My simple understanding...
If you display the Sun's location and daylight/nighttime line on your display along with the ground coverage of the satellite, the intersection of the daytime line and the satellite's circle of visibility will indicate when the sat is in sunlight.
As most satellites "progress" daily in longitude in relation to standard time you will be able to visualize their approach toward eclipse or non-eclipse.
By increasing your time increment in the program (fast forwarding) you can guesstimate when these transitions will occur in the future.
I say most satellites because some satellites such as the NOAA's are launched to be almost "sun synchronous" and will pass overhead almost at the same time every day.
For the more technical explanation I must bow to the real orbital engineers.
I have never been able to get a straight answer on this one, but does InstantTrack or any other program show you the long term non-eclispse/eclispe period, or is there a way to calculate this?
How do we know that PCSAT and UO11 are going to HIT sunlight or not for a period of time?
I can see from Orbitron the realtime, but not anything in the future?
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