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CONSTELLATION GROWTH

IP.com Disclosure Number: IPCOM000009717D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2002-Sep-12
Document File: 6 page(s) / 201K

Publishing Venue

Motorola

Related People

David Gaylor: AUTHOR

Abstract

Because of their ability to cover the earth, satel- lite constellations are becoming commonly used for the following kinds of applications: 1. Communications 2. Navigation 3. Earth Observation/Weather Large-scale use of constellations has been slowed by the large initial investment required to construct an entire. constellation before any revenue can be generated. Constellation Growth provides a solution to this problem, allowing the business to begin with a smaller number of satellites and adding satellites to a constellation as the business grows. Thus, the size of the constellation can be scaled to fit the business case.

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MO7VROLA Technical Developments

CONSTELLATION GROWTH

by David Gaylor

INTRODUCTION

  Because of their ability to cover the earth, satel- lite constellations are becoming commonly used for the following kinds of applications:

1. Communications

2. Navigation

3. Earth Observation/Weather

  Large-scale use of constellations has been slowed by the large initial investment required to construct an entire. constellation before any revenue can be generated. Constellation Growth provides a solution to this problem, allowing the business to begin with a smaller number of satellites and adding satellites to a constellation as the business grows. Thus, the size of the constellation can be scaled to fit the business case.

  Currently, the only way to add capability to an existing constellation is to replace the existing satel- lites with more capable satellites, usually called "block upgrades". In order to provide increased capability over the globe, the entire constellation must be replaced with the new satellites. This means either replacing fully operational satellites before they reach the end of life or stretching the block upgrade program over many years or possibly decades. In addition, the need to retain backward compatibility may restrict how much new capability can be added. Also, improvement in availability can only be gained by increasing the satellite reliability, which may only yield marginal improvement since most satellite designs are optimized for reliability within cost constraints. Lastly, the replacement of operational satellites requires some amount of out- age while the new satellite is being brought online which will degrade the constellation performance during the retrofit.

  Constellation Growth provides a mechanism for incrementally adding capacity and capability to an existing constellation without having to discard use- ful satellites before the end of life. The additional capacity and coverage can be smoothly added by incrementally growing a constellation as shown in Figure 2, without the issue of maintaining backward compatibility. In addition, for most constellations, system availability can be increased by the addition- al multiple coverage gamed by adding satellites to the constellation.

  Constellation Growth is the process of adding satellites to an existing low earth orbit constellation. This process may be performed in several incre- ments. Satellites may be added to existing orbital planes or satellites may be added to newly created orbital planes. When adding one or more satellites to existing planes, the existing satellites are shifted in position (re-phased) to assume a new constella- tion configuration. This allows the constellation configuration to be optimized at the end of each growth increment. There are two techniques for adding satellites to existing planes: constant altitude re-phasing and increasing/decreasing altitude re- phasing.

CONSTANT ALTITUDE RE-PHASING

  The term "constant altitude" may be misleadin...