On-line software checkout facility for special purpose computers

An on-line software checkout facility for special purpose computers (referred to as the Flight Software Development Laboratory) has been created to aid programmer/engineers in the development of programs that will operate in a spaceborne computer aboard the Apollo/Saturn IB and V Launch Vehicles. The Flight Computer operates as an integral part of various vehicle subsystems in the Instrument Unit (IU). The subsystems provide onboard navigation, guidance, control, sequencing, data compression, and ground communications. These functions are illustrated in Figure 1. Continued emphasis is placed on error-free flight software, since it is an essential element in overall vehicle performance. No opportunity exists to test or exercise the flight program in its actual flight environment prior to a mission. Therefore, to ensure the integrity of the flight program, simulators are used to accomplish flight testing. The purpose of this paper is to present the organization of one such simulator that has been created for the sole purpose of the development and checkout of Saturn flight software. The emphasis throughout the design and implementation of the Laboratory has been that it must be user-oriented for program checkout. Before the existence of the Laboratory, available facilities for checking out flight programs were oriented to hardware checkout. Although such facilities can be, and have been, rigged for program checkout, they have not provided the type of assistance required to produce the quality of software demanded by spaceborne computers. The Laboratory is believed to be unique in the capabilities it provides to the programmer/engineer in controlling and affecting the operation of the Flight Computer in a real-time environment.