FERSAT missiondr. sc. Dubravko Babić

Associate ProfessorFaculty of electrical engineering and computing, Zagreb (FER)

Oct 4, 2019

Mission objectives: (1) Demonstrate measurement of light pollution

(form space): identify the type of light sources contributing to light pollution and determine the fraction of solid-state lighting in overall lighting.

(2) Demonstrate a simple ozone thickness measurement using solid-state detectors.

(3) Implement efficient high data-rate downlink in the X-band for images and payload data.

Launch a nanosatellite (CubeSat) in 2021.

Funding and resources: Croatian Science Foundation (HRZZ IP-2018) Croatian industry: Croatel, Geolux, Ultima. Multiple donations

Ten faculty members and 50 students involved. Collaboration with Faculty of Mechanical

Engineering and Naval Architecture (FSB) and with the Faculty of Science (PMF) in Zagreb

FERSAT nanosatellite

Cube‐shaped satelite with volume of 1 liter andmass ≤ 1.33 kg.Sun‐synchronous orbit at altitude 500 km

Payloads

1 Light‐pollution

2 Ozone thickness

3 X‐bandtransmitter

Payload 1: Light pollution measurement

• Worldilluminationischanging:conventionalsodium/mercurylighting isbeingreplacedwithsolid‐stateligthing(LED).

• Question:CanweestimatethefractionofgloballightinghasbeenconvertedtoLEDs?

Payload 1: The challenge LEDlightingexhibitshighintensityof

bluelight,whichdisturbsanimalbehaviorandhumancircadianrhythm.

Lightpollutiondataisavailablefromsatelliteimages(LandSat),butonlyinthe500–900nmwavelengthrange,whichwefoundisnotsufficienttoresolvethelightsource.Sentinelsatellitestake onlydaylightimages.

Tobethebestofourknowledge,light‐sourceidentificationinlightpollutionispresentlynotpubliclyavailableinformation.

Payload 1: Objectives• Developanalgorithm toextractthecontributionofLED

lightinginworldillumination.• DemonstratethealgorithmusingaCCDcameraand/ora

miniaturespectra‐photometerona CubeSat.• Provideaworld‐widemapofLEDinstallation.

MiniatureUSB‐controlledspectra‐photometer (350–1000nmrange)

2.1MPixVIS+IR camera(Geolux/Zagreb)

Studentsmeasuringstreetlightingemissionspectra

Payload 4: Ozone layer thickness• OzoneisdistributedfromthesurfaceoftheEarthtothestratosphere(~100km).• OzonelayerabsorbsmostoftheharmfulultravioletradiationcomingfromtheSun

• https://ozonewatch.gsfc.nasa.gov/facts/SH.html

UVBackscatter(SBUV,TOMS)

IRradiometer(LIMS,ISAMS)

Dobsoninterferometer

UVforwardscattering(SAGE)

LIDAR

Microwave

Balloonprobe

Ozonelayer

Payload 4: Ozone measurementsFERSATwillmakeUV

backscattermeasurementsandpossiblyUVforward‐

scattermeasurements

Payload 4: Objectives Developasimpleopticaltechnique,suitedforananosatellite,tomeasuretotal

thicknessofozonelayer. DemonstrateoperationofPure‐B(UV)detectorsinspace. Provideworld‐widescanofozonethicknessusingananosatellite.

Method:• ComparingtheoutputsofUVAandUVBdetectorsandabluevisible‐light

detector(similarapproachasintheDobsonSpectra‐photometer).• Spectralresolvingdoneusingopticalfilters.• Detectorswillbenadir‐pointing.• ResultstobeexpressedinDobsonUnits.

Payload 4: Pure-B ultraviolet detectors

PureB detectors(elementalborondepositedonsilicon)arebeingusedforelectrondetectioninscanningelectronmicroscopes,butarealsoexcellentUVdetectors.

TEMimageofPureB/Siinterface

PureB detectorspackagedforcharacterization

Dualtransimpedance amplifier

Payload 5: Implement X-band downlink

• CubeSatdownlinksaregenerallyintheVHF/UHFamateurradiobandandittakesmultiplesatellitepassestodownload2MPixelimage.

• Question:Canwespeedthisuptodownloadtensorhundredsofimagespersatellitepass?

Theobjective:• Demonstrateahigh‐efficiencyX‐bandcommunicationbetweena1U

CubeSat andEarthstation atatleast5Mbpslinerate.

Payload 5: Challenges and approach

Challenges:CubeSatpowerbudgetandweightbudgetisverylimited,whilecommercialX‐bandtransmittersdissipatealotofpower(>10Watts).

Theapproach:

GaN‐FETClassAB/FRFPA

• Phase‐onlymodulation(BPSKorQPSK)allowsforhigheramplifierefficiency.

• Modulationbandwidthisatleast5MHz

• DesignAlGaN/GaNHEMTClassFRFPA

Payload 5: Approach

Radiationpatterns

4patch‐antennaarraywithcircularly polarized emission

X-band ground station• Antennarequiresveryhighgain(~50dBachievablewith3mparabolicantenna).• Frequencies:8GHz(EarthObservation)and10.45GHz(AmateurRadio)• Linkbudgetforh =500km,BPSK/10.45GHzshowsabout3minvisibility.

o energyharvesting

o attitudecontrol

o controlsoftware

o communicationelectronics

Satellite build isan interdisciplinary engineering project

o sensordata acquisitonelectronics

o imageandsignalprocessing

FERSAT development team

plus 50 students