Projected baseline flagging

How does it work?

jolly_roger will recompute the (u,v,w)-coordinates of a measurement set as if it were tracking the Sun, from which (u,v)-distances are derieved for each baseline and timestep. An updated FLAG column can then be inserted into the measurement set suppressing visibilities that would be sensitive to a nominated range of angular scales. This mode also allows for flagging based on the elevation of the target source.

Example

jolly_roger has a CLI entry point for projected baseline flagging that can be called as:

jolly_flagger scienceData.EMU_1141-55.SB47138.EMU_1141-55.beam00_averaged_cal.leakage.ms --min-horizon-limit-deg '-2' --max-horizon-limit-deg 30 --min-scale-deg 0.075

Here we are flagging visibilities that correspond to instances where:

• the Sun has an elevation between -2 and 30 degrees, and

• they are sensitive to angular scales larger than 0.075 degrees.

CLI

Flag a measurement set based on properties of the Sun

usage: jolly_flagger [-h] [--min-scale-deg MIN_SCALE_DEG]
                     [--min-horizon-limit-deg MIN_HORIZON_LIMIT_DEG]
                     [--max-horizon-limit-deg MAX_HORIZON_LIMIT_DEG]
                     [--dry-run] [--flip-uvw-sign]
                     ms_path

Positional Arguments

ms_path

The measurement set to flag

Inputs for JollyRogerFlagOptions

--min-scale-deg

Minimum angular scale to project to UVW

Default: 0.075

--min-horizon-limit-deg

The minimum elevation for the sun projected baselines to be considered for flagging

Default: -3

--max-horizon-limit-deg

The minimum elevation for the sun projected baselines to be considered for flagging

Default: 90

--dry-run

Do not apply the flags

Default: False

--flip-uvw-sign

Flip the sign of UVWs (may be required for LOFAR)

Default: False