Laser Communication with CubeSats · 11/10/2017 · Laser (red line) and radio (yellow cone)...

Laser Communication with CubeSats

K. Cahoy, MITSpace Telecommunications, Astronomy and Radiation

(STAR) Laboratory

Overview

• Motivation• Radio Frequency for CubeSats• RF and Free Space Optical (FSO, lasercom) pros and cons• Enabling CubeSat technologies for FSO• Current and developing CubeSat FSO• New technologies for CubeSat FSO

2

MIT PorTeL Ground Station: Portable Telescope for Lasercom

What’s a CubeSat?

3

• “Invented” in 1999– Jordi Puig-Suari (Cal Poly SLO)– Bob Twiggs (Stanford)– “OPAL” Orbiting Picosatellite Automatic

Launcher – Launch integration, deployment complicated– Spacecraft size: Beanie babies vs. Klondike bars

• 1 standard CubeSat unit (1U) – Volume: 10 cm x 10 cm x 10 cm– Mass: < 1.33 kg– Common sizes: 1U, 1.5U, 2U, 3U – Now 6U, 12U…

• Low cost and short development time

• Increased accessibility to space

https://directory.eoportal.org/web/eoportal/satellite-missions/o/opal, credit SSDL

https://directory.eoportal.org/web/eoportal/satellite-missions/o/opal

Poly-Picosatellite Orbital Deployer

4

http://www.nasa.gov/centers/ames/images/content/152693main_genebox-015.jpg

Spring-loaded box,bolt to rocket interface plate

3U CubeSat goes inside

Launch integration on Rocket

5

CubeSat deployment pods on top of the Bion-M1 spacecraft: BeeSat-2, BeeSat-3 and SOMP in front;OSSI-1 (1U) in a 3U-Pod back left; DOVE-2 (3U) in back right. http://amsat-uk.org/tag/beesat-2

SmallSat vs. CubeSat

6

http://www.nasa.gov/content/what-are-smallsats-and-cubesatshttps://directory.eoportal.org/web/eoportal/satellite-missions/d/dubaisat-2

• Small Satellites have total (wet) mass less than 180 kg

– About the size of a small refrigerator

• Minisatellite, 100-180 kilograms

• Microsatellite, 10-100 kilograms

• Nanosatellite, 1-10 kilograms

• Picosatellite, 0.01-1 kilograms

• Femtosatellite, 0.001-0.01 kilograms

DubaiSat-2, 300 kg

SkySat-1, 83 kg

Dnepr fairing2013 cluster launch

Can launch many CubeSats easily

7

8Animation courtesy Bill Litant ☺

Images courtesy NASA/NanoRacks

Small Satellite Challenge: Resources

9

Clements, et al., Optical Engineering, 2016

Orbital power usage [Wh]

30

20

10

0

~ 13 Wh/orbit generated by 3U CubeSat with deployable solar panels [11]

0.2 MB/orbitMagnetometer [6]

200 MB/orbit3Mp camera [8]

28,000 MB/orbitLow-resolution video [4,10]

7500 MB/orbitHyperspectral [9]

Payload Power3 Mbps UHF Consumed Power [12]

5 Mbps S Band Consumed Power [13]

100 Mbps X Band Consumed Power [14]

50 Mbps Lasercom Consumed Power (NODE with 1m ground station)

~ 26 Wh/orbit generated by 6U CubeSat with deployable solar panels

Clements 2016

CubeSat Lasercom Motivation

• Commercial CubeSat companies have invested tens of millions of dollars to address the data downlink bottleneck from CubeSats

– Currently have satisfactory RF solutions >200 Mbps

• But the commercial systems are not available to scientific and defense research programs

– IP and security concerns, limited commercial resources (usually skilled employee time)

• Others have not yet invested tens of millions of dollars to make a data downlink system for research CubeSats operational, fast, reliable, cost effective,and available

• Budget-constrained scientific and technology demonstrations on CubeSats still have limited communications capability, which prevents emergent functions

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Planet: 22 global ~5-m X-band dishes

Lasercom Downlink Motivation

• What if there were a low cost way for a CubeSat to downlink 100 Gb/day?

– Most CubeSats downlink << 10 Gb/day (UHF or S-band systems)

• Radio frequency (RF) downlinks challenged by resource constraints

– Limited by ground station size, transmitter power, or spectrum

• Lasercom is more power-efficient for given size, weight, and power (SWaP) & has no spectrum constraints

– CubeSat lasercom could scale to Gbps, but tech development still required

• Many groups working on it: MIT, The Aerospace Corporation,Sinclair Interplanetary, UF, DLR, JAXA, Space Micro, Fibertek, ATA, compact UAV lasercom from Google and Facebook…

Wallops UHF dish used by MiRaTA

UHF, 18.3 m S band, 11 m

11

MiRaTA CubeSat

Lasercom Crosslink Motivation

12Credit: Kit Kennedy, Patrick Kage

Swarm Crosslink Applications

13

George Lordos (MIT)

Spectrum access and agilityAnti-jamGPS augmentation/resiliencyPrecision timing and ranging

Overview


14

Integrated Solar Array and Reflectarray Antenna (ISARA)JPL, The Aerospace Corporation, Pumpkin, Inc.30 cm x 70 cm, ~35 dB gain at 32 GHz (Ka-band)Launched Nov. 10, 2017

Radio Frequency for CubeSats

• Research CubeSats typically use:– Beacons, VHF or UHF– Low-rate (1200-9600 baud) command and

control, UHF– Mid-rate (1-3 Mbps) data downlink, UHF, L-

band, or S-band

• Commercial CubeSats use:– Low-rate (1200-9600 baud) command and

control, UHF– Mid-rate (> 1 Mbps) data downlink, S-band– High rate (>200 Mbps) data downlink, X-band or

Ka-band

• LEO comm constellations, e.g., Globalstar, offer:

– Continuous operation at low rate, 9600 baud; too expensive for data downlink

• Software defined radios for CubeSats:– Allow agility in frequency (within constraints of

RF front end), modulation, and coding 15

Cal Poly “Friis” UHF ground station

Overview


16

RF vs. Free Space Optical (Lasercom)

Lasercom Advantages

• High gain (narrow beam width)

• Few spectrum regulations

Lasercom Limitations

• Requires high-accuracy pointing

• Clouds

17

Radio Waves Visible/NIR

1 cm - 2 m 0.4 μm - 2 μm

Laser (red line) and radio (yellow cone) communication beam width comparison

NASA.gov LLCD Fact Sheet

Lasercom wavelengths: λ = 0.4 um to 2 um RF: 1 cm to 10 m

Lasercom Gain increases by several tens of dB

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2

Free Space Optical vs. RF

Radio Optical

“Lasercom”

SpaceSegment

Radio modem,patch antenna

Laser transmitter,steering systemMIT NODE $15k

Spectrum / License

10-100 MHzHeavily regulated

THz availableUnregulated

GroundSegment

5 m to 18 mLarge dish and facility> $1M each

30 cm amateurastronomy telescope

MIT PorTeL $40k

18

Lasercom offers superior link efficiency(less power per bit)

due to its ability to better direct signal toreceiver

Comparison of RF and Optical

Opticalλ = 1000 nm

RF (10 GHz)λ = 3 cm

Units

TX Power (Pt) 0 0 dBW

TX Losses (Lt) -2 0 dB

TX Aperture (Gt) 119 30 dB

Path Loss (Lpath) -259 -169 dB

RX Aperture (Gr) 119 30 dB

RX Power (Pr) -23 -109 dBW

RX Sensitivity -97 -114 dBW

Margin 74 5 dB

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Optical system has a 70 dB advantage

Adapted from: Caplan, D. “Free-Space Laser Communications”, 2008

• TX aperture is 30 cm• RX aperture is 30 cm

• Link range is 700 km (LEO)• Receiver sensitivities typical for 1 Gbps link

All system parameters are matched, except

wavelength

Overview


20

Enabling CubeSat tech for FSO

• Pointing control needs to be 1/10 the laser beamwidth– Star trackers – Reaction wheel assemblies– Fine pointing actuators

• Compact amplifiers • High speed, power-efficient interfaces and sampling • Components/electronics for high rate mod/demod• Precision timing for clock recovery; also ranging

– Chip scale atomic clocks (CSAC)• Propulsion for constellation and swarm applications

to control range– Electrospray, green monopropellant

21

“Small” Lasercom Missions

22

Lunar Laser Communications Demonstration(MIT LL)

Optical Payload for LasercomScience(JPL)

Optical Communicationand Sensor Demonstration (The Aerospace Corporation)

Nanosatellite Optical Downlink Experiment (MIT)

Data Rate 622 Mbps 50 Mbps 40 Mbps /300 Mbps 10 Mbps / 100 Mbps

Tx Power 0.5 W 2.5 W 6 W 200 mW

Orbit Lunar LEO (ISS) LEO LEO

Payload mass 30 kg 180 kg 2 kg 1 kg

Beamwidth 2.5 urad ~0.01 deg 0.30 deg 1.3 mrad

Ground station

White Sands OCTL 1-m MOCAM / MAFIOT PorTeL / OCTL

Overview


23

Accessible CubeSat Lasercom

24

• MIT-affiliated examples (others exist*)

• Downlink– Nanosatellite Optical Downlink

Experiment (NODE)

• Ground Station– Portable Telescope for Lasercom

(PorTeL)– “Beaver Signal”

• Crosslink– CubeSat Lasercom Infrared CrosslinK

(CLICK)

NODE EM space terminal at vibe on Nov. 27, 2017

*e.g., OCSD, NASA/MIT LL DTE, Fibertek, SA photonics, SPAWAR MRR, Sinclair, SpaceMicro, Analytical Space…

PorTeL on MIT 37 Roof

NODE Architecture

25

Optical ground station

LEO satellite

Uplink beacon(976 nm)

Ground station tracking

Downlink beam(1550 nm)

Communication channel

Pointing, Acquisition & Tracking

• Satellite autonomously slews from mission-defined attitude

• Acquisition on satellite sensor stares for beacon signal from ground

– Centroid algorithm estimates boresight offset

– ADCS closes loop using beacon offset

• Integrated fine-steering mechanism(if you have one) rejects residual error

– Fast mirror steers downlink– If you don’t then your beam has to

match body pointing ability

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Lasercom Space Segment

27

NODE Space Terminal

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Application Low-cost (<$15k in COTS hardware) compact lasercom transmitter

Approach Direct detection master oscillator power amplifier (MOPA) with downlink

at 1550 nm. Uses uplink beacon at 976 nm.

Size < 1.0 kg, < 1.2 U

Beamwidth NODE: 1.3 mrad half power (first generation, initial demo).

Downlink

Data Rates

10 Mbps, initial demo to COTS 30 cm diameter amateur telescope, MIT

PoRTeL

100 Mbps (1 m diameter, JPL OCTL)

Power

Interface

0.2 W (average transmit power), < 15 W (consumed power). Needs 5V

(3A, 25 mVpp ripple) and 3.3V (3A, 25 mVpp ripple) from bus.

Attitude

Control

Desired Bus coarse pointing: accuracy: +/- 0.15 deg (3-sigma), stability

+/- 0.023 deg/s (3-sigma). Allows open loop operation with Bus.

Can support coarse pointing < Beacon FOV but would require closed loop

ADCS with Bus.

NODE FSM fine pointing capability (experimentally verified in lab):

Pointing accuracy: +/- 0.05 mrad (3-sigma). Beacon receiver for pointing

knowledge (0.01 mrad).

Beacon

Camera

FOV: +/- 5.4 degrees (10.8 degrees full angle)

Detector: mvBlueFOX-MLC205wG, Aptina MT9P, 2592 x 1944 pixels

Signal PPM, RS(255,239), 8 bits per symbol

MirrorcleMEMS fine steering mirror

NODE in 3U host

Flight electronics boards

PorTeL Ground Terminal

Image credits: Clements (above), Riesing (below)

Yoon, Hyosang, Kathleen Riesing, and Kerri Cahoy. "Satellite Tracking System using Amateur Telescope and Star Camera for Portable Optical Ground Station." (2016).

Downlink with JPL OCTL telescope:

Data rate 10 - 50 Mbps

GS Parameters 30 cm, 50 kg, < 120 W consumed

Detector Direct detection w/ Voxtel APD

Receiver electronics NODE electronics (APD & custom electronics)

Coarse PointingFine Pointing

< 60 arcsec, IR camera and star tracker < 5 arcsec, FSM to keep spot on APD (no AO)

Uplink beacon OCTL beacon (976 nm, 10 W tx power, 1 mrad beam)

Current Status Satellite tracking, over the air testing

Downlink with PorTeL amateur telescope:

FSM

APD

Beam splitter

IR camera

Data rate 50 - 100 Mbps

Receiver Diameter 1 m

Receiver electronics NODE electronics (APD & custom electronics)

Uplink beacon 976 nm, 10 W tx power, 1 mrad beam

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PorTeL Ground Terminal

30

Observed closed-loop tracking errors when tracking the International Space Station on January 24th, 2018.

The red line shows the area of the receiver. The signal stayed within the area 95% of the time. (K. Riesing, PhD thesis work in progress)

Portable telescopes (here in FL in January) are graduate-student-approved

LED Uplink Beacon

• 80 W transmit from Wallace Astrophysical Observatory successfully detected and centroided by on-orbit CubeSat (more info not releasable publicly yet)

31

A. Bosh, J. Figura, and K. Cahoy

Next Generations of NODE

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Initial Demonstration (NODE) 10 Mbps downlink to 28 cm diameter telescopePPM at 1550 nm1.3 mrad half power0.2 W transmitter

NODE Generation 2 400 Mbps downlink to 1 m diameter telescopePPM at 1550 nm0.2 mrad beamwidth0.5 W transmitter

NODE Generation 3 > 1 Gbps downlink to 1 m diameter telescope (some electronics redesign)Possible OOK at 1064 nm with different amplifier< 0.2 mrad beamwidth3 W transmitter

D. Barnes and K. Cahoy

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CLICK: CubeSat Lasercom Crosslink

34

Launch Operations

Launch Vehicle: TBD

Launch Site: TBD

Orbit: 400-600 km TBR

Inclination: TBD

Launch Date(s): TBD

Launch Vehicle Separation

and Ejection

CubeSat Launcher: TBD

Deployment

Attached

Degraded and Failure Mode Operations

Sun-Safe Mode

Survival Mode

Pre-Operations

Spacecraft Separation

Deploy Solar Panels

System Diagnostic

Initiate Drift

Pre-Link Operations

Update internal propagators from

GPS

Exchange orbit determination info

Typical Separation times

after checkout

(for reference orbit as

defined in MRD):

5 km: 2.3 days

25 km: 11.4 days

100 km: 44.7 days

500 km: 127.8 days

1000 km: 188.1 days

Ground Station

Location: MIT

Receiver Assets: TBD

Transmitter Assets: TBD

~1550 nm Lasercom

crosslink

UHF

401 MHz

(downlink)

450 MHz

(uplink) De-orbit

CLICK Concept of Operations

Transmit divergence: 0.07 mrad (FWHM)

Beacon divergence: 10.47 mrad (FWHM)

LaserCom Operations

5-minute lasercom crosslink tests

450 MHz

RF crosslink

G

PSG

PS

~1550 nm

Lasercom

downlink

https://drive.google.com/open?id=1MOKY1Zdj4mmf9xDOnNwCb4ySvJwczMbP32puORW9nso

CLICK Payload Overview

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Courtesy M. LaRocca

Use Cases:

● Optical crosslink >20 Mbps at >580 km

with BER <10-4

● Optical downlink >10 Mbps to a 30 cm

ground aperture from a 400 km to 600

km LEO orbit

Development Status:

● Optical design and analysis complete

● Prototype Miniature Optical

Communications Transceiver (MOCT)

and Pointing, Acquisition, and Tracking

(PAT) testing complete

● All boards in design and testing, some

from NODE

● Mechanical design for 1.5U payload is

complete. 3D printed model complete.

Engineering model fab is planned.

Telescope

Beacon

Beacon Camera

FSM

Tx/Rx Optics

Board Stack

Optical Table

1.5U

110 mm

96 mm

CLICK Link Budget - Crosslink

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Inter-satellite Crosslink Budget

Range (km) 850.00

PPM Order 16.00

Transmit Power (dBW) -6.99

Full Width Half Maximum

(mrad) 0.07

Beam Solid Angle (steradians) 3.96E-09

Transmitter Gain (dBi) 95.02

Transmitter Loss (dB) -1.74

Receiver Gain (dBi) 92.16

Receiver Loss (dB) -1.75

Path Loss (dB) -256.77

Atmospheric Loss (dB) 0.00

Pointing Loss (dB) -3.00

Photons Per Bit 768.70

Power Received (dBW) -83.00

Power Required (dBW) -86.10

Margin 3.03

CLICK Link Budget Beacon/Quadcell

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Link Range (km) 10 100 500 850 1000 1500

Beacon Optical Power

(dBW) -3.01 -3.01 -3.01 -3.01 -3.01 -3.01

Beacon Wavelength

(m) 9.76E-07 9.76E-07 9.76E-07 9.76E-07 9.76E-07 9.76E-07

Pointing Loss (dB) -0.50 -0.50 -0.50 -0.50 -0.50 -0.50

Half Power Beamwidth

(rad) 0.01 0.01 0.01 0.01 0.01 0.01

FSO Path Loss (dB) -216.17 -242.20 -256.17 -260.78 -262.20 -265.72

Tx Optical Loss (dB) -0.40 -0.40 -0.40 -0.40 -0.40 -0.40

Rx Optical Loss (dB) -0.10 -0.10 -0.10 -0.10 -0.10 -0.10

Receiver Aperture

Diameter (mm) 20.00 20.00 20.00 20.00 20.00 20.00

Sensor Responsivity

(A/W) 0.62 0.62 0.62 0.62 0.62 0.62

SNR (dB) 36.67 26.63 18.91 15.64 14.51 11.49

Overview


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New Tech for CubeSat FSO

• Photonic integrated circuits (PIC)• High performance detectors• Optical preamplification (AO)• Multiple-access systems•Phase modulated systems for CubeSats•Digital coherent combining•Compact, power-efficient ADCs and

demodulators

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Photonic Integrated Circuits

• Examplefrom OpSISfoundry:

• 48 channel WDM in 1 mm x 2.5 mm, including Ge high-speed photodetectors (>10 GHz) for receiver.

– Input grating couplers and amplitude and phase modulation

• Also Acacia, others: single chip transceivers40OpSIS: Optoelectronics Systems Integration in Silicon

High performance detectors

•Example, Superconducting Nanowire Photodetectors (SNPDs)

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Optical Preamplification

•Couple to single mode fiber for additional gain• MIT DeMi to test MEMS DMs on orbit

42http://proceedings.spiedigitallibrary.org/pdfaccess.ashx?url=/data/conferences/spiep/73606/

Multiple Access Systems

•Terminals to support multiple users

43

Not an actual lasercom terminal but imagine each color was an independentbeam (with FSM or gimbal) http://www.rle.mit.edu/FSOnetworks/wp-

content/uploads/2017/07/YUKSEL.pdf

Coherent CubeSat Lasercom

•Leveragingcommercialcoherent lasercomtechnology, e.g.Acacia networks

44http://www.rle.mit.edu/FSOnetworks/wp-content/uploads/2017/08/HAMILTON.pdf

Digital Coherent Combining

• Ground terminals with large collection areas are costly• Instead, many small apertures are coherently combined while maintaining excellent

receiver sensitivity• Coherent detection behind each aperture followed by digitization• The digitized signals are then combined

45Yarnall et al., 2015, 10.1109/ICSOS.2015.7425078

Compact, high speed ADC or TDC

• Need minimum 2x and typically 4-8x sampling for high speed signals

• Evaluating performance of TDC vs. ADC (time to digital vs. analog to digital) conversion

• Power consumption, cost, complexity are challenges at high sampling rates

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DRS4 based example, used up to 5 GSPS

Summary

• CubeSats successfully use RF communication systems– But higher data rates would be enabling

• Research CubeSats cannot cost-effectively access higher rate solutions (space and ground terminals)

• Lasercom may be a solution– Many research applications can tolerate occasional

weather outages, or can afford to field multiple low-cost ground stations

• Free space optical (FSO) technologies are good candidates for CubeSat demonstrations

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Coherent Detection

• Use intensity and phase information• LO oscillator laser mixes received & local light waves

– Current depends on the amplitude, phase, and polarization for both tx and LO lasers

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Hamid Hemmati NELC, Ch4

Laser Communication with CubeSats · 11/10/2017 · Laser (red line) and radio (yellow cone)...

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Transcript of Laser Communication with CubeSats · 11/10/2017 · Laser (red line) and radio (yellow cone)...