Adding a piecewise drag force model
For operational uses it would be useful to have an implementation of DragForce that would allow for piecewise definition of the drag and lift coefficients.
Each coefficient would be defined with a timespan validity and the orbit determination would be able to estimate each one of them separately.
This is useful in operational context where the solar activity is unknown or badly known. Generally a daily solar activity is used based on data provided by different services. With this drag force model, the orbit determination would for example estimate a drag coefficient for each day and the uncertainties derived from the daily solar activity could be estimated separately.