Big LEO tables

There's an older mirror of this page in Spain, and a modified version of these tables in the slides for Business Data Communications.

Preface

Be particularly careful when comparing the data with that for Iridium and Teledesic, as these two systems are very different in design from the others, thanks in part to their use of intersatellite links. Note also that Teledesic focuses on high-bandwith data while the Big LEOs focus on voice while supporting low-bit-rate data.

You can't draw conclusions from this table without knowing a lot about how the individual systems work, and comparisons between the networked and non-networked constellations can be particularly misleading, especially if you forget that Teledesic isn't really aimed at the mobile voice communications market.

Since this table was drawn up, development on Odyssey has stopped development and Teledesic has undergone a redesign, details of which are not publically available. This is not reflected in the data presented here, which is only applicable to the original 840-active-satellite design discussed in various papers.

Information on the Ellipso [ELL96] and Constellation [CAS95] systems has been removed from this version of the tables. Although these constellations finally received their FCC licences on July 1 1997, the data available when these pages were compiled is particularly sketchy.

[JOH95] is one of the more comprehensive overviews of technical data for the Big LEOs, and contains many tables, also including link budget parameters. The data is however slightly dated; it reflects the situation as perceived at the beginning of 1994.

Services and cost

Caution:The system cost figures reflect the information provided by the systems; they contain different elements and may not be comparable. For instance, the Globalstar cost does not include the cost of the earth stations, whereas the Odyssey cost figures do. The figures may include only initial capital cost - this would make a significant difference when comparing the cost of the short-lived LEO systems (5-7.5 years) to the longer-lived MEO systems (10 - 15 years.)

Note also that the call rates may entail different elements; Globalstar's, for instance, do not include the the additional cost the service providers will have to add to recover the cost of a Globalstar earth station gateway, and additional costs incurred from charges from terrestrial networks to complete the call are not included. These costs are estimates from 1996, and have been outdated by subsequent events.

Orbits and Geometry

Orbits and Geometry	Odyssey	ICO	Globalstar	Iridium	Teledesic
Orbit class	MEO	MEO	LEO	LEO	LEO
Altitude (km)	10354	10355 (changed to 10390, late 1998)	1410	780	695-705
Number of satellites	12 active 3 in-orbit spares	10 active 2 in-orbit spares	48 active 8 in-orbit spares	66 active 6 in-orbit spares	840 active up to 84 in-orbit spares
Number of planes	3	2	8	6	21
Inclination (°)	50	45	52	86.4	98.16
Period (minutes)	359.5	358.9 (changed to 360.9)	114	100.1	98.8
Satellite visibility time (minutes)	94.5	115.6	16.4	11.1	3.5
Minimum mobile terminal elevation angle (°)	20	10	10	8.2	40
Minimum earth-space link one-way propagation delay (ms)	34.6	34.5	4.63	2.60	2.32
Maximum earth-space link one-way propagation delay (ms)	44.3	48.0	11.5	8.22	3.40
Minimum earth station elevation angle (°)	--	--	10	--	40
Number of earth stations	7	12	100 ~ 210	15 - 20 planned; 11 constructed	--
Coverage	global (at least one satellite in view above 20° at all points of the globe)	global	within ±70° latitude	global	nearly global (2° hole at each pole)

Beam and re-use characteristics

Frequencies and miscellaneous

L-band is 0.5 to 1.5GHz
C-band is 4 to 8 GHz
Ku-band is 10.9 to 17 GHz
Ka-band is 18 to 31 GHz

The band names originate from the names of the original waveguide sizes chosen in the 1940s - Ku is under K-band, while Ka is above K-band.