The definition of Avionics architecture has changed over the past 30 years. The initial definition of avionics was too described the weapon system of an aircraft. NASA defined avionics as anything dealing with the command and control of a spacecraft. This would include command and Data Management Systems, Sensors, and Effectors. Initially Power Systems, and Communication were not considered part of avionics. Recently, the definition of avionics has become synonymous with anything associated with electronics, thus including Power Systems and Communications. For a spacecraft, there are typically sensors related to Guidance Navigation and Control (GN&C), sensors related to environmental control, and other general purpose sensors. Effectors are typically dedicated to GN&C and environmental control functions. The sensors most commonly associated with the GN&C control the main propulsion system, reaction jets, and momentum exchange devices such as Reaction Wheel Assemblies (RWAs), Control Moment Gyroscopes (CMGs), and Magnetorquers (magnetic torque devices, also known as torque rod). Spacecraft stabilization can also be completed using passive techniques such as painting one side of the satellite white and the opposite side black. These passive techniques are usually not considered part of the avionics, but are necessary to understand as an overall spacecraft avionics implementation.As implied by the name, Arrowhead System Engineering provides services covering three System Engineering disciplines:
Avionics systems differ vastly based upon the vehicle they control. The control of a small satellite (e.g. a 3U of 6U form factor) is very different from a medium or large satellite (such as those used for geosynchronous television broadcast). A satellite with an anticipated 18 to 20 year mission also has vastly different requirements from a launch vehicle which has an mission life of 8 minutes (or 20 for a recoverable booster). A Human rated vehicles vary even more, with different requirements for the various classes of vehicles:
The choice of redundancy management including the potential requirement for Byzantine fault management, PAVE Pace or PAVE Pillar architecture, parts quality, probability of success, mission environment (see space mission generic requirements), and other factors have to be specified and controlled uniquely for each of these applications. Arrowhead System Engineering leadership has over four decades of experience in planning the implementation of spacecraft avionics. This includes selection of relevant components and sizing of such components to perform the stated mission. This decomposition uses the DoDAF process to specify a functional spacecraft that meets the operational requirements for a given mission or for a multi mission spacecraft. The following is a list of programs that arrowhead System Engineering has participated in defining and avionics system for launch vehicle or space element avionics systems. This required the coordination of all subsystems with the avionics subsystem to achieve the mission operational requirements. This required the organization of the avionics with all other subsystems. It also included doing trades of other subsystems requirements and avionics requirements.