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early

Section: User Commands (1)
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NAME

early - Flag data which has early/normal problems.  

PERSON RESPONSIBLE

rjs  

CATEGORIES

calibration, uv analysis  

DESCRIPTION

EARLY is a Miriad task which flags visibility data that it suspects contains early/normal problems. The input must be a multi-channel dataset (NOT channel 0). Early works by comparing the scatter of data within a visibility record with that expected because of thermal noise. If the scatter exceeds some number of sigmas, then the data are assumed to be affected by the early/normal problem, and the entire record is flagged.

Several assumptions about the data are make: Firsly there is significant signal in the visibility record so that the phase slope across the band causes a substantial increase in the scatter. This will not be true if the signal is weak, and the visibility records are noise dominated. If the signal is noise dominated, no early/normal problems can be detected, and the data will not be flagged.

Secondly the data have been bandpass calibrated. EARLY always applies a bandpass correction to the data if there is one present.

Thirdly that the noise level is fairly constant across the band,

Fourthly that any end channels that might be bad have already been flagged.

Fifthly there is no substantial variation of the signal across the band. This will be true for continuum, but not spectral line work.  

PARAMETERS

vis
The input visibility data-set to flag. Several files can be given. Wildcards are supported. No default.
select
Normal uv selection. This selects which data to check for early/normal problems.
sigma
Number of sigmas. Default is 10.
log
Output log file for messages. The default is the terminal.
options
Extra processing options. Several can be given, separated by commas. Possible values are:
  noapply    Do not do any flagging -- just check the data, and
             produce the appropriate messages.
  verbose    Give details about what is (or would be) flagged.


 

Index

NAME
PERSON RESPONSIBLE
CATEGORIES
DESCRIPTION
PARAMETERS

This document was created by man2html, using the manual pages.
Time: 18:35:38 GMT, July 05, 2011