AMSAT Fox-1 Overview
AMSAT Engineering Team
2011 Space Symposium
Fox-1 Introduction
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AO-51 replacement
1-Unit CubeSat (4" x 4" x 4")
Target orbit 650 km
Magnetically stabilized
FM transponder
IHU for telemetry and command
Science experiment
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Fox-1 Operational Modes
• Transponder Mode
– FM repeater
– Telemetry data sent as low-speed FSK in sub-audible
band
• Command Mode
– Transmitter dedicated for data downlink
– High-speed FSK
– More power available for running experiment
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Special "ZombieSat" Features
• Designed to extend usable life
• FM Transponder will operate with dead cpu
• FM Transponder will operate without ground
station intervention
• FM Transponder will operate while in sunlight
even with dead (shorted) battery
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Fox-1 Systems
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Power System
Internal Housekeeping Unit (IHU)
RF System
Antennas
Science Experiment
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Fox-1 System Diagram
Solar
Cells
Power
System
Battery
Power bus
70 cm
Antenna
Science
Experiment
IHU
2m
Antenna
Sensors
RF
System
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Power System - Solar Panels
• 6 solar panels
• 2 cells per panel
• Spectrolab Ultra Triple
Junction
• Space-rated, high
radiation tolerance
• 28% conversion
efficiency
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Solar Cell Characteristics
Spectrolab UTJ, 27cm2, Full Sun, 28C
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volts / watts
2.5
2
volts
watts
1.5
1
0.5
0
0
100
200
300
400
500
milliamps
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Maximum Power Point Tracking
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volts / watts
2.5
2
volts
watts
1.5
1

0.5
0
0
100
200
300
400
500
milliamps
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Generated Solar Power
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Power (watts)
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X,Y
+Z
-Z
Total
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2
1
0
0
90
180
270
360
Degrees
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MPPT Operation
Solar
Panel
Switching
Supply
Pulse Width
Control
Power Bus
Max-voltage
Sense
Tracking
Algorithm
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Power System - Block Diagram
SPV1040
+Z Panel
MPPT
SPV1040
X,Y Panels
Power Bus
MPPT (x2)
Battery
Protection
SPV1040
-Z Panel
MPPT
Battery
3 x NiCd
PIC
I2C Interface
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Power System - Battery
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3 x NiCad cells
3.6 V nominal
10 watt-hours
10% depth of discharge
Charge: 0 to +45 C
Discharge: -20 to +60 C
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DC Power Available
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1.9 watts min in sunlight (no battery)
2.2 watts average (max eclipse)
2.8 watts average (no eclipse)
10 watts peak power
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Internal Housekeeping Unit
• Collects telemetry information
• Supports science experiment
• Sends telemetry as low speed FSK w/FEC in
transponder mode
• High speed FSK w/FEC in command mode
• Executes commands from ground control
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IHU Block Diagram
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IHU Microcontroller
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STMicroelectronics STM32L151VBT6
ARM3 Cortex CPU (32-bit)
Up to 33 MIPS @32 MHz
Designed for "ultra" low power consumption
128K FLASH program memory
16K RAM
On board RTC, D/A, A/D
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IHU Non-volatile FRAM Memory
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RF System
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70 cm FM receiver (uplink)
2 m FM Transmitter (downlink)
Transponder mode provides FM repeater
Command mode for running experiment
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Transponder Mode
70 cm
Antenna
CTCSS
Decoder
FM
Receiver
Commands
2-minute
Timer
Audio
IHU
PTT
2m
Antenna
FM
Transmitter
Low Speed FSK
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Command Mode
70 cm
Antenna
2m
Antenna
FM
Receiver
Commands
IHU
FSK
FM
Transmitter
Experiment
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RF System Design
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RF Power Amp
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Antennas
2 meter whip
70 cm whip
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VHF Antenna Pattern
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VHF Antenna SWR
2.0
1.5
SWR
1.1
1.0
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UHF Antenna Pattern
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UHF Antenna SWR
2.0
1.5
SWR
1.1
1.0
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Science Experiment
• Penn State University - senior design project
• 3-axis MEMs gyro sensor
• Measures satellite spin rate, spin direction
and wobble about the magnetic axis in orbit
• May include GPS receiver
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Fox-1 Team
Developers
Advisors
Logo by Steve Kenwolf
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Sound Like Fun?
• AMSAT is always hiring!
• Engineering: mechanical, electrical, systems,
software, project management
• Satellite construction: PCB layout, parts
procurement, surface mount construction,
parts machining, testing
Contact Tony Monteiro, aa2tx@amsat.org
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Any Questions?
AMSAT Engineering Team
2011 Space Symposium