A Prototype Attitude Determination
System for High Altitude Research
Balloons
Catholic University of America
Erin Doody, Fernando Esteves, Devon Gonteski,
Michael Lamos, Jason Quisberth, Peter Schramm,
Raissa Silva, Gary Uritskiy, Patricia Yoritomo
Mission Overview
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Table of Contents
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•
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Mission Overview
o
Components
o
Theory and Concepts
o
Expected Results
System Overview
o
Block Diagrams
o
Mass Budget
Subsystem Design
o
Star Camera
o
Flight Computer
o
Pressure Vessel
o
Electrical Box
o
Gyros
Prototyping Plan
o
Assembly and Testing
Mission Overview
Overall goal:
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•
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Design, fabricate, test, and launch a system that collects data
20kg payload
Measure altitude to arc-second precision
Use of commercially available and low-cost components
Meets Columbia Scientific Balloon Facility (CSBF) requirements
o Meets Undergraduate Student Instrument Project (USIP)
Main Components
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•
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Daytime-Capable Star
Camera
Gyroscopes
o Tilt Sensors
Flight Computer
o Magnetometer
o Clinometer
o Thermometer
Pressure Vessel
Box
Theory & Concepts
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•
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Electrical engineering, Mechanical engineering, and applied physics
ideas and concepts will be used to order to construct, build, test, and
fly payload
o heat transfer
o signal processing and filtering
o thermodynamics
Knowledge of computer programming languages such as python will be
used in order to operate the electronic components.
Similar projects are seen on the HASP carrier by NASA BPO and LaSPACE
o Successful flights and good data are signs that this project is
feasible within the timeline given
Expected Results
To develop a low-cost, low-mass system for real-time attitude
determination
Using of individual sensors including a daytime-capable
digital star camera, MEMS gryoscopes, magnetometers, and
tilt sensors (clinometers).
The fast, relative sensors (gyroscopes) that are continuously
updated by the slower, absolute sensors (star camera,
magnetometers).
The integration of the gyro output will demonstrate real-time
attitude determination to arc-second or better precision.
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System Overview
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System Level Block Diagram
AAS – Absolute Attitude Sensing
CCM – Climate Control and Monitor
MP – Mounting Plate
PV – Pressure Vessel
RAS – Relative Attitude Sensing
SP – Signal Processing
UB – Unpressurized Box
VRB – Voltage Regulator Board
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System Concept of Operations
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Mass Budget
Component
Unit Weight (kg)
Quantity
Total Weight
Magnetometer APS 113
0.025
1
0.025
Clinometer Shaevitz
Thermometers
Gyro(s)
Star Camera:
Body Canon EOS 7D
0.0567
0.0004
0.0017
2
10
12
0.1134
0.004
0.0204
0.82
1
0.82
Lens EF 50mm f/1.2L USM
Computer
0.545
1
0.545
Flight computer BeagleBone xM
0.0397
1
0.0397
Readout board PSyncADC
Other
Pressure vessels
Hard drive 2TB
0.46
1
0.46
5
0.36
1
1
5
0.36
Total:
7.3875
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Subsystem Design
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Star Camera DesignLens
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Star Camera Lens Section
• This system is design with the intent to to capture images of stars in both
the day and night during flight
• One of the requirements for the lens is that it must capture a minimum of
4 stars in the pipeline.
• By choosing a lens with a greater area we see an increase in performance
by a factor of 1.36.
• Another advantage of the smaller f-stop lens is the size of the filter,
72mm vs. 58mm. The larger diameter lens provides a larger area and gives
us a larger area of usable frame.
• Even though the f/1.2 lens is heavier (545g vs. 290g) the HASP payload
bay that we have acquired is 20Kg, well within our current estimate of
3.54Kg.
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Lens: Trade Studies
Model
Price
Weight
Performance
Intangables
Average
Rating From 1-10
Star Camera Lens Trade
Study
Canon f/1.4
Canon f/1.2
8
7
7
5
6.75
Product Chosen:
EF 50mm f/1.2L USM
Standard & Medium Telephoto
2
7
10
8
6.75
•Focal Length & Maximum Aperture -50mm f/1.2
•Lens Construction -8 elements in 6 groups
•Diagonal Angle of View -46° (with full-frame
cameras)
•Focus Adjustment AF with full-time manual
•Closest Focusing Distance -1.48 ft. / 0.45m
•Filter Size -72mm
•Max. Diameter x Length, Weight- 3.4 in. x 2.6
in./85.4mm x 65.5mm,19.2 oz./545g (lens only)
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Star Camera DesignCamera
Body
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Camera Body Design Section
• The camera body will be connected to the computer through the
means of a USB 2.0 cable.
• The software that will facilitate the communication between the
flight computer is called gphoto2 and it will give use the ability to
cycle shutter speed in flight
• The photos that will be take will be sent to the external hardrive.
• The reason for choosing the Canon 7D was that it is one of the only
camera that is compatible with the gphoto2 software.
– This limited the cameras that we could research thus almost
forcing us to choose the 7D.
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Camera Body: Trade Study
Product Chosen:
Model
Price
Weight
Performance
Intangables
Average
Star Camera Body
Trade Study
Canon 7D
Canon 70D
7
7
9
10
8.25
9
7
9
0
6.25
Rating From 1-10
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AAS: Risk Matrix
AAS.RSK.1: Mission objectives
AAS.RSK.2: Mission objectives
not been set right.
AAS.RSK.3: Mission objectives
with the flight computer.
AAS.RSK.4: Mission objectives
obstructed
aren't met if the Star Camera overheats.
are affected if the Star Camera parameters had
aren't met if the Camera fails to communicate
are affected if the camera lens becomes
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Flight Computer Design
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Flight Computer Design Section
• The flight computer will be responsible for the data acquisition and signal
processing. It should have a good processing potential, enough I/O ports to
connect all devices, compact size and be robust to different
environments.
• The first option we consider for the flight computer was a ASUS laptop. It
had all the processing potential we need and I/O ports. However, it had
some disadvantages such as high price, big size, power consuming and
produces too much heat.
• Single board computers are a very compact and cheap option that have
also a great processing potential. The BeagleBoard-xM (the flight
computer selected) have all the capacities we need for a very good price.
It has 512 MB DDR memory, 1 GHz ARM Cortex-A8 processor, provides 4
USB ports and runs differents versions of linux.
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Flight Computer: Trade Studies
• Show rationale for you choices in components. You basically weigh your
options against your requirements and what each component can offer. Don’t
forget things like: availability, cost, and prior knowledge. I recommend an
online search for examples if you are unsure, or contact me.
Flight Computer Trade Study
ASUS Laptop
Price
Weight
Performance
Power Requirements
Ease to program
Serial Ports
Low Level Peripherals
Size
Average
Raspberry Pi
5
5
10
4
10
9
0
4
5.875
Beagle Bone
10
10
7
8
7
5
5
10
7.75
Beagle Bone Xm
10
10
7
8
8
7
7
10
8.375
8
10
8
8
7
10
8
10
8.625
Rating From 1-10
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Subsystem Design Section
• This section is where you explain how each subsystem was
designed
• Start with your organization chart with each of your subsystems
labeled
• Discuss how you researched components that would meet your
requirements
– Show trade studies if necessary, and if you show them, be
prepared to explain the scoring and categories
• The most important part is explaining how you reached your major
design decisions in each subsystem
• After explaining components, discuss any risks associated with this
subsystem
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SP: Risk Matrix
SP.RSK.1: Mission objectives aren't met if the computer or the PSyncADC board
overheats.
SP.RSK.2: Mission objectives aren't met if the flight computer fails in communicating to
the PSyncADC.
SP.RSK.3: Mission objectives aren't met if the flight computer fails in processing sensor
data.
SP.RSK.4: Mission objectives will be affected if bad sensor data is not filtered.
SP.RSK.5: Mission objectives will be affected if the hard drive gets damaged on landing.
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Pressure Vessel and
Electrical Box Design
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Subsystem Overview – Block Diagram
Pressure Vessel and Electrical Box
Pressure
Vessel
Electrical Box
• The pressure vessel
will connect to the
electrical box that
will connect to the
large payload
(carrier)
Carrier
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Pressure Vessel
Pressure Vessel
• Top view
Star
Camera
• Side view
Flight
Computer
Hard drive
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Electrical Box
Electrical Box
• Top View
Gyro Board
• Side View
P-Sync
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EPS: Trade Studies
• Show rationale for you choices in components. You basically weigh your options
against your requirements and what each component can offer. Don’t forget things
like: availability, cost, and prior knowledge. I recommend an online search for
examples if you are unsure, or contact me.
• You should have completed a trade
µController
study for each block, but you only need
XMega
ATMega 32 L
Cost
to present the 2-3 most important.
8
10
Availability
• Numbers are relatively subjective, but
10
10
Clock Speed
10 should represent a perfect fit, 5 will
10
5
work, but is not desirable, and 0 does
A/D Converters
9
5
NOT meet expectations.
Programming Language
8
8
• The component with the highest
Average:
9
7.6
average should drive your choice for
design.
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PV: Risk Matrix
PV.RSK.1: Mission objectives aren't met if the pressure vessel leaks.
PV.RSK.2: Mission objectives aren't met if pressure vessel opens entirely/explode.
PV.RSK.3: Mission objectives are affected if the pressure vessel could not provide
the right pressure.
PV.RSK.4: Mission objectives are affected if the pressure vessel detached from other
components
PV.RSK.5: Mission objectives are affected if the pressure vessel gets dented after
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landing.
CCM: Risk Matrix
CCM.RSK.1: Mission objectives are affected if heaters could not provide enough
energy.
CCM.RSK.2: Mission objectives are affected if thermometers fails to measure
data correctly.
CCM.RSK.3: Mission objectives are affected if heaters fails provide excessive
energy;
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VRB: Risk Matrix
VRB.RSK.1: Mission objectives aren't met if power supply cannot give enough
power for the whole system.
VRB.RSK.2: Mission objectives are affected if voltage regulation board fails in
provide the correct voltage.
VRB.RSK.3: Mission objectives aren't met if power supplies excessive amounts
of current.
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UB: Risk Matrix
PV.RSK.1: Mission objectives are affected if the unpressured box opens.
PV.RSK.2: Mission objectives are affected if the unpressured box gets damage.
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Gyro Selection
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Gyro Overview – Block Diagram
• Show your subsystems, now with more detail inside the boxes, and the
connections between them
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Subsystem Design Section
• This section is where you explain how each subsystem was
designed
• Start with your organization chart with each of your subsystems
labeled
• Discuss how you researched components that would meet your
requirements
– Show trade studies if necessary, and if you show them, be
prepared to explain the scoring and categories
• The most important part is explaining how you reached your major
design decisions in each subsystem
• After explaining components, discuss any risks associated with this
subsystem
*
Gyro: Trade Studies
• Show rationale for you choices in components. You basically weigh your
options against your requirements and what each component can offer. Don’t
forget things like: availability, cost, and prior knowledge. I recommend an
online search for examples if you are unsure, or contact me.
Gyro Trade Study
ITG3050
L3G4200D
LPY403AL
G200
Price
9
9
7
2
Range
10
10
10
10
Sensitivity
7
7
9
10
Noise Performance
4
4
9
10
Robustness
7
8
8
9
7.5
7.5
8.75
8
Average
Rating From 1-10
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RAS: Risk Matrix
RAS.RSK.1: Mission objectives are affected if a gyro fails or sends corrupted
data to signal processing.
RAS.RSK.2: Mission objectives are affected if the Magnetometer fails or sends
corrupted data to signal processing.
AAS.RSK.3: Mission objectives are affected if the Clinometer fails or sends
corrupted data to signal processing.
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Prototype Assembly and
Testing
Payload Prototype Assembly
• Construct metal box of identical dimensions to
actual payload in order to test different part
positioning
• Things to consider:
– Positioning of all the parts relative to each
other
– Vacuum chamber integrity
– Insulation positioning
Sensor Testing
• Once all the parts are hooked up together and
functioning, the multiple sensors present on the
payload must be tested
• Things to consider
– Sensor calibration
– Sensor positioning within the payload
– Reliability and accuracy of each sensor
Gyroscope Testing
• After the completion of gyro fabrication, test all
gyros for proper functioning separately, then
together as a system to guarantee that each
board operates both by itself and in a system
• The accuracy and precision of the final gyroscope
unit will be measured in a variety of tests
Temperature Regulation Requirements
• The payload electronic parts must remain in a
certain temperature range to ensure proper
function
• Temperature of the electric board(s) must be
above 5°C but below 60°C
• To ensure this is met, the prototype of the
payload must be put under extensive testing in
extreme temperature conditions
Important Factors to consider
• Insulation – a insulating layer must be present to slow
down heat dissipation from and into the vessel
• Ventilation – there must be circulation in the payload to
ensure that the hottest parts do not overheat too quickly
• Thermostat heating – we plan on having an on-board
thermostat with a heating element to heat up the system
if the air inside goes too low
Testing the Prototype
• There are two conditions under which the system must be
able to function
– Room temperature: the heat dissipation from the
prototype vessel must be great enough so that it does
not overheat, which means the excessive insulation
must be avoided
– Upper stratosphere temperature (-5°C): the
thermostat must be able to heat the system in the case
in which the heat from the functioning parts is
insufficient to maintain functional temperature
Final testing
• Once the payload prototype is fully assembled and
all its parts are functional, it is important to leave
the entire system running for several days at a time
to identify any weak links in the physical and
software design
• Running for long testing periods will reveal elusive
coding bugs, design flaws, and system glitches that
could potentially occur in flight
Project Management Plan
Schedule
Work Breakdown Structure
Pressure Vessel:
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Trade studies
Designs and brainstorming
Sketch SolidWorks drawings
Electronic simulation and testing
in SolidWorks
Purchase materials
Preliminary fabrication process
Thermal testing and insulation
design
Test preliminary fabrication
design
Final compiling with electrical
components
Unpressurized Box
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Trade studies
Designs and brainstorming
Sketch SolidWorks drawings
Electronic simulation and testing in
SolidWorks
Purchase materials
Preliminary fabrication process
Thermal testing and insulation
design
Test preliminary fabrication design
Final compiling with electrical
components
Work Breakdown Structure (con’t)
Absolute Attitude Sensing:
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Trade studies
Determine memory storage method
Purchase lens
Test equipment
Install software
Test software
Write and test program for camera
Program automated storage of photos
Decide how the camera will be powered
Relative Attitude Sensing:
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•
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Trade studies
Purchase materials
design circuit
test design
assembly
mounting
Work Breakdown Structure (con’t)
Climate Control Monitor:
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•
•
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Trade studies
Purchase materials
determine climate stabilization
methods
design
Signal Processing:
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Trade studies
purchase materials
set-up and test computer
Test communications
set up downlink communication
Kalman filtering
Work Breakdown Structure (con’t)
Voltage Regulator Board:
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•
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Trade studies
design system
purchase materials
test
Budget
Team Contact Matrix