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--- blog:articles:general:orbital_shenanigans [2019/08/03 11:19] – Phil Ide
+++ blog:articles:general:orbital_shenanigans [2019/08/03 11:25] (current) – Phil Ide
@@ Line 27: / Line 27: @@
 So, back to the drawing board. Let’s tackle this another way. Another orbit, what you might call a ‘regular’ orbit, doesn’t have this problem. At least, not so much. One suggestion was to use a lower orbit at an elevation of 5,000km. Consider that at the geostationary orbit (17,025km), the satellite can see 75 degrees of the planet either side of the point it is above. That’s a 150 degree spread. At 5,000km, this reduces to 107 degrees.
-A 5,000km orbit has a period of approx 0.26 days (that’s Earth days, not Martian ones, which are about half an hour longer). Using my orbital calculator, I finessed the orbit down to 4,696km. That gives it an orbital period of 6hrs 9mins and 13secs. If you do the sums in your head, you’ll see that four orbits come to approximately 24hrs 39 mins 53 secs – the same as a Martian day. So now we have exactly four orbits per day.
+A 5,000km orbit has a period of approx 0.26 days (that’s Earth days, not Martian ones, which are about forty minutes longer). Using my orbital calculator, I finessed the orbit down to 4,697km. That gives it an orbital period of 6hrs 9mins and 13secs. If you do the sums in your head, you’ll see that four orbits come to approximately 24hrs 39 mins 53 secs – the same as a Martian day. So now we have exactly four orbits per day.
-At any part of the planet the satellite can see means, from an observer's point of view from the ground, the satellite is above the horizon. At 4,696km the satellite can see 29% of the Martian surface, with a spread of 104.45 degrees. However, that is its //visual// footprint. It probably has a radio transceiver aboard to talk to objects/people on the ground, and that is very likely to have a much smaller //radio// footprint. On Earth, this is typically 60 degrees, and if our satellite had such a radio footprint, it would be high in the sky when radio contact could be established, reducing the ill-effects of mountains etc. casting radio shadows.
+At any part of the planet the satellite can see means, from an observer's point of view from the ground, the satellite is above the horizon. At 4,697km the satellite can see 29% of the Martian surface, with a spread of 104.45 degrees. However, that is its //visual// footprint. It probably has a radio transceiver aboard to talk to objects/people on the ground, and that is very likely to have a much smaller //radio// footprint. On Earth, this is typically 60 degrees, and if our satellite had such a radio footprint, it would be high in the sky when radio contact could be established, reducing the ill-effects of mountains etc. casting radio shadows.
 The satellite will be above the same point on the ground every 6hrs 9mins and 13secs. The radio footprint is 60 degrees. 60 degrees is exactly one sixth of a circle. This means a ground station will be in the radio footprint for approximately one hour. It will also be in in this footprint four times a day at exactly the same times each day.