Example Observing session with OVRO-LWA
========================================

Start with some common initial steps to set up the controller in Python (development or deployment environment)::

  from mnc import control 
  con = control.Controller()
  con.status_xengine()
  con.status_dr()

The status methods display details about how subsystems are set up or if they have errors. This info is also displayed on the OVRO-LWA System Health Dashboard.

Next, set up the x-engine. To set it up to route data for both slow visibility recording and beamforming with beam 1::

  con.configure_xengine(recorders=['drvs', 'dr1'], full=True)

After this step, the x-engine status on the dashboard should be green, which means data is being routed from the GPU servers to the data recorders on the Cal-Im nodes. If the x-engine was already set up correctly, then this step will go faster with ``full=False``.

Next, you need to turn the data recorders on. To start slow visibility recording::

  con.start_dr(recorders='drvs')

The default is to start immediately and record without end (until the ``stop_dr`` command). However, the ``t0`` and ``duration`` arguments can define the start and length of an observation. ``t0`` can be in MJD or ISOT format and ``duration`` must be in milliseconds (e.g., ``duration=30*60*1e3`` for 30 minutes).

To start beamformer recording::

  con.start_dr(recorders='dr1', t0='now', duration=None, time_avg=1)
  con.control_bf(num=1, targetname=<name or (hourangle, deg)>, track=True)

The number in the name of the data recorder is the same as that used by ``control_bf``. Note that the ``control_bf`` command will start a loop in Python to update the beam pointing. You'll need to Ctrl-C to stop tracking and/or open a new terminal to issue other commands (e.g., stop the data recorder).

Finally, to stop observing::

  con.stop_dr()
  con.stop_xengine()


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