Questions about satellites

First of all, polar orbit, also known as lightning orbit or large elliptical orbit. Mainly used for communication in high latitudes and polar regions, Russia has been using 10 years, with an orbital inclination of >: 60. This satellite can see for 8 hours at high latitudes, and three lightning-orbiting satellites can be used as 1 synchronous orbit satellites.

Secondly, the stars you see are not necessarily polar satellites. In the outer space of the earth, there are more than 3,000 satellites (stars) orbiting the earth, with orbital heights ranging from several hundred kilometers to tens of thousands of kilometers; They are distributed in low orbit, medium orbit, synchronous orbit and large elliptical orbit respectively. Generally, the visibility time of low-orbit satellites is 15-20 minutes per day, and that of medium-orbit satellites is 2-8 hours per day.

According to your description, you can see that its flight speed is relatively fast, which may be near the perigee of low-orbit satellites or (large) elliptical orbit satellites; Among them, there are resource satellites (taking photos of the earth's surface and broadcasting photo information to the ground) and communication satellites (such as global satellites and iridium satellites). Low-orbit communication satellites are generally composed of many satellites, providing mobile satellite communication services to the ground.

Finally, the height and period of the satellite are a pair of related parameters. The lower the height, the shorter the period (the principle of circular motion of gravity). So the visible time mentioned above is a range.

I can see that you like to observe and think. By observing the running speed (visible time) of the star, the orbital height of the star can be calculated.

I hope it helps you.

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