parameters than can possibly fit on one screen, but, if something is not on the main screen, it is guaranteed to have a sensible default. More detailed screens are available from the main screen, but they are not essential to much routine observing.
An observing table is an ASCII file that may be created by any text editor. The header line may contain any number of parameter keywords which define the columns of the command lines that follow. Header keywords and column entries are separated by any number of whitespaces (tabs or blanks) so you are free to format for readability. The table may contain any number of header lines. Each header line affects only the table entries that follow it until another header line is encountered. The simplest way to create a new table is to steal a header line from an existing table that does a similar type of observing. There should be many example tables to choose from. Most procedures that you will need, such as track, ramap, cross, tipping, etc., are predefined, but if necessary you can define your own according to a recipe which is described elsewhere.
header sourcename ra dec velocity bandwidth procedure
3C286 13:28:49.7 30:46:02 +500 10 cross
M82N 09:51:36.0 70:05:00 +500 10 ralongmap
M82 09:51:42.0 69:56:00 +500 5 declatmap
M81 09:51:30.0 69:18:00 +400 5 ralongmap
M81S 09:51:30.0 69:05:00 +400 10 ralongmap
3C286 13:28:49.7 30:46:02 +400 10 cross
The observing table has a more extensive syntax than is implied by the example above. If you want to construct a table with a bit less formality or construct repeat loops or macros, see the GBT Observing Tables and Procedures document for a more complete syntax description.
An observing table is executed from a table control subscreen, shown below, that is invoked from the main graphical control screen. This table subscreen is actually another form of interactive observing because you can start and stop table execution on any line, re-execute lines, verify the table syntax, pause for user input, etc.
This document last updated July 25, 1998