1. Air Force Satellite Control Network Interoperability
Space Internet Workshop #4
June 2004
John Pietras
Global Science and Technology, Inc

2. Contents Background of the AFSCN Interoperability Project
CCSDS Space Link Extension – candidate for AFSCN interoperability
Summary of Interoperability Project Phase 3
Completed in Summer 2003
Transition from legacy- to standards-based infrastructure
Overview of Phase 4 activities
Spring-Summer 2004
Interoperability with other US space organizations

3. AFSCN Interoperability Project Background
Project is managed by AF Space and Missile Systems Command Satellite and Launch Control SPO as part of AF Satellite Control Network (AFSCN) modernization program
Space vehicles to be supported will use legacy AFSCN radio frequency (RF) and modulation standards for another decade
Goals
Adopt/define services that will facilitate interoperation among US government satellite ground control networks
Base services on packet-switched network technology to continue the AFSCN’s migration from circuit-switched technology
Approach
Adopt existing space data standards where available and appropriate
Adapt standards where necessary
Feed enhancements back to standards community for broader acceptance
Feed results into Satellite Control Network Contract (SCNC) Architecture development
Multi-phase study and demo project started in 2001
Phase 1: Standards assessments and lab tests
Phase 2: Field tests with AF R&D assets
Phase 3: Field tests with commercial and civil agency ground stations
Phase 4: Develop standards profile for national infrastructure, field test vendor implementations

4. CCSDS Space Link Extension – Candidate for AFSCN Interoperability
Consultative Committee for Space Data Systems (CCSDS) has developed standards for the exchange of space vehicle (SV) command and telemetry data between mission ground facilities (e.g., satellite operations centers) and TT&C ground stations
Dubbed Space Link Extension (SLE) because they extend the space link protocols across the terrestrial WAN
Originally developed to transport CCSDS-defined space link data units
Adoption of SLE by the international civil space community makes SLE attractive as interoperability standard for AFSCN
Adaptations to CCSDS SLE services were prototyped and demonstrated in Interoperability Phases 1 & 2
SLE Return All Frames (RAF) service adapted to support AFSCN’s time-correlated streaming telemetry (in contrast to discrete CCSDS space link data units)
SLE Forward Communication Link Transmission Unit (FCLTU) service adapted to support time-critical streaming command data

5. CCSDS Space Link Extension Services
Standard services for exchanging space link data between ground termination of the space link and remote users
Evolution of mission-unique/provider-unique services
Formally assumes that CCSDS link protocols are used on the space-ground link
AFSCN project has loosened even this assumption
Appropriate for missions that do not use Internet-interoperable protocols
Domain of
Space Link
Extension
Control Center
CCSDS (or legacy) space link interface
CCSDS (or legacy) space link data structures tunneled thru IP WAN
Return Link Data
Processing Facility

6. Phase 3 Service Architecture
Johns Hopkins University
Applied Physics Lab
(JHU APL) Laurel, MD
VPN
FCLTU (cmd)
RF &
Mod
TACO 1
ioNET cmd)
CERES SOC
RAF (echo)
FCLTU (cmd)
ioNET (echo)
COBRA
SV C2
system
ioNET cmd)
ioNET (tlm)
Az/El
RAF (echo)
RAF (trk)
ioNET (echo)
TACO 2
ioNET (tlm)
NOAA Command
and Data Acquisition (CDA)
Wallops Flight Facility, VA
RAF (tlm)
This diagram shows the various configurations of services as they were provided by the three ground stations that were used. All services from all stations were provided across the Internet. In addition, a dedicated T1 link was used between the JHU APL site and the CERES SOC to support testing using the 1Mbps downlink channel generated by one of the TACO vehicles.
All inter-facility data transmissions were conducted a VPN that was formed by using IPsec routers to access the Internet and T1 connections (not explicitly shown).
Two Telemetry data transfer services were tested in Phase 3. The CCSDS-standard RAF service was used, but the input and output had to be in non-RAF-standard way to accommodate streaming telemetry and AFSCN time-data correlation requirements. The Avtec ioNET, which implements a proprietary multiplexing algorithm, was also tested. Fundamental difference in approaches – conveying timestamps and syncing output to a separately-generated IRIG signal, vs digitizing the analog IRIG signal at the ground station and conveying it across the WAN.
Two command data transfer services were tested for in Phase 3. The CCSDS-standard FCLTU service was used, but the input and output had to be processed in non-FCLTU-standard way to accommodate streaming commands and AFSCN time-critical command requirements. The Avtec ioNET was also tested.
For command echo, two DT services were again tested. Because CCSDS does not have, and is not planning to develop, a standard command echo service, we pressed the SLE RAF service into use, with input/output modifications to allow the service to handle the streamed data. Again, the Avtec ioNET was the other service tested.
Finally, CCSDS is only in the early stages of developing a standard for the delivery of tracking data from the GS to a user of tracking data (such as the SOC). But the work to-date has been based on the SLE data transfer service model. We chose to use the RAF service as the basis for our Phase 3 tracking data transfer capability, in anticipation of a future CCSDS SLE Tracking Data Transfer Service standard
FCLTU (cmd)
RF &
Mod
RAF (trk)
RAF (echo)
RAF (tlm)
TACO 3
COBRA COTS-based Research Architecture
FCLTU Forward Communication Link
Transmission Unit (CCSDS SLE)
ioNET Avtec multiplexer/demultiplexer system
RAF Return All Frames (CCSDS SLE)
TACO Test And CheckOut SV
Dual connectivity: Internet and dedicated T1
Internet connectivity only
NASA Experimental 5.4 m,
Wallops Flight Facility, VA
RF &
Mod
GST implementation
RAF (tlm)
Avtec implementation

7. Phase 3 Service Management Interfaces
DataLynx Ops Center
Columbia, MD
CERES SOC
DataLynx Sched/Mgmt system
JHU APL
client
Service Request
and Response
XML file
attachments
client & SLE-SM provider application
Internet
Service Request
and Response
XML files
1/sec service status messages
None of the Phase 3 TT&C networks supported for the AFSCN SIS-509 resource management interface, so we used the emerging XML-based CCSDS Service Management Service Request standard as the basis for a scheduling prototype. Service requests (schedule requests) were exchanged between CERES and the DataLynx Operations Center (which service as the control agent for the APL station) and the NASA WFF. Scheduling of the NOAA Wallops CDA station.
Service monitoring from the APL station was accomplished by reporting selected status parameters in 1/sec XML-formatted messages that were sent to CERES over a TCP connection and and displayed on the service management workstation there.
None of the ground stations supported real-time user control of the station resources, so no such capability was provided.
NASA WFF
WFF Sched/Mgmt system(s)
SLE-SM SOC application
Service status display
client & SLE-SM provider application

8. Summary of Phase 3 Results*
Telemetry
Use of TCP and data buffering (~2-4 seconds additional delay) provided reliable delivery of the serial telemetry stream
Telemetry TDC of SLE RAF implementation was accurate to within several tens of milliseconds, but not required 1 msec
ioNET TDC was accurate to within 1 msec, but 170kbps digitized IRIG-B signal deemed overly consumptive of bandwidth
Command
Time-critical commanding was successful using both the FCLTU and ioNET based implementations
Command echo
Command echo was successful using both the RAF and ioNET based implementations
Service Management
Contacts scheduled using SLE standard format schedule requests/responses
Ad hoc methods needed for tracking data and ground station status
* Full results are documented in the SCNC Interoperability Phase 3 Project Report, Honeywell Technology Solutions, Inc. 28 October 2003, prepared by Lance Williams

9. Transition from Legacy to Standards - Based Infrastructure (1 of 3)
3 reference points for a transition architecture
RF & modulation interface with the SV
Currently SIS-502D
New standards-based interoperable interface between ground station and SOC
Telemetry, command, and command echo interface as seen by the user C2 system
Currently SIS-508E
SIS interoperable SIS-508
I/F
Ground Station
SOC
Range
Segment
Communication
Segment
Current
AFSCN
C2 System
Remains in place as long as compliant SVs are flying
Put in place ASAP
Can be replaced or eliminated as SOC technology and designs evolve

10. Transition from Legacy to Standards - Based Infrastructure (2 of 3)
3 sets of “standards” to enable interoperability for AFSCN-client SVs using SLE transfer services
SLE service production specifications that define the processing required to transform the data transferred by the SLE transfer service to/from RF
Currently SIS-502D
SLE transfer service specifications provide the interoperable interface
SLE service adaptation specifications that define the required transformations between SLE and legacy user interfaces
Currently SIS-508E
SIS SLE Transfer SIS-508
Service
Ground Station
SOC
SGLS/
SLE service production
SLE TS
entity
SLE TS
entity
SIS-508/
SLE
adaptation
Current
AFSCN
C2 System

11. Transition from Legacy to Standards - Based Infrastructure (3 of 3)
Adaptations eventually disappear as SOC designs natively incorporate SLE transfer services
SLE service productions evolve with SV evolution
SLE Transfer
SIS Service
Ground Station
SOC
Packet mode C2
system eliminates
Adaptation
USB augments SGLS
SGLS/
SLE service production
SLE TS
entity
AFSCN
packet mode
C2 System
SLE TS
entity
Updated SIS-502
Ground Station
SOC
SGLS & USB/
SLE service production
SLE TS
entity
AFSCN
packet mode
C2 System
SLE TS
entity

12. Phase 4 Implementation of SLE Services
Telemetry
Vendor-supported implementation of prototype modifications of RAF SLE service to transfer and time-correlate serial stream of telemetry data
Command
Vendor-supported implementation of prototype modifications of FCLTU SLE service to transfer AFSCN SGLS-formatted command data
SGLS command FCLTU service supports two modes:
Discrete commands (inter-command idle added at ground station)
Streaming commands (all symbols, including inter-command idle) used to transfer discrete commands
Command Echo
Vendor-supported implementation of prototype modifications of RAF SLE service to transfer serial stream of command echo symbols
Service Management
Continue exploring use of SLE scheduling and configuration standards

13. Establishing Interoperability With Other US Space Organizations
Telemetry
Develop new CCSDS Return Telemetry (RT) SLE service
Supports AFSCN serial telemetry
Supports civil space needs not met by current RAF SLE service
CCSDS Birds of a Feather (BOF) group formed
Adopt time-correlated telemetry adaptation in 508-legacy AFSCN SOCs
Command
Adopt SGLS command production for FCLTU as US national interoperability capability
USTAG13 BOF group formed
Adopt SGLS command adaptation in 508-legacy AFSCN SOCs
Command echo
Adopt SGLS command echo production for RT service as US interoperability capability
Adopt SGLS command echo adaptation in 508-legacy AFSCN SOCs

14. Acknowledgements
U.S. Air Force Space and Missile Systems Center Satellite and Launch Control SPO (SMC/RN)
AJ Ashby, 1Lt, USAF, project officer
Carl Sunshine, The Aerospace Corporation, technical lead
Satellite Control Network Contract
Lance Williams, Interoperability project lead
JHU APL ground station
AF Center for Research Support (CERES)
NASA WFF and NOAA Wallops CDA ground stations
Avtec Systems
General Dynamics Advanced Information Systems

15. Phase 4 Participants
U.S. Air Force Space and Missile Systems Center Satellite and Launch Control SPO (SMC/RN)
Satellite Control Network Contract
The Aerospace Corporation
GST, Inc.
AF Center for Research Support (CERES)
Avtec Systems
NOAA WFF
GD-AIS
L3Com
RTLogic
JPL, NASA