Meridian flip planning for satellite passes

[bgottula]

German equatorial mounts can't track far past the meridian before limits are reached or hardware collisions occur. Consider the following approaches to planning for and executing meridian flips during satellite passes:

• [ ] If trajectory information is present (hybrid or blind tracking), determine the optimal hemisphere to start in (east or west) based on the trajectory and the current RA axis limits. The best case would be that the pass can fit entirely within one hemisphere in which case the choice is easy. If not things get more complicated.
• [ ] When the RA limit is reached perform a meridian flip and continue tracking

When a meridian flip is required in the middle of a pass and trajectory information is available there are some considerations to take into account:

• How long will the meridian flip take to perform? In some cases the flip may take long enough that the best we can do is track part of the pass in one hemisphere.
• When is the optimal time to perform the flip? Waiting until the RA limit is reached may not be the ideal time to perform the flip. There may be cases where it would be better to start the flip prior to reaching the limit.
• For how much of the pass is the satellite visible? If it is only visible for a portion of the pass this would influence the plan. The trajectory alone only indicates where the satellite appears in the sky so we would need to do additional processing or use extra information to take this into account.

[bgottula]

I attempted to perform a meridian flip in the AxisLimitException handler in Tracker.run when the RA axis limit is reached. This sorta worked but the exception was raised a few dozen times in quick succession so the meridian was also flipped a few dozen times. Need to figure out how to apply some kind of hysteresis to prevent this from thrashing.

[bgottula]

The need for this has been significantly reduced by a couple of things:

• Full alignment automation that allows us to place the mount pole at any location that the mount hardware allows. This allows us to place the mount pole in a location that in many cases eliminates the need to perform a meridian flip during an entire pass.
• Addition of a skyplot tool that helps with deciding where to place the mount pole and which meridian side to pick

With these two items it is possible to track nearly any single pass in an evening without any meridian flip necessary. Where this could still be useful is the case where we want to track multiple important passes in a single session without breaking alignment.