Is there a way to do an initial OD when multiple measurements of just range or just range and range rate are available.
Something like Gibbs that uses 3 position vectors that we can get from az, el, range, or Gauss that does angles only.
Alternatively is there a way to back out az/el values from range/range rate?
Thanks in advance.
Do you know the time values and origins of your range measurements? If you do and have at least 3, that would give you enough for time-of-arrival location (though I don’t think there’s any built-in orekit algorithm that will do it for you - you’ll have to work out the math).
TOA/TDOA is an interesting idea thank you for the suggestion. I have closely spaced sequential measurements that are time tagged and I have the ground observer’s location, in some cases there may be data from multiple passes but I don’t have simultaneous measurements from multiple observers.
One warning. I forgot to mention the first time around that TOA depends on the range values having the same time of arrival at the receive point, which I am presuming in this case is the satellite whose position you are trying to calculate. Otherwise you’d be combining a range value received when your satellite is at Position A with a value that was received when your satellite had moved to Position B. This would be a recipe for much confusion and frustration.
Unfortunately my measurements are two way range from the ground to sv back to ground, I think TOA would only work with time tagged pseudo-range that originates at the satellite being picked up at multiple observers.
I’m going to put my limited math skills towards trying to solve for the orbit plane vector by leveraging range and rate and try to go from there. I’m hoping that since these are measurements from the surface some of these parameters become observable.
Yeah… Orekit has classes Range and RangeRate that can handle such measurements, and you can plug those measurements into the least-squares orekit solver. But in order to function the least-squares solver needs an initial guess, and in terms of IOD I know of no simple way to get an initial time/position/velocity guess for the orbit using such measurements.