True, but for some applications of constellations -- e.g., communications satellites -- where 100% coverage is desired, the ability to choose equal periods is helpful. Since the period is chosen by the length of the major axis, one could have satellite constellations with different minor axes but identical periods. However, achieving this would require multiple altitudes. A clever scheme could organize the satellites so that the major axes point in different directions; one might even have overlapping orbits, so long as the orbits have satellites in different phases so that they don't collide. I've even considered "stacking" orbits of the same period, all of whose major axes coincide (i.e., on the same line, but in different translations), but all with different minor axes. They don't even have to be in the same plane. Some Molniya constellations have 3 satellites in the same orbit, but in different phases. At 01:48 PM 3/20/2018, Brent Meeker wrote:
Why does it matter that the periods aren't the same?
They still can't collide.
Brent
On 3/20/2018 6:28 AM, Henry Baker wrote:
But a simple altitude-sorting strategy won't work for satellites, even for those in perfectly circular orbits, because different circular altitudes produce different periods.