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Ionosphere TEC (Total Electron Content) Corrections - Knowledgebase / CASA - NRAO Science Helpdesk

Ionosphere TEC (Total Electron Content) Corrections

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It is now possible to apply TEC (Total Electron Content) corrections within CASA. Note that the following procedure currently only corrects for Faraday rotations, and no corrections will be applied to dispersive delays as is possible with the AIPS TECOR task.

For instructions on applying TEC corrections, please see the CASA P-Band guide found at

It is known that certain distributions of the Linux OS (i.e. Scientific Linux) have had issues in generating a TEC map. A few reasons for this are:

1. Linux is not able to uncompress the downloaded file with the provided command within

2. Linux is missing the curl tool, which is used to download online content.


Manually download the IONEX file from NASA's Crustal Dynamic Data Information System (CDDIS) webpage, which can be found at

You can search for the IONEX file via their ftp server

Search by YYYY/DDD/igsgDDD#.YYi.Z where,

YYYY = Year

DDD= 3-digit day

#= file sequence number for the day. 0: file contains all existing data of the current day

e.g. For an observation conducted on 2014/01/04, the IONEX file is /2014/004/igsg0040.14i.Z

Uncompress the file with the command "gzip -d <filename>", and place the unzipped file in your current working directory. Following the instructions in the CASA P-Band guide should now produce a TEC map successfully.