Impact of Ionospheric Correction via TEC files

[jonathanbahlmann]

I am trying to gather information about procedure of and possible problems with near-real time processing the NISAR L0 RRSD data up to Level2 GSLC independently of the official processing (viewtopic.php?t=7970). In the thread it came up that for the RSLC -> GSLC processor (https://github.com/isce-framework/isce3/blob/static-layers-wip/python/packages/nisar/workflows/gslc.py) I would need the TEC (total electron content) file of the day of the acquisition date. I've since learned that TEC is about signal interference with the ionosphere, caused by sunlight. What is the magnitude that this effect could have on geolocation accuracy of the GSLC product?

As the TEC files seem to be published per day, they're a bit slow for my NRT case. I would be interested in the consequences of using an older TEC file, say the one from the day before. Would that still represent the atmospheric/sun conditions reasonably well or would I make it worse by applying an unrelated dataset? My area of interest are the Polar latitudes.