text: Traditionally, spacecraft customers order one or two spacecraft at a time from a spacecraft manufacturer for its business venture because of the cost associated with the purchase and launch of the spacecraft. A spacecraft manufacturer may have two to four spacecraft designs in its portfolio, from which the customer typically picks. The manufacturer will customize the payload and antennas to fit the customer's needs, thus leveraging the economies possible with a standardized manufacturing process while maintaining flexibility in design. Spacecraft manufacturers typically need from 15 months to 2 years to build a standard spacecraft.
  Every spacecraft has a payload section and a bus section. The payload section houses the transponder/repeaters and the antennas of the spacecraft. The bus section of the spacecraft is the structure that supports many of the functions needed to operate and control the spacecraft. Manufacturing of a spacecraft is organized into areas of specialization, such as structures, propulsion, power, telemetry and command, attitude control, thermal control, and solar array assembly hardware and electronics, and payload integration and test, antenna fabrication, spacecraft integration and test. As a spacecraft is constructed, it passes through each of these areas of specialization. The spacecraft undergoes final integration and test before shipment to the launch site. Specialized test equipment, alignment tools, and large rollover fixtures, which allow technicians to reposition the spacecraft for easy access, are featured in the area of final integration.
  With as many as seven specialization areas to be completed sequentially during the manufacture of the bus section of the spacecraft, the manufacturing process itself is time consuming and complex. It would be nice if the manufacturing process could be shortened. However, each of the functions carried by the bus section is necessary for spacecraft operation.
  Much effort by the spacecraft manufacturer goes into research and development of new materials to make the bus section lighter weight, while maintaining its strength requirements. However, due to the small size of typical spacecraft orders, it had not been economically feasible for the spacecraft manufacturer to redesign the spacecraft bus to improve manufacturability. Much work has been done to continuously improve the existing manufacturing processes each year to stay competitive.
  As in the manufacture of any product, the more of that product that you sell, the more feasible and desirable it becomes to streamline the manufacturing process and reduce production costs and risk. The same is true in the spacecraft manufacturing business. Satellite communications have become such an intricate part of society that more and more satellites are being purchased each year. The spacecraft manufacturers are realizing backlogs in the manufacture of spacecraft as much as 5 to maybe 10 years.
  A more recent trend is the large volume orders of identical spacecraft for satellite constellations to support mobile telephone services, paging, faxing, videoconferencing, broadband multimedia and remote monitoring and tracking around the world. Motorola has recently launched approximately 66 satellites for its Iridium program and is working on another large volume satellite constellation with Teledesic having over 200 satellites. The assignee to this application is manufacturing 12 satellites for ICO Global Communications for estimated launches starting in 1999 and has another constellation of 8 satellites in development for its SPACEWAY.TM. Program. Therefore there is a need to streamline the design and manufacture of these satellites to reduce manufacturing time and cost and to maintain reliability to meet the competitive and ambitious schedules of the customer.
  Thus, it would be advantageous to have a low cost, lightweight spacecraft telemetry, command and control architecture which integrates into a single electronic system many functions that previously have been implemented as physically separate systems on the spacecraft.