IRNSS RINEX files provides you raw measurements (observation file), satellite ephemeris (nav files). They do not have slant TEC values, you will need to compute them from these measurements.

Hi Ashish,

You can try using open source software to compute the TEC values from the RINEX files. Here's a GitHub Python project (that I haven't tested) that seems pretty straight forward:

https://github.com/gregstarr/PyGPS

You can also take a look at GPSTk (http://www.gpstk.org/bin/view/Documentation/WebHome) which I think also computes ionospheric TEC.

I hope this helps,

Demián

Thank you everyone..