## page was renamed from Orbits
= 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.  

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=== 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       ||

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=== 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 ||

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[[ LightOrbit | Light Pressure Modified Orbits ]]

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=== References ===

[[ http://en.wikipedia.org/wiki/Orbit | Wikipedia : Orbit ]]

[[ http://en.wikipedia.org/wiki/Orbital_elements | Wikipedia : Orbital Elements ]]

[[ http://en.wikipedia.org/wiki/Two-line_elements | Wikipedia :  Two Line element description (with SGP4 fortran) ]]

[[ http://www.oc.nps.edu/~garfield/ellipse_app2.pdf | Ellipse Geometry Review (pdf) ]]

[[ OrbitSoftware ]]

[[ http://www.wolffdata.se/gps/gpshtml/anomalies.html | Notes on GPS satellite orbits ]]

[[ http://personal.ee.surrey.ac.uk/Personal/L.Wood/software/SaVi/ | SaVi  satellite constellation visualization ]]

[[ http://www.astronautix.com/ | Encyclopedia Astronautica ]]

[[ http://science.nasa.gov/Realtime/rocket_sci/orbmech/state/2line.html | Description of NORAD 2 line elements ]]

[[ http://www.space-track.org/ | NORAD Space Tracking Information ]]  requires account.

[[ http://celestrak.com/ | Celestrak ]]

[[ http://www.n2yo.com/database/ | Real Time Satellite Tracking ]]

[[ http://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html | NASA 3D Realtime Satellite Tracker (Java) ]]

[[ http://www.satsig.net/sslist.htm | Geosynchronous Satellites ]]

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