[AR] Re: [OT] Convention for describing elliptical orbits?
- From: John Schilling <John.Schilling@xxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Mon, 23 May 2016 19:04:59 -0700
On 5/23/2016 11:22 AM, Nathan Bergey wrote:
I've also usually seen altitude rather then center. I think that's
because you care about the satellite in comparison to *you* (for
calculating link budgets for radios, etc.) rather than to the center
of the Earth.
Right, because satellites so frequently pass directly over my head
and that's really the only time I want to communicate with them. For
doing slant range calculations, radius is I think more convenient than
altitude.
For low circular orbits, I can see that it is sometimes intuitively
useful to think altitude rather than radius. But since the issue comes
up, are there any common elliptical orbits where this is the case?
Molniya is elliptical, but we're only really interested in the apogee
for that and if we're planning to look at or talk to a hemisphere the
slant range will be closer to the radius than the height. Really,
that's going to be the case for anything much higher than 1 Re, and
most everything lower than that is going to be pretty circular.
Were it up to me, radius would be the default and we'd have a
simple rule for specifying low circular orbits as altitude when
that makes more sense. And since it only really makes sense below
1 Re, there wouldn't be much room for confusion.
But it's not up to me, customary usage is to express orbits as
altitudes not radius, and as with the bastard formulation of specific
impulse, you use the tribal code or guarantee misunderstanding.
John Schilling
john.schilling@xxxxxxxxxxxxxx
(661) 718-0955
Other related posts:
