1

Demonstration of amateur radio technology using a Cubesat

Tomohiro Suzuki1) , Yasuyuki Miyazaki 1), Kan Fukai2

1) Department of Aerospace Engineering , The Nihon University, Chiba, Japan 2)JAMSAT , Tokyo, Japan

Suzuki@forth.aero.cst.nihon-u.ac.jp

This article is written by amateur satellite that name is “NEXUS”. NEXUS has four main mission of amateur radio and

camera component. Theπ/4 shift QPSK transmitter can 38400 bps communication by using amateur radio band. FSK

transceiver can change the bitrate from 600 to 14400 bps. The liner transponder can relay the data in the orbit. The Camera

component can shoot the FHD picture, and it size is very small. We think that those mission components will sell in the

future. Furthermore we hope the its can promote the new entry by lowering the hurdle of satellite development.

Key Words: π/4 shift QPSK transmitter, Linear transponder, FSK transceiver, Amateur radio satellite

1. Outline of “NEXUS”

1.1. Back ground and the purpose of satellite

CubeSat has been explosive growth in recent years at home

and overseas. And the amateur radio band are often used by

cubesat radio communication. In addition to that, the capacity

of communication data will be increase by sophistication of the

mission. But the amateur radio, which has been sale at a market

are not so fast of communication speed. Therefore we spend

more time to downlink some mission data. In the result, it is a

problem that the time until mission achieved to extend more

than necessary. For this reason, it is very important for us to

downlink by amateur radio operator to reduce mission period.

In recent years, the components of the parts for the cubesat are

megatrend. Among them the camera module has come to be

mounted on almost all of cubesat.

In such background, the authors works out following four

missions.

1. Relatively high-speed downlink using the 435MHz band.

2. Data relay of amateur radio communication.

3. The data downlink using small and power-saving

transceiver.

4. Photographing high resolution photos using small and

right weight component.

These mission will be worked out with cubesat. And we will

disclose the technical information and drawing for design by

this project. In doing so we believe that it can promote the new

entry by lowering the hurdle of satellite development.

1.2. Lunch information

NEXUS has been appointed as epsilon rocket unit3 which will

lunch in 2018. The information such as inject of orbit is shown

in Table 1.

Table 1 Lunch information

Lunch Vehicle Epsilon rocket Unit3

Launch date January 2018

Orbit sun-synchronous orbit

Altitude 500km

Orbital inclination TBD

Eccentricity TBD

1.3. Mission contents

We are planning a four mission from the above background an

purpose at the NEXUS. Its missions and those success criteria

are shown in Table 2.

Table 2 Mission and success criteria

Mission contents Full success Extra success

Demonstration of

π/4 shift QPSK

transmitter

To downlink the some data in

38400bps by using the QPSK

transmitter.

N/A

Operation of liner

Transponder

To relay some data by using

liner transponder.

To make a map of

140MH band field

intensity in the

space

Demonstration of

FSK transceiver

To downlink some data in the

communication rate are

specified between 600~14400

bps by using FSK transceiver.

N/A

Demonstration of

CAM system

Photographing the earth image

of Full HD by using camera

component and downlink those

data.

N/A

2. System summary

NEXUS is a 1U(10cm×10cm×10cm) sized CubeSat, and its

weight is about 1.3kg. After orbit ,NEXUS deploy four mono-

2

pole antenna. The appearance and introspection of NEXU are

shown in Figure 1.

Figure 1 Appearance of satellite (Left: Right:)

2.1. The name and function of each subsystem

NEXUS is configured by bus system and mission system. The

details of those system are shown in Table 3, Table 4.

Table 3 Bus system of NEXUS

Name of subsystem Function of subsystem

FMR(Fright

Management Receiver)

Subsystem for receiving the uplink and

processing the command. This subsystem

is most high level of NEXUS

CW(Continuous Wave) Subsystem for Transmitting HK data

(House Keeping data) form satellite to

ground by using CW beacon.

EPS(Electrical Power

Supply)

Subsystem for supplying stabilized

power supply of 5V from Sola-cell and

battery. This subsystem can switch power

of other subsystem.

C&DH(Command &

Data Handling)

Subsystem for sampling and saving the

HK data. This subsystem can make data

packet and send to some transmitter.

RTC(Real Time Clock) Subsystem for time count of satellite.

And send that information to other

subsystem.

This subsystem is uplinked time

information by ground station to

synchronize the time. And it can count

number of rest time of other subsystem.

SG(Sensor Group) Subsystem for sampling HK data and

send other subsystem.

Table 4 Mission components and system of NEXUS

Name of subsystem Function of subsystem

π/4 shift QPSK

Transmitter

To communicate in 38400bps at amateur

radio band(Down:435MHz))In addition to

communicate by FX.25 protocol.

Liner Transponder To relay uplink data at amateur radio

band(up:144MHz/Down:435MHz)．

FSK Transceiver To transmit and receive data at amateur radio

band(Up:144MHz/Down:435MHz). In

addition this transceiver can be variable the

communication speed from 600 to 14400 bps.

CAM System To shoot of FHD(1920×1080) picture .

2.2. System configuration

The system of NEXUS is as described above. A system

diagram are shown in Figure 2.

Figure 2 System diagram

2.3. Structure of NEXUS

NEXUS has two panel , two truss and center box. Center box

also serves as the battery box. These structure member can be

subjected to a load. The both of side of the panel has two

support rod. In fact total four support rod fix the two truss and,

its be subjected to a load. In addition to its slide along the guide

rail when the satellite is released from the separation pod.

Panel and supported rod is casting. The main structure is shown

in Figure 3. The introspection of NEXUS is shown in Figure

4.

Figure 3 main structure

Figure 4 Introspection of NEXUS

NEXUS has switches which detect the separation of satellite from

release pod. These switches are kept by guide rail of release pod.

Satellite are powered on along with the release of switches.

Z

Y X

113.5

[mm

]

YX

Z

430MHz_Downlink

144MHz_Uplink

430MHz_Downlink

144MHz_Uplink

CW

MPU

CDH

Modem

Transmitter FEPROM

MPU

CAM

FEPROM

FIFO

Camera Module

MPU

Regulator

FMR

MPU

ReciverModem

ANT140MHz

ANT430MHz

FSKTransceiver

π /4 shift QPSKTransmitter

Transponder

ANT430MHz140MHz

ANT140MHz

Sensor Group

MPU

A/DConverters

Thermal Sensors

Galvanometers

Geomagnectic Sensor

Gyro Sensor

EPS

BatterySolar cells

5V booster

MPURelay

SwitchRelay

Switch

Power Source Line5V Line3.3V Line

Command LineData Line

Y

Z

X

+Y side Truss

Center box Lid

Center box

+X side panel

+Y side Truss

+Y side Panel

-X Side column

+X side column

-X Side Solar Panel

-Y Side Solar Panel

+Y Side Solar Panel

Y

Z

X

+X Side Solar Panel

+Z Side Solar Panel

-Z Side Solar Panel

-Y Side Truss

+X Side Panel+Y Side Truss

-X Side Panel

π/4 shift QPSK

Transmitter

FM Receiver

FM Transmitter

Center Box

Linear Transponder

Camera

Electronic Substrate

Battery×4

Mother BoardFSK Transceiver

3

2.4. Antenna deployment system

NEXUS has four mono-pole antenna. These antenna are

looped it around +X panel of NEXUS. Its are kept by nylon

wire. After separation the nylon wire is melted by heat of

nichrome wire for deployment of antennas.

Antennas are kept by two nylon wire to prevent

misdeployment. If one of nylon wire is melted ,antennas are not

deployment. But all of nylon wire are melted, antennas are

deployment. The constitution of antenna deployment

mechanism is shown in Figure 5

．

Figure 5 Antenna deployment mechanism

3. Detail of mission

3.1. π/4 shift QPSK Transmitter

The bit rate of the QPSK transmitter is 38400bps, which is

faster than the bitrate of the transmitters widely used for

cubesats, e.g. AFSK transmitter with 1200bps or GMSK one

with 9600bps.[1] Moreover it power consumption is lower than

conventional ones. In addition to these merit, the QPSK

transmitter adopts FX.25 protocol that is tolerant for the noise

compared with the AX.25 protocol. Therefore we can expect to

reduce the electric wave interference which is the demerit in

using amateur radio band.

The appearance of π/4 shift QPSK transmitter is shown in

Figure 6 and, its speck is shown in Table 5.

Figure 6 π/4 shift QPSK Transmitter

Table 5 The speck of π/4 shift QPSK Transmitter

item content

Size[mm] 83.5×47.5×11.5

Mass[g] 74.1

Operation voltage[V] 3.7

Power consumption[W] 0.4

Transmission rate[bps] 38400(QPSK)

Frequency Down:435MHz band

3.2. Liner Transponder

There is no satellite which equippes with a transponder in the

amateur satellites in Japan now. Therefore many amateur radio

operators are interested in the transponder that is mounted in

the foreign satellite.[2]

From these background, we will operate the transponder as a

repeater of amateur radio. By doing so we can be promoted

amateur radio operator, who are not engaged in satellite

communication in satellite operation.

And transponder can measure an electrical intensity at

144MHz band. We will create a map of electrical intensity on

the orbit by using this function. This is an our extra success of

mission.

The appearance of transponder is shown in Figure 7. The

speck of transponder is shown in Table 6.

Figure 7 Liner transponder

Table 6 The speck of Liner transponder

item content

Size[mm] 80×80×10

Mass[g] 150

Operation voltage[V] 3.7

Power consumption[W] 0.8(During operation)

Frequency Up:144MHz band, Down:435MHz band

3.3. FSK Transceiver

We think that the mission of future satellite will be diversification.

So that operation will be diversification too. If the operation is

changed, the amount of downlink data will change.When the

amount of data is large, increase the bit rate. When the amount of

data is small, reduce the bit rate . By doing so we can raise the gain

of communication, when bit rate is low. So we can get data

certainty.

To

Switch

Nylon line1Nylon line2

To

Antenna

Nichrome wire

Ground line

Power line

Fixed point

4

FSK transceiver can change the bit rate from 600 to 14400 bps.

This transceiver can modulate AFSK and GMSK which has been

used ever before. So this transceiver is more multifunctional than

ever before. The appearance of transponder is shown in Figure 7

and, its speck is shown in Table 6Table 5.

Figure 8 FSK transceiver

Table 7 The speck of FSK transceiver

Parameter Value

Size[mm] 53.8×36×5

Mass[g] TBD

Operation voltage[V] 3.7

Power consumption[W] 0.4

Transmission rate[bps] 600~14400(variable, FSK)

Frequency Up:144MHz band, Down;435MHz band

3.4. Components of telemetry signal

NEXUS has CW/FM combo transmitter witch has proven in

other amateur satellite. This transmitter is sold by NISHI

MUSEN laboratory. [3]

NEXUS has receiver made by same laboratory. This

transmitter and receiver is used by amateur radio

band(Up:144MHz/Down:435MHz).

The appearance of transponder is shown in Figure 9 and, its

speck is shown inTable 8

Figure 9 Transmitter and receiver for telemetry signal

Table 8 Speck of transmitter and receiver

Parameter Value

Size[mm] 88.5×60×10.5

Mass[g] 99

Operation voltage[V] 5.0

Power consumption[W] 0.1(CW operation) , 0.8(FM operation)

Transmission rate[bps] 1200(AFSK) , 9600(GMSK)

3.5. CAM system

In recent years the components of the parts for the CubeSat is

in the mainstream. Camera is no exception it. However the

camera components for cubesat that is currently sold, is large

and heavy. So it is difficult for 1U size cubesat to mount these

component. Therefor we develop the small camera component

that can mount in 1U size cubesat. It can also shoot Full HD

picture. The appearance of camera component is shown in

Figure 10,the system diagram is shown in Figure 12. Its speck

is shown in

Table 9.

Figure 10 The camera system component

Table 9 The speck of camera system

parameter Value

Size(Board) [mm] 70×30×3

Size(Camera)[mm] 30×30×23

Mass[g] TBD

Operation voltage[V] 5.0

Power consumption[W] TBD

Image sensor [pixels] 2592×1944

ROM[MB] 32

RAM[MB] 16

MPU STM

Picture extension JPEG,RAW,PNG

3.6. Breakdown of antenna

NEXUS has two receive antenna and two transmit antenna. To

use one as an antenna for telemetry reception, the one to send.

SG System C&DH System EPS System 5V Line

3.3V Line

2.5V Line

Command Line

Data Line

MPU MPURelay

Switch

Main MPU

STM32F103RBT6

FIFO

Camera Module

FEPROM

Regulator

Camera System

FIFO

FEPROM

Regulator

π /4　shift QPSK

Transponder

MPU

Figure 11 The system diagram of camera component

5

In addition, the radio mission use the other two antenna.

There are three radio mission components in NEXUS. But we

can use only two antennas. So we use switch for change the

antenna to use all transmitter and receiver. The switching of the

switch is run by received command.

The diagram of antenna switching circuit is shown in Figure

12.

Figure 12 system diagram of antenna

One of the antenna has 435MHz and 144MHz band. So in

order to use two frequency bands, it is necessary to matching of

two band. The result of matching is shown in Figure 13.

Figure 13 Result of 2BAND matching

4. Operation plan

We are planning the operation of the three stage after the lunch.

Show the plan to Table 10.

Table 10 Duration of each part of the mission

Phase Action item Duration

Early

orbit

phase

Link verification between the satellite and

the ground station.

The acquisition of HK data by CW

beacon.

1~3 day

after

launch

Specific object 3~7days

after

lunch

Test operation of satellite system and

equipment.

a) FM transmit and receive(1200[bps]，

9600[bps]).

b) Acquisition of sensor data.

c) Confirmation of the power and heat

balance.

Within 3

month

after

lunch

Mission

phase

Mission equipment operation check.

a) π/4 shift QPSK transmitter test

transmission.

b) Operation of the transponder.

c) FM transmitter and receiver test

operate.

d) Photographed by the on board

camera.

Within 6

month

after

lunch

Late

orbit

phase

Evaluation of the success level

a) Performance evaluation of the π/4

shift QPSK transmitter.

b) Demonstration of the transponder.

c) Demonstration of camera system.

Within

1 yare

after

lunch

This operation plan is based on the SPROUT which was made

by Nihon University.[4]

5. Ground Station

We can expect the support on receiving the downlink data by

many amateur radio operators if we use the amateur radio

band for satellite tele-communication, which is a big merit on

operating the satellite. But it is difficult for amateur radio

operators to decode the QPSK modulation by using commercial

radio. Therefore we can’t expect the support by amateur radio

operators. So, we focused on the software radio equipment

which is growing in these days. We will develop the decode

software of ground station, and release it on our web site.

6. Development phase

The bus system of “NEXUS” is under the BBM development

phase now. The communication devices of the mission system

are under the Pre-Engineering model phase now. And we

finished radial ray test , vacuum test and thermal test.

We will make a transition from BBM to engineering model.

7. Future prospects

If we success the all mission, we will sell the all mission

EPS

Liner transponder

π /4 shift QPSK

transmitter

140MHz band430MHz band

140MHz bandC&DH

Command Line

Data Line

3.7V Line

FSK transceiver

RF switch

RF switch

RF switch

Relay

switch

6

components. The π /4 shift QPSK transmitter ,FSK

transceiver and camera component will sell in home and abroad.

The liner transponder will sell in abroad. By doing so we

believe that we will promote the diversification of the mission

by using cubesat.

In addition to we release the information, which is design

ofcubesat . By doing so we think that the span of development

of cubesat is shorter than before. Furthermore mission

components has synergistic effect. So we hope that it can

promote the new entry by lowering the hurdle of satellite

development.

8. Acknowledgments

NEXUS is developed with JAMSAT. We have direct

technical support on mission component by member of

JAMSAT. In addition to we are supported by member of

Nihon University. So we would like to thank everyone.

Reference

[1]JARL The cube sat satellite of JAPAN

http://www.jarl.org/Japanese/7_Technical/cubesat/cubesat.htm

[2] Mikio Mouri ,JAMSAT Newsletter Vol. 44, No. 2-pp.33 Phase-4A

Building a the ground system

[3] NISHI MUSEN laboratory

http://www.nishimusen.co.jp/

[4] Kento Ohinta :2K01 Deployment of Combined Membrane

Structure of Nano-satellite "SPROUT"「SPROUT」 2014