Satellite Constellation Networks

Abstract

Abstract:Satellite constellations are introduced. The effects of their orbital geometry on network topology and the resulting effects of path delay and handover on network traffic are described. The design of the resulting satellite network as an autonomous system is then discussed.Key words: satellite constellation, network, autonomous system (AS), intersatellite link (ISL), path delay and latency, orbit geometry, Walker, Ballard, star, rosette, Iridium, Teledesic, Globalstar, ICO, Spaceway, NGSO non-geostationary orbit, LEO low earth orbit, MEO medium earth orbit. INTRODUCTIONA single satellite can only cover a part of the world with its communication services; a satellite in geostationary orbit above the Equator cannot see more than 30% of the Earth's surface [Clarke, 1945]. For more complete coverage you need a number of satellites -a satellite constellation. We can describe a satellite constellation as a number of similar satellites, of a similar type and function, designed to be in similar, complementary, orbits for a shared purpose, under shared control. Satellite constellations have been proposed and implemented for use in communications, including networking. Constellations have also been used for geodesy and navigation (the Global Positioning System [Kruesi, 1996] and Glonass [Börjesson, et al., 1999]), for remote sensing, and for other scientific applications.The 1990s were perhaps the public heyday of satellite constellations. In that decade several commercial satellite constellation networks were 14 INTERNETWORKING AND COMPUTING OVER SATELLITE NETWORKSconstructed and came into operation, while a large number of other schemes were proposed commercially to use available frequency bands, then loudly hyped and later quietly scaled back or dropped.1998 saw the long-awaited launch of commercial services using the 66-active-satellite LEO (low-earth-orbiting) Iridium system constructed by Motorola [Leopold and Miller, 1993]. Iridium demonstrated the feasibility of Ka-band radio intersatellite links (ISLs) directly interconnecting satellites for wide-scale intersatellite networking. However, Iridium's commercial feasibility was not demonstrated before its operating company had filed for bankruptcy protection. The widespread adoption of mobile telephony and roaming between cellular networks worldwide, largely due to the European GSM standard, had usurped much of Iridium's expected target 'business traveller' market for voice telephony to satellite handsets during the Iridium system's decade-long design and construction period. Iridium's services were later relaunched by a second company, which did not suffer from the original company's need to repay crippling construction debtsThe 48-active-satellite LEO Globalstar system [Wiedeman and Viterbi, 1993], relying heavily on CDMA-based frequency-sharing technology from Qualcomm, followed Iridium, and found the market for a voice telephony service just as difficult. Its operating company filed for bankruptcy protection in early 2002. As the mass market for satellit...

Analysis of Uncoordinated ISL Networks

“…Writing the ISL distance L as a function of angle ψ gives L(ψ) 2R h = sin ψ 2 (4) or using cos(ψ) = 1 − 2 sin 2 (ψ/2) gives L 2 (ψ) = 4R 2 h sin 2 (ψ/2) = 2R 2 h (1 − cos ψ). The ISL data rate is constrained by the usual link budget parameters including modulation and coding methods, link distance, operating frequency, RF power, antenna gains, noise temperature, equipment losses etc.…”

“…In addition, apart from a few exceptions such as [1], [2], and [3], current LEO systems make relatively little use of inter-satellite links (ISLs). See [4] for an introduction to coordinated satellite constellations.…”

A new generation of sensors and monitoring tools to support climate-smart forestry practices

“…A continued increase in both temporal, spatial and spectral resolution is expected, depending on the size of the satellite constellation, i.e. the set of similar types of satellites with an identical function designed to operate in similar, complementary orbits for a shared purpose, under shared control (Wood 2003). Commercial operators claim hourly revisit times are possible, with sub-metric spatial resolution.…”

CR-MDC: A Method of Constrained Route for Avoiding Congestion of the Satellite Sensor Network for Agriculture

“…So it is much more suitable to transfer real-time business like video and audio than single sensor satellite. Moreover, a LEO satellite constellation also can provide more system capacity by frequency reuse across its coverage [21]. Rosette constellations are described to exhibit better worldwide coverage properties [22].…”