Much thanks to Li Wen Hao who has helped me to retrieve the inter-satellite ranging data from GRACE A and B from the KBR1B data! I am working on precise orbit determination and also baseline determination algorithms using GNSS data processing. From Wikipedia, it seems that the nominal distance separation between GRACE A & B ~ 220km during normal mission operations.
To my dismay however, I found it a bit strange that the KBR data for 27-07-2010 shows that the range was ~ 330km instead. Even with the ionospheric, antenna-offset, and light time corrections, it was nowhere near the nominal 220km. I would like to ask if anyone has any idea as to whether this data is correct, or perhaps is it meant to be in some other form of units (although the L1B hand book says it is in meters).
Here is a snapshot of the KBR range values from the ASCII KBR file that Wen Hao has kindly sent to me:
https://drive.google.com/open?id=1o6ehy ... 3JTD0TwTas
Fortunately, or unfortunately, both my POD results (with header DSOLPD) and my double-differenced baseline measurement results (with header DSOLDD) show that the range between GRACE A & B was ~ 227km nominally, which seems close enough to the reported 220km formation distance for the mission. The simulations were done for the 27-07-2010 epoch, same as that for the date of KBR results. I used the RINEX observation files of the GRACE satellites A & B to do the POD and the baseline determination on Bernese GNSS software v5.2.
My simulation results, tabulated in Excel, are shown here:
https://drive.google.com/open?id=1cMORO ... AYihGfxHNU
My question would be, why does the ASCII KBR data show 330km? Is this range really correct or am I missing something here? I am assuming it is in meters. If it is a separate unit, please kindly correct me! I don't think my algorithm is perfect, but I did found it a bit strange that two distinctly separate algorithms gave me such close values from the same RINEX file, but the KBR values were unexpected far off from ~220km. Thank you very much. I have attached the KBR ASCII file here too (thank you Wen Hao).
https://drive.google.com/open?id=15phAb ... -Bbc90v2kX
Once again, I appreciate the time taken by users and administrators in the PODAAC community for reading my queries. Thank you all