How to Prepare a Schedule File

Observations normally consist of a sequence of scans: a scan is a short period of observing where a single source is observed. A complete observation is made up of a number of scans. Observations typically alternate between program source scans and calibrator scans. Details of scans are kept in a schedule file.

The main observing task, CAOBS, reads the schedule file in order to determine what sources are to be observed, for how long, and in what order. The schedule file also defines the frequencies, integration averaging unit and correlator setup to use.

You can use the program ATCASCHED (Section3.3.1) to prepare schedule files. (ATCASCHED is the linux version of the program SCHED than ran on the VAX computers. It is often referred to simply as SCHED for that reason.)

You should prepare at least two schedule files:

• A schedule file for setting up and primary calibration. It should include 1934$-$638 and, if 1934$-$648 will not up when your observations start, another calibrator. (Generally this will be 0823$-$500 or 0407$-$658.)
• A schedule file containing your program source(s) and secondary calibrator(s), and perhaps contingency schedule files in case your frequency is seriously affected by interference, or your calibrator proves to be resolved.

If your observation involves looking at five or more sources you are advised to create a text `command procedure' as described below. ATCASCHED can then read this file and convert it to a schedule file.

For observations of many sources, use the ATMOS program in MIRIAD to solve the ``travelling salesman'' problem and optimise the order in which your sources are observed.

It is often the case with synthesis instruments that system errors lead to artefacts at the centre of the field. It is therefore advisable to displace the source position a few synthesised beamwidths from the field centre. Note that ATCA software never checks to see how close you are to the sun!