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EGOS Workshop 2005

GDSS - Ground Data System Services:a Service Oriented Architecture for Mission OperationsRoger Thompson, Nestor Peccia, Stewart Hall, Oliver Page

Presented by:Roger Thompson

EGOS Workshop 20059th November 2005

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GDSS Study ContextDefinition of Standardised Ground Data System

Services

Study for ESA/ESOC commenced in 2004: Considering Service Architecture for EGOS Infrastructure Builds on Reference Architecture developed in context of

European GS Technology Harmonisation Builds on Mission Operations Service Framework being

developed by CCSDS Spacecraft M&C Working Group

Study Outputs GDSS Service Framework document Draft Specifications produced for:

GDSS-C Common Service GDSS-MO Core M&C Service GDSS-MO Schedule Execution Service


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GDSS Objectives Definition of a Service Oriented Architecture for

the Mission Operations domain Focussed on Ground Segment, but capable of

extension to Check-out and Space Segment Compatible with evolving CCSDS SM&C Standards

Standardised Services enable: Open Interfaces between Major Components Development of Re-usable [and Replaceable]

Plug-in Components Rapid Mission Specific Deployment Isolation of Domain Software from Deployment

Technology Legacy Software to be wrapped for Re-use


4

CCSDS Context See Presentation by Mario Merri

CCSDS Spacecraft M&C Working Group MOIMS Area WG, Established October 2003 Active Participation from ESA, BNSC, CNES, CSA, DLR,

JAXA and NASA (JPL, GSFC) Mission Operations Services: end-to-end

Application level services for spacecraft operations interactions

Current Status Mission Operations Service Framework available High Priority Service Specifications in production

SM&C Core, Common and Protocol Layers Early work on other Service Specifications Prototyping of High Priority Services about to start


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Integrated Systems vs. Modular Components


6

Service-Oriented Architecture:Plug-in Components

Components

Services

Infrastructure


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Benefits of the SOA Approach Components exchangeable for others supporting same Service

Interfaces Plug-and-play interoperability of MCS components

Common Service Framework Re-use of common infrastructure across multiple systems Independence of mission configuration data and history from

system implementation Infrastructure Implementation can be changed without change

to core Applications Independence of core application software from underlying

implementation technology – platform and communications Components rapidly deployable in different combinations

Reduced mission-specific deployment costs Extensible: easy to add new components

Scope to evolve a system, by replacing components or changing underlying technologies

Success is dependent on the Granularity of the service architecture selected


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Identification and Modelling of Services UML-2 Model with different “Views” (cf. RM-

ODP) Functional View Information View Service View [Multiple] Deployment Views: Physical Architectures

Functional View Application Level Mission Operations Functions

Initial Selection based on ECSS and Ground Segment Harmonisation

Separation of Functions at Potential Distribution Boundaries:Space-Ground; Geographical Sites; Client-ServerDifferences in Cardinality (Scalability)

End-to-End Interfaces Omits Data Transfer and Storage Functions Point-to-Point; Defined by Interfaced Functions; Wire Protocols


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Mission Operations Functions

MES: Mission Exploitation

MCS: Mission Operations

GSTS: Ground Station Network

Spacecraft

StationM&C

GSUS: Ground Support System

EGSE

On-boardAutomation

GroundAutomation

Tracking &Ranging

AOCS

FlightDynamics

SpacecraftM&C

OperatorInteraction

Analysis &Reporting

MissionData Processing

MissionData Acquisition

MissionProduct

Distribution

ExternalData

Distribution

OperationsPlanning

StationScheduling

MissionPlanning

On-boardSoftware

OB SoftwareDevelopment &

Validation

OB SoftwareManagement


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Information View Same Information Type flows on Multiple Interfaces Identify Fundamental Information Types for Domain

M&C: Parameters; Actions [Commands]; Alerts [Events] Operator Interactions Automation: Activities [Procedures]; Tasks ; Schedules Planning Requests Time; Position; Orbit & Attitude Vectors; Predicted Events Software Images Data Products; Reports

Identify Operations [Use Cases] that can be performed on these Information Types

Function A Function B

Data Flow: Message A

Data Flow: Message BInformation Object Y

Information Object X


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Service View Interfaces: Point to Point, Data Flow Oriented, Full Protocol Stack Services: Many to Many, Information Oriented, One Layer of Stack

Service Objects: represent Domain Specific Information Event Messages synchronise the Consumer’s View Control Messages allow the Consumer to invoke Operations

Each Domain Service has its own specialised Information Model Generic Common Service: publish Events and invoke Operations

ServiceProvider

ServiceConsumer

Object Object View

Events

Service Object

Operations


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OtherGSUSMES

Spacecraft

GSTS

MCS

OB Data ProductStorageSpacecraft M&C OB Procedure

ExecutionOB Schedule

Execution OB Software

Tracking &Ranging

MissionPlanning

MissionData

ProcessingExternal

User

OperationsPlanning

FlightDynamics

OperationsAutomation

OperatorInteraction

StationM&C

StationScheduling

ExternalData User

Analysis &Reporting

OB SoftwareDevelopment

OB SoftwareManagement

Spacecraft M&CProxy

OB ScheduleProxy

OB ProcedureProxy

OB Data ProductProxy

OB SoftwareProxy

Mission Operations [MO] Services

GDD

LOC

PEXSEX

DPM

AUTOPI

OSM

SRI

FDSREP

MC

SLE-Man

PRQ

TIM


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GDSS Mission Operations ServicesID Name Description

MC Core Monitoring & Control Parameters: publish status; setActions [Commands]: publish status; invoke/sendAlerts [Events]: notify; raise

AUT Automation Specialisation of MC for automation of proxy functions

DPM Data Product Management Data Product [Payload Data File]: directory; transfer

FDS Flight Dynamics Orbit/Attitude: determination, propagation, manoeuvre preparation

GDD Generic Data Dissemination Product: catalogue; order; deliver

LOC Location Position: tracking, ranging, onboard positioning

OPI Operator Interaction Message/Alarm/Query: notify; operator response

OSM OB Software Management On-board Software: load; dump

PEX Procedure Execution Procedure/Function: control; progress reporting

PRQ Planning Request Planning Request: request; response

RBM Remote Buffer Management Buffer: catalogue; retrieve; clear

REP Report Reports: publish; catalogue; retrieve; generate

SEX Schedule Execution Schedule: distribute; edit; control; progress reporting

SRI Software Reference Image On-board Software Image/Patch: distribute

TIM Time Time: report; set; correlate; notify


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Service Definition Platform Independent UML Model [Model Driven

Architecture] Includes:

Information View:defines Domain Level information common to Service Providers and Consumers

Service Configuration Data (e.g. for a specific Spacecraft) allows customisation of a Service Instance

Configuration Data is Open, not specific to Implementation Service View:

messages exchanged between Service Providers and Consumers

Service History/Logging allows for recording, retrieval and even replay of past Service Messages

sequencing of messages Expected Service Interaction, Error Conditions, etc.

Relationships: to other Objects in other Domain Services Other Characteristics:

Security, Quality of Service, Parallelism, etc.


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The Service Model and Generic Structure

Service Versions Capability Sets

Service Consumer Service Provider

Service Directory

Invoke

Lookup Publish

Service Layer

Service Provider

Service ConsumerHCI Displays

Other Applications

ServiceConfiguration

Database

ServiceHistoryArchive

Service EditorOperationsPreparation

Invo

ke

Archive

History

ServiceDirectory

Publish

Lookup

Configure

Configure

Edit

Active Service Interface


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Events and Operations: Parameter Example

Service Layer

Service Provider

Service ConsumerHCI Displays

Other Applications


Database

ServiceHistoryArchiveO

bser

ve C

ontr

ol Man

age

Archive

Replay, Retrieve

Access

Access

Parameter Class

Parameter Object Definitions

Parameter History

Parameter Events

Set Parameter Action

Disable/Enable Monitoring Checks

Dynamic History Replay:Observer view

Block Retrieval


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Operations ExecutionService Status Data

Object Identity 1 1 Object Definition

Concurrent Sessions(Live + Simulated + Replay)

1 1 Object Status

UpdateE

OperationO

1 n Object Instance

InstantiateO

Generic Service Object Information Model

Pres

ent

Operations AnalysisService History

Historical Sessions

Object Identity 1 n 1 nObject Definition Object StatusPast

Status UpdateEvent

Definition UpdateEvent

EE

1 n Object Instance

InstantiationEvent

E

Replay

E

Replay

E

Replay

E

Operations PreparationService Configuration Data

Object Identity 1 n 1Object Definition Version

Version Series

Install

Edit SaveValidate

Futu

re

1

Retrieve

EEE

Retrieve

EEE

Retrieve

EEE


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Service Layering

Stack of Layered Services or Protocols Stack must match on both sides for

Interoperability Low-level Communication does not ensure

Compatibility at the Application Level

?!!


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Service Layering

Application Level Services

Common Services

MO DomainServiceFramework

ConsumerApplication

ProviderApplication

MO DomainSpecificApplications

TechnologyAdaptors

SAP: Service Access PointPlug-inApplications

Infrastructure ServicesMessage Exchange; File Transfer; Mail

TechnologySpecificInfrastructure

Communications Services


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Service Layering

Application Level Services

Common Services

ConsumerApplication

ProviderApplication

SAP: Service Access Point

Infrastructure ServicesMessage Exchange; File Transfer; Mail

Communications Services

Technology Adapters


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Common Interaction Patterns

Common to multiple MO Services Generic Service Elements implemented in Common Layer MO Services “specialise” Generic Objects:

define Attributes, Operations and Events 2 Principal Patterns: Operations and Product Distribution

Generic Infrastructure to Support all Services

Service Layer

Service Provider

Service Consumer

Obs

erve C

ontr

ol Man

age

Archive

ServiceHistoryArchive

RetrieveReplay Control

Replay (Observe)


Database

MC


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Conclusions Benefits of SOA

Flexibility / re-usability in mission architecture Common Layer

Independence from technology Granularity of Services

Achievable standardisation SOA Modelling Guidelines

Guidance for future development Community Review

Benefit of wide review by space system experts Relationship to CCSDS Spacecraft M&C WG

Continue to track parallel work Prototyping

Needed to prove / improve the service definitions Extending the model

Management of future service definition work


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Recommendations1. Build a Prototype of the basic MC service over

the Common service as soon as possible

2. Embark on a study to develop the Event Archive (EARC) and produce a prototype implementation

3. Develop more service definitions, integrated with the service framework UML model

4. Continue to participate in / lead the CCSDS equivalent activities

5. Widely circulate the GDSS Study and encourage wide community review of subsequent work

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