World Broadcasting Unions Digital Radio User Manual - page 73

DIGITAL RADIO GUIDE

SATELLITE TRANSMISSION - SIRIUS / XM

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Figure 5.5. Sirius Ground Track

The decision to use inclined, elliptical orbits rather than geostationary orbits for Sirius was

made approximately one year into the design and manufacturing phase of the project.  At 

the same time, modifications were made to the payload requirements, affecting

spacecraft configuration and support subsystems. While the majority of the satellite

hardware remained unchanged, a number of modifications were required.  Several

design trades and decisions were influenced by the existing state of design and

development.  The program was carefully replanned to accommodate late arrival of new

or modified hardware and software, while maintaining the integrity of the overall system

testing.  The highest priority was given to quality and reliability of the end product.  No

“shortcuts” were taken during the development or qualification of new hardware or

software.  The overall success of the program demonstrated the ability to respond quickly 

to a change in the implementation plan.  The following table summarizes the

modifications made to the 1300 design for the Sirius application.