Jonathan PISANE

University of Liège

The first student satellite of Belgium

2

OUFTI-1 IN A NUTSHELL

Ham-radiooperator

Ham-radiooperator

OUFTI-1 CubeSat

D-STAR amateur-radio

(ham)communications

Educational project,hands-on experience

Ground stationScientific

experimentsin space

3

WHY HAM-RADIO FREQUENCY BANDS?

- Amateur-radio has a long history of satcom(since OSCAR-1 in 1961)

- Freely, quickly accessible resourceto licensed users

- Support from ham-radio operatorsworldwide, with …

- ..., in exchange, access to D-STAR satellite

4

FAIL-SAFE STRATEGY

• Ground-based D-STAR repeater(Ground segment )

- Hands-on experience with D-STAR- Independently useful to ham community- Linked to future ground station

• CubeSat and ground station (Space segment )

5

WHY D-STAR?

• Digital S mart T echnologies for A mateur-R adio

• Latest digital radiocommunication protocol ( ≠FM)

• Simultaneous voice & data (files, GPS…) transmission (≠ AX.25)

• Complete routing capability, including roaming

• 3 frequencies and 2 data rates - 144 MHz (2 m, VHF), 4.8 kbit/sec- 435 MHz (70 cm, UHF), 4.8 kbit/sec- 1.2 GHz (23 cm, SHF), 4.8 kbit/sec or 128kbit/sec

• “Cross-band” capability

6

D-STAR: A WORLDWIDE NETWORK

7

BASELINE D-STAR REPEATER

Local connectivity(± 50-km zone)

Worldwide connectivity

User A

VHF C

UHF BController

Gateway GRepeater

User B

Internet

8

FROM TERRESTRIAL TO SPACE D-STAR

User A

VHF C

UHF BController

Gateway GRepeater

User B

Internet

CubeSat

Ground station

VHF

UHF

9

GOALS OF MASTER’S THESIS

• High-level definition of space and ground segments

• Get full mastery of D-STAR protocol

• Build testbed to produce and decode D-STAR signals

10

ULG REPEATER IN PICTURES (1)

11

ULG REPEATER IN PICTURES (2)

12

ULG REPEATER LOCATION

13

DETECTIVE WORK …

VoicevT(t)

DatadR[n]

AMBE voicecoder

Modulating-phase

generator

D-STARcoder

vT[n]

bT[n] RFangular

modulator

∆ω∆ω∆ω∆ωT(t) sT(t)

(a) Transmit chain

(b) Receive chain

RFangular

demodulator

Bitdecoder

D-STARdecoder

sR(t) ∆ω∆ω∆ω∆ωR(t) bR[n]

AMBE voice

decoder

vR[n] VoicevR(t)

DatadT[n]

Digital-to- ∆ω∆ω∆ω∆ω converterGMSK modulator

∆ω∆ω∆ω∆ω-to-digital converterGMSK demodulator

14

… SUPPORTED BY EXPERIMENTS …

Data

Rx chain

RFangular

demodulator

Bitdecoder

D-STARdecoder

sR(t) ∆ω∆ω∆ω∆ωR(t) bR[n]

AMBE voice

decoder

vR[n]Voice

∆ω∆ω∆ω∆ω-to-digital converter

Descrambling,deinterleaving,deconvolution

(Viterbi)∆ω∆ω∆ω∆ωR(t) bR[n]

t (sec) n (samples)

dR[n]

15

∆∆∆∆ω-to-digitalconverter

D-STARdata

processor

Uplink ( ≡ Rx)144 MHz

Downlink ( ≡ Tx)435 MHz

RFangular

demodulator

RFangular

modulator

sR(t)

sT(t)

∆ω∆ω∆ω∆ωR(t)

∆ω∆ω∆ω∆ωT(t)

Commands

Telemetry

Digital voice

Data in

Data outDigital-to- ∆∆∆∆ωconverter

Digital voice

… LEADS TO A COM ARCHITECTURE

16

DOWNLINK LINK BUDGET

Ham-radiooperator

OUFTI-1 CubeSat

PT = 0.5 W = - 3 dB(W)

GT = 0 dB

LT = 1.1 dB

LS = 157.5 dB

GR = 17.5 dB

LR = 1 dB

PR = -138.6 dB

Eb = - 175.5 dB

N0 = - 203.8 dB

Eb/N0 = 19.9 dB

Minimum E b/N0 = 10.6 dB (for BER = 10^(-5))

Margin of about 9 dB

4,110 km

Ts = 300 °K

17

ESA PROPOSAL

• Project defended at ESA workshop on educational CubeSats(Jan. 2008)

• OUFTI-1 selected to be on VEGA Maiden Flight(June 2008)

• …

• World’s first D-STAR satellite

• Belgium’s first student satellite

VEGA

18

GEARING UP FOR THE BIG CHALLENGE

13 students (ULg + technical schools),2 PhD students, 6 academics, 7 space companies

19

THE PIECES OF THE PUZZLE

Structure

Attitude control

Electrical power system

Thermal system

Commands & telemetry

Radio-communications

Mission

On-board computer Antenna deployment

Emergency beacon

Radiations

Electrical Mechanical

Ground segment

1 Kg, l, W

20

EXAMPLE ELECTRONIC CIRCUITS

7.2V converter

Power dissipation circuit

D-STAR transmitter

OVERALL OUFTI-1 SYSTEM

Ham operator

145 MHz 435 MHz

145 MHz

435 MHz

VHF (2m)

UHF (70cm)

Tracking system

VHF (2m) UHF (70cm)

D-STARrepeater

Controller

Gateway

Internet

Control station

Other repeaters

22

STRONG EDUCATIONAL FLAVOR

“L’espace, j’en rêve”Euro Space Center

1 Oct 2008

23

ACCOMPLISHMENTS• One of the two CubeSat pioneer students at ULg

• Full mastery of D-STAR protocol

• First D-STAR repeater in Benelux

• Won ESA competition for spot aboard VEGA

• Award for Master’s thesis

• OUFTI-1 project co-manager

• Supervisory role in detailed design and implementationof ground and space segments

• Several presentations, interviews, and press articles

INTERNATIONAL VISIBILITY!

BACKUP SLIDES

MS THESIS EXPERIMENTAL SETUP

2820 ON0ULG Repeater

VHF CUHF B

ControllerGateway G

2820

2820

Sound card

Indirect

Direct (Lab setup)

EXAMPLES OF GMSK SIGNALS

∆ω∆ω∆ω∆ωT(t) = ∑ cT,σ,l(τi)

cT,σ,l(τi) = Q[(τ i – T/2)/σ] - Q[(τ i + T/2)/σ]

Synthetic signalReal signal

0 0 1 0 0 1 1 0 0 1 0 0 1 0 0 1 1 0 0 1

∆ω∆ω ∆ω∆ωT[n

] (ra

d/s)

Time index, n Time index, n

∆ω∆ω ∆ω∆ωT[n

] (ra

d/s)

GENERATION OF D-STAR FRAMES

Radio header328 bits

Data (D)Voice+ FEC (V)

Sync

Convolution

Scrambling

Interleaving

Scrambling

Radio header End-offrame

V Datasync

…

Every 21 st

data block

…

64 + 15bits

660 bits

72

V

72

V

72

V

72

V

7224

D

24

Datasync

24

D

24 48bits

29

OUFTI-1 PROJECT ORGANIZATION

30

ELECTRICAL SUBSYSTEMS

COM

EPS: analog & digital

OBC

BEACON

31

MECHANICAL SUBSYSTEMS

Attitude controlThermic

Antennadeployment

SwissCube view

0-45°°°°C

32

VIBRATIONS

Theory… Experimentation

33

ORBIT

354 km

1441 km

71°