1. EGOS Workshop 2005
GDSS - Ground Data System Services: a Service Oriented Architecture for Mission Operations
Roger Thompson, Nestor Peccia, Stewart Hall, Oliver Page
Presented by:
Roger Thompson

2. GDSS Study Context
Definition 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
9th November 2005
EGOS Workshop 2005

3. 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
9th November 2005
EGOS Workshop 2005

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
9th November 2005
EGOS Workshop 2005

5. Integrated Systems vs. Modular Components
9th November 2005
EGOS Workshop 2005

6. Service-Oriented Architecture: Plug-in Components
Services
Components
Infrastructure
9th November 2005
EGOS Workshop 2005

7. 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
9th November 2005
EGOS Workshop 2005

8. 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
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-Server Differences in Cardinality (Scalability)
End-to-End Interfaces
Omits Data Transfer and Storage Functions
Point-to-Point; Defined by Interfaced Functions; Wire Protocols
9th November 2005
EGOS Workshop 2005

9. Mission Operations Functions
GSUS: Ground Support System
EGSE
On-board Software
OB Software Development & Validation
OB Software Management
MES: Mission Exploitation
Mission Data Processing
Mission Data Acquisition
Mission Product Distribution
External Data Distribution
Operations Planning
Station Scheduling
Mission Planning
MCS: Mission Operations
Spacecraft M&C
Operator Interaction
Analysis & Reporting
Tracking & Ranging
AOCS
Flight Dynamics
On-board Automation
Ground Automation
GSTS: Ground Station Network
Station M&C
Spacecraft
9th November 2005
EGOS Workshop 2005

10. 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
Data Flow: Message A
Function B
Information Object Y
Information Object X
Data Flow: Message B
9th November 2005
EGOS Workshop 2005

11. 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
Service Object
Object
Object View
Service Provider
Service Consumer
Events
Operations
9th November 2005
EGOS Workshop 2005

12. Mission Operations [MO] Services
MES
GSUS
Other
Tracking & Ranging
Mission Planning
Mission Data Processing
External User
Operations Planning
Flight Dynamics
Operations Automation
Operator Interaction
Station M&C
Station Scheduling
External Data User
Analysis & Reporting
OB Software Development
OB Software Management
PRQ
FDS
DPM
OSM
SRI
GDD
MCS
REP MC
SLE-Man
SEX
LOC
TIM
OPI
PEX
AUT
Spacecraft M&C Proxy
OB Schedule Proxy
OB Procedure Proxy
OB Data Product Proxy
OB Software Proxy
GSTS
Spacecraft
OB Data Product Storage
Spacecraft M&C
OB Procedure Execution
OB Schedule Execution
OB Software
9th November 2005
EGOS Workshop 2005

13. GDSS Mission Operations ServicesID
Name
Description MC
Core Monitoring & Control
Parameters: publish status; set
Actions [Commands]: publish status; invoke/send
Alerts [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
9th November 2005
EGOS Workshop 2005

14. 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.
9th November 2005
EGOS Workshop 2005

15. The Service Model and Generic Structure
Service Consumer
Service Provider
Service Directory
Invoke
Lookup
Publish
Service Versions
Capability Sets
Service Layer
Service Provider
Service Consumer HCI Displays Other Applications
Service Configuration Database
Service History Archive
Service Editor Operations Preparation
Invoke
Archive
History
Service Directory
Publish
Lookup
Configure
Edit
Active Service Interface
9th November 2005
EGOS Workshop 2005

16. Events and Operations: Parameter Example
Parameter Class
Set Parameter Action
Disable/Enable Monitoring Checks
Service Consumer HCI Displays Other Applications
Dynamic History Replay: Observer view
Block Retrieval
Service Layer
Access
Replay, Retrieve
Observe
Control
Manage
Service Configuration Database
Service History Archive
Archive
Service Provider
Parameter History
Parameter Object Definitions
Parameter Events
9th November 2005
EGOS Workshop 2005

17. Generic Service Object Information Model
Operations Preparation Service Configuration Data
Object Identity 1 n
Object Definition
Version
Version Series
Install
Edit
Save Validate
Future O E O
Concurrent Sessions (Live + Simulated + Replay)
Instantiate
Update
Operation
Operations Execution Service Status Data
Present
Object Identity 1 1
Object Definition 1 n
Object Instance 1 1
Object Status
Operations Analysis Service History
Historical Sessions
Object Identity 1 n
Object Definition
Object Status
Past
Status Update Event
Definition Update Event E
Object Instance
Instantiation Event
Replay E
Retrieve E
9th November 2005
EGOS Workshop 2005

18. Service Layering Stack of Layered Services or Protocols
Kali mera
?!!
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
9th November 2005
EGOS Workshop 2005

19. Service Layering Consumer Application Provider Application
MO Domain Specific Applications
SAP: Service Access Point
Plug-in Applications
Application Level Services
Common Services
MO Domain Service Framework
Technology Adaptors
Infrastructure Services
Message Exchange; File Transfer; Mail
Technology Specific Infrastructure
Communications Services
9th November 2005
EGOS Workshop 2005

20. Service Layering Common Services Application Level Services
Consumer Application
Provider Application
SAP: Service Access Point
Infrastructure Services
Message Exchange; File Transfer; Mail
Communications Services
Technology Adapters
9th November 2005
EGOS Workshop 2005

21. Common Interaction Patterns
Service Layer
Service Provider
Service Consumer
Observe
Control
Manage
Archive
Service History Archive
Retrieve
Replay Control
Replay (Observe)
Service Configuration Database M C
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
9th November 2005
EGOS Workshop 2005

22. Conclusions Benefits of SOA Common Layer Granularity of Services
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
9th November 2005
EGOS Workshop 2005

23. Recommendations
Build a Prototype of the basic MC service over the Common service as soon as possible
Embark on a study to develop the Event Archive (EARC) and produce a prototype implementation
Develop more service definitions, integrated with the service framework UML model
Continue to participate in / lead the CCSDS equivalent activities
Widely circulate the GDSS Study and encourage wide community review of subsequent work
9th November 2005
EGOS Workshop 2005