Initializing a new SIM from the conditions of another SIM at a specific time

[lucapizzuto99]

Hi everyone,

I recently started to experiment with starting a new simulation from the snapshot obtained by another simulation. In the simplest case where only 1 satellite is simulated, I am receiving the TM and taking it to modify the 42 Input files. In this way, I start again the simulation and the satellite is able to start from where the previous sim was stopped/when the screenshot was taken.

In particular I am modifying:

• Sc_Simple.txt: here I initialize the attitude of the satellite using the quaternions and the angular velocities retrieved at the moment of the screenshot. Also, I insert the RW initial moments and the accelerometer initial bias. In particular, for the accelerometer, I take the IMU linear acceleration values. I keep the other subsystems and parameters the same, since they appear to me as constants.
• Orb_LEO.txt: here I compute the true anomaly from the ECI position and velocities retrieved by the GPS, and I substitute that value to update the orbital position of the satellite.

In this way I should have the satellite with the right attitude and orbital position, so that the newly initialized simulation can reproduce the exact same TM as the original one, for the same interval of time of course.

Also, I have the sunsafe mode activated since the beginning of the simulation.

With this logic, I was able to reproduce the orbital position (and thus the gps TM), the RW and angular velocities with good accuracy, but I still have problems for the accelerometer (linear acceleration parameters) and the quaternions.
Here I post some pictures from the test I run:

Am I missing something for the initialization of the accelerometer? And for the attitude? The quaternions are totally off.

Thanks in advance and please ask me more info in case something results unclear.