Space-based Telemetry And
Range Safety (STARS)
Study
James Rash - GSFC
Ed Criscuolo - CSC
Keith Hogie - CSC
Ron Parise - CSC
Overview
• Brief Description of STARS
• Goals of the STARS IP Formatter
• Key issues using standard HW for
constant-rate Telemetry
• Design and Development
• Testing and Performance
• Status
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2004 Space Internet Workshop
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Space-based Telemetry and Range Safety
• The STARS project is investigating the use of a
reliable communication link between flight vehicles
and satellites in order to support range operations
such as those used in flight termination systems.
• The project goals are to evaluate the system's
reliability and performance, and to define a detailed
design for the range system user that will reduce
costs associated with dedicated groundstations.
• Previous flights evaluated the reliability of satellite
communication links with TDRSS
• Next flights will incorporate the use of Internet
Protocol (IP) for all downlink telemetry, and use a
phased-array antenna to track TDRSS
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2004 Space Internet Workshop
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Space-based Telemetry and Range Safety
NASA Photo / Tony Landis
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2004 Space Internet Workshop
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IP Formatter Goals
• Transport all range user telemetry to
groundsystem using standard Internet Protocols
– Build on previous flight experience
• Increase Flexibility, Reduce Costs
– Off-The-Shelf PC-104 hardware
– Open-Source operating-system (Linux 2.4.18)
– Standard "C" code and scripting languages
• Simplify Telemetry System
– data capture
– onboard logging
– data transfer
• Simplify Ground System
– data routing and distribution
– data logging
6/9/2004
2004 Space Internet Workshop
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Key Issues Using Std Sync Serial H/W
• Issue: Telemetry Framing
– Sync Serial I/O cards are designed to handle discrete frames which
may arrive asynchronously
– PCM telemetry has continuous nonstop frames
• Solution:
– Use hardware to initially locate sync
– Use back-to-back reads and software to flywheel & check sync
– Use hardware to re-acquire sync if lost
• Issue: Bit order
– PCM telemetry is msb first
– Communications industry (eg - hdlc/frame-relay) uses lsb first
• Solution:
– Use hi-speed software bit-reversal via table lookup
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2004 Space Internet Workshop
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Telemetry Formats
F-15 PCM Telemetry Stream
153 byte telemetry data
IP Header (20)
3 byte (24 bit) Sync
UDP Header (8)
153 byte telemetry data
156 byte telemetry frame
3 byte (24 bit) Sync
4 byte Seq #
8 byte timestamp
UDP/IP Telemetry Packet
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2004 Space Internet Workshop
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Telemetry Formats
In
F-15
Telemetry
Range Safety
Telemetry
Antenna
Telemetry
1 Mbit/sec
PCM stream
156 byte frames
w / 3 byte sync
10Kbit/sec
PCM stream
124 byte frames
w / 4 byte sync
Fixed size UDP packets
with one 80-byte frame
per packet.
IP Formatter
Status
IP Formatter
Out
6/9/2004
Fixed size UDP packets
with 1 frame per packet.
Includes sync chars.
Fixed size UDP packets
with 1 frame per packet.
Includes sync chars.
Fixed size UDP packets
with one 80-byte frame
per packet.
2004 Space Internet Workshop
UDP packets with
one ascii text line
per packet.
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IP Formatter System Architecture
TDRS
Network Int.
IP-192.168.0.11
Ethernet
RJ-45
Linux Console
Character terminal
9600 baud N81
RS-232
DB-9
Ground Use Only
Network
Phased
Array
Antenna
Console
Phased Array Status
UDP/IP packets
Ethernet DB-9
Port 40000
Phased
Array
Control
Antenna
Control
Audio
Video
CPU
Net-Ser
F-15 Telem
RS Telem
Char-Ser
IRIG-B timecode
IRIG-B
WAN
Formatter Output
UDP/IP packets
HDLC Sync serial
RS-422
DB-37
Enerdyne Mux
Coding PCB
Ethernet
Conv
Decode
Power
GDDS
PCM frames in
bitstream
Synced PCM
frames
Individual PCM
frames in
UDP/IP packets
Coded Enerdyne
muxed data bitstream
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Packets addressed to
specific UDP ports on 111.222.0.x
Port
FLAPS system
F-15 PCM Data
10000
Receiver
F-15 Data
Range Safety
Data
R/S PCM Data
Receiver
192.168.0.11
111.222.0.x
Port
Port
20000
UDPcapture 20000
#2
IP Formatter
Status Gen
192.168.0.11
111.222.0.x
Port
Port
30000
UDPcapture 30000
#3
Timekeeper
Time Stamps
Telemetry
Sync
Serial Driver
RS-422
RS-422
192.168.0.11
111.222.0.x
Port
Port
40000
UDPcapture 40000
#4
Phased Array
Antenna Data
Linux Operating System
Minimal Kernel &
2.4.18 kernel
File System
IRIG-B
Driver
IRIG-B
IP Formatter
Software
Architecture
Ethernet
Driver
Ethernet
192.168.0.11
Console
Driver
RS-232
IP
Network
HDLC Sync
Serial Driver
RS-422
111.222.0.x
Ports10000, 20000,
30000, 40000
RF
System
RS-422
LAN
Switch
F-15
Range
Safety
IRIG
Test
Access
Phased
Test
Array Access
Antenna
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FLAPS
2004 Space Internet Workshop
Serial to
Enerdyne Mux
Enerdyne
Enerdyne
Router
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IP Formatter Development Bench
Router
PC/104 Proto
Board
PC/104 Cable
Kit
STARS
IP Formatter
PC/104 stack
Serial line to
Enerdyne/Rout
er
RS-422
Breakout Box
384MB
Disks
On
Chip
6/9/2004
2004 Space Internet Workshop
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Testing
• "Gizmo" programmable telemetry generator
used to simulate F-15 PCM telemetry
• ParaScope serial line analyzer used to
playback simulated Range Safety PCM telemetry
• Custom data-generator program (provided by
STARS) used to simulate Antenna telemetry data
in UDP packets sent over ethernet
• TrueTime 800 timecode generator for IRIG-B
• Etherpeek network monitor SW used to
monitor performance
• Post-run analysis of captured telemetry on
groundstation to determine packet loss rate
6/9/2004
2004 Space Internet Workshop
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Testing
F-15 Telem
Gizmo
RS Telem
ParaScope
CPU
Net-Ser
Antenna
Sim
HDLC
Link
Ground
System
Router
Char-Ser
IRIG-B
Ethernet
Ethernet LAN
Power
Timecode
Generator
IP Formatter
PC/104
Stack
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2004 Space Internet Workshop
EtherPeek
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Performance
• Test Conditions:
– Full telemetry rates on all inputs (1.45 Mbits/sec aggregate)
– HDLC output clock at 1.8 Mbits/sec (35 Kbits/sec headroom)
– Onboard logging of all telemetry except F-15
• Results:
– 40 - 50% CPU Utilization
– All telemetry ingested with NO loss
– Full output rate (average) with 1 - 2% packet loss
• Attempted Mitigations:
– DMA output driver: Reduced CPU usage, but loss unchanged
– Reduced F-15 rate to 500 Kbits/sec: Loss reduced to 0%
• Analysis:
– Insufficient kernel buffer pool causing dropped packets on output
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Status
• IP Formatter delivered to STARS project on
March 5, 2004
• Currently being integrated at the STARS facility
at Dryden Flight Research Center (DFRC)
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2004 Space Internet Workshop
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