What are the factors affecting a satellite's Repeat Ground Track period?

Question

I understand the Repeat Ground Track (RGT) period of a satellite will be affected by its altitude. A similar post: How Do I determine the ground track period of a LEO satellite, describes a simple approach to determine the RGT period by using the ratio of the rotation periods of the planet and spacecraft. My question is whether other orbital parameters would as well, and how?

For instance, a satellite at 574km (and thus having an orbital period of 5,760s) could have a RGT period of 3 or 4 days [since the earth's rotation period of 86,400s times 3 and 4 are both multiples of 5,760]. If that's the case, surely altitude is not the only factor affecting the RGT period?

I wouldn't think of three or four days as the Repeat Ground Track period in this case; 15 x 5,760s is 86,400s, so after just one day the ground track should repeat (one rotation of the planet, 15 orbits of the satellite). Hence also why you notice that both 3 and 4 days are solutions: they're both multiples of 1 day. — Erin Anne, Mar 04 '24 at 03:17
Apologies, perhaps I phrased my question incorrectly. I recently chanced on a satellite mission brochure stating they are capable of having a 3 or 4 day RGT period at 574km. I'm aware in reality the math isn't as clear cut. I'm questioning how it would be possible for the RGT to be different at the same altitude as they have stated — Shawn Lim, Mar 04 '24 at 03:42
@ShawnLim Welcome to Stack Exchange! btw I wrote that answer and sorry if it is overly confusing. See also Are there terms for Earth orbits with rational number multiples of 1 sidereal day? and to see how flexible the term "repeat"can be when it comes to Earth observation see Why can Amazônia-1 observe the Amazon "every day or two" while Landsat takes 16 days between observations? Is "orbital magic" at play here? Also, use a siderial day of 23h 56m 4.09s for Earth's rotational period, not 24h. — uhoh, Mar 05 '24 at 05:09
And just fyi, from FAQ see How do comment @replies work? (at)ErinAnne may not receive a notification of your reply unless you use this. — uhoh, Mar 05 '24 at 05:10
See also Revisit time estimation for a SAR constellation and Satellite Revisit Time Analysis and what is revisit rate — uhoh, Mar 07 '24 at 00:20

score 2 · Answer 1 · answered Mar 04 '24 at 06:18

Along with orbital dynamics there may be some commercial factors for anything advertised as re-visit rate rather than just repeat ground track rate.

Assuming this is a sun-synchronous orbit given the altitude the advertised re-visit rate may be limited by potentially other users consuming pointing time, storage or downlink availability, especially if this is a public facing/low cost service selling spare capacity of a constellation paid for by a primary/priority customer.

What are the factors affecting a satellite's Repeat Ground Track period?

1 Answers1