Re: Globalstar flares; definition of "LEO"
Jim Varney (jamesv@softcom.net)
Mon, 16 Feb 1998 09:20:05 -0800
Daryl Bahls wrote:
>Although I don't think the definition of orbit regimes is a "science", I'll
>give my 2 cents worth. In my experience (~21yrs doing Space Mission
>Analysis for two US commercial aerospace companies), I've seen the LEO
>definition used primarily for objects below about 2000-2500 km
>altitude (or semi-major axis).
David Vallado in his new book "Fundamentals of Astrodynamics and
Applications" applies this orbital classification scheme:
LEO: 800 km or less. Primary perturbation factor: drag
MEO: 800 km to 30000 km. Primary perturbation factor: gravitational forces
GEO: The geosynchronous belt
Deep Space: beyond GEO
800 km may seem low at first, but it does make sense when you consider the
orbital behavioral differences for a satellite at 600 km versus 1000 km.
Sean Sullivan wrote:
>So, if someone comes along and asks "where's LEO?" how does one answer?
>The basic idea is that it's the area high enough to permit an orbit and
>low enough that it's below the "null zone" where there aren't any
>spacecraft. Just where you put the numerical upper bound depends on
>how close to zero you want the "spacecraft per 100 km" statistic to be.
A population-based definition is too fluid. Once all of the comm
constellations are in orbit then the null zone will be pushed too deep into
MEO to call it LEO.
____________________________________________________________
Jim Varney 121.398 W, 38.458 N, 8m Sacramento, Calif.
Member, Sacramento Valley Astronomical Society