Space Segment for Global Autonomous
Sensors
Development, Deployment, Test &
Operation of a Constellation of
Host
Spacecraft
International
Space
Station
TacSat-X
Microsatellites or Payloads for,
UAV
Two-way Communication with,
P-3 ASW
A Variety of Sensors Deployed Near or
Below Surface of the Ocean
Distributed Arrays of Small Instruments (DASI)
Workshop 8 June 2004
Sonobuoy
Field
Unattended
Ground
Sensors
Bob McCoy
ONR Code 321SP
703 696 8699
mccoyr@onr.navy.mil
Ocean Data Telemetry MicroSat Link (ODTML)
Argo Profiling Floats
 Operational Characteristics
 Surface to 2,000 m
 Salinity, Temperature and Pressure
 Argos DCS Constraints:
 Repeat Transmission every 60 to 72
seconds, 10-12 hours every 10
days
 Normally around 50 pressure levels
(range 33 to 115)
 Data 348 to 464 bytes (12 to 16
Argos messages)
 $1.2 M “value-added” processing
 Future Requirements
 On Demand transmission 500 pressure levels (4 Kb) within one hour
with reduced power demands for communications
 Two-way communications (not necessarily on demand) for programming
 $100-150K Target data telemetry cost
Data Assimilation for Meteorological Forecast
Over 3000 aircraft provide reports of pressure, winds and temperature during flight.
Argos Data Collection System (DCS)
in the NPOESS Era
Iridium, GlobalStar & ORBCOMM
 Existing ground-to-space/ground networking (Orbcomm, Iridium) were
developed for voice and data, and rely heavily on fixed infrastructure, and
power-intensive transmissions at VHF frequencies
 ORBCOMM/Iridium are good for large littoral buoys where transmit power is
not an issue and where L-Band attenuation (wave shadowing or
microorganism growth) is not an issue
 Current market (~20M/yr) is sufficient to sustain current systems but is
insufficient to replenish the satellite constellation
 Industry focus is not on low data-rate (<10,000 b/s) customers
 Existing systems are not IP-like and require extensive groundstations and
satellite monitoring
 Operational Expense & Operations over the ocean
Ocean Data Telemetry
MicroSat Communications Relay System
• Global Data Communications “On the Move”
– Small, Mobile and Disadvantaged Platform
Transceiver Terminals (PTTs)
– Laptop Computers/Transceivers
• Availability
– Robust RF Links – In Water and Under Cover
• Capacity
– Many Users in the Field
• Service
– Simultaneous Data Nets
• Assured Access
– Acknowledgement That Messages Got
Through
• Interoperability
– Seamless Connectivity to Other
Systems
A Global
Communications
System Providing
Near Real-Time
Situational Awareness
Is Essential
for the Next Generation
Ocean Observing
System
Microsatellite Constellation Goals
• Demonstrate 2-Way communication with small disadvantaged sensors
anywhere in the world
– UHF transmission compatible with Service ARGOS, But with the
following enhancements:
- Significantly higher bandwidth (4800 b/s vs <256 b/s)
- 2-Way delay-tolerant communication
- “IP-like” message packaging
- New protocol for increased battery life & Non-GPS geolocation
- Method to provide acknowledgement that command sequences were
received (ACK/NACK)
- Increased signal-to-noise at the host satellite via coding, a bidirectional software radio, similar to e-mail to forward messages to
user/sensor with defined addressing schemes
- Enhanced computer speed & storage for on-board data processing
- System architecture allows evolution and expansion for future
sensors
- System capable of being deployed as a mix secondary payloads
aboard host space vehicles (e.g. International Space Station, DMSP,
TACSAT) or low-cost micro-satellites e.g., STP (Navy PG or USNA).
Multiple Access With Collision Avoidance
by Invitation (MACA-BI) Network Protocol
GeoLocation Determination via Doppler Shift
Doppler Shift Metrology
• Spacecraft (S/C) Avionics Measure Doppler Shift on Uplink Carrier
Frequency As S/C Approaches and Moves Away From Location of PTT
• At Point of Inflection of Doppler Curve (i.e., Rx vs. Tx Frequencies Are
Equal), PTT Position Is Perpendicular to S/C Ground Track
– Slope of Curve at Inflection Point Determines Distance From PTT to S/C
Ground Track
• Location Errors of ~125m to 3000m (i.e, PTT Local Oscillator Stability,
Number of Samples, and S/C Ephemeris Errors)
Sources of Location
• Location Errors Are Greatest When PTT Is ~170 km
of the S/C Ground Track or More Than 2,700 km
From S/C Ground Track
• Other Factors:
– PTT Oscillator Stability – Mean PTT Short Term
Frequency Stability <4x10E-5 (20 Minutes)
– Mean PTT Frequency Must Not Vary > 24 Hz
Between Multiple Passes (Two Overpasses)
– PTT Altitude Creates Errors Due to Changes in
Assumed Altitude (Sea Level)
- Coupled in the “Across-Track” Coordinate of
the Fix With Little Effect on the “Along-Track”
Coordinates
Spacecraft Requirements
• Location Determination
Requires Ephemeris
Within 300m (“AlongTrack”) and 250m
(“Across-Track”)
• Location Determination
Requires >5 Doppler
Measurements w/ >420
sec Interval Between First
and Last Measurements
w/ 240 sec Separation
(Minimum Accuracy)
ODTML Key Performance Parameters
Data Exfiltration, All Floats
 Floats to be serviced
 In view
 Data per float per SBIR announcement
 total, daily float data collected
 # in-view orbits per day (single satellite)
 Total, downlinked data bits per in-view pass
Data Exfiltration, Single Satellite
 Total data bits per orbit w/ single grd station
 Data overhead @ 15%
 Total, data downlink per pass
 Data encoding (symbol rate)
 Downlink time (1/2 of mid-latitude pass)
 Downlink rate
Data Exfiltration from Single Float
 Data per float
 Data overhead @ 15%
 Total, data per float
 Data encoding (symbol rate)
 Data exfiltration rate
 Data exfiltration time
 XMT power out
 Total XMT power (eff = 15%)
 XMT power consumed
 Joules per data bit
3,000
600
50,000
30.0
13.0
2.3
2.3
0.3
2.7
5.3
180.0
29.5
50,000
7,500
57,500
115,000
4,800
24
0.50
3.33
80
0.0014
Global float population (assumed)
Assume 20% in view per 24-hour day
bits per day
Mbits
Single grd station, high latitude, LEO
Mbits
Mbits
Mbits
Mbits
Assumed factor of two (K=7, R=1/2)
sec
kbit/sec
bits per day
bits per day
bits per day
Assumed factor of two (K=7, R=1/2)
b/sec
sec
watt
watts
watt-seconds (joule)
< 0.1 Joule/bit (rqmt from SBIR N02-062)
Communications Relay
Payload Breadboard
DC-DC Converters
3.3V, 5V, ±12V
24VDC Input
1553 Interface
Configurator
Discrete I/O
Motor Drive Interfaces
(0 Populated)
Actel
54SXnn FPGA
MCU RS232
Linear Regulators
2.5V, ±5V Analog
Local SRAM
Shared SRAM
EEPROM
Expansion Interface
(0 Populated)
LVDS Interface
PROM
Expansion Interfaces
0 Populated)
Expansion
Interface
(0 Populated)
XILINX
Virtex400 FPGA
Expansion
Interface
RS232 Interface
RS422 Interface
ODTML MicroSat Configuration
Payload Minimum Resources Available:
• ~25 Watts Orbital Average Power (OAP) - Basic
• ~5 kg Mass (Basic)
• 0.3m x 0.75m x 0.8m Size
• 350 b/s Average Payload Stored Data +
100 b/s Payload Housekeeping Stored Data
Communications
Relay Processor
Communications
Relay Transceiver
Spacecraft
Avionics
(Includes 3
Micro Gyros)
ODTML Payload
Provides
Uplink/Downlink
Communications
Three Axis
Magnetometer
Magnetic
Torque Rods
Heritage
LightBand
Separation
Thermally Stable
With Constant Dark
and Sun Sides
Spacecraft
Structure
Lithium Ion
Battery
Hydrazine
Propulsion
System
Body Mounted GaAs Solar Arrays:
Simple Design and
Interfaces Enable Ease of
Development and
Integration
• Allows Common Satellite Design for All Orbit
Planes
• Minimizes Body Drag Perturbations on
Gravity Gradient (G-G) Stabilizing Torques
• Improves Reliability
• Reduces Cost and Simplifies Integration
Low Cost Communications Gateway
Uses Same Electronics Suite As Buoy
System Characteristics
• UHF Eggbeater Antenna
– Omni-Directional
– Circular Polarization (RHCP)
• Communications Relay Payload Repackaged for
Ground Environment Plus High Power Amplifier
(HPA)
• Laptop Interface (Portable Ops) OR PC-Based Mail
Server and Remote Intelligent Monitoring System
(RIMS) for Fixed Gateway
Potential Launch Opportunities
EELV
Low-cost launch opportunities:
• Alternate Launch Vehicles
SpaceEx Falcon
– EELV Secondary Launch
- 4 tons excess for each DMSP
launch
– SpaceEx Falcon - TacSat follow-on
• University MicroSat Designs
– CubeSat
CubeSat
Cubesat
PC Sat
– ASTRID/MUNIN
MUNIN
– USNA PC Sat
ChipSat
TacSat-1 Program Elements
Navy Highlights
•
$12M
MICROSATELLITE:
– 1 yr Life, 110kg, 186W
– 40in dia. x 20in high
– 500km, 64º inc.
•
PAYLOADS:
– CopperField-2S: Navy TENCAP
– SEI: NRL/ONR? Developed
– Visible & IR Cameras (Army NVL)
• GROUND STATION: Blossom Point MD
– Navy Facility
– With VMOC (Virtual Mission
Operations Center) for SIPRNET
Tasking & Data Dissemination
•
LAUNCH VEHICLE: Falcon by SpaceX
– New, Privately Developed
– LOX-RP1 gives ~1000 lb to 500km
– 60klb, 70ft by 5.5ft dia.
– Navy Contract
$3M
•
AIRCRAFT:
– EP-3’s: 1 Fixed & 3 Mobile RORO
Units; Also RJ’s (TBD #) Expected
– Implementing an Naval, ONR
Cross-Mission CONOP
TacSat-1 Spacecraft Components
• Specific Emitter Identification (UYX-4) &
Copperfield-2S Payload Hardware
•
IR Camera & UHF Radio
UYX-4
IR Camera Does NOT
Require Cryo-Cooling
CURRENT Technology by
COMPUTER INDUSTRY
STANDARDS
(3 Million Gate FPGA)
•
SEI Hermetically Sealed
Chassis (CuF-2S is Similar)
• Spacecraft Bus & EAGE Hardware
Fans
2 Places
•
Rubidium Clock & Low Cost
Receivers (0.5-18GHz Range Used)
Receivers
Clock
Program Plan
• Build satellite/aircraft payload and test via aircraft flight(s) (2005)
• Orbital test using existing orbital UHF satellite (2005)
– (10kg NanoSat; half duplex mode – SpaceQuest)
• Deliver satellite payload on International Space Station (2006)
– 57º Inclination (via Space Test Program)
• Launch polar payload/satellite (2007) on TacSat-n, DMSP or STP payload of
opportunity
• Test ocean to space system with realistic RF & ocean environment
– Communication links with actual Doppler
– Distance fading
– Actual environment (shadow fading - wave height)
– Operate autonomously, unattended
Tac-Sat n
Near Term
2 Planes
6-8 Hrs Revisit time
International
Space
Sp Station
Ultimate goal
6 Satellites
in 3 Planes
2.5 Hr revisit
Ocean Data Telemetry
MicroSat Link (ODTML)
Concept of Operation
• ONR Small Business Innovation Research (SBIR)
Topic N02-062 (ODTML)
• DOD Space Exp Review Board (SERB) ONR-0301
(Ranked Experiment)
Operational Capability
• Communications Relay Payload to Support an Integrated Global
Ocean Observing System via MicroSat or Host Platform
• Data Infiltration and Exfiltration for Small, Mobile, and LowPower Ocean Buoys and Sensor Transceiver Nodes
• Two-Way, Delay-Tolerant, “Internet-Like” Messaging Services on
Global or Theater Basis
• Allows Users to Send Commands and Receive Telemetry From
Autonomous Buoys or Distributed Sensor Nodes
• Decouples Nodes From Space Segment Allowing Evolutionary
Upgrades or Expansion of Capabilities
• Higher Bandwidth, Lower Power Than Existing Service Argos
> 50 Kilobits Per Node Per Day
< 0.1 Joule Per Bit Transmitted
Schedule & Budget
Technical Approach
• Global Data Collection System Architecture via “AdHoc Wireless Networking” and “Instant Messaging”
• “Router in the Sky” via MicroSat or Aircraft Host
Enabling Technology
• Flight-Proven FPGAs, Router and Cellphone
Concepts, and Low-Cost On-Orbit Commercial
MicroSats (Spacequest / Aprize, Ltd)
Two-Way Global Communication to Provide
Near Real-Time Awareness Is Essential
for Next Generation Ocean Observing Systems
• Phase I – Lab Demonstration Completed
• Phase II – Non-Flight Engineering Unit (6/04 ONR SBIR Funds)
6/04 – 6/06 System, H/W & S/W Designs/Demos
1/06 – 12/06 Engineering Unit Build, Integration & Test
1/07 – 3/07 Field Demonstrations
• Requesting Official: Dr. C. Luther, ONR, 703-696-4123
• Phase II Sponsor: Dr. R. McCoy, ONR, 703-696-8699
Contact
Praxis, Inc., 2200 Mill Road, Alexandria, VA 22314
Mr. R. Jack Chapman, Principal Investigator
703-837-8400, chapmanj@pxi.com