realtime jpl ionosphere TEC

[drdgl]

The real time ionosphere data here:
https://cddis.nasa.gov/archive/gnss/products/realtime/jpl_ionosphere

Contains negative total electron count values in the atec column. Somebody asked a question here:
viewtopic.php?t=5484

But the answer did not provide enough information to calculate the real-time ionosphere values and my follow up question 5 days ago has had no response.

I thought that maybe there was a per site and/or per satellite bias that needed to be calibrated, but when I looked at the data here:
https://cddis.nasa.gov/archive/gnss/products/realtime/jpl_ionosphere/2025/210/GUAM_250729.csv

I see that the atec value for GPS44 changed by 104 to -88 between two passes.
5950,250729013852,GPS44,3.40111,143.68368,104.154563,-0.005992488,0
15660,250729042042,GPS44,8.17164,153.46122,-88.3894316,0.01091436,0

-88 is clearly not a valid TEC measurement. The UQRG post processed slant TEC changed from about 145 to 146 between those two times. So there appears to be a bias that changes between passes in the real time ionosphere data. How can one get an unbiased TEC measurement from that data?

Thanks,

Dave

[CDDIS - rlimbach]

The best people to direct your questions to would be Siddharth Krishnamoorthy (Siddharth.Krishnamoorthy@jpl.nasa.gov) and Camille Martire (camille.martire@jpl.nasa.gov).