SNAP commands

The Field system gets its schedules in SNAP format. These are interpreted in real time to control and check the operation of the Mk3 hardware. SNAP also includes source positions and UT times and these must be converted by the program STFMA for the online system to point the telescopes and perform the delay and fringe stopping. STFMA needs a default observation before starting this.

The SNAP language is fully documented in the MkIV Field System Documentation (SNAP Commands). Help on individual commands can also be obtained from the field system by typing

  HELP= command name

at the field system prompt.

Minimum SNAP commands

The following minimum SNAP commands will be needed in normal operations:

SCHEDULE

To start (or restart a new schedule)

LABEL

To give a tape label to the field system after a tape mount. This lets the field system know when it can continue, and allows the label to be entered into the log file.

STATUS

To examine the status of the current observation

"

(double quote). To insert your own comment into the computer log. This is used to note system changes (like numbers of telescopes in the array) that will not be seen by the field system. A closing doublequote mark is not needed.

HELP

Seek help on a SNAP command

TERMINATE

to stop the schedule and exit the field system

Other useful SNAP commands

These commands may be needed to solve minor problems in a running schedule. They are also useful as diagnostic commands:

TAPE

request tape status

ET

Stop ('End') the tape

ST

Start the tape

ENABLE

Turn recoding of various tracks (or groups of tracks) on or off

FF

Fast forward the tape

RW

Rewind the tape

PASS

request status from or set the head positions

FORM

request status from or set the formatter

VCnn

request status from or set a video converter

IFD

request status from or set the MK3 IF distributor

To reset the alarm on any unit use the syntax

  unit=ALARM

for example

  VC07=ALARM