Satellite System and Engineering Procedure-An Introduction Instructor: Roy C. Hsu Computer Science and Information Engineering Department National Chia-Yi University 10/05/2006
OUTLINE • Introduction • Satellite System • Engineering Procedure • Cases Study
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.
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.
INTRODUCTION (Cont.) . • list of countries with an independent capability to place satellites in orbit, including production of the necessary launch vehicle.
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.
INTRODUCTION (Cont.) • Possible missions • Communications • Earth Resources • Weather • Navigation • Astronomy • Space Physics • Space Stations • Military • Technology Proving
SATELLITE SYSTEM Space Segment Payload Bus Structure Attitude Determination And Control Thermal Propulsion Power Command and Telemetry Data Handling
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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
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.
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
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
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
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
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).
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
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
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
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
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
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
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
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)
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
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.
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
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
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
Q&A More Case Studies from Student Teams