Introduction

Most scheduled observing is done by observing scripts and have to be written by the astronomer responsible for the observation. These scripts are basically UNIX C-shell scripts (other shells work just as well in their basic form), and were described in detail in Chapter . Although we expect that most BIMA (Hat Creek) observations can be done with simple observing scripts, there will always be highly specialized projects which need the full power of a programming language like the C-shell and associated UNIX utilities. This chapter details how you can check your observing scripts for their correctness and lists some of the caveats associated with this approach.

You do this by switching your shell into checker mode. In checker mode you can:

• check your script for (C-shell) syntax errors and follow command flow logic of your script.
• check used keywords and their values: warn about illegal keywords and seemingly out-of-range values.
• check LST ranges for the different sources, and see if your stop criteria work.
• estimate the efficiency of your observations (by keeping the slewing/observing ratio small).
• check parameters for automatic online quality check.
• simulate taking data with specified noise characteristics

In checker mode the observing programs exist in an emulated or stubbed version. A local copy of the shared memory COMMON  block (see also 1.6) is used, as well as an emulated local LST clock  (which is advanced as observing programs execute), though currently telemetry information (or any other that needs the mbus ) is not available yet. Since the checker is really an emulator, there will always be some flaws with this approach. Be sure to read about known caveats in Section 1.5.

Section 1.2 gives an overall view of the checker, and how to run it. Section 1.3 and the examples in Chapter  list a few simple but general observing scripts, which is followed by a detailed discussion how to write observing shell scripts. Some caveats are listed in Section 1.5

The checker environment could even be used to plan observations at observatories other than Hat Creek. Some examples will be given in Section 1.4.5 how to do this.