Satellite System and Engineering Procedure-An Introduction

1. Satellite System and Engineering Procedure-An Introduction Instructor: Roy C. Hsu Computer Science and Information Engineering Department National Chia-Yi University 10/05/2006

2. OUTLINE • Introduction • Satellite System • Engineering Procedure • Cases Study

3. INTRODUCTION • Definition (from Wikipedia) • A satellite is any object that orbits another object (which is known as its primary). • Satellites can be manmade or may be naturally occurring such as moons, comets, asteroids, planets, stars, and even galaxies. An example of a natural satellite is Earth's moon.

4. INTRODUCTION (Cont.) • Human-made devices: artificial satellite • From Science Fiction • the first fictional depiction of an artificial satellite launched into Earth orbit –by Jules Verne's The Begum's Millions (1879). • Jules Gabriel Verne (February 8, 1828–March 24, 1905), a Frenchauthor and a pioneer of the science-fiction genre. • Verne was noted for writing about cosmic, atmospheric, and underwater travel before air travel and submarines were commonplace and before practical means of space travel had been devised. • The first artificial satellite was Sputnik 1 launched by Soviet Union on 4 October1957.

5. INTRODUCTION (Cont.) . • list of countries with an independent capability to place satellites in orbit, including production of the necessary launch vehicle.

6. First launch by country

7. INTRODUCTION (Cont.) • MISSION AND PAYLOAD • Space mission: the purpose of placing in equipment (payload) and/or personnel to carry out activities that cannot be performed on earth • Payload: design of the equipment is strongly influenced by the specific mission, anticipated lifetime, launch vehicle selected, and the environments of launch and space.

8. INTRODUCTION (Cont.) • Possible missions • Communications • Earth Resources • Weather • Navigation • Astronomy • Space Physics • Space Stations • Military • Technology Proving

9. SATELLITE SYSTEM Space Segment Payload Bus Structure Attitude Determination And Control Thermal Propulsion Power Command and Telemetry Data Handling

10. SATELLITE SYSTEM(Cont’d) • A satellite system is composed of the spacecraft (bus) and payload(s) • A spacecraft consists of the following subsystems • Propulsion and Launch Systems • Attitude Determination and Control • Power Systems • Thermal Systems • Configuration andStructure Systems • Communications • Command and Telemetry • Data Handling and Processing

11. SATELLITE SYSTEM (cont’d) • Propulsion and Launch Systems • Launch vehicle: used to put a spacecraft into space. • Once the weight and volume of the spacecraft have been estimated, a launch vehicle can be selected from a variety of the manufacturers. • If it is necessary to deviate from the trajectory provided by the launch vehicle or correct for the errors in the initial condition, additional force generation or propulsion is necessary • On-board propulsion systems generally require a means to determine the position and attitude of the spacecraft so that the required trust vectors can be precisely determined and applied.

12. SATELLITE SYSTEM (cont’d) • Attitude Determination and Control System (ADCS) • ADCS are required to point the spacecraft or a component, such as solar array, antenna, propulsion thrust axis, and instrument sensor, in a specific direction. • Attitude determination can be accomplished by determining the orientation w.r.t. the star, earth, inertial space, geomagnetic field and the sun. • Attitude control can be either passive or active or combination.

13. SATELLITE SYSTEM (cont’d) • Power Systems • Spacecraft power can be obtained from the sun through solar cell arrays and thermal electrical generators and from on-board devices such as chemical batteries, fuel cell, and nuclear theem-electronic and therm-ionic converters. • Most satellites use a combination of solar cell array and chemical batteries.

14. SATELLITE SYSTEM (cont’d) • Thermal Control Systems • The function of the thermal control system is to maintain temperatures to within specified limit throughout the mission to allow the onboard systems to function properly and have a long life • Thermal balance can be controlled by using heaters, passive or active radiators, and thermal blankets of various emissivities on the exterior.

15. SATELLITE SYSTEM (cont’d) • Configuration and Structure Systems • The configuration of a spacecraft is constrained by the payload capability and the shape of the fairing of expendable launch vehicle. • Large structures, such as solar arrays and antenna are erected in the space through deployable components. • Explosive devices, activated by timing devices or command, are used to separate the spacecraft from the launch vehicles, release and deploy mechanisms, and cut cables.

16. SATELLITE SYSTEM (cont’d) • Command and Telemetry • TheCommand and Telemetry system provide information to and from the S/C respectively. • Commands are used to provide information to change the state of the subsystems of the S/C and to se the clock. • The Telemetry subsystem collects and processes a variety of data and modulates the signal to be transmitted from the S/C.

17. SATELLITE SYSTEM (cont’d) • Data Handling and Processing • Data processing is important to help control and reconfigure the spacecraft to optimize the overall system performance and to process data for transmission. • Consists of processor(s), RAM, ROM, Data Storage, and implemented by machine, assembly or high level language. • Low mass, volume, and power requirements, insensitivity to radiation, and exceptional reliability are important characteristics of processor.

18. SATELLITE SYSTEM (cont’d) • Communications • Radio frequency communication is used to transmit information between the S/C and terrestrial sites and perhaps other S/Cs. • Information transmitted from the S/C include the state and health of the subsystems in addition to data from the primary instruments. • Information transmitted to the S/C generally consists of data to be stored by on-board processors and commands to change the state of the on-board system either in real-time or through electronic logic that execute them as a function of time or as required.

19. Engineering Procedures • Space Systems Engineering • System Definition • System, Subsystem, Components, and Parts • A large collection of subsystems is called a segment. • In a space mission, the spacecraft, the launch vehicle, the tracking stations, the mission control center, etc., may each be considered a system or segment by their principle developers but are subsystems of the overall system. • Value of a System • System’s ability to satisfy criteria generally called system level requirements or standards for judgment.

20. Engineering Procedures (Cont’d) • Engineering a Satellite • Mission Needs • Conceptualization and system requirements • Planning and Marketing • Research and Technology Development • Engineering and Design • Fabrication and Assembly • Integration and Test • Deployment, operation and phase-out

21. Engineering Procedures (Cont’d) Mission Needs Conceptualization and system requirements Planning and Marketing Research and Tech. Development Engineering and Design Fabrication and Assembly Integration and Test Development, Operation And Phase-out

22. SMALL SATELLITE CASE STUDY ROCSAT-1 • A low-earth orbiting (LEO) satellite jointly developed by TRW of U.S. with a resident team of NSPO engineers. • Launched on January 27, 1999 into an orbit of 600 kilometers altitude and 35 degrees inclination. • Three scientific research missions/Payloads: • ocean color imaging/OCI, • experiments on ionospheric plasma and electrodynamics /IPEI, • experiments using Ka-band (20-30 GHz) communication payloads/ECP.

23. ROCSAT-1 COMMAND AND TELEMETRY SYSTEM • S-band • Consultative Committee for Space Data Systems (CCSDS) Packet Telcommand and Telemetry • Uplink data rate: 2 kbps • Downlink data rate: 1.4 mbps • Data storage: 2 gb

24. ROCSAT-1 COMMAND SYSTEM 2039 MHZ 2Kbps NRZ-L SPECIAL COMMANDS BILEVEL TIE PCU RCVR ADE,GPS,PCUDDC,SAR,DIE DSE SERIAL OUTPUT CIRCUIT SOFTWARE BILEVEL MDE,OBC,PCU TDE,DDC RCVR ANA MDE 1553 OBC TIE,RIU OCI,IPEI

25. ROCSAT-1 Telemetry Processing Overview GPSE Spacecraft Subsystems Spacecraft 1553 BUS RF Assembly Transponder TIE OBC IPEI Science Data RS 422 Recorded / Playback Data OCI Science Data RS 422 Serial SSR RIU ECP Downlink FDF SDDCs TT&C Station MOC SSC Ground

26. ROCSAT-1 DATA HANDLING SYSTEM • On Board Computer（OBC）: 80C186 CPU • Real-time operation system: Versatile Real-Time eXecutive (VRTX32/86), a real-time multi-tasking OS • Employing software engineering approach for the development of the flight software. • A real-time embedded system

27. Microsatellite Case Study-MOST • The MOST (Microvariability and Oscillations of Stars) astronomy mission is Canada's first space science microsatellite and Canada's first space telescope. • Satellite's mission: to conduct long-duration stellar photometry observations in space • A secondary payload on a Delta II launch vehicle (with Radarsat-2 as the primary payload).

28. Case Study-MOST (Cont’d) • Payload: a 15cm diameter aperture Maksutov telescope • Team led by Dr. Matthews of Department of Physics and Astronomy, University of British Columbia • Spacecraft: • Dynacon Inc. as prime contractor for PM and the Attitude Control and Power subsystems designer • Institute for Aerospace Studies' Space Flight Laboratory, Univ. of Toronto: structure, thermal, on-board computers and telemetry & command, along with the ground stations following AMSAT-NA), with support from AeroAstro

29. MOST ARCHITECTURE

30. MOST ARCHITECTURE (Cont’d) • AMSAT based designs • housekeeping computer: V53 processor with 29 MHz • Communication: two 0.5W RF output BPSK transmitters and two 2W FM receivers. • All radios operate at S-band frequencies

31. MOST ARCHITECTURE (Cont’d) • Power subsystem • based on a centralized switching, decentralized regulation topology • switches are controlled via the housekeeping computer • 35W in fine pointing operations and 9W in safe-hold or tumbling operations • NiCd battery provides power during eclipses and supports peak power draws from equipment such as the transmitters • High-efficiency silicon solar cells on all sides of the satellite

32. MOST ARCHITECTURE (Cont’d) • ACS equipment: consists of magnetometers, sun sensors, and a star tracker for sensing, and magnetorquers and reaction wheels for actuation. • maintain pointing accuracy of less than 25 arcseconds by using • reaction wheels: for three-axis attitude control, • star tracker: a fundamental part of the science telescope • attitude control computers : Motorola 56303 DSP

33. MOST ARCHITECTURE (Cont’d) • Structure: • a tray stack design • consists of aluminum trays that house the satellite's electronics, battery, radios, and attitude actuators • these trays are stacked forming the structural backbone of the satellite • Six aluminum honeycomb panels, acting as substrates for solar cells and carriers for attitude sensors, enclose the tray stack/telescope assembly

34. Nanosatellite Case Study-CanX-1 • The Canadian Advanced Nanospace eXperiment 1 (CanX-1) • Canada's first nanosatellite • Built by graduate students of the Space Flight Laboratory (SFL) at University of Toronto Institute for Aerospace Studies (UTIAS) • Launched on June 30, 2003 at 14:15 UTC by Eurockot Launch Services from Plesetsk, Russia

35. Case Study-CanX-1 (Cont’d) • one of the smallest satellites ever built • mass under 1 kg, • fits in a 10 cm cube, and • operates with less than 2 W of power • mission: to evaluate several novel technologies in space • a low-cost CMOS horizon sensor and star-tracker • active three-axis magnetic stabilization • GPS-based position determination • central computer

36. Case Study-CanX-1 (Cont’d)

37. Case Study-CanX-1 (Cont’d) • CMOS Imager • comprised of color and monochrome CMOS imagers • used for ground-controlled horizon sensing and star-tracking experiments • Both communicate with the On-Board Computer (OBC)

38. Case Study-CanX-1 (Cont’d) • Active Three-Axis Magnetic Stabilization • Three custom magnetorquer coils and a Honeywell three-axis digital magnetometer are used in conjunction with a B-dot control algorithm for spacecraft detumbling and coarse pointing experiments

39. Case Study-CanX-1 (Cont’d) • GPS Position Determination • Accurate position determination is accomplished using a low-cost commercial Global Positioning System (GPS) receiver that has been modified to work in low Earth orbit • ARM7 On-Board Computer (OBC) • operates at 3.3 V, consumes 0.4 W at a speed of 40 MHz, equipped with 512 KB of Static-RAM and 32 MB of Flash-RAM • Runs housekeeping and payload application routines, as well as B-dot detumbling and error-detection and correction algorithms, No OS.

40. Case Study-CanX-1 (Cont’d) • Telemetry and Command • handled by a half-duplex transceiver operating on fixed frequencies in the 430 MHz amateur satellite band • 500 mW transmitter downlinks data and telemetry at 1200 bps using a MSK over FM signal • The antenna system consists of two quarter-wave monopole antennas oriented at 90° and combined in phase to produce a linearly polarized signal

41. Case Study-CanX-1 (Cont’d) • Power system with Triple-Junction Solar Cells and Lithium-Ion • Power: provided by Emcore triple-junction cells (26% maximum efficiency) • Energy: stored in a Polystor 3.7 V, 3600 mAh lithium-ion battery pack to handle peak loads and provide power during eclipse periods • incorporates peak-power tracking, over-current protection, power shunting, and an emergency load shed system

42. Case Study-CanX-1 (Cont’d) • Structure: Aluminum 7075 & 6061-T6 • total mass of structure is 373 g, 37% of the total satellite mass, including the frame, all exterior surfaces, and internal mounting hardware • Simulations with 12 G loads showed a 30% margin to the maximum allowable stress • thermal analysis predicted a -20 to +40°C temperature range using passive thermal control • Vibration testing shown a natural frequency of approximately 800 Hz

43. Q&A More Case Studies from Student Teams