An Improved SDARS Orbital Constellation

Paper number

IAC-07-B2.4.01

Author

Mr. Robert D. Briskman, Sirius Satellite Radio, United States

Coauthor

Mr. Joseph Foust, Space Systems/Loral, United States

Year

2007

Abstract

Over seven years ago, a Satellite Digital Audio Radio Services (SDARS) system was established to provide broadcast service to mobile and fixed subscribers throughout North America.  The system has been operating with extremely high availability providing over 65 commerical free music channels, over 70 voice channels (i.e., news, sports, comedy, traffic, ethnic languages, weather, etc.) and a few television channels to more than 6 million subscribers. 

The system employs three satellites forming an orbital constellation.  The satellites are in inclined, elliptical geosynchronous orbits whose planes are separated from each other by 120 degrees. The constellation provides high elevation angles to all subscribers, with a distinct advantage in the northern half of the United States where elevation angles from geostationary satellites would be low.  High elevation angles from the satellites to mobile subscribers are vital for achieving the service availability previously noted.

This paper describes plans to include a high powered geostationary satellite in the constellation which is then called a "hybrid" constellation.  The hybrid constellation will provide increased service availability by enhancing spatial diversity and improving elevation angles during daily periods of non-geostationary orbit satellite transitions. The geostationary satellite will also provide in-orbit sparing capability to the existing constellation.

The paper describes the new geostationary satellite implementation which, besides doubling the total power of the existing satellites and providing peak EIRPs of over 10 megawatts, contains other state-of-art features such as plasma thrusters, a 9-meter diameter antenna, lithium ion batteries and an attitude and orbit control star sensor.

Abstract document

IAC-07-B2.4.01.pdf

Manuscript document

IAC-07-B2.4.01.pdf (🔒 authorized access only).

To get the manuscript, please contact IAF Secretariat.