satellite navigation & sensing: a match made in...
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University of ColoradoBoulder
Satellite Navigation & Sensing: A Match Made in Heaven
Jade MortonUniversity of Colorado Boulder
Satellite Navigation and Sensing Lab
Stanford PNT Symposium 10/30/2019 1
University of ColoradoBoulder
Society’s Increasing Dependence on GNSS
2
University of ColoradoBoulder
Satellite Navigation ModernizationGPS GLONASS BeidouGalileo QZSSIRNSS
SBAS
1 Civil Signal 6 Civil Signals, 3 frequencies
2023: >160 navigation satellites> 400 signals
Now: 25~35 satellites in view
PNT: Need 4 SVs in view
Position, Navigation, Timing3
, & Sensing (PNTS)
University of ColoradoBoulder
GNSS and Propagation Environment
Multipath reflection
Ionosphere
TroposphereGNSSRadio Occultation GNSS
Reflectometry
Interference
Propagation effects: • Absorption• Bending• Delay • Reflection• Scattering
What GNSS has to offer: • Free• Large number• Distributed • Well-defined • Diversity
The Last 5% of the Trip
University of ColoradoBoulder
GNSS Receiver
5
• Foliage• Indoor/urban• Interference• Ionosphere• Multipath• TropospherePlatform
• Aircraft• Spacecraft• UAV• Ground
Sensingand
SituationAwareness
Characterization
InformationRetrieval
PNTunder
Challenging Conditions
Impac
t
Mitigati
on
Techniques
University of ColoradoBoulder
Classification of GNSS Receiver Challenges
6
• Indoor/Urban• Interference• Foliage• Multipath• Ionosphere• Troposphere
Weak Signal
• Aircraft• Spacecraft• UAV
Dynamic Platform
ScintillationAmplitude Fluctuation
Phase Fluctuation
University of ColoradoBoulder
Ionosphere
Water vapor
Volcano plumes
Scintillation: amplitude, frequency, phase
fluctuation
What Do Ionosphere, Troposphere, Foliage, and Multipath Have In Common?
7
Low-elevation satellites suffer more but contain more information
University of ColoradoBoulder
A Simple Simulation: Sum of 2 Rays
Singapore Multi-GNSS Update 8
!"!#
= 0.95)" − )#= -1Hz
!"!#
= 1.1)" − )#= 1Hz
University of ColoradoBoulder
Example: Ionosphere Scintillation
Singapore Multi-GNSS Update 9
L1L2
L5
University of ColoradoBoulder
10
Mountain Top Data Collection ExperimentHaleakala Summit: 10,023 ft
University of ColoradoBoulder
11
Elevation
Troposphere Scintillation & OceanMultipath Reflections
5/6/2017HaleakalaMaui
L1L2
L5
University of ColoradoBoulder
12
A Closer View at 21-22 min
L1
L2
L5
University of ColoradoBoulder
13
L1
L2L5
Multipath On L5 Disappears As SV Elevation Increases
University of ColoradoBoulder
Application Objectives
14
PNTunder
Challenging Conditions
Sensingand
SituationAwareness
Disturbance signaturesRange accuracy
RobustnessMaximize MaximizeMaximize Don’t CareMinimize Maximize
University of ColoradoBoulder
Two Challenges in GNSS Sensing Applications
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1. Data availability
2. Data quality
• RX lose lock in challenging propagation environments
• Discontinuity in measurements• Noise
• Need more robust RX architecture
• Need better filter design and better aiding mechanisms
University of ColoradoBoulder
Multi-Domain GNSS Receiver Processing
• Adaptive tracking• Inter-frequency aiding• Vector processing• Semi-open loop• Open loop• Array processing
Parameter optimizationFrequency diversitySignal spatial diversity
Receiver diversityEnvironment informationTemporal diversity
16
University of ColoradoBoulder
Commercial ISM Receiver
RF Front End 1
RF Front End 2
RF Front End N
Space Weather Events
Data Collection and Control Server
Space Weather Event Monitoring & Trigger
Software
Circular Buffer
Circular Buffer
Circular Buffer
Data
Storage
VPN
Data Center at Home Institution
Inte
rnet
Receiver Signal Processing Algorithm Library
Ionosphere Studies
ImproveGNSSReceiver
Event-drivenDataAcquisitionSystem
18
University of ColoradoBoulder
Software-Defined GNSS NetworkToolik Lake
Poker FlatGakona Greenland 1
Andoya, Norway
Hong Kong
Singapore
McMurdo
Chile
Peru
Puerto Rico
Svalbard, Norway
EthiopiaAscension Island
Hawaii
Boulder
Ecuador
India
South Korea
Resolute Bay
Greenland 2
Funded, to be deployed by 2020
Existing
University of ColoradoBoulder
GNSS Event-Driven Data Acquisition System (EDAS)
University of ColoradoBoulder
Three Application Examples
• Ionosphere: – Ground-based GNSS Network for Space Weather Monitoring
• Troposphere: – Radio Occultation Detection of Planetary Boundary Layer
• Surface: – Coherent Reflection for Precise Ocean Altimetry
20
University of ColoradoBoulder
September 7-8, 2017 Storm Impact on PPP
Storm Commencement
University of ColoradoBoulder
University of ColoradoBoulder
Spatial-Temporal Machine Learning Architecture
⋯
Input"#$% "#$%&' "#Forecast
"#&(
Spatial Fusion
Fused Featuresat "#$%
Spatial Fusion Spatial Fusion
Fused Featuresat "#$%&'
Fused Featuresat "#
Temporal Fusion
PNT Impact
Forecast
Machine Learning Framework
Forecast Model
⋯
⋯ External Features (e.g. Sunspot #, F10.7, etc.)
University of ColoradoBoulder
GNSS Radio Occultation
24
cosmic.ucar.edu
University of ColoradoBoulder
Large Errors in Lower Troposphere
25
Altit
ude
(km
)
Refractivity Error
University of ColoradoBoulder
Mountaintop Radio Occultation Experiment Concept
GNSS LEO
High gain antenna
Multipath reflection/scattering from ocean surface
26
University of ColoradoBoulder
RO Application Example: Planetary Boundary Layer Height
27
Carrier phase à bending angle à refractive index à refractivity gradient à minimum gradient à PBLH
19 20 21 22 23 24 25 26 27 28 29 30 31 32Time (min)
Sig
nal I
nten
sity
(dB
)
40
20
PBL
University of ColoradoBoulder
28
Dense Data Samples
University of ColoradoBoulder
CYGNSS: A NASA GNSS Reflectometry Mission
29
Zenith Antenna GPS L1 (RHCP)
2 Nadir Antenna (LHCP, up to 14dB Gain)
University of ColoradoBoulder
Machine Learning for Wind Speed Retrieval
University of Michigan 3/28/2019 30
2 Challenges:• High wind speed• Wind direction
University of ColoradoBoulder
Coherent vs. Non-coherent Reflections
31
University of ColoradoBoulder
CYGNSS Raw IF Data Coverage
136 DatasetsAug 2017 – Apr 2019
32
Processed by CYGNSSRaw IF (Gain<0dB)Raw IF (Gain>0dB)
University of ColoradoBoulder
Rain Forest
Bolivia
1/28/2018
University of Michigan 3/28/2019 33
University of ColoradoBoulder
University of Michigan 3/28/2019 34
Open Ocean
Java Sea
2/7/2018
University of ColoradoBoulder
Java Sea 2019-01-10 01:52:44UT SPIRE SVN 86 & GPS 15
University of ColoradoBoulder
Conclusions• Satellite navigation applications go far beyond PNT.• Navigation satellites offer signals-of-opportunity for a wide range
of high impact sensing applications.– Low cost, low power, small volume, distributed– Ionosphere, troposphere, land cover, ocean surface, urban area, EM
• Synergy between satellite navigation and sensing:– Sensing capability improves navigation solutions– Navigation signals enable sensing
• Challenges and opportunities– Sensing on dynamic platform, computation resources, data assimilation