PRECISE ANGLE AND RANGE MEASUREMENTS: ADVANCED SYSTEMS FOR DEEP SPACE

148 Pages·2013·3.89 MB·Italian

Dipartimento di Ingegneria Astronautica, Elettrica ed Energetica
Dottorato di ricerca in Ingegneria Aerospaziale
Ciclo XXV
PRECISE ANGLE AND RANGE MEASUREMENTS:
ADVANCED SYSTEMS FOR DEEP SPACE MISSIONS
Author Advisor
Francesco Barbaglio Prof. Luciano Iess
Anno Accademico 2011-2012
Aknowledgements
WorkingonthePh.D.hasbeenawonderfulandunforgettableexperience.Manypeople
havehelpedandsupportedmeininnumerableways,duringthe3yearsspenttocarryout
theresearchandcompletethisdissertation.
Firstofall,IamdeeplygratefultomyadvisorProf. LucianoIessforhiscontinuossup-
port. Hiswideknowledgeandhisenthusiasmhavebeenofgreatvalueforme. Moreover
hegavemetheopportunitytobepartofasoexcitingscientificcommunityandtohavean
extraordinarylearningexperience.
I would like tothankAlessandroArditoandGabrieleRapino, who haveworked with
me in the ∆DOR activities and have become true friends. Our collaboration has been a
wonderfulexperienceandtheirconstantsupport,guidanceandgenerosityhavemadethis
workpossible. IwouldlikealsotothankMattiaMercolino,fromESOC,forhissupport,his
valuableadviceandforthefunnymomentsspentinDarmstadt.
Inaddition,IhavebeenprivilegedtogettoknowandtocollaboratewithRadioscience
laboratory colleagues. I wish to express my thanks to them, for their invaluable support
and the fun we had during the working days. A special and warm thank goes to a good
friend, MarcoDucci with whom I shared many experiences, professionalor otherwise, in
these three years. Another particular mention to Mauro di Benedetto, whose friendship
andsupportwasimportant.
IespeciallythankmyMum,mysisterAnnaandmynephewFrancisco. Theirindescrib-
ablelovingsupporttomethroughoutmywholelifeisinvaluable.Iamalsodeeplygrateful
to my Dad. What I have become and what I have achieved is because of him. I am sure
he would be veryproud of me. Mywarm thank goes also to my grandmother and other
familymembers,fortheirinterestandsupport.
Finally,IowemylovingthankstoAlessandra,forherunderstanding,endlesspatience
andencouragement. Ourloveisthebestresulttomeinmylife.
i
Table of Contents
ListofFigures iv
ListofTables vi
Introduction viii
1 Earth-basedradiotrackingsystemsfordeepspacemissions 1
1.1 Radiometricobservables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Errorsources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 ClockInstability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.2 Instrumentaleffects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.3 TransmissionMedia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.4 Platformparameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
∆
I Delta DifferentialOne WayRanging ( DOR) 12
2 ∆DORsystemoverview 13
2.1 Spacecraftcorrelation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2 Quasarcorrelation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.3 ∆DORsystemaccuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
2.3.1 ThermalNoiseeffect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.3.2 Quasarpositioningerror . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3.3 Errorbudget. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
2.3.4 Fragmentedcorrelation . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3 ∆DORenhancement:WidebandandLow-SNR 33
3.1 Widebandfunctionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.2 Low-SNRfunctionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
4 ∆DORenhancement:Testsandresults 43
4.1 Widebandfunctionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.1.1 Quasaronly: wideband-likeacquisition . . . . . . . . . . . . . . . . . . 44
4.1.2 VenusEXpress: wideband-likeacquisition . . . . . . . . . . . . . . . . 45
ii
TABLEOFCONTENTS iii
4.1.3 Juno: widebandacquisition . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.2 LOW-SNRfunctionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.2.1 Realdatawithaddednoise . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.2.2 Simulateddata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
II Pseudonoise rangingsystem 57
5 Rangingsystemsoverview 58
5.1 Sequentialranging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
5.1.1 NASAtoneranging: signalstructure. . . . . . . . . . . . . . . . . . . . 61
5.1.2 ESAcoderanging: signalstructure . . . . . . . . . . . . . . . . . . . . . 63
5.1.3 Powerallocationinatransparentchannel . . . . . . . . . . . . . . . . . 65
5.1.4 Acquisitionperformance . . . . . . . . . . . . . . . . . . . . . . . . . . 69
5.2 Pseudonoise(PN)ranging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
5.2.1 PNcodestructureandproperties. . . . . . . . . . . . . . . . . . . . . . 72
5.2.2 PNacquisition,trackingandmeasurementapproaches . . . . . . . . . 74
5.2.3 Powerallocationinaregenerativechannel . . . . . . . . . . . . . . . . 76
5.2.4 Acquisitionperformance . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.3 Rangingsystemaccuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.3.1 Rangingjitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
5.3.2 Errorbudget. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
6 Pseudonoiseopenloopreceiver 92
6.1 Simulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
6.1.1 Mathematicalmodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
6.1.2 SWarchitecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
6.2 Correlator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
6.2.1 Mathematicalmodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
6.2.2 SWarchitecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
7 Pseudonoiseopenloopreceiver:Testsandresults 110
7.1 Nonoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
7.2 Thermalnoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
7.3 Computationaloptimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
8 Conclusions 121
A ESAmission:BepiColombo 123
B PhaseestimatethroughIandQintegration 126
C ChipTrackingLoopperformance 130
Bibliography 135
List of Figures
2.1 VLBItechniquescheme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2 ∆DORtrackingscheme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.3 ESA∆DORacquisitionsystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4 ∆DORacquisitionbandwidths. . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.5 VenusEXpress(2012-214)spectra. . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.6 Topleveldiagramofthestandardspacecraftcorrelationmethod. . . . . . . . 20
2.7 Ambiguityremovalprocess. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.8 QuasarS148spectra. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.9 Topleveldiagramofthequasarcorrelationprocess. . . . . . . . . . . . . . . . 25
2.10 ∆DORerrorbudget. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.1 GShardwareconfigurationfor∆DORacquisition. . . . . . . . . . . . . . . . . 33
3.2 ESA∆DORerrorbudgetwithstandardandwidebandconfiguration. . . . . . 37
3.3 Topleveldiagramoflow-SNRspacecraftcorrelationalgorithm. . . . . . . . . 39
4.1 Differentfuntionalitiesfor∆DORcomputation. . . . . . . . . . . . . . . . . . 44
4.2 QUASAR2012-173:Acquisitionconfiguration. . . . . . . . . . . . . . . . . . . 45
4.3 VEX2012-214:Acquisitionconfiguration. . . . . . . . . . . . . . . . . . . . . . 46
4.4 VEX2012-214:Resultsobtainedwithtwodifferentconfigurations,standard-
narrowband(IFMS2)andwideband-like(IFMS3).Differentalgorithmsused. 48
4.5 Juno2012-267:Acquisitionconfiguration. . . . . . . . . . . . . . . . . . . . . . 48
4.6 Low-SNRVEX2012-214:Correlationresults. . . . . . . . . . . . . . . . . . . . 51
4.7 Low-SNRTESTA:Montecarloresults. . . . . . . . . . . . . . . . . . . . . . . . 53
4.8 Low-SNRTESTB:Noiseconfiguration. . . . . . . . . . . . . . . . . . . . . . . 54
4.9 Low-SNRTESTB:Montecarloresults. . . . . . . . . . . . . . . . . . . . . . . . 55
4.10 Low-SNRTESTC:Noiseconfiguration. . . . . . . . . . . . . . . . . . . . . . . 55
5.1 NASA-DSNsequentialrangingspectrum. . . . . . . . . . . . . . . . . . . . . . 62
5.2 ESAcodesequentialrangingspectrum. . . . . . . . . . . . . . . . . . . . . . . 64
5.3 PNRanging-Sequencewaveform.. . . . . . . . . . . . . . . . . . . . . . . . . . 71
5.4 PNrangingsignalspectrum.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5.5 Functionalblockdiagramofregenerativerangingchannel. . . . . . . . . . . . 75
iv
LISTOFFIGURES v
5.6 Downlink ranging power gain achievable using regenerative approach in-
steadtransparentchannel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.7 Signal-spacerepresentationforthedecisionbetweenthein-phasecyclicshift
andoneofitsout-of-phasecyclicshiftsofanarbitraryprobingsequence. . . 80
5.8 Rangeerrorbudget. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
6.1 Simulatorandcorrelator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
6.2 Simulatortop-leveldiagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
6.3 Frequenciesonatwo-waycommunications. . . . . . . . . . . . . . . . . . . . . 95
6.4 SimulatorSWdiagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
6.5 Datapackagingforcomplexsignal. . . . . . . . . . . . . . . . . . . . . . . . . . 99
6.6 Openlooprangemeasurementprinciple. . . . . . . . . . . . . . . . . . . . . . 100
6.7 Openlooprangemeasurementtopleveldiagram. . . . . . . . . . . . . . . . . 102
6.8 CorrelatorSWdiagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
7.1 NonoiseTEST:Montecarlosimulationsresults. . . . . . . . . . . . . . . . . . . 112
7.2 TH.NOISETEST:Montecarloresults. . . . . . . . . . . . . . . . . . . . . . . . 116
7.3 TH.NOISETEST:Montecarloresults. . . . . . . . . . . . . . . . . . . . . . . . 117
7.4 TIMETEST:Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
C.1 CTLblockdiagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
C.2 Mid-phaseintegration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
C.3 CTLlinearizemodel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
List of Tables
2.1 Parametersusedfor∆DORerrorbudget. . . . . . . . . . . . . . . . . . . . . . 31
2.2 ∆DORErrorbudget . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.1 ∆DORErrorbudgetwithstandardandwidebandconfiguration. . . . . . . . 37
4.1 QUASAR2012-173:Correlationresults. . . . . . . . . . . . . . . . . . . . . . . 45
4.2 VEX2012-214:Frequencyplan. . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
4.3 VEX2012-214:Correlationsettings. . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.4 VEX2012-214:Correlationresultsinwideband-like(IFMS3)andnarrowband
(IFMS2)configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.5 VEX2012-214:Correlationresultsinwideband-likeconfiguration(IFMS3).. . 47
4.6 Juno2012-267:Frequencyplan. . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.7 Juno2012-267:Correlationsettings. . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.8 Juno2012-267:Correlationresults. . . . . . . . . . . . . . . . . . . . . . . . . . 49
4.9 Low-SNRVEX2012-214:Correlationsettings.. . . . . . . . . . . . . . . . . . . 50
4.10 Low-SNRVEX2012-214:Correlationresults. . . . . . . . . . . . . . . . . . . . 50
4.11 LOW-SNRTESTA:Frequencyplan. . . . . . . . . . . . . . . . . . . . . . . . . 51
4.12 Low-SNRTESTA:Montecarloresults . . . . . . . . . . . . . . . . . . . . . . . 52
4.13 Low-SNRTESTB:Frequencyplan. . . . . . . . . . . . . . . . . . . . . . . . . . 54
4.14 Low-SNRTESTB:Montecarloresults . . . . . . . . . . . . . . . . . . . . . . . 55
4.15 Low-SNRTESTC:Frequencyplan. . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.16 Low-SNRTESTC:Montecarloresults . . . . . . . . . . . . . . . . . . . . . . . 56
5.1 TonesfrequenciesusedinNASA-DSNsequentialranging. . . . . . . . . . . . 61
5.2 Definitionforthemodulationscheme. . . . . . . . . . . . . . . . . . . . . . . . 65
5.3 T2B/T4BPNcodes: DCproperties. . . . . . . . . . . . . . . . . . . . . . . . . . 73
5.4 T2B/T4BPNcodes: Correlationproperties. . . . . . . . . . . . . . . . . . . . . 73
5.5 T2B/T4BPNcodes: Rangeclockattenuation. . . . . . . . . . . . . . . . . . . . 74
5.6 Definitionforthemodulationscheme. . . . . . . . . . . . . . . . . . . . . . . . 77
5.7 T2B/T4BPNcodes: Acquisitionproperties. . . . . . . . . . . . . . . . . . . . . 82
5.8 T2B/T4BPNcodes: Acquisitiontime. . . . . . . . . . . . . . . . . . . . . . . . 84
5.9 Rangeerrorbudget: Systemconfigurations. . . . . . . . . . . . . . . . . . . . . 88
5.10 Rangeerrorbudget: Radiolinkconfigurationandlinkbudget. . . . . . . . . . 89
vi
LISTOFTABLES vii
5.11 Rangeerrorbudget. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
6.1 Simulationparameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
6.2 Correlationparameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
7.1 NonoiseTEST:Generalparameterssetup.. . . . . . . . . . . . . . . . . . . . . 111
7.2 NonoiseTEST:Residualdynamicsetup.. . . . . . . . . . . . . . . . . . . . . . 111
7.3 NonoiseTEST:Montecarloresults. . . . . . . . . . . . . . . . . . . . . . . . . . 112
7.4 TH.NOISETEST:Generalparameterssetup. . . . . . . . . . . . . . . . . . . . 113
7.5 TH.NOISETEST:Residualdynamicsetup. . . . . . . . . . . . . . . . . . . . . 113
7.6 TH.NOISETEST:Noisesetup. . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
7.7 TH.NOISETEST:Montecarloresults. DynamiccaseA. . . . . . . . . . . . . . 115
7.8 TH.NOISETEST:Montecarloresults. DynamiccaseB. . . . . . . . . . . . . . 115
7.9 TH.NOISETEST:Montecarloresults. DynamiccaseC. . . . . . . . . . . . . . 115
7.10 TIMETEST:Generalparameterssetup. . . . . . . . . . . . . . . . . . . . . . . 118
7.11 TIMETEST:Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
A.1 BepiColomboscientificinstruments. . . . . . . . . . . . . . . . . . . . . . . . . 124
Introduction
Thenavigationofspacevehiclesisperformedbymeansofradiowavescommunication
withEarthgroundstations. Suchradiolinkpermitstosendcommands,receivetelemetry
andtotrackthespaceprobes. Theradiometricobservables,providedbytheradiotracking
system, are used to reconstruct, in a process called orbit determination, the space probe
position and orbit, whose knowledge is fundamentalfor navigation aswell asfor science
purposes. Infact,radioscienceandplanetarygeodesyexperimentsneedanaccurateorbit
reconstruction;thereforethequalityofradiometricdatadeterminesultimatelynotonlythe
navigationaccuracybutalsothesciencereturn. Forthisreasonthetrackingradiosystems
aresubjecttocontinuousdevelopmentsandimprovements.Newandadvancedtechniques
are implemented to reduce the contribution from the many errors sources and therefore
toprovidehighlyaccurateobservablesdemandedbymorechallengingnavigationperfor-
mance.
The work here presented regardsthe radio tracking systems used, in deep space mis-
sions,toprovideangularandrangemeasurements.Inparticular,afterachapteraboutradio
trackingsystems(ch.1)ingeneral,theworkconsistsintwodistinctiveparts,involvingthe
enhancements of the European Space Agency (ESA)∆DOR system and the development
ofanopenloopsoftwarecorrelatorforrangingsystembasedonpseudonoise(PN)codes.
DeltadifferentialOne-wayRanging(∆DOR),providingadirectmeasurementofthean-
gularpositionofaspacecraft,isapowerfultechniqueusedfornavigationofinterplanetary
probes.Itsprinciple,simplebuteffective,consistsinmeasuringthedifferenceinthearrival
time of a spacecraftsignal at two ground stations, and calibrating it with an ICRF (Inter-
national Celestial Reference Frame) quasar signal. In 2005, Sapienza University of Rome
undertookthedevelopmentofa∆DORcorrelatorforEuropeanSpaceAgency(ESA).Since
thefirstdevelopment,andforthelastsevenyears,thatsystemhasbeenusedsuccessfully
to navigate the Venus Express and the Rosetta ESA probes. After first enhancements, in
2008 ESA provided support also to NASA (National Aeronautics and Space Administra-
tion)missionPhoenixandthentoJAXA(JapaneseAerospaceExplorationAgency)mission
Hayabusa.In2011,furtherenhancementsofthecorrelatorhavebeenundertaken. Thetwo
enhancements presented in this work regard the increase of the ∆DOR system accuracy,
extendingthebandwidthcurrentlylimitedbythegroundstationshardware,andtheoper-
abilitywithsignalsatvery-lowsignaltonoiseratio(SNR).Thefirstpartoftheworkstarts
with chapter 2, treating the ∆DOR system and in particular the ESA one. The new algo-
viii
ix
rithmsandmethodsdesignedandimplementedtobecompliantwiththeESArequestsare
explainedinthefollowingchapter3whilethecampaignofteststhathasbeencarriedout
tovalidateoperativelythe newalgorithms andfunctionalities, and toinvestigate the per-
formanceofthe∆DORcorrelator,isreportedinchapter4.
Therangingsystemsarebasedonthesimpleprincipleofmeasuringthetimeofflightof
anelectromagneticwaveinvacuum. Inparticular,thesesystemsconsist,inthemostcom-
mon configuration, in a known ranging signal modulated onto an uplink, retransmitted
bythespacecraftandthendetectedonthedownlink. Theround-triplighttime,measured
correlating the received ranging signal with a replica of what was transmitted, yields a
measurement of the range. The current ranging system uses as ranging signal a series of
tones, or components with different frequencies, transmitted sequentially. The need for
greater ranging accuracies required by the new generations of interplanetary space mis-
sion, like ESA BepiColombo mission, or the need to travelto more distant planets results
in a development of new kind of ranging systems based on PN codes. The ranging sig-
nalconsistsinacode, comingfromalogicalcombinationofseveralsequences, whichhas
particular cross correlation properties. This new system permits to adopt a regenerative
approach at the spacecraft. The ranging signal, instead of being only de-modulated and
re-modulated (transparentapproach) as for sequential ranging, is regenerated, before be-
ingretransmittedtowardsEarth. Removing substantially the uplinknoise onthe ranging
signal, this approach results in an increase of the signal-to-noise ratio at the ground sta-
tionofupto30dBandthereforeinabettermeasurementsprecisionachievable. Currently
ESAstationsdon’thavereceiverscapabletooperatewithPNrangingsignal,whileNASA
Deep Space Network (DSN) has only a limited capability. Given the cost and complexity
ofclosed-loopreceiver,asoftwarecorrelatorintrinsiccheapnessandflexibilitymakeitsde-
velopmentmeaningful. Thesecondpartofthisworkregardsthereforethedesignandthe
developmentofasoftwarecorrelator,aspartofanopenloopreceiver,abletoproviderange
measurementsbymeans of anoffline processingof the signalacquiredatthe ground sta-
tion. Afterafirstgeneralchapter(ch.5)onrangingsystem,thechapter6showsthesoftware
architectureofthecorrelatorandthatofthesimulatoroftheradiolinkthathasbeendevel-
oped.Then,acampaignoftestscarriedouttoinvestigatethebehaviorandtheperformance
ofthecorrelatorisreportedinthe7thchapter.