2001 University of Tokyo CUBESAT Project University of Tokyo CubeSat Project CRITICAL DESIGN REVIEW...

2001 University of TokyoCUBESAT Project

University of TokyoCubeSat Project

CRITICAL DESIGN REVIEW

April, 6, 2001

Intelligent Space Systems Laboratory

University of Tokyo

2001 University of Tokyo CUBESAT Project

■Contents

•Project Overview

–CubeSat program, Organization, Management, Schedule

•Mission Overview

–Design Assumption, Mission Objective, Mission Profile, Success Level

•System Design

–Design Strategy & Concepts

•Subsystem Details

–Electronics, Power, Communication, Structure, Environment, Ground Segment

•Concerns


Project Overview


■CubeSat Program

・ Proposed in University Space Systems Symposium. (Nov. 1998, Hawaii)

・ International educational program to improve students’ skill of space engineering and project management.

・ Quick and low cost development policy.

・ 10cm cubic satellite weighing less than 1kg.


■Project Constraints

・ 10cm cubic shape, weight less than 1kg.

・ Installed in the carrier called “P-POD”, developed by CalPoly.

・ P-POD is to be installed in MPA (Multiple Payload Adopter), developed by One Stop Satellite Solutions Inc.

・ Launched by Russian rocket “Dnepr” from Baikonur in November, 2001.

・ Orbit 600-800km circular, 60 degree inclination

・ HAM band operation


■CubeSat Developers

・ California Polytechnic State U ・ Dartmouth College・ Florida Space Institute・ Leland High School・ Montana State University・ Stanford University・ Stellar Innovations

・ Taylor University ・ Tokyo Institute of Technology・ University of Arizona・ University of Tokyo・ Wilcox High School


■CubeSat Program Organization

ISC Kosmotras OSSS Inc. Stanford U

CalPoly

Astro Reserch Co.

Japan・ U of Tokyo・ Tokyo Inst. of Tech.

U.S.A.10 Facilities

Launcher Provider

Japan-side Agency

Carrier Provider

OS2 Mission Organizer

CubeSat Developers

U.S.A.Japan

Russia


Dnepr LVLaunch weight 211 t Propellant amyl + heptyl Number of stages 3 LV diameter 3m LV length 34m Reliability 0.97Payload 400kg (800km)

1400kg (600km)(inclination 65deg)

MPAMass < 300kgIsogrid SpaceframeDeploys Payload SatellitesThree-axis Stabilization

P-PODDeployes 3 CubeSats

CubeSat

■Payload Configuration


■UT’s Project Organization

Prof. Nakasuka

Program Director

Y.Tsuda

Project Manager

Y.Arikawa

Electronics

Y.TsudaN.MiyamuraS.IshikawaT.MurakamiE.HwanK.Kanairo

T.Ito

Communication

Y.KatoT.EishimaS.UkawaS.Ihikawa Y.Kuwata T.Yamamoto S.Ganryu

N.Sako

Power

T.EishimaY.ArikawaS.UkawaR.FunaseS.Hori

N.Miyamura

Structure

T.ItoS.Ogasawara

P.Seo

Environment

N.SakoK.KanairoK.Muramatsu

S.Ogasawara

Ground Seg.

Y.TsudaT.MurakamiY.OdaI.Ikeda

・ 21 active members・ General meeting every 1-2 week(s)・ Subsystem meeting every week


■Development Milestone

XI-I・ Basic functional check

・ Technological demonstration for USSS conference

XI-II・ Bread board model

・ Validation of all technology to be used

XI-III・ Engineering model

・ Served to the integration & environmental testing

XI-IV,V・ Flight model & back up model

・ One for flight, the other for operation practice etc.

Communication test model, Mass model, CDR

Development code : XI [sai] (X-factor Investigator)


Mission Overview


■“XI” Outlook

Antenna

Camera Hole

Flight Pin Hole

Solar cells are to be attached on whole surface

Antenna Latch Mechanism

photo: XI-II (BBM model)


■Mission Description

■Mission Statement"To acquire the indispensable technology in developing super-

small satellite system"

■Mission・ Gathering the satellite’s health information via beacon signal.・ Command uplink & data downlink.・ Telemetry data broadcasting service.・ On-orbit verification of the commercial-off-the-shelves (COT

S) components.・ Imaging experiment as an extended mission. (TBD)・ Sending everyone’s message into space.


■Success Level (1)

■Project’s Minimum Success--- Acquiring the important technology and knowledge through designing and fabricating the spacecraft. ・ Establishing overall work flow of the satellite development project. ・ Establishing a methodology of spacecraft design. ・ Raising the fabrication technique. ・ Conducting several kind of testing and feeding back its results to the design. ・ Keeping the project progressing smoothly so as to bring it to be the launchable condition.

■Mission Success--- Receiving signals from the spacecraft. ・ Surviving in the actual launch environment. ・ Successfully verifying the function of the communication system. ・ Gathering house keeping data.


■Success Level (2)

■Full Success--- Succeeding in uplink & downlink. ・ Successfully commanding the spacecraft by uplink. ・ Getting downlink data as a reaction to the command uplink.

■Advanced Success--- Successfully verifying the function of the advanced mission components. ・ Verifying that sensors planned to be equipped as advanced mission components

should work normally.


■Mission Profile (1)

・ Launched by Dnepr from Baikonur in Nov. 2001.

・ MPA is put in 600-800km circular orbit with 60 degree inclination.

・ MPA deploys some of its payloads & activates P-POD.

・ P-POD deploys CubeSats.

・ CubeSat starts operation after a certain elapsed time.


■Mission Profile (2)

1. 2. 3.

■Post Ejection Stand-by

Main OBC is activated while the other components are off.

■Nominal Operation

Antenna is deployed. All components including beacon are activated except telemetry transmission system.

■Telemetry Transmission

This mode occurs as a reply to the uplink command from ground station.


System Design


■Basic Specifications

●Structure 10cm cubic, 1kg, Aluminum A7075 body

●Main ProcessorOBC PIC16F877 4MHz （ Program memory 8k, RAM 368)Data Recorder EEPROM 32k + 224k

●Communication SystemDownlink 437.490MHz, FSK, AX.25, 1200bps, 600mWUplink 145.835MHz, FSK, AX.25, 1200bpsBeacon 436.8475MHz, CW, 100mW

●Power SystemBattery Manganese type lithium-ion battery, 8 parallelSolar Cells Single crystal silicon, 60 cellsBus Voltage 5V

●Attitude Control Passive stabilization using permanent magnet

●Sensors Voltage, Current, Temperature, Area sensor

StructurePower

Com1Main

Com2

Important Analog Sensors

Analog Sensors

Digital Sensors Antenna Latch

Battery

Solar Cell

DC-DC1

DC-DC3 OBC

ROM TX TNC

RX TNC

CW Gen

TX

RX

CWCharge Circuit

OBC

RX TNC

Analog SW

TX

uSW

Flight Pin

Flight Pin PWR5V

TLM

TLM

CMD

TLMACK

DC-DC2

OBC

PWR5V


■Internal Function Design Strategy

Battery

Solar Cell

Camera Module

Temperature Sensors Communication Unit

Power Unit

Data Handling UnitMother Board

Electronics Subsystem

Power Subsystem

Communication Subsystem

Structure Subsystem

■Mother board intervenes inter-subsystem signal & power flow．


Structure Subsystem


■Structure Subsystem

3. 　 Antennae DeploymentMechanisma) 　 Magnetic Plungerb) 　 Folding Method

1. 　 Body of CUBESATa) 　 Assemblyb) 　 Weight and Center Of Massc) 　 Materiald) 　 Size

4. 　 Strength Analysisa) 　 Behavior as Cantilever Beamb) 　 Ceiling panel’s vibrationc) 　 Load Estimationd) 　 Countermeasure　　 for vibration(Antennae)

2. 　 Interfacea) 　 Flight Pinb) 　 External Input/Outputc) 　 Connectord) 　 Kill Switch


■Body of CUBESAT

a) 　 Assemblyb) 　 Weight and Center Of Massc) 　 Materiald) 　 Size

Center Of Massx

y

z


■Assembly of XI-II

■ First, Subsystem Boards are attached to Mother Board.

■ Then,that module is attached to 4 pillars.

■ Finally,Solar Cell panels covered CUBESAT’s surface.

Panels to put up solar array on

The mainstay of XI-II+x panel

+y panel

+z panel


■Construction of subsystem board

■ Each subsystem board is attached to Mother Board.

■ Battery and I/F connectors are also attached to Mother Board.

Transceiver

Communication board

Main motherboard

Sub motherboard

Battery box

Power board

Electronic board

I/F board


■Center Of mass

■ The difference of geometric center between center of mass

is 　 7.8mm　　(within 20mm)

■ Total mass is

990g　 (within 1kg)

Center Of Massx

y

z


■Material

■ A7075 is the same material of P-POD which means that

thermal expansion is equal.

USE PRODUCTMain Structure A7075PCB Glass EpoxyBattery Li- ion Rechargeable batterySolar Cell Si- CellIC Plastic PackagedWiring Teflon coated

Bolt,Nut SteelAntenna Convex tape


■Front view of XI-II

■ Solar cells mounted on EXTERNAL MOUNTING SURFACE do NOT exceed 6.5mm

■ Antennae are also mounted on EXTERNAL MOUNTING SURFACE.


■Bottom view of XI-II

■ Antennae are mounted within 6.5mm.

■ 2 Kill Switches are mounted on this plane.


■Interface

a) 　 Flight Pinb) 　 External Input/Outputc) 　 Connectord) 　 Kill Switch


■Installation of CUBESAT

■ 3 CUBESATs can be installed in a P-POD carrier.

■ We can get some experimental data from I/F hole before launch.


■Interface System

Plunger

Flight PinV up

V down

Antenna Deployment Order

Charge up

Charge down

GNDBattery VDCDC 5V for electronicsDCDC 5V for communicationDCDC 10V V operate 4VExternal TxExternal Rx

Subsystem

External InterfaceRJ-45

12345678

MicroSwitch Switch Unit

Switch Unit

Flight Pin 2


■Mother Board

■ All Subsystem Boards are attached to Green connector.


■Interface Board

■ All External I/F is allocated to Interface Board■ Interface Board has some module as follows.

• Kill Switch

• Before-Flight Pin

• External I/O Connector

RJ-45 Connector

Before-Flight Pin

Kill Switch


■External Interface

■ We use RJ-45 connector.■ Even if CUBESAT is installed in the P-POD , we can get the data

witch the table shows.

No(Ext) Name Function

1 GND(1) Ground

2 BATT(2) Battery

3 E- DC(3)DCDC- Converter(for Erectricsubsystem) output

4 C- DC(4)DCDC- Converter(for Communicationsubsystem) output

5 Tx- DC(5)DCDC- Converter(for TelemetryTransmitter) output

6 EXT Tx(36) External serial Tx

7 EXT Rx(37) External serial Rx

8 VTO CMOS Image sensor NTSC signal

8,7,6,5,4,3,2,1

RJ-45 Connector

RJ-45 Plug


■Kill Switch

■ We use 2 Kill Switches in parallel for redundancy.■ When one of 2 switches is ON , all system can get

power.

OFF ON

Kill Switch


■Flight Pin

■ Switch1:Supplying power to the system.■ Switch2:OPEN/CLOSE battery charging circuit.

Sw

itch

1

Sw

itch

2


■Antennae Deployment Mechanism

a) 　 Magnetic Plungerb) 　 Folding Method


■Antenna Deployment System

■ Antenna is deployed using Electromagnetic Plunger

+V is impressed

The piece is capturedby the magnet Magnetic Power decreases

And the piece is released

Electromagnetic Plunger fa = 3.5 [N] min. fb = 0.8 [N]

fa

fb


■Antenna Deployment System

Antenna Deployment Video


■Strength Analysis

a) 　 Behavior as Cantilever Beamb) 　 Ceiling panel’s vibrationc) 　 Load Estimationd) 　 Countermeasure for vibration(Antennae)


■Behavior as Cantilever Beam[1]

■ If CUBESAT experiences very strong vibration, it may behave as a cantilever beam.

■ In this case , the Harmonic

Frequency is around 20[kHz] (witch is enough high, comparing to the launch vehicle’s

frequency)


■Ceiling panel’s vibration[1]

■ Harmonic Frequency is around 1 - 2 [kHz]

■ The Harmonic Frequency largely depends on the thickness of the panel.

■ The thicker the panel is designed , the higher the Harmonic Frequency becomes.


■Ceiling panel’s vibration[2]

■ To avoid ceiling panel’s vibration we have to design it as possible as thick.

■ For this design , Total Mass is large problem

■ Eventually,we have to choose around

1.0-1.5mm

Thi ckness of panelvs Harmoni c f requency

0. 0

0. 5

1. 0

1. 5

2. 0

2. 5

3. 0

0. 0 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5

Thi ckness of panel [mm]

Harm

onic

Freq

uenc

y(n=

m=1)

[kHz

]

920

940

960

980

1000

1020

1040

1060

1080

1100

Tota

l Ma

ss[g

]

Harmoni cFrequencyTotal Mass


■Load Estimation

■ The 3rd CubeSat experiences maximum load while 2nd stage flight• The maximum stress is

0.011kgf/mm2

(enough for Aluminum use)

P-POD

Maximum Stress

7.7g

(max

)


■Countermeasure for vibration(Antennae)

■ To complete any mission , fastening and deploying antennae is very important.

■ It is difficult to simulate the behavior of the antenna , so we conduct some experiments to confirm the feasibility of this design.

■ Fixing antennae with several points.


■Function of Electronics

• Health monitoring • Command & data-handling• Resetting DCDC• Antenna deployment • Controlling area sensors

Our Works

• Satellite system management• Capturing images with area sensors

Our Goals


■Block Diagram

OBC

OBC Program&

ROM Read/WritePins

SDA Line

SCL LineROM0ROM0ROM0ROM0ROM0ROM0ROM0ROM0

Thermometer0 to 7

MPX

MPX_SEL0 ~2

Battery VoltageCharge Current

Reset Signal (Power Sub Sys.)

Battery Charger IC Reset Signal

SEL Detect

C-DCDC 5VTo CommSub Sys.

E-DCDC 5V

CW-CtoE

CW-TNC

Tx-TNCTx-CtoE

CW-EtoC

Tx-EtoC

Rx-EtoC

Rx-CtoE

Rx-TNC

(Structure Mother Board)

Solar Cell Current 1 to 6MPX


■Command　 & Data-Handling

Ground Station in UT

OBC

Tx-TNC CW-TNC

ANTD /CRNT /DCDCMTQC /POWR/ROMDSOLA /TEMP /VOLT

Uplink Command

CRNT /ROND /SOLATEMP /VOLT

Fixed length = 17 bytes


■Command & Data-Handling(2)

●Antenna deployment ●Requesting current data (Total , Solar Array , C-DCDC , E-DCDC) ●Resetting C-DCDC ●Resetting charging circuit ●Requesting EEPROM data ●Requesting temperature data (Battery , Solar Array , FM-Transmit) ●Requesting voltage data (Battery , Solar Array)



●Current ----- 9 bytes (Total , Solar Array , C-DCDC , E-DCDC)●EEPROM Data ----- Undecided●Current & Temperature of Solar Array ----- 12 bytes●Temperature ----- 8 bytes (Battery , Solar Array , FM-Transmit)●Voltage ----- 2bytes (Battery , Solar Array)



Time

Status

Picture

Current

Voltage

Additional Data

3 bytes

1 bytes

1 bytes

2 bytes

9 bytes

1 bytes


■Components of Electronics

ROM Module

ROM READ/WRITE Pin

For Thermometer

For Camera

JumperPin For ROM

XI-II model


■Components of Electronics-(2)

OPAmp Module

Thermometer Module

Program Pin

XI-II model


■Components of Electronics-(3)

ROM (24LC256)

　　　　　　

PIC 16F877

• Clock :4MHz• Memory :8kword• RAM :368bytes• EEPROM :256bytes• Operative Voltage:2.0~5.5V

• I2C serial EEPROM• Memory :256Kbit(32Kbyte)• Max erase/write cycles:100,000• Max write-cycle time :5ms• Max clock frequency :400kHz


■Thermal Monitoring

Thermal Sensor ( Thermal Sensor ( LM335Z )LM335Z ) ・ Power consumption:5mW ・ Measuring range :-40~100℃ ・ Characteristic :10mV/℃ ・ Precision :±1℃

MonitoringMonitoring ・ Temperature of Battery, Solar Panel(6) and Transceiver. ・ AD converting a data & sending it to comm subsystem.

Thermal Sensor Calibrationy = 99.218x - 270.29

-505

10152025303540

2.7 2.8 2.9 3 3.1Voltage[V]

Tem

pera

ture

[℃]

● data―linearized


■Function of Reset-(1)

E-DC OBC

Rx-TNC

V in

Pch FET

Pch FET

ac

P.U.

P.U.

P.U.

P.D.

P.D.

P.U. = Pull UpP.D. = Pull Down

C-DC

SEL Detect

Nch FET

Nch FET

SEL Detect

CW-GEN

Tx-TNCPch FET

bd

e

A

A

ba c d

Tx-DCe


■Function of Reset-(2)

CPU

If a=1&b=0

DCDCVin

Two wire AND reset system using FET

• PchMOSFET• NOT gate

Switching CircuitSwitching Circuit

For SEL tolerance, reset function is needed.Reset system requires high reliability so as not to shut off continuously even in CPU malfunction case.


Communication Subsystem


■Communication System Diagram

OBCOBC

Tx TNCPIC16C622

Rx TNCPIC16C711

ModulatorMX614

DemodulatorMX614

Telemetry data Beacon data Up-link command

AD Convert

AX25 Coded datawith Parity

FSK modulated command

AX25 Coded command

Morse Coded dataPTT Control

Half wave lengthdipole antenna

Half wave lengthmonopole antenna

Nishi RF Lab.Custom made

FM transmitter

Nishi RF Lab.Custom made

CW transmitter

Nishi RF Lab.Custom madeFM receiver

SensorsSensors

FSK modulated data

Antenna SW

switching

NegotiationMorse encoder

PIC16C716

PLLControl

PLLControl

PLLControl


Telemetry Transmission System


■Tx TNC (AX.25 encoder)

■Tx TNC ： Micro controller PIC16C622－program memory(EPROM) : 2 kbyte－data memory(RAM) : 128 byte－clock : 4 MHz－I/O port : 13 (4 AD Converters)－power consumption : 2.0 mA @ 5V

■Tx TNC receives telemetry data from OBC ■Puts Parity byte for error detection■Encodes the telemetry data with AX.25 protocol■Sends encoded data to FSK modulator

PIC16C622

AX.25 Protocol■This protocol is mainly used for data transmission by HAM■Every Amateur Radio Station all around the world can decode our telemetry data!!!

Flag Destination Source Control PID parity data parity data FCS Flag

AX.25 frame structure(with Parity)


■Tx TNC Program

Receive data from OBCReceive data from OBC

Packetize into AX25 formatPacketize into AX25 format

data from OBC ?data from OBC ?

Yes

No

Send packet to FSK modulatorSend packet to FSK modulator

Start & InitializationStart & Initialization


■FM Transmitter

FM transmitter System Diagram

■FM Transmitter is used to transmit telemetry data■Nishi RF Laboratory custom made transmitter

－frequency:－band width:－RF output power:－input power:－operative temp.:－volume:　　　　　　　　　　　　　　 (including CW transmitter)

437.490MHz20kHz1Wunder 6W-30℃ ～ +60℃90×60×10cm FM transmitter


Beacon Transmission System


■CW Generator (Morse encoder)

■Morse encoder ： Micro controller PIC16C716－program memory(EPROM) : 2 kbyte－data memory(RAM) : 128 byte－clock : 4 MHz－4 AD Converters (8bit)－power consumption : 2.0 mA @ 5V

■CW generator receives beacon data from OBC■Monitors sensor data independently from OBC (Countermeasure of OBC’s hang up)■Generates Morse code ■Controls the KEY of CW transmitter■Data rate : human decodable speed

Beacon data format"UT1" "UT4"

"UT2" time1 time2 time3 "UT5"tmp.

battery1tmp.

battery2tmp.

battery3tmp.

battery4tmp.

battery5tmp.

battery6

"UT3" Status Camera status battery V "UT6" tmp. Panel1

tmp. Panel2

tmp. Panel3

tmp. Panel4

tmp. Panel5

tmp. Panel6

"www.space.t.u-tokyo.ac.jp" total I tmp. battery tmp. Panel

PIC16C716


Data Sampling

■CW Generator Program

Start & InitializationStart & Initialization

Data sensing (AD Convert)Data sensing (AD Convert)Receive data from OBCReceive data from OBC

UT1 www.space.t.u-tokyo.ac.jpUT1 www.space.t.u-tokyo.ac.jp

Yes

No

No

YesOBC ready

to send data?

OBC ready to send data?

Counter < 10secCounter < 10sec

UT2 AA BB CC UT2 AA BB CC

UT3 DD EE FF UT3 DD EE FF

UT4 GG HH II UT4 GG HH II

UT5 JK LM NO UT5 JK LM NO

UT6 PQ RS TUUT6 PQ RS TU

Data Sending


Command Receiving System


■Rx TNC ： Micro controller PIC16C711－program memory(EPROM) : 1 kbyte－data memory(RAM) : 64 byte－clock : 4 MHz－4 AD Converters (8bit)－power consumption : 2.0 mA @ 5V

■Rx TNC receives AX.25 encoded command from FSK demodulator■Decodes it and sends command to OBC

OBC Reset System■If the command is “Reset Command”, resets OBC■Monitors OBC’s current and resets OBC in case of SEL (Countermeasure of OBC’s SEL)

■Rx TNC (AX.25 decoder)

PIC16C711


■Rx TNC Program

Interruption RoutineStart & InitializationStart & Initialization

set ‘Receiving’ flagset ‘Receiving’ flag

Reset OBCReset OBC

Command = “rset”or flag_rst = 1 ?

Command = “rset”or flag_rst = 1 ?

clear ‘Receiving’ flagclear ‘Receiving’ flag

Receive Uplink commandReceive Uplink command

Wait 10 [ms]Wait 10 [ms]

Send serial data to OBCSend serial data to OBC

Yes

OBC ready to receive?OBC ready to receive?

flag_rst = 0flag_rst = 0

No

No

Main Routine

Yes

‘Total I’ > Threshold ?‘Total I’ > Threshold ?

flag_rst = 1flag_rst = 1

A/D convert ‘Total I’A/D convert ‘Total I’

Yes


■FM Receiver

■FM Receiver is used to receive up-link command■Nishi RF Laboratory custom made receiver

－frequency:－input power:－receive sensitivity:－receive output:－operative temp.:－volume:

145.835MHzunder 100mWunder -16dBμ16dBV typ.-30℃ ～ +60℃50×60×10cm

FM receiver


■Antenna Configuration

Antenna for Receiver144MHz Half wavelength monopole antenna

Antenna for Transmitters430MHz band Half wavelength dipole antenna


■Antenna Pattern (Transmitter)

Antenna Absolute GainTransmitters' Half wavelength dipole Antenna

(dBm)

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

5.00

Gt

Gt,req

The gain which we can decode the data in our ground station


■Antenna Pattern (Receiver)

Antenna GainReceiver's Half wavelength monopole antenna

(dBm)

- 55.00

- 50.00

- 45.00

- 40.00

- 35.00

- 30.00

- 25.00

- 20.00


■Link Budget (Telemetry Tx)

Symbol Unit Telemetry RemarkFrequency f MHz 437.400Transmit P ow e rP W 0.600 ParameterTransmit P ow e rP dBW -2.218Transmitter Line Loss Ll dB -3.000 Usually -1dB -3dB～Transmit Antenna Half-Power Beamwidthθ t deg 110.000 Ideal dipo l ePeak Transmit Antenna Gain Gpt dB 2.148 Ideal dipo l eTransmit Antenna Pointing Offset et deg 90.000 UncontrolledTransmit Antenna Pointing Loss Lpt dB -8.033Transmit Antenna Gain Gt dB -5.885Equiv. Isotropic Radiated Power EIRP dBW -11.103Propagation Path Length S km 1439.940 50kbyte/1passSpace Loss Ls dB -148.434Propagation & Polarization Loss La dB -0.470 Polarization (-0.3dB)Peak Receive Antenna Gain Grp dB 12.500 GS 435HS20Receive Antenna Half-Power Beamwidthθ r deg 29.000 GS 435HS20Receive Antenna Pointing Error er deg 15.000 AssumptionReceive Antenna Pointing Loss Lpr dB -3.210Receive Antenna Gain Gr dB 9.290System Noise Temperature Ts dBK 25.700Data Rate R bps 1200.000 MX614Eb/ N 0 Eb/ N 0 dB 21.390Bit Er ro r Ra t eBER 0.000Required Eb/N0 Req Eb/N0dB-Hz 13.000 FSK, BER=10-5

Implementation Loss dB -5.000Margine dB 3.390

Link BudgetTelemetry (TDMA)

UT’sGround Station

CUBESATComm. System


■Link Budget (Command Rx)

Symbol Unit Uplink RemarkFrequency f MHz 145.835Transmit P ow e rP W 20.000 ParameterTransmit P ow e rP dBW 13.010Transmitter Line Loss Ll dB -3.000 Usually -1dB -3d B ～Transmit Antenna Half-Power Beamwidthθ t deg 33.000 GS 144HS12Peak Transmit Antenna Gain Gpt dB 10.000 GS 144HS12Transmit Antenna Pointing O ffs e tet deg 15.000 AssumptionTransmit Antenna Pointing Loss Lpt dB -2.479Transmit Antenna Gain Gt dB 7.521Equiv. Isotropic Radiated Power EIRP dBW 17.531Propagation Path Length S km 1439.940Space Loss Ls dB -138.894Propagation & Polarization Loss La dB -0.470 Polarization (-0.3dB)Peak Receive A nte nn a Ga i nGrp dB -2.521 MonopoleReceive Antenna Half-Power Beamwidthθ r deg 100.000 MonopoleReceive Antenna Pointing Error er deg 90.000 UncontrolledReceive Antenna Pointing Loss Lpr dB -9.720Receive Antenna Gain Gr dB -12.241System Noise Temperature Ts dBK 31.100Data Rate R bps 1200.000Eb/ N 0 Eb/ N 0 dB 32.634Bit Er ro r Ra t eBER 0.000Required Eb/N0 Req Eb/N0dB-Hz 13.000 FSK, BER=10-5

Implemention Loss dB -5.000Margine dB 14.634

Link BudgetUplink Command

CUBESATComm. System

UT’sGround Station


Power Subsystem


■Power Subsystem

AAAAAAA

ChargeCircuit

Batteries

A

SwitchingRegulator


A

SwitchingRegulator

Communication Subsytem

DCDCConverter

Tx

TNC OBC OBC


■Power Subsystem(CONT’D)

■ Supply a continuous source of electrical power to loads.• Power source is solar panels.• Batteries are used for storage• Regulated DC power and unregulated power is

supplied for loads.• Power consumption is monitored for SEL.


■Power Regulation & Control

■ Bus voltage: main 5[V]■ Regulated to 5V using

switching regulators and DCDC converter

■ Elect. subsystem power line & Comm. subsystem power lines are independent so that they monitor each other and shutdown in case of SEL


■Source

■ Power is supplied by body mounted solar cells.

■ Cells are arranged on all 6 CubeSat surfaces.

■ Average power 1228 [mW] (typ @ 80 )℃


■Solar Panel

■Cell type : Si Crystal (SHARP)■Efficiency : 16%■10 cells in series / panel■Cell size:

+X :28.25x13.8mm-X,+Y,-Y:47.75x13.8mm+Z,-Z :47.75x15.8mm

Bass bar

Photo:3 cells in series


■Solar Array Layout (+X panel)

+X panel:

4.5V x 172mA = 774mW(typ. @ 25 )℃

4.5V x 162mA = 727mW(typ. @ 80 )℃


■Solar Array Layout (-X,+Y,-Y panel)

-X,+Y,-Y panels:

4.5V x 297mA = 1336mW(typ. ＠ 25 )℃

4.5V x 279mA = 1256mW(typ. ＠ 80 )℃


■Solar Array Layout (+Z,-Z panel)

+Z,-Z panels:

4.5V x 340mA = 1530mW(typ. @ 25 )℃

4.5V x 319mA = 1438mW(typ. @ 80 )℃


■Energy Storage

■ Batteries will be used during eclipse and downlink

■ Liion secondary batteries are selected.

■ 8 batteries are set in parallel.■ DOD is 3%■ Batteries only lifetime is 38 hr

s


■Liion battery

Cathode Material Lithium Manganate

Anode Material Carbon

Operating Voltage 3.8[V]

Discharge Capacity 780 [mAhr]

Single Cell Spec.


■Battery Charger

■ 3 candidates for Battery Charge Circuit

MAX1679

•Small package (8 pins), small power dissipation•Voltage&Temperature protection•Pre-charge, Timeout

•Need constant reset before IC’s timeout

MM1333

•Small package (8 pins), small power dissipation•Const. Voltage & Current Charge Mode

•No pre-charge func or temperature protection

MM1485

•Small power dissipation•Const. Voltage & Current Charge Mode•Pre-charge Temperature protection

•Large package (16 pins) and may be difficult to assembly


■Energy Consumption

OBC 20 All timessensors 20 All timesTx TNC 20 During downlinkTx 6000 During downlinkCW 300/125 All times (ON / OFF)CW TNC 20 All timesRx 125 All timesRx TNC 20 All timesCamera 150 SometimesMagnetic Plg. 800 Antennae deployment

Components Power[mW] Frequency in use


■Power Balance

■ Points• Beacon can be sent by solar panels direct drive• Source and consumption must be balanced

■ Solar cell average output 1228[mW] > Consumption at beacon use 900[mW]

■ Maximum average supply power: 669[mW] > Average consumption 616[mW]

OK

OK


■Attitude Control

■ Objectives• To make CubeSat tumble in order to smooth thermal

input• Point antennae to the ground station

■ Methods• Use a permanent magnet and a libration damper


■Control Mechanism

■ Torque will be generated to align earth magnetic direction and CubeSat’s dipole moment.

■ Libration is damped by energy dissipater.

Magnetic Field

Dipole Moment

Antennae

Ground Station


■Torquer Sizing

Required Torque1.0E-6 [Nm]

Required Magnetic Dipole Moment 0.046 [Am^2]

AirDrag 2.26E-10

Solar Pressure 1.38E-9

Gravity Gradient 1.25E-8

To follow the change of magnetic field

Disturbance Torque[Nm]

1.0E-6At 800km magnetic field


■Permanent Magnet

Material Alnico-5

Magnetic Dipole Moment 0.05 [Am^2]

Size φ4*25 [mm]

Weight 2 [g]

Residual Magnetic Flux Density 1300 [mT]


■Libration Damper

■ Libration damper dissipates energy to stable attitude change.• Dissipation caused by hysteresis loss and eddy curre

nt loss• High permeability iron is used for the damper• 3days are expected (8 days for worst case) to damp o

scillation


Environment Subsystem


■Environmental Tests (outline)

Tried and Tested

Future Works

■Heavy ion testing(PIC16F877 F84 C622 C774)

■Heavy ion testing(PIC16F877 C774 C622)

■Li -ion battery testing (in a vacuum) ■C-MOS Camera testing

(in a vacuum)

■ Thermostat EM-Plunger , Li -ion battery , C-MOS camera,Solar Panels

■ SEL testing DCDCs,OP-AMPs,Tx,Rx etc

■ Vibration testing Solar Panels , EM-Plunger,EM

■ Thermal Vacuum Chamber XI-II α , EM , FM1 , FM2


■Analysis (outline)

■ 　 thermal analysis We construct a model of heat transfer by means of the node point method using C-programming. We will complete building 50nodes model and fixing the value of every parameter from XI-IIα 　 testing.

■ 　 SEE analysis We calculated SEE rate using the CRÈME software and provided reset functions to XI-IIα.

( http://crsp3.nrl.navy.mil/creme96/ )


■Tried and Tested

■Heavy ion testing 　 ( at NASDA)2000.09.12 source ; Calfornium (Cf252)

Device Numberof SEU

Numberof SEL

Irradiationtime[sec]

Fluence[/cm 2̂]

SEE Cross Section[cm 2̂/bit]

F877 102 0 2502 332353 7.49272E-08

F84 101 3 1040 137956 3.57477E-07

C622 101 0 2599 344759 1.43046E-07

C774 101 0 2563 205669 1.19892E-07

(for quick look)


■Tried and Tested

■Heavy ion testing　 ( at JAERI Takasaki)2000.10.09 source ; 20Ne4+, 40Ar8+, 84Kr17+

Device SEU(Ne)LET=6.01

SEU(Ar) LET=15.1

SEU(Kr) LET=38.3

F877 1.6468E-07 2.1559E-08 ----

C622 8.4045E-10 9.6120E-09 -----

C774 1.8376E-08 2.4405E-08 4.1931E-08

■Using CREME96 Results,We decided to use PIC16F877.

Device SEUs/device/dayF877 2.3514E-05C622 1.26733E-06C774 2.550029E-07

(height 600km,incrination=60°)

cf. LET[MeV/(mg/cm^2)],SEU[cm^2/bit]


■Tried and Tested

■ Vacuum chamber testing- Li ion battery test (2001.01.21 - 23 at UT-Arakawa Lab.) No deterioration observed in 10^-5 Torr evacuated chamber.


■Analysis

Quick look

Height=600kmincrination =60°6 nodes (CUBE planes) mass density = Al densityspecific heat=920*9[J kg^-1K-1]conductivity=240[W m^-1K^-1]ε=0.825α=0.805

Temperature of 6- nodes

- 8- 6- 4- 202468

10

0 20000 40000 60000 80000 100000

time[sec]

Temp

erat

ure[

degr

ee C

]

T1T2T3T4T5T6


■Future Works

We have a plan to execute EM-Plunger and XI-II α test with thermal vacuum chamber. (2001.04.10. - at ISAS Ohnishi Lab.)

CW CW

Rx-TNCRx-TNC

Tx-TNCTx-TNC

OBCOBC

Battery

Vin(5V)

GND

PIC 5VMpx.B

A/D

Serial

SW

9-wires

Thermocouple sensor

flanged１flanged２(Dsub50)

BNC→ ONS

flanged２(Dsub50)

flanged２(Dsub50) Temperature sensor

Wires× 3GND


■Future Works

Battery ON

OBC status(Serial)with checking telemetry

Communication system status

CW,Rx-TNC,Tx-TNC

Long timerunning

RunningOBC only

E5V C5V 10V Vop

RunningThermometerfor checking

yes

yes

yes no

no

Executing partial test.


■Future Works

CW Rx Tx

Rx and Txcommunicate 300times per 5 minutesand suspend for25 minutes .

CW speak at all times.

...

...

...

...


■Outgas Examination

We choose following products from out-gas point of view.

USE PRODUCTWiring Fluorocarbon wires (Hitachi Cable Ltd.)RTV LTV rubber KE1204(AL or BL)Rubber Si rubber KE9610/C-8BBonding Agent SYLGARD184 ; FSXA-2869

※However, they are not fixed yet.

USE TML CVCM WVRWiring <0.1 <0.01RTV 0.597 0.117 0.007Rubber 0.846 0.052 0.736Bonding Agent 1.740 0.660 0.040


■Work Room

Work Room Environment

We will construct isolated work space to manufacture EM,FM1,FM2.(aiming at 1000-level clean room)

※Air conditionerHEPA Unit(SS-MAC) YAMATO science co.


Ground Segment


■When can we contact?(1)

Pass time for 1 week

0

100

200300

400

500

600

700800

900

1000

05.

212

.427

.134

.349

.056

.161

.376

.197

.897

.810

6.7

121.

313

0.1

144.

715

1.7

166.

3

Simulation passage time[hr]

Pass

tim

e[s

ec]



最大迎角

0

10

20

30

40

50

60

70

80

90

1 3 5 7 9 1113 15171921 232527 29313335 373941 43454749

Max

imum

ele

vati

on a

ngle

(de

g)

Pass #



•There are 49 passes. which means we can contact with our CubeSat 6 or 7 times per day.•In those passes, 22 passes have an elevation over 20[deg].•The longest pass time is about 900[sec].•We have 1 or 2 chances to contact for 900[sec] everyday.


■Necessary Time for Communication

CW Beacon Downlink•CW Beacon is consist of 73 words.•If duty ratio is 0.3, it takes about 240[sec] to send 73 words. (60 words per minute )

FM Packet Telemetory downlink•Packet length is about 80 bytes.•Baud rate is 1200 [bps] , so it takes 0.54[sec] to receive a packet.


■Operation Plan

CW Beacon Uplink Command

If we can receive the CW Beacon,we send Uplink Command once or twice a day.

FM Packet 1200bps


■How to handle Downlink Data

We expect it may be difficult for us to receive and decode downlink data perfectly,so we prepare backup system to get something of traces of downlink data.

•Recording CW Beacon & Telemetry Packet to Mini Disk.•Original TNC skipping CRC (check sum).


■Ground Station Equipment(1)

144MHz/430MHz Antenna Transceiver, TNC, etc.



•144MHz/430MHz cross Yagi antenna [WHS32N, MASPRO]•430MHz cross Yagi antenna (TBD)

•Antenna rotator & controller for azimuth [750FX, EMOTATOR]•Antenna rotator & controller for elevation [EV800, EMOTATOR]

•VHF/UHF multi band all mode transceiver [IC-970J, ICOM]•VHF/UHF multi band all mode transceiver (Equipped for 9600bps packets) [IC-910D, ICOM]



•TNC [TNC505,TASCO]•TNC (With function to co-decode CW signal) [TNC555, TASCO]•TNC (Skipping CRC) [handmade]

•Signal converter [I/F between PC and rotators]•Level converter [CT17, ICOM (I/F between PC and Tranceivers]

•PC (OS:Window98)

•MDLP mode MD recorder (TBD) [MDS-S50, SONY]×2


■Ground Station Configuration

IC-970J

IC-910D

TNC-505

TNC

TNC-555

PC(Windows98)MD recorder

MD recorder

Telemetory

Command

CW beacon

144MHz uplink

430MHz Telemetory downlink

430MHz CW downlink

EV-800

750FXSignal

converterCT17

Frequency, Azimuth, Elevation

http://www.space.t.u-tokyo.ac.jp/cubesat


■Message Mission

■ Message from all over the world will be microfilmed and packed in CubeSat

■ Themes are • Dreams for space• CubeSat mission proposal etc.

■ Messages are accepted by postal cards.

■ Details are uploaded to WebPages


■Program Timeline

CDR(3/19)*postponed

TCDR FM DeadlineMass Model Shipment

Long Range Comm. Experiment

74 5 63 8 9 10 11

EM Deadline

FM Shipment (8/15) Launch

red char. : contract matter


■Concerns (Electronics)

■ We made a reset system for countermeasure against SEL, but still do not decide the SEL threshold current. How do we decide it and how much should we have a margin for it?

■ For countermeasure against SEU, we will set only Watch Dog Timer. Is it enough? How can we detect SEU?


■Concerns (Communication)

■ When and by whom will our CubeSat’s call sign be distributed?

■ Only one frequency band is allocated for up-link command. If some developers uses the same protocol (ex. AX.25), ho

w each Cubesat distinguishes its GS’s command from other GS’s command? Are there any regulations?■ Does our Cubesat require an impedance matching circuit between transceiver and antenna? ■ Is it necessary to conduct a radiation environment test to FS

K modulator-demodulator?■ Must our Cubesat equip space rated coaxial cable? Now, we

are planning to use normal one (1.5D2V).


■Concerns (Environment)

■ the thermal vacuum testing regulation for Flight Model

■ TML,CVCM limits

■ the Vibration testing on Flight Model.


■Concerns (Power)

■ Is the use of a permanent magnet permitted?

■ When can we charge batteries last?


■Concerns (Ground)

■ How can we get the orbital information of our CubeSat?

2001 University of Tokyo CUBESAT Project University of Tokyo CubeSat Project CRITICAL DESIGN REVIEW...

Documents

Transcript of 2001 University of Tokyo CUBESAT Project University of Tokyo CubeSat Project CRITICAL DESIGN REVIEW...