SpaceOps 2002

1
An Interface Specification for Requesting Space
Link Extension Services from NASA TTC
Networks John Pietras, Global Science and
Technology, Inc. Erik Barkley, Jet Propulsion
Laboratory Emily Law, Jet Propulsion Laboratory
SpaceOps 2002 Houston, Texas 912 October 2002
2
Agenda

• Space Link Extension Service Request background
• SLE Service Request requirements and operational
  concepts
• Spaceflight mission SLE service provider
  lifecycle
• Use of the eXtensible Markup Language (XML)
• Prototype SLE Service Request message structure
• Progress to-date and future plans

3
SLE Service Request Background

• In 1991, CCSDS began an initiative to standardize
  the transfer of spacecraft command and telemetry
  data among ground stations, mission operations
  centers, data processing facilities, and other
  parties that communicate with the spacecraft
• The resulting Space Link Extension (SLE) service
  architecture has two components
• SLE transfer services that move CCSDS-standard
  space link data units (e.g., packet telemetry
  frames, command link transmission units)
• SLE service management services that facilitate
  the requesting of services from an SLE service
  provider
• CCSDS Cross-Support Reference Model (CSRM) for
  SLE Services identifies 16 SLE transfer services
• Draft CCSDS SLE Service Management Specification
  addresses the management of all of the transfer
  services identified in the CSRM, and supports
  interactions among multiple service providers to
  deliver SLE services to the user
• More details on the features of the SLE transfer
  services can be found in the presentation CCSDS
  Space Link Extension (SLE) Service Overview and
  Progress Report by Fred Brosi, and in the list
  of references for this paper in the SpaceOps 2002
  Proceedings

4
Example SLE Use Configuration
Ground station provides SLE Forward CLTU service
to Control Center
Space-ground link carrying CCSDS-standard space
link data units
Ground station provides SLE Return Channel Frames
service to Control Center
Domain of Space Link Extension
Control Center
Ground station provides SLE Return All Frames
service to Return Link Data Processing Facility
Service Management interface between Ground
station and Control Center
Return Link Data Processing Facility
5
SLE Service Request Initiative

• Under the auspices of CCSDS Panel 3, NASA has
  begun to develop a focused version of the SLE-SM
  specification
• The SLE transfer services to be managed are
  limited to the 3 that will be supported by NASA
  in the foreseeable future
• Return All Frames (RAF) service, which delivers
  to the user all CCSDS telemetry frames on a
  single symbol stream
• Return Channel Frame (RCF) service, which
  delivers to the user all CCSDS telemetry frames
  for a selected master channel or virtual channel
• Forward Command Link Transmission Unit (CLTU)
  service, which delivers to the service provider
  CLTUs for forwarding to the spacecraft
• Initial emphasis will be on the management
  information exchanged to request and confirm TTC
  and SLE services
• The eXtensible Markup Language (XML) will be used
  as the specification language

6
SLE Service Request Requirements and Operational
Concepts

• Scope of SLE Service Request encompasses the
  configuration of RF and modulation services,
  standard CCSDS protocol processing, and standard
  SLE CLTU, RAF, and RCF transfer services
• Although the specification does not explicitly
  address non-SLE services (e.g., legacy delivery
  of undelimited bitstreams), the framework
  supports the addition of such services
• SLE Service Request service is intended to be
  applicable to all TTC networks
• Black box approach confines Service Request to
  service-oriented parameters, not
  provider-internal details
• Modularity allows Service Requests to be tailored
  to specific capabilities and requirements of
  individual service providers (TTC networks)
• The SLE Service Management operational concept
  anticipates increasing automation across the
  lifecycle of the relationship between a
  spaceflight mission and an SLE service provider
• However, the initial emphasis will be on the
  Service Request phase of that lifecycle

7
Spaceflight Mission SLE Service Provider
Lifecycle

• Registration and Mission Service Agreement phase
• Spaceflight mission operations center registers
  with the SLE service provider to establish the
  context (user IDs, security credentials, etc.)
  for management interactions
• Mutually-agreed Mission Service Agreement
  establishes
• Bounds and constraints on individual service
  requests
• Mission communications model (number of carriers,
  coherence, turn-around ratios, etc.)
• Non-variant service parameters
• Pre-defined configuration sets

Registration Mission Service Agreement
Start time of first space link session
T0 - years
T0
8
Spaceflight Mission SLE Service Provider
Lifecycle
Registration Mission Service Agreement
T0 - years T0 - months T0
weeks T0 days
T0
9
Spaceflight Mission SLE Service Provider
Lifecycle
Registration Mission Service Agreement
Scheduling of Space Link Sessions
Submission of SLE Service Requests
T0 - years T0 - months T0
weeks T0 days
T0
10
Spaceflight Mission SLE Service Provider
Lifecycle
Exchange of transfer service security information
Submission of trajectory data
Registration Mission Service Agreement
Scheduling of Space Link Sessions
Submission of SLE Service Requests
T0 - years T0 - months T0
weeks T0 days
T0 T1
11
Spaceflight Mission SLE Service Provider
Lifecycle

• Service package monitor and control
• Process is asynchronous with respect to the
  lifecycles of individual service packages

Service package monitor and control
Exchange of transfer service security information
Submission of trajectory data
Registration Mission Service Agreement
Scheduling of Space Link Sessions
Submission of SLE Service Requests
T0 - years T0 - months T0
weeks T0 days
T0 T1
12
Use of the eXtensible Markup Language (XML)

• Platform and vendor independent
• Supports loose coupling between systems
• Can be used with legacy systems, affording
  easytransformation to legacy data types
• Development support tools are available
• Core standards are open and readily available
  through W3C
• XML technology being aggressively developed
  byfor-profit concerns ample opportunity for
  leveragingthese efforts
• Allows for flexible message formats and contents
  because of clear markup of all components/elements

13
Prototype Example of SLE Service Request Message
Common to all SLE SR Messages
Varies per SLE SM transaction type
14
Content Model Overview
Sequence
Sequence
Substitution Group Members (SLE SM Transaction
Body)
Substitution Group Members (SLE SM Request)
SLE SM Transaction Schema Revision ID
SLE SM Schema Revision ID
SLE SM SR Registration
Substitution Head Element
SLE SM SR Mission Service Agreement
SLE SM Request
Agency Identification, Credentials, Authorization
SLE SM Transaction Tracking ID
SLE SM Service Request
Root Element
SLE SM Response
1..n
SLE Service Management
SLE SM Trajectory
SLE SM Query
SLE SM Sequence of Events
SLE SM Transaction
Substitution Head Element
Legend
SLE SM Notification
Schema Element Schema Element Present for
Service Request
1..n
SLE SM Configuration Profiles
SLE SM Transaction Body
SLE SM Monitor Updates
SLE SM (Limited) Exec. Control
15
Progress to Date and Future Plans

• SLE Service Request Operational Concept Green
  Book in progress
• SLE Service Request XML Specification in progress
  
• DSN support for ESA Rosetta and ISAS Muses-C
  missions will be prototyped
• GSFC-managed Ground Network is a candidate for
  implementation of the SLE-SM Service Request
• Target of opportunity for prototyping for GN
  through SLE Testbed
• Limited reconfiguration of service and production
  parameters during the contact
• Automation of service agreement development
  process