A Model of the AFSCN Common Core TT&C System Using the Rapide ADL

Transcription

1 A Model of the AFSCN Common Core TT&C System Using the Rapide ADL by by Charles B. B. Simmons Information Technology Department Computer Systems Division The Aerospace Corporation El El Segundo, CA

2 Outline Background Overview of AFSCN Common Core TT&C System Common Core TT&C Reference Architecture Study Architecture Evaluation Criteria The Rapide ADL Lessons Learned Future Efforts

3 Background USC DARPA EDCS Contract Aerospace Subcontracted to USC Aerospace supporting USC by providing expertise in the SGS domain Goal is to define a draft reference architecture for satellite ground station domain Aerospace Approach Identify evaluation criteria for architectures for satellite ground stations Evaluate Architecture Definition Languages (ADLs) to represent, develop, and evaluate reference architecture

4 Target Domain: Air Force Satellite Control Network (AFSCN) Mission SV Space Vehicle to Ground Antenna Range Segment Dedicated RGFs Range/Comm to MCS AF SCN Voice Comm Communications Segment Resource Management Segment (RMS) Mission Control Segments TT&C Core TT&C Core Core TT&C Common Core TT&C DSCS MILSTAR SBIRS GPS Core to MUE Common User Element (Network Operations) RMS to MCS = Standard Interface

5 AFSCN Common Core TT&C Ground System Programs will plug into the core for common functions, and provide their own mission unique functions Use of core will vary from program to program Based on the evolution of an existing Object Oriented Architecture

6 Common Core TT&C Reference Architecture Study Goal was to define a reference architecture to help us evaluate contractor proposed architectures Documented in Aerospace Report TOR-96(1571)-3 Based largely on the Common Core TT&C Functional Requirements Document (FRD) Provides a high level description of system components Defines relationships between components Defines interfaces to external components Identifies performance drivers and capacity requirements Architecture represented as diagrams

7 Notional Common Core TT&C Reference Architecture Satellitespecific Information Base Msn Pln TLM CMD Orbit Att Core Internal Grnd Sys Sat Res Mgmt Mission-specific SV Sim Mission Payload Mission-specific External to Satellite Operations Apps. Mission Planning TLM CMD Orbit Attitude Grnd Sys Sim Sat Ops Res Mgmt SV SIM Mission/ Maneuver Planning & CMD Gen Payload Pre- Processing & Data Analysis SV Ext User Veh. Cont. Distribution Services System Services DBMS O/S HCI Security File Network Services Config Mgmt Timing DSS Appl Mgmt RMS, Comm, and Range Core Internal Mission-specific Core Internal External

8 What we would like to know about our architecture The extent to which architecture supports implementation of functional requirements of the FRD The extent to which the core architecture supports anticipated variations in system requirements for the various Mission Control Segments The degree to which the architecture can tolerate changes to requirements based on past experience and future trends The degree to which the component interfaces and behavior are clearly defined and understood The extent to which the architecture supports the reuse of components, both existing and future (e.g. COTS products, legacy systems)

9 What we would like to know about our architecture (continued) The extent to which architectural style is justified and style mismatches are identified and understood The degree to which architecture is suitable for the performance requirements (what are the drivers?) The scalability of architecture that is possible without the need for architecture modifications The degree to which the architecture uses open system standards (e.g. CORBA) The degree of modularity of the architecture The allocation of software to hardware resources

10 Overview of Rapide An Executable Architecture Definition Language (EADL) and associated tools for defining and analyzing system architectures Based on event-based execution model of distributed, time sensitive systems -- the timed poset model Architectures defined in Rapide can be executed Generates events and causal relationships between events Rapide tools support automated analysis of posets that result from execution of Rapide architectures Rapide tools display posets for human analysis

11 Applying Rapide to the Common Core TT&C System Developed models for the telemetry & commanding portions of the system Defined components of architecture Defined interfaces between components Specified behavior of components Executed model under various scenarios Analyzed poset output

12 Rapide SSCS Model: Telemetry Front End Telemetry Front End Architecture satellite frame / packet sync extract raw PCM_Stream Mainframes Raw_SOH_Measurands form derived Derived_Measurands eu convert Raw_SOH_Measurands assess data quality Quality_Assessed_ store / retrieve / distribute eu data Request_ Requested_

13 Rapide SSCS Model: Telemetry Front End & Telemetry Back End Telemetry Front End Architecture (Server) satellite frame / packet sync extract raw measurand PCM_Stream Mainframes Raw_SOH_Measurands form derived Derived_Measurands eu convert Raw_SOH_Measurands assess data quality Quality_Assessed_ store / retrieve / distribute eu data Telemetry Back End Architecture (Client) Request_ Request_ Requested_ Requested_ Anomaly_Message display state Request_SV_State SV_State determine state Request_SV_State Request_SV_State detect anomalous condition SV_State SV_State Request_SV_State SV_State Anomaly_Condition diagnose anomalous condition Anomaly_Diagnosis resolve anomalous condition Anomaly_Response

14 Rapide SSCS Model: Telemetry Front End & Commanding Front End Telemetry Front End Architecture (Server) satellite frame / packet sync extract raw measurand PCM_Stream Mainframes Raw_SOH_Measurands form derived Derived_Measurands eu convert Raw_SOH_Measurands assess data quality Quality_Assessed_ store / retrieve / distribute eu data Commanding Front End Architecture (Client) Request_ Request_ Requested_ Requested_ satellite Command_Stream transmit command Checked_Command_Element check constraints Command_Element select command Command_Transmitted

15 Rapide SSCS Model: Telemetry Front End & Commanding Back End Telemetry Front End Architecture (Server) satellite frame / packet sync extract raw measurand PCM_Stream Mainframes Raw_SOH_Measurands form derived Derived_Measurands eu convert Raw_SOH_Measurands assess data quality Quality_Assessed_ store / retrieve / distribute eu data Commanding Back End Architecture (Client) Request_ Request_ Requested_ Requested_ resolve command anomaly eval command function check command decoder check command authentication Unverified_Unvalidated_Command

16 Rapide SSCS Model: Telemetry Front End & Multiple Clients Telemetry Front End Architecture (Server) satellite frame / packet sync extract raw measurand PCM_Stream Mainframes Raw_SOH_Measurands form derived Derived_Measurands eu convert Raw_SOH_Measurands assess data quality Quality_Assessed_ store / retrieve / distribute eu data Request_ Requested_... Client Arch. #1 Client Arch. #2 Client Arch. #3 Client Arch. #n

17 Lessons Learned in Applying Rapide Helped us maintain consistencies between interfaces of components Resulted in identifying several interface mismatches and omissions in the published reference architecture For example, telemetry was mismatched to space vehicle state in several instances Forced us to be explicit in defining behavior of components For example, behavior of anomaly detection and diagnosis components was not completely described

18 Lessons Learned in Applying Rapide - continued Provided insight into the dynamic behavior of the system Capable of partially addressing our needs in evaluating architecture in at least the following areas: component interfaces and behavior scalability of architecture performance requirements changes to requirements

19 Future Efforts Add more detail to Rapide model Work with TRW to enhance telemetry and commanding models Add additional components to model: Orbit, Attitude, and Mission Planning Investigate architecture tools that address other important criteria Acquire and Evaluate other ADLs