This paper highlights the Space Infrared Telescope Facility (SIRTF) program efforts in resolving the unique situation when the SIRTF makes the transition from a Shuttle sortie mission with liberal margins of user services to a free-flyer with a dedicated spacecraft capable of providing a modest but adequate level of services and a mission life of several years. SIRTF is a 1-m-class, cryogenically cooled, IR astronomical observatory. Since the SIRTF studies began in 1972, there have been several conceptual designs from which the familiar sortie design associated with SIRTF evolved. With the success of the Infrared Astronomy Satellite (IRAS), the SIRTF design was changed to the current, free-flying long-life astronomical observatory in the summer of 1983. The transition from a sortie mission to a free-flying, long-life observatory required a basic change: a dedicated spacecraft now provides services previously provided by the Shuttle and Spacelab. These services are (1) pointing and control, (2) communications, command, and data handling, and (3) electrical power. In addition, propulsion from Shuttle orbits to the observatory working orbit and back is required. This paper covers several alternative SIRTF designs and the development of a conceptual baseline spacecraft. These evaluations were conducted with user inputs to arrive at the level of service required of the spacecraft in power, data handling, and control. For example, details such as the need to moderate the data-handling requirements with the transition from sortie to free-flyer are covered. The data-handling capability of the Shuttle/ Spacelab is a very liberal 101° bits of storage capability and an extremely fast 300-Mb/sec communication rate. The spacecraft cannot provide these capabilities without major new com-ponent development -- a costly endeavor and one to be avoided unless justified by the user community. Also, preliminary plans considering on-orbit repair and refurbishment of the spacecraft are covered.