Abstract
Small satellite platforms are experiencing increasing interest from the space community, because of the reduced cost and the performance available with current technologies. In particular, the hardware composing the attitude and orbit control system (AOCS) has reached a strong maturity level, and the dimensions of the components allow redundant sets of sensors and actuators. Thus, the software shall be capable of managing these redundancies with a fault tolerant structure. This paper presents an attitude and orbit determination system (AODS) architecture, with embedded failure detection and isolation functions, and autonomous redundant component management and reconfiguration for basic failure recovery. The system design and implementation has been sized for small satellite platforms, characterized by limited computing capacities, and reduced autonomy level. The discussion describes the system architecture, with particular emphasis on the failure detection and isolation blocks at the component level. The set of functions managing failure detection at system level is also described in the paper. The proposed system is capable of reconfiguring and autonomously recalibrating after various failures had occurred. Attention is also dedicated to the achieved performance, satisfying stringent requirements for a small satellite platform. In these regards, the simulation results used to verify the performance of the proposed system at the model-in-the-loop (MIL) level are also reported.
Highlights
Today’s space sector is experiencing an increasing demand for small satellite platforms, ranging from the class of microsatellites down to that of nanosatellites
Accelerometers for small satellites are based on strap-down inertial sensor technology [20], which requires to have an estimation of the attitude of the body to which the sensor is rigidly attached in order to generate a coordinate transformation that operates on the accelerometer measurements, giving an acceleration resolved into inertial axes
Despite this paper describes the sensor post processing from the raw signals of the measured physical quantities, the simulations include all the post processing operations to convert the sensor’s output in the measured quantity
Summary
Today’s space sector is experiencing an increasing demand for small satellite platforms, ranging from the class of microsatellites down to that of nanosatellites. Attitude estimation by Kalman filtering [8] has been implemented in nanosatellites [9], and even in the extremely small picosatellite platforms [10] These systems commonly have only a single operative mode and they are not frequently designed to handle failures in the nominal components. Kalman filtering is limited to the orbit determination section, while attitude determination makes use of a complementary filter [12,13] This is motivated by the fact that meter-level position accuracy is more demanding to be achieved, with respect to degree-level attitude estimation. This is true with typical inertial sensors for small satellite platforms based on micro electro mechanical systems (MEMS) [14]. The capability to handle the main failures and Aerospace 2022, 9, 46 set the spacecraft into a mode compatible with the current operative status, satisfying the fundamental system requirements, is demonstrated at model-in-the-loop (MIL) level
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