SATSIL Avionics Test Bench R&D Project based on Indigenous OBDH System

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1 SATSIL Avionics Test Bench R&D Project based on Indigenous OBDH System Selim Serdar (1), Taner Yaldız (2) Turkish Aerospace Industries, Inc. (1) Fethiye Mahallesi Havacilik Bulvari No: Kazan Ankara Turkey Turkish Aerospace Industries, Inc. (2) Fethiye Mahallesi Havacilik Bulvari No: Kazan Ankara Turkey ABSTRACT Simulators play an important role in Spacecraft Projects at each phase of design, verification, validation, integration and operations. In order to reduce cost and manage risks and complexity of these projects, Simulators are used in all stages of spacecraft development, from mission design to the operations phase, with different simulator configurations and types. For the purpose of reducing time, risk and cost of design, TAI has performed the SATSIL (Satellite Integration Laboratory) Research and Development Project, bringing together ECSS Standards, European space industry and ESA practices. SATSIL, which is an Avionics Test Bench Project, aims to develop a basic Avionics Test Bench infrastructure for an AIV test facility intended to integrate and test a spacecraft at system or sub-system level. It consists of ESA s SCOS2000 based Central Checkout System and Satellite Database, a Real Time Simulation Environment executed on EuroSim, Frontend equipment, a 3D graphics application based on OpenIGS2, AOCS Models and Algorithms, Onboard Data Handling System (developed by TAI), and Interface software and drivers. This paper describes the integration of the Avionics Test Bench Project with the OBDH Development R&D project to perform Hardware-in-the-Loop testing where the OBDH system includes an indigenous OBC (Leon3), AOCS I/F Card, SSDR and TM/TC board. The project aims to use TAI indigenous OBDH System for setting up a verification and validation infrastructure for use in future space programs. The paper also will focus on the architecture and system design used in SATSIL Project. Turkish Aerospace Industries, Inc. (TAI) is Turkey s center of technology in design, development, modernization, manufacturing, integration and life cycle support of integrated aerospace systems, from fixed and rotary wing air platforms to UAVs and satellites. TAI is the main/prime local contractor for all national satellite programs in Turkey. 1

2 INTRODUCTION A satellite is in general composed of structure and mechanisms, a thermal control system (TCS), electric power system (EPS), attitude-orbit determination and control (AODCS), reaction control system (RCS), onboard data handling (OBDH), communication and payload subsystems. Design, integration, verification and validation of these kind of complex and inter disciplinary subsystems are difficult and time consuming processes. Regarding the development and progress in Information Technologies and simulation technics, it s possible to build a satellite more reliable with lower cost. Nowadays, Modelling and Simulation (M&S) as a requirement of the satellite manufacturing process is used from mission analysis phase to design, development, integration, verification, validation and operation phases. According to configuration types (Fig.1), Simulators can be divided into software in the loop (SIL) and hardware in the loop (HIL) in general. Regarding to their functions, they may be divided into design and development simulators, verification and validation simulators, and operation/training simulators. In order to reduce cost and satisfy different subsystem s needs, these simulator configurations and types are used with some customization by satellite manufacturers and subcontractors. The SATSIL R&D Project is designed and performed to fulfil and satisfy these kinds of needs for Hardware in the Loop and Real Time Validation and Verification Simulator configurations (Avionic Test Bench). Hence, all the simulation models and algorithms which are executed on SATSIL are designed reusable and portable; it allows the simulation models to be deployed in the operational simulator with minimum changes and less effort. Satellite Integration Laboratory (SATSIL) performs the following functions: OBC and OBSW validation and verification, Validation and verification simulated and real Spacecraft units, System/Subsystem validation, verification and performance analysis, Functional tests, error detection and correction analysis, Operation procedures preparation, validation, Satellite database population. In current configurations, SATSIL uses TAI OBDH as a main HIL configuration component. It communicates over a MIL-STD-1553 data bus. While AODCS algorithms are executed on the TAI ODBH in real time, Space environment, Satellite dynamic models and satellite subsystem models are executed on the simulation environment. The TM/TC flow is provided by means of a Central Checkout System based on the ESA product SCOS e. 2

3 Fig. 1. Adopted SVF Hardware in the Loop Configuration (ECSS-E-TM-10-21A) Satellite Integration Laboratory (SATSIL) SATSIL (Fig.2, Fig.4) is composed of following subsystems: Real Time Dynamic Simulator: Attitude and Orbit Determination and Control System models and algorithms, space environment models, dynamic models Onboard Computer (OBC) Developed by TAI based on LEON 3 Central Checkout System and Satellite Database based on SCOS2000 Data bus and frontends (MIL-STD-1553, Spacewire, Analog I/O) 3D Visualization based on OpenIGS 2 Real Time Dynamic Simulator The Real Time Simulator provides an infrastructure to simulate space environment, spacecraft dynamics, and simulated/real units synchronously. The Simulation manager provides main functions needed for the simulation process such as execution, state save, simulation control via script files, scheduling and so on. The AODCS subsystem is composed of actuators and sensors models which determine the satellite attitude and control in orbit. 3

4 Fig. 2. TAI Satellite Integration Laboratory Onboard Data Handling The Onboard Data Handling System (Fig.3) is responsible for the control and synchronization of the thermal control system (TCS), electric power system (EPS), attitude-orbit determination and control (AODCS), reaction control system (RCS), and communication and payload. Onboard Data Handling System (OBDH) performs functions listed below: Validates and distributes the telecommands and telemetry requests received from the ground station to the subsystems via the satellite data bus, Collects, storess and formats all satellite telemetry/housekeeping/payload data and transmits to ground station, Manages satellite attitude-orbit determination and control, Manages FDIR Fault Detection Isolation & Recovery. Due to the mission of the satellite, the OBDH subsystem has to be designed, manufactured and qualified for operation during the satellite life-time. Because of the usage of space qualified components, the cost of electronicc equipment building up the OBDH is a major issue compared to the airborne and industrial applications. Since it is mandatory to run and test software on the target OBDH during the development process, industrial and cost effective data bus (CompactPCI, VME, etc.) and form factors (3U/6U) are selected and used. Flexible and reconfigurable Antifuse/SRAM based FPGAs are used during the design phase. Hence, cost effective engineering models are achieved for laboratory studies and tests. The TAI Indigenous Onboard Data Handling System (OBDH) is composed of an onboard computer, solid state data recorder, AOCS I/ /F card, telemetry/telecommand encoder/decoder and the power supply unit. 4

5 Fig. 3. TAI OBDH (Conceptual Presentation) Central Checkout System and Satellite Database The Central Checkout System (CCS) is a central controller which provides the user interface used to configure the system and test execution. Test Scenarios can be prepared and traced by means of CCS. The SATSIL CCS is based on the ESA s Mission Control System because of the common functionalities and similarities which are TM/TC monitoring, sending, alpha numeric and mimic displays. Some of the CCS functions and database parameters are listed below: Transmission of commands to the OBDH, Telemetry stream received from the OBDH, Archive of commands and telemetry history, Test scripts execution, Alpha Numeric and Graphical Displays, The Satellite database which includes TM and TC definitions such as parameter, limit values, and alarms. Data bus and Hardware The data bus provides the communication mechanism for units to interact and work together. MIL- STD-1553 is a military standard often used for both military and civil airborne applications since It is based on a periodic query communication model. MIL-STD-1553 data bus is used on various scientific, military and communication satellite platforms. Spacewire is being used often in space applications since it is developed and standardized by ESA. It has many advantages for communication between equipments on space platforms, especially on implementation. LVDS (low-voltage differential signalling) based Spacewire, supports high speed data transfers. There is a 16-channel high-resolution analog output unit in order to stimulate the sun sensor and magnetometer analog outputs according to simulation models running on EuroSim. Hence, stimulated sensor dataa is an input for the AODC I/F board in the OBDH subsystem. Since every sun sensor is characterized, a look-up table for each sun sensor is also provided for its application on EuroSim. 5

6 The AOCS I/F converts the sun sensor and magnetometer analog signals to digital signals for the AOCS algorithms running on OBC Software. 3D Visualization The SATSIL outputs are presented via numerical and graphical displays. For showing the real space environment, ESA s OpenIGS2 three dimensional visualization tool is used. Fig. 4. SATSIL Components and Development Environment Conclusion High fidelity simulators and interface modules are required in order to verify spacecraft performance in a realistic space environment. The SATSIL project provides an infrastructure to validate the on board computer software, the satellite mission control system and the satellite database. Due to its reusable software architecture, SATSIL can be used for the Software Validation Facility (SVF) and operational simulator with minimum configuration changes. SATSIL provides the opportunity to verify and fly satellites on the table before launch. As a satellite system integrator in Turkey, TAI s approach is to establish a modelling and simulation based satellite manufacturing infrastructure. 6

7 REFERENCES [1] ECSS-E-TM-10-21A, System modeling and simulation, ESA, April 2010 [2] Jens Eickhoff, Simulating Spacecraft Systems, Springer, 2009 [3] R.Klar, C.Mangels, S.Dykes, M.Brysch, Design Considerations For Adapting Legacy System Architectures To Spacewire, Spacewire Conference, 2008 [4] Larry B.Rainey, Space Modeling and Simulation, The Aerospace Press, AIAA, 2004 [5] M. Neefs, M. Haye, Flexible Hardware In the Loop Configuration in Spacecraft Test Benches, SESP 2010, ESA/ESTEC, September 2010 [6] Brouwer, M.P.A.M.; Casteleijn, A.A.; van Ingen Schenau, H.A.; Oving, B.A.; Timmermans, L.J.; Zwartbol, T., Developments In Test And Verification Equipment For Spacecraft, National Aerospace Laboratory NLR, December 2000 [7] Osman Kalden, Peter Fritzen, Stephan Kranz, SimVis A Concurrent Engineering Tool forrapid Simulation Development, VEGA IT GmbH, June