# Earth Orbits

Orbits are complicated, because they involve both position and velocity in three spatial dimensions and time. Simple two-body "Kepler" orbits relate the position and velocity at one time to the position and velocity at other times. In reality, orbits are also complicated by drag, light pressure, and gravitational perturbations by other bodies, and in the extreme by relativistic effects. For this discussion, we will not consider the complications, so that we get closed-form algebraic solutions. Of course, in real life, we will need to include all the complications in our calculations of orbital properties. Thinsats are deployed in closely packed orbital families. One central orbit, perfectly circular and in the orbital plane, with a sidereal period of 14393 seconds and a radius of 12789 kilometers, surrounded by slightly inclined and slightly elliptical orbits that fill a toroidal region around that central orbit. By carefully assigning orbital parameters, this region can be filled with densely packed orbits and objects in them.

### Describing Earth Orbits

Orbits are ellipses in a plane which also contains the center of the mass that defines the orbit.

### Earth Orbit Parameters

 system status number planes #/plane perigee apogee inclination period uplink GHz downlink GHz Space Station in use 1 1 1 6727 6736 51.6 5480 x x Iridium in use 66 6 11 7158 7158 86.4 6027 Ka band Ka band Teledesic bankrupt 288 12 24 7778 7778 98.2 6827 28.6-29.2 18.9-19.3 Globalstar in use 48 x x 7792 7792 52 6845 x x m288 core empty 0 1 0 12789 12789 0 14393 x x m288 outer empty 0 many 0 12739 12839 2.24 14393 x x O3b planned 12? 1 12 14441 14441 0 17271 x x Molniya in use 3? 3? 1 7885 45683 63.4 43082 x x GPS in use 31 6? - 26600 26600 55 43082 x x GEO in use 361 1 - 42164 42164 0 to 14.3 86164 - - Moon natural 1 1 1 364397 406731 5.14 2360592 x x

### M orbits

 orbit passes radius radius altitude sidereal max 45N max 45N azim 45N visible rads / day km RE km per secs latitd elevation degrees ping ms fraction /sec m120 12 7639 1.2 1261 6645 33.5 -10.2 --- --- --- 2e-4 m160 9 9099 1.4 2721 8638 45.6 0.6 22.5 43 0.04 6e-3 m240 6 11540 1.8 5162 12338 56.5 12.4 97.1 56 0.21 8e-3 m288 5 12789 2.0 6411 14393 60.1 16.5 109.9 63 0.25 2e-3 m360 4 14441 2.3 8063 17271 63.8 20.6 121.1 73 0.29 2e-3 m480 3 16756 2.6 10378 21585 67.7 24.8 131.5 87 0.32 2e-3 m720 2 20295 3.2 13917 28774 71.7 29.1 141.4 110 0.35 2e-2 m1440 1 26586 4.2 20208 43141 76.1 33.5 151.4 150 0.39 1e-2 GEO 0 42164 6.6 42164 86164 81.3 38.2 162.4 253 0.43 5e-4

### References

NORAD Space Tracking Information requires account.

EarthOrbits (last edited 2014-05-30 20:53:59 by KeithLofstrom)