From BLS estimator optimum to physical orbit residuals

Orekit Python Wrapper usage
1

Hello everyone :slight_smile:
I am trying to obtain the orbit residuals after a BLS estimation of a GEO orbit starting from AngularRaDec measurements.
I obtain the residuals as follows:
normalized_residuals= estimator.getOptimum().getResiduals().toArray()
I understand that these values do not have a physical dimension. I am confused regarding the following points:

  1. How can i find the defined scaling factor of the determination to apply to the normalized_residuals?
  2. What is the unit of measure of the scaling factor?
  3. If I determine the orbit with RaDec measurements, do the residuals have the same unit of measure or are they given as meters (after the multiplication with the scaling factor)?
  4. Is there a faster way to obtain the physical residuals?
    Thank you in advance
2

Hi there,

This post about estimated measurements could be of interest to you

Cheers,
Romain.

3

Thank you. I understand from the linked post that the getLastEstimations() method returns the observed measurements related to the penultimate iteration, so it would not be suitable for residuals calculation. Does this also happen to the getOptimum.getResiduals() vector? I am inclined to say that this being the optimum, the residuals are related to the latest iteration of the algorithm. Is it right?

4

If your convergence threshold is tight enough, there should be negligible difference between the last two iterations.

Cheers,
Romain

5

Thank you Romain!