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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

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Satellite system and engineering procedure an introduction l.jpg

Satellite System and Engineering Procedure-An Introduction

Instructor: Roy C. Hsu

Computer Science and Information Engineering Department

National Chia-Yi University

10/05/2006


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OUTLINE

  • Introduction

  • Satellite System

  • Engineering Procedure

  • Cases Study


Introduction l.jpg
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.


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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.


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INTRODUCTION (Cont.)

.

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



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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.


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INTRODUCTION (Cont.)

  • Possible missions

    • Communications

    • Earth Resources

    • Weather

    • Navigation

    • Astronomy

    • Space Physics

    • Space Stations

    • Military

    • Technology Proving


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SATELLITE SYSTEM

Space Segment

Payload

Bus

Structure

Attitude Determination

And Control

Thermal

Propulsion

Power

Command and

Telemetry

Data Handling


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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


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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.


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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.


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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.


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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.


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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.


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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.


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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.


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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.


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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.


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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


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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


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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.


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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


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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


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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


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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


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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).


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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



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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


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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


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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


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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


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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


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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



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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)


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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


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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.


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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


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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


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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


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Q&A

More Case Studies from Student Teams


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