CubeSat Communications Ri dC tReview and Concepts · 2009-07-08 · Presentation Outline •Introduction slides for reference •Link Budgets •Data HandlingData Handling •Near

CubeSat CommunicationsR i d C tReview and Concepts

CEDAR CubeSats Constellations and CommunicationsCEDAR CubeSats Constellations and Communications Workshop, July 2, 2009

Charles SwensonCharles Swenson

Presentation Outline

• Introduction slides for reference• Link Budgets• Data HandlingData Handling • Near Term Concepts • Considered “wild and crazy” ideas involving a community effortinvolving a community effort.

CEDAR CubeSat Communications Review and Concepts (7/2/09) 2

C b S t Lif tiCubeSat Lifetime• 0.01 m2/kg Altitude Decay (4/1/12 L aunch) 0.01 m /kg• NRLMSIS model• NASA/Hathaway 300 00

400.00

500.00

titude (km

)

2 S igma

1 S igma

Nominal

NASA/Hathaway Predictions 200.00

300.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Year

Al

CubeSat Lifetime

6789

10

year

s)

500 km450 km400 km

0123456

2009 2010 2011 2012 2013 2014 2015 2016 2017

Life

time

(y

June 27, 2007 CEDAR Small Satellite Workshop

Launch date

Encode Binary Signal

• Binary “0” encoded as 1

2

udeBinary 0 encoded as

-1

00% 20% 40% 60% 80% 100%

Am

plitu

2

-2Bit Period

• Binary “1” encoded as0

1

plitu

de

-2

-10% 20% 40% 60% 80% 100%

Am

p

Bit Period

Directions In Ionosphere-Thermosphere-Mesosphere Research (2/11/2009) 4June 27, 2007CEDAR Small Satellite Workshop

Bit Period

Encode Binary Signal + Noise


2


-1

00% 20% 40% 60% 80% 100%

Am

plitu

2

-2Bit Period


1

plitu

de

-2

-10% 20% 40% 60% 80% 100%

Am

p

Bit Period


Bit Period

Encode Binary Signal + More Noise


2


-1

00% 20% 40% 60% 80% 100%

Am

plitu

-2Bit Period

2


1

plitu

de

-2

-10% 20% 40% 60% 80% 100%

Am

p

Bit Period


Bit Period

Optimal Algorithm (Is it a “0”?)

2 2

e

Binary “0” Binary “0”

-1

0

1

0% 20% 40% 60% 80% 100%

Am

plitu

de

-1

0

1

0% 20% 40% 60% 80% 100%

Am

plitu

de

×-2

A

Bit Period-2

Bit Period

Energy in Bit Period

= Σ 0.501

2

ower


= Σ 0.46, 0.22,0 57

-1

00% 20% 40% 60% 80% 100%

Po

Bit Period

Directions In Ionosphere-Thermosphere-Mesosphere Research (2/11/2009) 7

0.57, ….

Optimal Algorithm (Is it a “1”?)

2 2

e

Binary “0” Binary “1”

-1

0

1

0% 20% 40% 60% 80% 100%

Am

plitu

de

× -1

0

1

0% 20% 40% 60% 80% 100%

Am

plitu

de

-2

A

Bit Period-2

Bit Period


=0

1

0% 20% 40% 60% 80% 100%ower Σ -0.50


=-2

-1Po

Bit Period

Σ 0.41, 0.12,0 58


0.58, ….

Frequency of Occurrence

Bit ErrorBit Rate

1

2

wer

Signalto

-1

00% 20% 40% 60% 80% 100%

Pow

Bit Period

to Noise


Band Width

Required Signal to Noise Ratio

• Noise Spectral Density Modulation (notes) Eb/No BandwidthFor BER of 10-5

FSK 13 3 2 R

• Energy in bit

FSK 13.3 2 RFSK-4FSK-8 9.2 2.6 RBPSK 9.6 RDPSK 10.3 R• Energy in bit QPSK 9.6 0.5 RConvolutionally Coded PSK 4.4

S

Link Type (notes) Margin UnitsFlight Termination 9 dBCommand & Control 6 dB

• Space Loss Data Dump 3 dBOther 0 dB


Link Budget

• Space LossDesign Element Symbol Units Link 1Link Frequency f GHz 0.45Transmitter Power Ptx Watts 1Transmitter Power Ptx dBW 0.00

TransmitterAntenna Gain Gtx dB 0.00

– 14 to 15 dB difference in going from VHF (~440 MHz) to S-Band (~2.2 GHz)

Antenna Transmitter Losses Ltx dB -0.5Antenna Beamwidth θtx Deg 186.7Antenna Misalignment αtx Deg 30Alignment Loss Lθtx dB -0.31Equivalent Isotropic Radiated Power EIRP dBW -0.81

LossesPropagation Path Length S Km 2078.0Space Loss Ls dB -151.86

• Low Gain Antenna– Omni Directional

p s

Atmospheric La dB -0.1Polarization Loss Lp dB -3Total Losses L dB -154.96

ReceiverAntenna Gain Gr dB 26.6Antenna Receiver Loss Lr dB -0.5Antenna Beamwidth θr Deg 8.6 Omni Directional

• High Gain Antenna

Antenna Misalignment αr Deg 1Alignment Loss Lθr dB -0.16Total Receiver G dB 25.98Sky (Antenna) Noise Temperature Ta K 30Receiver Temperature Tr K 100.00System Noise Temperature Ts K 130.00Receiver Merit G/T DB(1/K) 4.84

Powers High Gain Antenna– Directional

PowersPower Flux Density φ dB(W/m^2) -138.15Carrier Power Received Prx dBW -129.80Noise Spectral Density No dB(W/Hz) -207.46Carrier to Noise Density Prx/No dB(Hz) 77.66

RatesData Rate R Bps 1.00E+05Eb/No Eb/No dB 27.66R i d Eb/N dB 9 6


Required Eb/No dB 9.6Required Margin dB 6Margin dB 12.06

Data Flow

Onboard Instruments 10º

40º

SpacecraftM

40

R

Rtransmitted

MemoryRcollected

Simulate for 1 year in STK andreport contact and gap times


report contact and gap times.

Percentage time in Contact


Straw Man Telemetry

Quantity Symbol Value UnitsFactor of Safety α 1.05UnitlessC t t Ti P t 1 00%U itlContact Time Percent τ 1.00%UnitlessPacket Overhead 7%UnitlessVelocity 7.5km/sWord Size 16bitso d S e 6b ts

Transmitted Rate

Collection Rate

Data Samples

Spatial Sampling

kbit / kbit / Hkbits/s kbits/s Hz m1.20 0.01 0.66 11290.329.60 0.09 5.31 1411.29

115.20 1.02 63.77 117.61Now

2 3 115.20 1.02 63.77 117.61256.00 2.27 141.71 52.92

1000.00 8.86 553.57 13.552000.00 17.71 1107.14 6.77

2-3 years

3-6 years


10000.00 88.57 5535.71 1.35

Regulations “The Law”

• The NTIA– US Frequency Allocations

• Amateur– 430 - 440 MHzq y

– http://www.ntia.doc.gov/osmhome/redbook/redbook.html

– http://www.ntia.doc.gov/osmhome/redbook/4b.pdf

Th ITU

– 2.4 GHz• ISM “industrial, scientific and medical”

433 05 434 79 MH• The ITU– All satellites go through

international licensing

– 433.05 - 434.79 MHz – 2.402 - 2.417 GHz

• Government (Primary)g

• Category of usage

Government (Primary)– 137-138 MHz– 400 - 402 MHz

– Earth to Space– Space to Earth

– 450 MHz– 2.2 – 2.3 GHz

5 25 5 46 GH


– 5.25 – 5.46 GHz

Drinking the Kool-Aid

CONCEPS• Optical Communications

Advantages/Disadvantages• CubeSat PointingOptical Communications

– Retro modulators– Lasers and Telescopes

CubeSat Pointing Requirements

• No Licensing Concerns

• Ground Station NetworksE GENSO (A t

• “Real Time” data from t ll ti– European GENSO (Amateur

Frequencies) constellations

• Power (Tx on time)

• High Gain Ground Stations– SRI 20 meter dish, etc • Facility Costs

S t R i t


• Spectrum Requirements (Licensing Concerns)

Example 1 - Summary of Ground StationNetworkNetwork

Data from 2008 survey of station capability

Maximum capacity estimatesstation capability

http://gs.engin.umich.edu/gs_survey/

Cubesat community stations

10kbps (UHF): 150 GB200kbps (S-Band): 1273GB

stations

Assessing Global Ground Station Capacity James Cutler, Dylan BooneUniversity of Michigan

Constellation Data Flow for HiDEFConstellation Data Flow for HiDEF90 Small Satellites

10 km spatial sampling55 Mbits/day2 GBytes onboard storage2 GBytes onboard storage

Big Ear On the Ground

Image courtesy of http://si.smugmug.com/gallery/1674201 UxZmP/1/457184513 4s3Agg y p g g g y _ _ g

Regulations on 460 to 470 MHz


Regulations on 460 to 470 MHz

• 5.289 Earth exploration-satellite service applications, other than the meteorological-satellite service, may also be used in the bands 460-470 MHz and 1690 1710 MHz for space to Earth transmissions subject470 MHz and 1690-1710 MHz for space-to-Earth transmissions subject to not causing harmful interference to stations operating in accordance with the Table.

US201 I th b d 460 470 MH t ti i th E th• US201 In the band 460-470 MHz, space stations in the Earth exploration-satellite service may be authorized for space-to-Earth transmissions on a secondary basis with respect to the fixed and mobile services When operating in the meteorological satellitemobile services. When operating in the meteorological-satellite service, such stations shall be protected from harmful interference from other applications of the Earth exploration-satellite service. The power flux-density produced at the Earth’s surface by any spacepower flux density produced at the Earth s surface by any space station in this band shall not exceed -152 dBW/m²/4 kHz.

10 MHz Bandwidth !CEDAR CubeSat Communications Review and Concepts (7/2/09) 20

10 MHz Bandwidth !

Straw Man Concept

• Power on ground limited– -152 dBW/m²/4 kHz

Design Element Symbol Units Link 1Link Frequency f GHz 0.465Transmitter Power Ptx Watts 1Transmitter Power Ptx dBW 0.00

TransmitterAntenna Gain Gtx dB 0.00

– -158 dBW / m² kHz• CubeSat at reentry

Antenna Transmitter Losses Ltx dB -0.5Antenna Beamwidth θtx Deg 180.0Antenna Misalignment αtx Deg 15Alignment Loss Lθtx dB -0.08Equivalent Isotropic Radiated Power EIRP dBW -0.58

LossesPropagation Path Length S Km 250.0Space Loss Ls dB -133.76

– 250 km altitude• Entire bandwidth,

Atmospheric La dB -0.1Polarization Loss Lp dB -3Total Losses L dB -136.86

ReceiverAntenna Gain Gr dB 35.9Antenna Receiver Loss Lr dB -0.5Antenna Beamwidth θr Deg 2.5Antenna Misalignment αr Deg 1

– 10 MHz.• Isotropic antenna on

CubeSat

Alignment Loss Lθr dB -1.91Total Receiver G dB 33.44Sky (Antenna) Noise Temperature Ta K 60Receiver Temperature Tr K 120.00System Noise Temperature Ts K 180.00Receiver Merit G/T DB(1/K) 10.89

PowersPower Flux Density φ dB(W/m2) -119.53CubeSat

• Max Power Tx – 1-watt RF

Power Flux Spectral Density φf dB(W/m2/kHz) -159.53Power Flux Spectral Density Limit φf dB(W/m2/kHz) -158.02Carrier Power Received Prx dBW -103.99Noise Spectral Density No dB(W/Hz) -206.05Carrier to Noise Density Prx/No dB(Hz) 102.05

RatesData Rate R Bps 1.00E+07Eb/No Eb/No dB 32.05


b oRequired Eb/No dB 9.6Required Margin dB 3Margin dB 19.45

What can you do with 1-Watt Tx

• Assumptions– 465 MHz frequency– Isotropic antenna’s on CubeSat– 1 Watt RF power (~40mW orbit average power)– 180 K system noise temperature– 36 dBi ground station gain (18 meter dish)– BSPK or QPSK (Eb/No – 9.6 dB)

• Results– 10 Mbits/s for spacecraft at 600 km circular orbit– Continuous 1.36 m on orbit sampling with 16 bit words– Science


Last Thoughts

• Dishes– 18 Meter at Wallops– 20 Meter at SRI and MoreHead University– Develop an array of antennas and create multiple sites.

• Code division Multiple Access– Give each satellite their own spread spectrum code– Develop Custom ASIC for CubeSatsDevelop Custom ASIC for CubeSats

• Some engineering at this point would be useful

• The big advantage “Isotropic antenna”.– Low impact on spacecraft


– Low impact on spacecraft.

Misc SlidesMisc Slides

Data Flow


Small SatellitesClass Mass (kg) Cost ($M)Large satellite > 1000 > 100Small satellite 500 - 1000 50 - 100

NOAA-N Prime(1400 kg)

Mini-satellite 100 - 500 10 - 40Micro-satellite 10 - 100 4 - 8Nano-satellite 1 - 20 0.5 - 2Pi t llit 1 0 2Pico-satellite < 1 < 0.2

UniversityNanosatellite

TIMED(580 kg)

Program(25 kg)

Cubesats

ST5AIM (210 kg)SSTL MicroSat 70


(1 to 3 kg)(210 kg)SSTL MicroSat-70

(70 kg)

“CubeSat”

• Low mass, low volume, low power, low cost 3-U

1-U1.5-U

• Low, but increasing science capabilities

Enables missions not cost effecti e ith larger spacecraft


• Enables missions not cost effective with larger spacecraft

Documents

CubeSat Communications Ri dC tReview and Concepts · 2009-07-08 · Presentation Outline •Introduction slides for reference •Link Budgets •Data HandlingData Handling •Near