Support estimation of spacecraft parameters (Cr, Cd) #94
Labels
Kind: New feature
This is a proposed new feature
Priority: high
Status: Design
Issue at Design phase of the quality assurance process
Topic: Orbit Determination
Milestone
High level description
Operations require the estimation of the coefficient of reflectivity and coefficient of drag. The purpose of this ticket is to support Cr/Cd estimation.
Requirements
Test plans
0.5
), then run the filter assuming that the Cr is different (e.g.1.5
), and ensure that the filter eventually converges onto the correct Cr valueDesign
Reporting
In some software, it's the difference in Cr which is reported: I don't think that's necessarily a good approach because then the analyst needs to compare that difference with the original value. Hence, I think it's better for the analyst to have direct access to the estimated Cr throughout the duration of the tracking arc.
State estimation
One of the architecture choices with Nyx is that all computations use fixed size vectors and matrices. This is convenient because it enables compile-time dimension checking. This should be kept.
To support the estimation of Cr and Cd, I think that the
ODProcess
should define for each run (or at initialization?) what ought to be estimated. From the derivation of the Kalman filter, I think that setting a given row of the prefit residual to zero (and its associated sensitivity data to zero) is sufficient to lead to a zero correction on that specific row of the estimated state. Therefore, the computation of the prefit and the sensitivity should be aware of what state data ought to be estimated. I think that the measurement noise must also be nulled to not bias the Kalman gain in anyway.This approach would introduce the fact that the estimated state is not necessarily a
State
in the sense of being able to be propagated... unless these extra parameters have a simple nil function for the dynamics s.t. \let x in R, f(x) = 0, ensuring that the remain constant The propagation is required for covariance mapping.The text was updated successfully, but these errors were encountered: