Micro (Cost) Technologies for Spacecraft Control and Command: An Example, Balloon-Borne Stabilised Gondolas

Balloons are long-time known space vehicles for science missions and technology in-flight experiments, with instruments that need out-of-atmosphere or in-situ measurements, thus being complementary to the satellite. They carry micro (few hundred grams) to mega (few tons) payloads, but all of them require micro cost, short development, multiple flights. Among the big ones, CNES stabilised gondolas are versatile space platforms used to fly science instruments mainly coming for aeronomy and astrophysics communities, and requiring stabilisation and pointing capabilities, analogous to satellite attitude control subsystems. For them, cost and development constraints cannot be met without highly flexible architectures and off-the-shelf components. In order to increase gondola flexibility to new missions (or adaptability to mission evolutions), new hardware and software solution have been studied for control & command, including stabilisation and pointing functions. Promoted technologies are those of industrial computers, ground networks, free software and, over all, Ada language, for they are open, standard, powerful, low-cost and long-lasting solutions. After a brief description of domain-oriented characteristics of the stabilised gondola control & command, this paper introduces the various technologies and main design principles proposed to meet system-level goals. Then focus is put on on-board architectures: full Ada95 real-time distributed applications on an Ethernet-IP LAN of industrial PCs running Linux, and describes the prototyping work and preliminary development done to ensure feasibility. The paper then discusses the applicability of such solutions to global, ground-to-board, distributed control & command applications, through an IP-based telemetry & telecommand link, such as the one under development in CNES for balloon systems. As a conclusion, this paper shows how adoption of these technologies for other space programs such as satellite platforms and payloads may change design, development costs, duration and organisation, as well as it may open new ways in ground-to-board communication and spacecraft operation.