17.1.2 Low-earth-orbiting satellites

Figure 17.1: Example of a polar-orbiting LEO constellation. This figure was generated using the SaVi software package from the geometry center at the University of Minnesota.

Polar orbiting satellite systems, such as Iridium and the proposed Teledesic system, can be modelled in ns. In particular, the simulator supports the specification of satellites that orbit in purely circular planes, for which the neighboring planes are co-rotating. There are other non-geostationary constellation configurations possible (e.g., Walker constellations)- the interested user may develop new constellation classes to simulate these other constellation types. In particular, this would mainly require defining new intersatellite link handoff procedures.

The following are the parameters of satellite constellations that can currently be simulated:

The following table lists parameters used for example simulation scripts of the Iridium17.1 and Teledesic17.2 systems.

Table 17.1: Simulation parameters used for modeling a broadband version of the Iridium system and the proposed 288-satellite Teledesic system. Both systems are examples of polar orbiting constellations.
Iridium Teledesic
Altitude 780 km 1375 km
Planes 6 12
Satellites per plane 11 24
Inclination (deg) 86.4 84.7
Interplane separation (deg) 31.6 15
Seam separation (deg) 22 15
Elevation mask (deg) 8.2 40
Intraplane phasing yes yes
Interplane phasing yes no
ISLs per satellite 4 8
ISL bandwidth 25 Mb/s 155 Mb/s
Up/downlink bandwidth 1.5 Mb/s 1.5 Mb/s
Cross-seam ISLs no yes
ISL latitude threshold (deg) 60 60

Tom Henderson 2011-11-05