麻省理工学院：《Satellite Engineering》Lecture 19 Spacecraft Computer Systems

Spacecraft Computer Systems Colonel john e Keesee

Spacecraft Computer Systems Colonel John E. Keesee

Overview Spacecraft data processing requires microcomputers and interfaces that are functionally similar to desktop systems However, space systems require Low power. volume. and mass High reliability and fault tolerance

Overview • Spacecraft data processing requires microcomputers and interfaces that are functionally similar to desktop systems • However, space systems require: – Low power, volume, and mass – High reliability and fault tolerance

Outline · Definitions Computer system specification Estimating throughput and processor speed requirements Computer selection · Memory · Mass storage Input/Output · Radiation hardness Fault tolerance Error detection and correction Integration and test

Outline • Definitions • Computer system specification • Estimating throughput and processor speed requirements • Computer selection • Memory • Mass storage • Input/Output • Radiation hardness • Fault tolerance • Error detection and correction • Integration and test

Definitions Embedded system -a built-in processor providing real-time control as a component of a larger system often with no direct user interface Real-time processing- Handling or processing information at the time events occur or when the nformation is first created

Definitions • Embedded system – A built-in processor, providing real-time control as a component of a larger system, often with no direct user interface • Real-time processing – Handling or processing information at the time events occur or when the information is first created

Definitions(continued) Hard real-time- Requires precise timing to achieve correct results where missing at time boundary has severe consequences Soft real-time- Requires that the tasks be performed in a timely manner, where missing a time boundary results in degraded but continuous performance

Definitions (continued) • Hard real-time – Requires precise timing to achieve correct results, where missing at time boundary has severe consequences • Soft real-time – Requires that the tasks be performed in a timely manner, where missing a time boundary results in degraded but continuous performance

Definitions(continued) Operating system software-Manages the computers resources such as input/output devices, memory, and scheduling of application software Application software- Mission-specific software which does work required by the user or the mission rather than in support of the computer

Definitions (continued) • Operating system software – Manages the computer’s resources, such as input/output devices, memory, and scheduling of application software • Application software – Mission-specific software which does work required by the user or the mission rather than in support of the computer

Computer System Specification 1. Allocate mission and system requirements to computer systems 2. Define the computer system's operational modes and states 3. Functionally partition and allocate the computational requirements to space or ground, payload or spacecraft, individual systems, and to hardware or software

Computer System Specification 1. Allocate mission and system requirements to computer systems 2. Define the computer system’s operational modes and states 3. Functionally partition and allocate the computational requirements to space or ground, payload or spacecraft, individual systems, and to hardware or software

Computer System Specification 4. Evaluate internal and external interfaces 5. Select the baseline architecture 6. Form the baseline system specification

Computer System Specification 4. Evaluate internal and external interfaces 5. Select the baseline architecture 6. Form the baseline system specification

State Transition diagram ibit Prelaunch Standby Intelize or Trevel Fallure Resolve Checkout OK OK Failure On-station Self Teet Hard Eor Fallure Contingent Checkout Resolved

State Transition Diagram

Functional Partitioning Perform processing Perform processing In space d on ground Perform processing Perform processing In hardware In sottware Allocate processing do not allocate between spacecraft processing between bus and payloads spacecraft bus and ds payloads Allocate processing Do not allocate along processing along organizational lines organizational lines

Functional Partitioning P e r fo r m p r o c e s s i n g i n s p a c e P e r fo r m p r o c e s s i n g o n g r o u n d P e r fo r m p r o c e s s i n g i n h a r d w a r e P e r fo r m p r o c e s s i n g i n s o ft w a r e A l l o c a t e p r o c e s s i n g b e t w e e n s p a c e c r a ft b u s a n d p a y l o a d s D o n o t a l l o c a t e p r o c e s s i n g b e t w e e n s p a c e c r a ft b u s a n d p a y l o a d s A l l o c a t e p r o c e s s i n g a l o n g o r g a n i z a t i o n a l l i n e s D o n o t a l l o c a t e p r o c e s s i n g a l o n g o r g a n i z a t i o n a l l i n e s