Can Orekit determine an initial orbit for a satellite without providing an initial orbit, only given some observational data (time T, distance R, azimuth A, and elevation E)?

Hi @lebronjames

Congrats for the gold medal at the Olympic games!

Yes, it can. You can look at the Initial Orbit Determination (IOD) algorithms provided in Orekit. For your case (i.e., Az/El + Ranging) we have 3 IOD methods:

- Laplace
- Gooding
- Gauss

Laplace and Gauss only use 3 angles. Godding algorithm uses 3 angles + 2 ranging.

I can recommend you to start by using the Gauss method which provides an interesting accuracy.

Some documentation:

- Orekit IOD package: src/main/java/org/orekit/estimation/iod · develop · Orekit / Orekit · GitLab
- A very interesting thesis presenting the accuracy of IOD methods depending the orbit type (i.e., LEO, SSO, GEO, MEO): https://oaktrust.library.tamu.edu/bitstream/handle/1969.1/ETD-TAMU-2011-12-10242/SCHAEPERKOETTER-THESIS.pdf
- Some Orekit examples: src/test/java/org/orekit/estimation/iod/IodGaussTest.java · develop · Orekit / Orekit · GitLab

Best regards,

Bryan

I finally have an explanation for the success and accuracy of the American team’s shots. The guys calculate the trajectory of the ball with Orekit. As a result, the success rate for 3-point shots is hardly surprising.

Hi，bcazabonne！

I looked at the IOD package link, but I couldn’t find the underlying implementation of the `estimate`

function in the Gauss algorithm. Do I need to write the underlying code for the `estimate`

function myself, or is it located elsewhere?

Cheers，

James