Transcript Satellite Command And Data Handling Subsystem

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
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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 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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First launch by country
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
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Israel
1988
Ofeq 1
?
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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
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Communications
Earth Resources
Weather
Navigation
Astronomy
Space Physics
Space Stations
Military
Technology Proving
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SATELLITE SYSTEM
Space Segment
Payload
Structure
Bus
Attitude Determination
And Control
Power
Thermal
Command and
Telemetry
Propulsion
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
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Propulsion and Launch Systems
Attitude Determination and Control
Power Systems
Thermal Systems
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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 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 theemelectronic 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
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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
PCU
SERIAL
RCVR
SOFTWARE
TIE
OUTPUT
CIRCUIT
RCVR
OBC
ADE,GPS,PCU
DDC,SAR,DIE
DSE
BILEVEL MDE,OBC,PCU
TDE,DDC
ANA
1553
MDE
TIE,RIU
OCI,IPEI
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ROCSAT-1 Telemetry Processing Overview
GPSE
Spacecraft
Subsystems
Spacecraft
RF
Assembly
1553 BUS
Transponder
TIE
OBC
IPEI
Science Data RS 422
Recorded /
Playback Data
Serial
Science Data RS 422
SSR
RIU
OCI
ECP
Downlink
FDF
TT&C
Station
Ground
MOC
SDDCs
SSC
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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 AMSATNA), 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
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 safehold 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)
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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 errordetection 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 quarterwave 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