You requested some info from me as a new subscriber. From 1980 to 1982, I was a software developer for the ALTAIR radar in Kwajalein, Marshall Islands. I was responsible for the satellite database (elsets and observations), as well as the main software developer for tracking algorithms. I enjoyed the work so much that it also became my hobby, along with astronomy, which was my minor in college. In the mid-80s, I got a copy of a tracking program from Dave Harvey at the Seward Observatory, and converted the graphics to VGA, as well as adding the SGP4 and SDP4 algorithms. Dave has since converted the program to C (originally Fortran) and sells it commercially. (we lost contact, so I get no royalties; besides it's a hobby to me anyway. Also in the mid-80's, I received the code for Felix Hoot's Hande elsets, which was an attempt by the Air Force to create a third elset card. I actually got the code to run (with his sample data) on a DEC VAX11-785, as well as an IBMPC. The project was dropped probably because of the impact on all the tracking radars for software conversion. In fact, I still have contacts at ALTAIR and apparently NORAD has told them that the elsets will have 00 for the year and it is up to the radars themselves to update the SGP/SDP code!!! Anyway, I am back again playing with my old PC programs, and am interested in any algorithms (Fortran, and I guess C) to convert tracking data to elsets. The one that I helped develop for ALTAIR used range, az, el and time. Cheers