Predict

Simulate visibilities for a given sky model.

inputs

type

type:

string

doc:

Case-insensitive step type; must be ‘predict’.

applycal.*

doc:

Set of options for applycal to apply to this predict. For this applycal-substep, .invert is off by default, so the predicted visibilities will be corrupted with the parmdb.

beam_interval

type:

double

default:

0

doc:

Time in seconds between beam evaluations. A value of 0 causes a beam evaluation every timestep, whereas a value of 120 would start by evaluating the beam 60 seconds ahead in time, and reuse this beam for all the next timesteps until the timestep that is 120 seconds removed from the start. Because beam evaluation is relatively expensive, this speeds up processing. A value of 120 seems a good value that improves speed considerably, without affecting accuracy.

beammode

type:

enum

doc:

Same as in ApplyBeam step.

symbols:

array_factor, element, default

beamproximitylimit

type:

float

doc:

Same as in ApplyBeam step.

coefficients_path

type:

string

default:

""

doc:

For beam models that require a coefficients file (like that MWA), this field should point to that filename.

correctfreqsmearing

type:

boolean

default:

False

doc:

Simulate frequency smearing based on the channel width, by multiplying the visibility with a sinc function.

correcttimesmearing

type:

boolean

default:

False

doc:

Simulate time smearing based on the integration time, by multiplying the visibility with a sinc function. This is an approximation. The change of u,v,w due to earth rotation over the integration interval is approximated by a straight line. The axis of rotation is the J2000 pole, so precession is ignored.

elementmodel

type:

enum

default:

default

doc:

Specifies which beam model to use. The default value of “default” means that the model is inferred from the MS. For a LOFAR MS the default is hamaker, and for an OSKAR MS the default is oskardipole.

symbols:

hamaker, lobes, oskarsphericalwave, oskardipole (or any other model EveryBeam supports)

onebeamperpatch

type:

boolean

doc:

Same as in ApplyBeam step.

operation

type:

string

default:

replace

doc:

Should the predicted visibilities be output as is (replace, default), should they be subtracted from the input visibilities (subtract) or added to them (add).

outputmodelname

type:

string

default:

""

doc:

Name for writing the predicted visibilities in the output DPBuffer. If empty (default), write the output in the main/default visibility buffer, thereby replacing the input visibilities. Otherwise, write the output to an extra (model) data buffer in the output DPBuffer with the given name.

parallelbaselines

type:

boolean

default:

False

doc:

Parallelize sky model prediction over baselines instead of sources. Will speed up performance in certain cases.

sourcedb

type:

string

doc:

Path of sourcedb in which a sky model is stored (the output of makesourcedb). When the path ends with .skymodel or .txt DP3 expects a skymodel file as used by makesourcedb. This makes it possible to directly use a skymodel file without using makesourcedb to convert the file. The sourcedb format is described at https://www.astron.nl/lofarwiki/doku.php?id=public:user_software:documentation:makesourcedb . In DP3 v5.3 a change was introduced to fix the projection of Gaussian sources. For backward compatibility, also the old behavior is still supported, using the key OrientationIsAbsolute in the sky model. To make sure you use the new (and most correct) behavior, add OrientationIsAbsolute=true to your sky models.

sources

type:

array

default:

[]

doc:

Patches to use in the predict step of the calibration.

usebeammodel

type:

bool

default:

False

doc:

Use the beam model in the predict part of the calibration.

usechannelfreq

type:

boolean

doc:

Same as in ApplyBeam step.

usefastpredict

type:

boolean

default:

depends on CMake configuration

doc:

Make use of the accelerated predict library. This is an experimental drop-in replacement for the current implementation in DP3, please use at your own risk! Note that the option is only available when compiling with USE_FAST_PREDICT=ON. If the aforementioned CMake option is enabled, the default value is set to true.