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()