Standards and Protocols to Achieve Satellite Control Network Interoperability

1
Standards and Protocols to Achieve Satellite
Control Network Interoperability
Space Ops 2002

• Carl Sunshine
• October 2002

AF Space Missile Center / SLCSPO
2
Standards Protocols Objectives

• Reduce risk, cost, and time for upgrades
• Use proven, efficient solutions
• Share development costs of COTS equipment and
  services over wider user base
• Enhance Interoperability
• Move toward Integrated Satellite Control Network
  with DoD, NASA, NOAA, commercial
• Increase sharing to broaden access and/or reduce
  total costs

3
Key Interfaces
1. RTS-SOC A. WAN hop for Space Vehicle
commands and telemetry B. RTS Control and
Status 2. Space-Ground Link Space hop for
Space Vehicle commands, telem 3. Status and
Scheduling A. SOC-NCC B. RTS-NCC 4. Space
Vehicle-SOC (end-to-end) Commands, status, data

Link 2
Link 4
RTS
Network Control Center
Link 3B
Link 1
SOC
WAN
Link 3A
4
Interface Evolution Vision
Vendor USERS Commercial
CCSDS INTERNET
Future AFSCN Standards Protocols
DoD Unique Legacy/Extensions
5
Test Bed Objectives

• Test DoD satellite control using Internet based
  protocol standards over WAN
• Assess alternate protocol options (UDP, TCP, SLE)
• Transmit encrypted serial bitstream telemetry and
  commands
• Accuracy, error rate
• Delay and delay variation (time critical
  commanding)
• Time tagging accuracy (time/data correlation)
• Show impact of COTS IP security software
• Working alongside NASA/JPL
• Develop and test feasibility in a lab setting
• Demonstrate in field with live satellite contacts

6
Evaluation Parameters

• Protocols
• UDP
• TCP
• SLE

• Metrics
• Delay
• Delay Variation
• Data Loss
• Time Tagging Accuracy

• Variables
• Data Rate 250 bps 5 Mbps
• Network Error Rate 0, 10-8 10-5
• Network Delay 0, 135, 270, 500 msec
• IP-Sec On/Off

7
Unframed Telemetry SLE Service Config
reconstructed timing
timing
Bitstream blocker time tagger
Test data generator
Bitstream re-serializer
Test data receiver
bitstream
reconstructed bitstream
Unframed telemetry SLE service
providerapplication
Unframed telemetry SLE service userapplication
Unframed telemetry SLE API SW
Unframed telemetry SLE API SW
JPL SLE API SW (core) modified
JPL SLE API SW (core) modified
RTS
SOC
TCP
UDP
TCP
UDP
IP-Sec
IP-Sec
IP
IP
WAN L2
WAN L2
WAN L1
WAN L1
KEY
GST-developed code JPL-developed code (with
GST modifications)
8
Protocol Comparison
9
Field Evaluation Phase
Test RTS
Net I/F
Net I/F
CERES SOC
WAN
Schriever AFB
Kirtland AFB
10
Observations and Analysis

• UDP useful only in a near error free WAN
• Standard TCP met a delay goal of 1.25 seconds for
  lower data rates and network delay/error values.
  Worse network quality required additional delay
  to ensure reliable delivery.
• Standard TCP slow start, congestion recovery, and
  retransmission window size are largely
  responsible for observed performance limits
• Preliminary tests with variants of TCP, such as
  TCP-Tranquility (SCPS-TP), improved performance

11
Observations and Analysis (2)

• SLE adds acceptable delay above straight TCP
  (200 msec)
• Live satellite contacts run well with 2 sec telem
  delay
• May need more delay in bad networks
• IP-Sec protocol has negligible effect on
  performance
• No multiplication of packet loss, insignificant
  added delay
• Benefits of SLE not fully realized with encrypted
  bitstream data
• Looking at frame or packet level security for
  future
• High potential for use of SLE management services

12
DoD-NASA Interoperability Concept
CCSDS User (SOC)
Telem Command Data Blocks Bitstreams
Provider (RTS)
SLE Transfer Service
SGLS
CCSDS TTC
Produc- tion 1
RF 1
SLE Transfer Service
CCSDS
WAN
SGLS User (SOC)
2
2
SGLS TTC
Mgmt
Sec
SLE Transfer Service
Mission Planning
NCC
Mgmt
Mgmt
13
DoD/NASA Interop Test Plan

• Utilize SLE architecture from DoD and NASA test
  beds
• Provide dual-mode net interface at NASA Wallops
  Island
• Connect with NASA and DoD test SOCs
• Near term demo of limited dual ops at Wallops
• NASA SOCs utilize CCSDS space link from Wallops
• DoD SOCs receive current DoD SGLS downlink from
  Wallops
• Longer term demo of full cross support
• DoD SOCs contact future DoD USB space vehicles
  (Wideband Gapfiller or TechSat 21) using NASA
  ground stations
• NASA (and other govt agency) SOCs contact their
  SVs using USB from new AFSCN RTS (first site in
  2005)
• Develop SLE management along with data transfer
• Scheduling, configuration, and RTS control
  directives

14
Acknowledgements

• Global Science and Technology for SLE
  adaptations, network test bed, and analysis
• Jet Propulsion Lab for SLE software
• Veridian for network test bed
• AF Center for Research Support (CERES) for test
  SOC and RTS
• Email contact sunshine_at_ aero.org