State transition matrix and mass

Orekit development
1

Hi folks,

I can’t find a native way of including the mass in the computation of the STM (with NumericalPropagator).
If confirmed, I think it’s a feature we need.

Cheers,
Romain.

2

Hello,

One would need to field everything so it should be simpler than that :sweat_smile:.

Cheers,
Vincent

3

Hi
It would be useful to include also the “longitude” (time dependent?) in the STM matrix; in the GTO transfer orbit, in my case, a cost function is defined that depends on the satellite’s longitude in the fixed terrestrial reference system (the same state vector with a different date at the end of the boost sequence generates different costs); in my experiments I added to the Jacobian matrix the derivative of the mass (calculated through the flow rates of the maneuvers) and of the time (calculated based on the stop time of the last apogee maneuver); for the mass everything works and the derivative of the cost function is well represented, while I cannot determine the gradient of the part of the cost that depends on the longitude.

1 Like
4

Yeah, that’s what I mean, it’s possible with FieldNumericalPropagator, but not the embedded STM in NumericalPropagator. It’s a bit weird actually. I’ll look how we could do this without breaking APIs.

@roccafrancesco I’m not sure to follow what you mean with the longitude. It’s a constraint on your final state, so it’s neither a state nor a parameter of the propagation model, therefore I don’t really see how it could be included in the variational equations. However with a full Field computation, there’s more applications (but it’s also slower).

Cheers,
Romain.

5

by longitude i mean the longitude of the spacecraft a the end of the last boost; the cost function include inclination cost,eccentricity cost and a “randevou cost”; the last component depend diereclty by longitude of spacecraft; By the way what i see is adding only derivative of the final time in the jacobian is not enough; the complete gradient is a combination of a cost function gradient respect to final state and the jacobian calculated with STM matrix; i wonder if using gast function directly can help; in this way maybe i dont need any transformation in Earth Reference frame and express the longidude derivative directly using cartesian element and time at the end of boorst;