Satellite System and Engineering Procedure-An

Introduction

Instructor: Roy C. HsuComputer Science and Information Engineering

DepartmentNational Chia-Yi University

10/05/2006

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OUTLINE

Introduction Satellite System Engineering Procedure Cases Study

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INTRODUCTION

Definition (from Wikipedia) A satellite is any object that orbits another o

bject (which is known as its primary). Satellites can be manmade or may be natura

lly 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 French author 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 October 1957.

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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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Country Year of first launch First satellite In orbit in 2006

    Soviet Union 1957 Sputnik 1 87

    United States 1958 Explorer 1 413

    Australia 1964 Title Unknown  ?

    France 1965 Astérix  ?

    Japan 1970 Osumi  ?

    China 1970 Dong Fang Hong I 34

    United Kingdom 1971 Prospero X-3  ?

    India 1979 Rohini-1 33

    Israel 1988 Ofeq 1  ?

First launch by country

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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 DeterminationAnd Control

Thermal Propulsion

Data Handling Command and

TelemetryPower

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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 and Structure 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 co

mponent, 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

The Command 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 electrodyna

mics /IPEI, experiments using Ka-band (20-30 GHz) communicati

on payloads/ECP.

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ROCSAT-1 COMMAND AND TELEMETRY SYSTEM

S-band Consultative Committee for Space Data S

ystems (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

RCVR

RCVR

TIESOFTWARE

OUTPUTCIRCUIT

OBC

SPECIAL COMMANDS BILEVEL

PCU

SERIAL

BILEVEL

ANA

1553

ADE,GPS,PCUDDC,SAR,DIE DSE

MDE,OBC,PCU TDE,DDC

MDE

TIE,RIU OCI,IPEI

2039 MHZ 2Kbps NRZ-L

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TIETransponderRF

AssemblyOBC

GPSESpacecraft

Subsystems

ECPRIUSSR

TT&CStation

MOC

FDF

SSC

SDDCs

Ground

Downlink

Spacecraft 1553 BUS

Recorded / Playback Data

Serial

Science Data RS 422

Science Data RS 422

ROCSAT-1 Telemetry Processing Overview

OCI

IPEI

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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 t

elescope 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

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MOST ARCHITECTURE (Cont’d) AMSAT based designs housekeeping computer: V53 processor

with 29 MHz Communication: two 0.5W RF output BPS

K 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, su

n 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 telesc

ope attitude control computers : Motorola 56303 DS

P

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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 eXperi

ment 1 (CanX-1) Canada's first nanosatellite Built by graduate students of the Space Flig

ht 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)

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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 M

Hz, 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 a

nd Lithium-Ion Power: provided by Emcore triple-junction cells (26%

maximum efficiency) Energy: stored in a Polystor 3.7 V, 3600 mAh lithium-i

on 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

Q&A

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