Hi folks,

I’ve got a question about SLR-based OD and the resulting covariance matrix. Essentially, the values I get in the matrix are much smaller than I would have expected and I am trying to figure out if that is something that I have done in my configuration, if this is a limitation of covariance estimation in general, or perhaps some inadequacy in the data I’ve provided.

I am using SLR data from the ILRS for Ajisai and I take three orbits worth of observations: 6 observations in this period and about 70 data points in total. Each data point is a “normal point” with a specified uncertainty sigma value ranging from about 5mm up to 5cm. If I do an estimated minus observered comparison after using BLS to perform an OD and then plot the residuals I find that they are about ± 6m which I am happy with for the time being. I would expect the trace of the sqrts of the covariance to be of the same order as the residuals but this isn’t what I find. Instead, the value is on the order of 1mm. Is there something I am not considering in this approach or anything that I need to be aware of when using these algorithms?

Thanks,

/Paul