AMSAT Fox-1 Overview

AMSAT Engineering Team

2011 Space Symposium

2

Fox-1 Introduction

• 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

3

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

• Power System• Internal Housekeeping Unit (IHU)• RF System• Antennas• Science Experiment

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Fox-1 System Diagram

RFSystem

BatterySolarCells

IHU

PowerSystem

SensorsScience

Experiment

Power bus70 cmAntenna

2 mAntenna

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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

8

Solar Cell Characteristics

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500

milliamps

vo

lts

/ w

att

s

volts

watts

Spectrolab UTJ, 27cm2, Full Sun, 28C

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Maximum Power Point Tracking

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500

milliamps

vo

lts

/ w

att

s

volts

watts

10

Generated Solar Power

0

1

2

3

4

5

0 90 180 270 360

Degrees

Po

wer

(w

atts

) X,Y

+Z

-Z

Total

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MPPT Operation

SwitchingSupply

SolarPanel Power Bus

Pulse WidthControl

TrackingAlgorithm

Max-voltageSense

12

Power System - Block Diagram

MPPT

MPPT (x2)

MPPT

BatteryProtection

Battery3 x NiCd

+Z Panel

-Z Panel

X,Y Panels

Power Bus

PICI2C Interface

SPV1040

SPV1040

SPV1040

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Power System - Battery

• 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

14

DC Power Available

• 1.9 watts min in sunlight (no battery)• 2.2 watts average (max eclipse)• 2.8 watts average (no eclipse)• 10 watts peak power

15

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

• 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

• 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

FMTransmitter

CTCSSDecoder

FMReceiver

70 cmAntenna

2 mAntenna

IHU

2-minuteTimer

Audio

PTT

Low Speed FSKCommands

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Command Mode

FMTransmitter

FMReceiver

70 cmAntenna

2 mAntenna

IHUFSK

Experiment

Commands

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RF System Design

23

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

1.0

1.1

1.5

2.0

SWR

27

UHF Antenna Pattern

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UHF Antenna SWR

1.0

1.1

1.5

2.0

SWR

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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 TeamDevelopers 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

Any Questions?

AMSAT Engineering Team

2011 Space Symposium