Hermes

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Hermes

• Space Based Migration Tracking Platform
• Princeton University
• Spacecraft Design Team
• August 1st, 2006

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Hermes A space-born solution to grand
challenges in environmental biology

• How can one track the migratory patterns of small
  winged birds, bats, and insects?
• Migrations of hundreds of kilometers per day
• Often over dense foliage or water

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From start to finish

• Student run design project
• 12-week design course
• First 6-weeks Two-team satellite design
  competition, similar to what is often seen in
  industry.
• Final 6-weeks Merge best ideas from both
  designs, focus on subsystems.

AVsat Preliminary Design
Winged Animal Migratory Behavior Observatory
Avian Tracking Satellite
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Why Track Small Animals? Social Concerns

• Spread of Disease
• Avian Flu, rabies, West Nile Virus
• Birds are vectors
• Prediction of migration patterns enables
  preventative measures
• Economic safeguard
• Crop protection
• Early warning
• Pattern detection
• Ecosystem Services

Starling Swarm
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Why Track Small Animals? Scientific Concerns

• Ecological Conservation
• Track and study rare species
• Identify a network of sites to ensure stopover
  habitats for migrating birds
• Scientific Knowledge
• Understanding navigation techniques
• Accurate models of migration patterns
• Behavioral and ecological studies

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Migration routes What we know
5,000,000,000
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Why dont we know more? Most birds/mammals are
too small to track!
Proportion of species
Small birds/bats Insects
Large enough to carry ARGOS-type satellite tag
Body size (log g)
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Cant We Track Them From Earth?

• Not well. Weve tried that.
• Tagging
• Tag it and hope someone else catches it
• Radar
• Trucks (and other ground-based methods)
• Time constraints
• Limited range
• Costly
• Birdwatchers identify calls
• Basic Patterns are too complicated
• Intercontinental range
• Long migrations
• Nonstop flights

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Tracking From Space

• Advantages
• Global Coverage
• Unmanned
• Continuous surveillance
• Tracks large volume
• Small cost to track extra animals
• ARGOS
• Tracks larger animals
• Doppler shift
• Very effective
• Problem cant be used to track small animals
• Transmitters too big!
• Need a satellite designed to track low-power
  signals!!!

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The future of biotelemetry
NEON National Ecological Observatory Network
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Designing Hermes Scientific Goals

• Reception Must receive RF signals from
  transmitter small enough to not affect migratory
  behavior
• Resolution Must be able to differentiate between
  multiple birds in view at the same time
• Duration Remain in operation for 10 years
• Coverage Continuous, global coverage every 4
  days
• Quantity Uniquely track hundreds of animals

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The Scientific Payload

• Signal Acquisition
• Bird Identification and Location
• Digital Sampling and Storage
• Data Downlink

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Signal Acquisition
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Signal AcquisitionTransmitters

• We are assuming use of Sparrow Systems 1g
  transmitters
• Peak power output of 1-2 mW, isotropic
• Frequency range selectable by harmonics of 75 MHz
  crystal
• Pulse frequency 10 ms limits battery life

Swenson, Wikelski, Smith. Tracking
very-low-power ground transmitters from near
earth orbit
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Frequency Selection

• 100 MHz and 360 MHz available
• Lower noise and better transmission through
  foliage at 360 Mhz
• Less power needed to transmit at 100 MHz
• ? 360 MHz selected
• Max Doppler shift 4.7 kHz
• Max carrier drift 2.5 kHz

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Signal Acquisition
Link Budget
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Pt Transmitter Power 1 mW Ll Line loss
.1 La Atmospheric Loss 1 Ls Space loss c2
/ (16 p2 R2 f2) Gt Transmitter Gain 1 Gr
Receiver Gain T System Noise Temperature 350
K B Bandwidth 100 Hz
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Antenna Gain Profile

• At 485 km orbit, S/N gt10 out to 29.
• ? Beamwidth 58 degrees
• ? Swath width 540 km

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Offset Parabolic Reflector

• Manufactured by Applied Aerospace Structures
  Corp.

Boresight Vector
Focal Point
Aperture (diameter)
Feed Axis
Axis of Rotation
Focal Length
Parent Parabola
Offset
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Bird Identification and Location

• How to go from incoming signal to bird ID and
  location?

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Identifying Birds

• Transmissions received from different locations
  on the Earth have different frequencies due to
  Doppler shift
• Birds also transmit different frequencies due to
  clock oscillator drift
• But what if two or more birds are in the same
  location on the same frequency? How do we tell
  which bird were looking at?
• ? Use an encoding scheme

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Pulse Code Modulation

• Assign a unique binary code to each bird
• - 1 corresponds to transmitter on
• - 0 corresponds to transmitter off
• Set each birds transmitter to pulse on/off in a
  sequence of 10-ms pulses
• Allows multiple users to transmit data at the
  same frequency
• This is the encoding scheme used by GPS!

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Unique IDs

• Science requirement need to track 1000 birds
• A code can be used more than once in different
  regions
• Within a region, simultaneous transmissions will
  add e.g. 1100011 0000110 1001101 2101222
• Need orthogonal codes (Gold codes)

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Determining Location

• Once we know which birds contribute to the
  incoming signal, we must determine their
  locations within the swath width
• ?Use the Doppler shifts of received frequencies
  for this task

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Doppler Shift
The base frequency will be set by the crystal
oscillator shift, which can be quantified as the
inflection point of the curve.
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Satellite Ground Track

• Assume bird is stationary
• Velocity over ground track is the vector sum
  of the earths rotation and the satellites
  speed in space

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Uncertainty

• The pointing error of ADC produces an uncertainty
  in position of approx. 10 km.
• This is a difference in relative
• velocity of 156.3 m/s (worst case).
• To detect a bird to this accuracy,
• we must be able to detect a Doppler
• shift frequency of approx. 200 Hz
• in the 360 MHz signal (approx. 4
• of the total Doppler shift).

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Data Sampling

• 2 types of information in signal
• Bird ID code
• Time dependent Doppler frequency info for
  positioning
• Amplify signal using low noise amplifier
• Beat down signal real-time using local
  oscillator
• Store signal digitally and compute on ground

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Data Sampling

• Space computer sampling limit 50 MHz
• Data must be stored at twice signal frequency
• Need 10 bits/sample to identify 1024 birds
  simultaneously
• Dump data to ground station 4 times per day
• Triggered data storage store only when seeing
  signal
• ? Conservative estimate store 10 of time in
  air
• Solid state storage limit 4 GB ? 2 GB with
  margin
• ? Beat signal down to 370 kHz

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CommunicationsSending and receiving data
10101110110110110101010101101100
1010111011011011010101010110110
Aaron Prescott Philip Kang Cameron Wheaton
10101110110110110101010101101100
10101110110110110101010101101100
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Science Data Link

• Ground Stations
• 3.6 meter diameter
• X-Band
• Ground stations based at Princeton and Copenhagen
• Lower recurring costs

• Satellite Antenna
• Wide Coverage
• Higher gain at longest path length
• 70º Half Angle Coverage
• No space-based pointing requirement

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Designing the Link
Minimum Signal-to-Noise Ratio 10.5 dB
Transmitter Power 50 Watts Transmitter Gain 5
dB Frequency 8.4 Ghz Line Loss -1.0 dB
Space Loss -173dB
11010101000101010100101010111010101000010101101001
0101010100101010010100100101
Atmospheric Loss -0.5 dB
Path Length 1400km
Receiver Gain 47.4 dB Pointing Loss -1.0 dB
Noise Temperature 220K
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Engineering Link

• Main Ground Station Svalbard
• Access every pass approximately every 84
  minutes
• Can link to NASA ground network, and NASA TDRS

Saab-Ericsson S-Band Conical Helix Antenna

• Frequency 2-2.15GHz
• Mass 240g
• Power 10W
• Highest gain at 70, ideal for link at worst
  point in pass

Emergency Omni
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Summary

• Transmitting engineering data is trivial (high
  Eb/No)
• May be able to install smaller S-band dishes at
  Princeton and Copenhagen
• Svalbard is pay per pass, and expensive over time
• Emergency access at any point in the orbit
• Hardware
• Two S-band wide coverage antennas
• Two S-band transponders one for redundancy

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Hermes Mission Analysis
Steven Batis Dominique Van de Sompel
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Orbit Parameters

• Circular Orbit, Altitude 485 km
• Repeating Ground Track
• Dawn-Dusk Sun Synchronous
• Inclination 97.35º
• Full Coverage in approximately 61 orbits, or 3.6
  days

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Groundtrack
3 orbits
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Groundtrack
10 orbits
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Number of Accesses
2.5 days
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Number of Accesses
4 days
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Average Number of Accesses
4 days
Average Number of Accesses in 4 days ? 2.7
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3D Orbit Animation
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Launch Vehicle

• Taurus 2210 Launch Vehicle
• Ground-launched version of Pegasus
• Approximate cost 24 million

Taurus Users Guide http//www.orbital.com/NewsIn
fo/Publications/taurus-user-guide.pdf
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Hermes Propulsion
Coleman Richdale Jeff Stein Ronnie Zownir
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Propulsion
Thruster Configuration

• Understanding the orbit degradation
• 18 m altitude lost every orbit due to drag at
  485km altitude
• ?V 11m/s lost each year

• 8 thrusters aligned parallel to velocity vector
  on two faces
• Rotation about two axes
• Translation along one axis
• Altitude maintenance
• Redundant system for momentum dumping

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Propulsion System Diagram
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Hermes Power
Eric Whitman Crawford Hampson Loan Le
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Light Intensity
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Full Circuit Diagram
- 2 m2 solar arrays produce 511 W at end of
life - Lithium-Ion battery stores 1120 W-hours of
energy - System mass 37 kg with 15 margin
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Attitude Determination and Control Subsystem

• Vera Dadok
• Jeff Hill
• Adam Reif

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Disturbance Torques

• Primary external disturbances
• Aerodynamic
• Gravity Gradient
• Solar Radiation Pressure
• Primary internal disturbances
• Misaligned/Mismatched Thrusters
• Residual Spacecraft Dipole
• Flexibility and Sloshing

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ADC Hardware

• Proposed Sensors
• 2 Coarse Sun Sensors
• 2 Horizon Sensors
• GPS w/ Attitude Capability
• Magnetometer
• Proposed Actuators
• 4 Reaction Wheels
• 3 Torque Rods
• Backup Thrusters

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Metrics
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Computing Subsystem

• Daniel Moser
• John-Paul Mitchell

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Computing Requirements

• Receive and store data from payload at 50Mhz
• Transmit data to downlink antenna at 70Mbits/sec
• Control actuators based on orientation data
  received from ADC
• Regulate power bus
• Control low frequency events of other subsystems
  (ie fire thrusters)

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6 x RH3000 SPM
RH3000 CPU 39 MIPS Each
512 KB Boot EPROM -EDAC
Internal Bus -EDAC -Auto Memory
Scrubbing -Resource Controller and Address
Interface
64 MB DRAM -EDAC
2 MB User EEPROM -EDAC
4 GB RAM Storage
40 Mbps Serial Port gt ADC, Thrusters, Payload
Comm. Module gt Power, ADC
Redundant MIL-STD-1553 and Fiber-Optic Bus
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Hermes Structure

• Fatou Bintou Sagnang
• Erik Kroeker
• Azuka Chikwendu

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Primary Structure
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Additional Schematics
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Internal Structure
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Static loading analysis
-Analysis based on maximum accelerations at
launch 10g axial, 2.5 g lateral -Model
approximated as beam structure with point masses
for secondary structure components -Analysis
done in Pro-E and Mechanica
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Hermes Thermal Control Design Analysis
Steve Farias Dean Sandin Jeffrey Byrne
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Sources of Heat and Radiation
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Spacecraft Pro-Engineering Analysis
Rear Exterior View
Rear Inside View
Front Exterior View
Front Inside View
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Thermal Control
Exterior Coatings Front a .9 Front and
Back eIR .85 Heat Pipes The best way to
reduce the temperature range between sun side
and back side panels. Require 3 Pipes 1.5
diameter 3 kg gt200 W transferred Aluminized
Kapton sheeting - to prevent thermal radiation
losses on sides, top, and bottom of hull -
eIR 0.05 Heat tape used during eclipses to
keep batteries within acceptable temperature
range
Heat Tape
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Mission Recap

• Can track 129 unique signals to within 10km
• Taurus 2210 launch vehicle, Vandenburg Air Force
  Base
• 97.35 inclined, 485 km circular orbit
• 360 MHz transmission frequency
• 1mW required ground transmitter power
• 1.8 m offset parabolic reflector
• 336 kg total mass
• 365 W steady state, 945 W peak power
• 300 kg available for secondary payload
• 10 year nominal mission lifetime

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www.IcarusInitiative.org
Webmaster Erik Kroeker
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Acknowledgements

• Prof. Wikelski, Princeton EEB Dept.
• Prof. Swenson, U. of Illinois
• Prof. Kasdin, Princeton MAE Dept.
• Prof. Choueiri, Princeton MAE Dept.
• Prof. Lyon, Princeton Electrical Eng. Dept.
• Prof. Joe Taylor, Princeton Physics Dept.
• Prof. Kasper Thorup, University of Copenhagen
• Prof. Per Enge, Stanford Univ.
• Dr. Jack Gelfand, Princeton Psychology Dept.
• Joe Troutman, Ocean Power Corp.
• Shey Sabripour, Lockheed Martin
• Justin Likar, Lockheed Martin
• Erik Lier, Lockheed Martin
• Hamilton Wong, Lockheed Martin
• Bob Danielak, Lockheed Martin
• Niel Haneman, Lockheed Martin
• Mayk Kalachian, Spectrolab
• Dawn Valero, Applied Aerospace Structures Corp.
• L3 Communications Cincinnati Electronics