Development, Test and Flight of the SMART-1 Attitude and Orbit Control System

Abstract

*This paper presents results from the development, test and flight of the SMART-1 Attitude and Orbit Control System (AOCS). SMART-1 was captured in lunar orbit on November 16, 2004 after more than one year of travel around the earth since its launch on September 27, 2003. The arrival to the moon marks the completion of the primary mission objective which is to demonstrate the use of Electric Primary Propulsion in a low-thrust transfer trajectory. The arrival to the moon also marked the start of the lunar science observation phase. The Swedish Space Corporation is the prime contractor for the SMART-1 spacecraft. The paper explains how the SMART-1 AOCS was developed and tested. The AOCS flight software was produced using automatic code generation. The use of automatic code generation has proven to be an efficient development approach in which accurate code models have been available throughout the development cycle of the software. The code has been developed starting from early analysis models. These models were integrated into one single AOCS subsystem model which was split up into one simulator part and one flight software part. The simulator part was delivered to the real-time spacecraft system simulator while the flight software part was integrated into the over-all on-board software. All the way through this development, it has been possible to simulate the AOCS subsystem in a MATLAB/Simulink environment using the very parts from which code was generated for the system simulator as well as the on-board software. The availability of these accurate code models has been useful for development of tests on unit and system level involving different degrees of hardware in the loop. The paper explains how the software was developed and how it was used in these different levels of testing. The paper also explains how the accurate code models have been used for analysis of in-flight performance.