Spirent
Taking PNT to the Moon
October 2023

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1Agenda1

PNT to the Moon - Phases

2

Simulation Challenges

3

Simulation Solutions

4

References

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2

Agenda1

PNT to the Moon - Phases
1.1

Earth-Based GNSS

1.2

LANS (Initial Services)

1.3

LANS (Enhanced Services)2

Simulation Challenges

3

Simulation Solutions

4

References

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3

PNT to the Moon – Phases
LANS(Initial Services)

LANS(Enhanced Services)2027 - 2035

2035 - onwards

Use of Earth-Based GNSS
constellations for PNT inlunar missions.

Dedicated initial lunar orbit
GNSS-like constellation toprovide South Pole surface
and cislunar PNT services.

Enhanced lunar constellation(including additional SVs andlunar surface PNT beacons)
to provide full lunar coverage.

• Earth-to-Moon transfer• Orbital navigation andtiming• Vehicle descent, landing
and ascent• South Pole lunar surface
PNT• Full lunar surface PNT• Service integrity

Earth-Based GNSS
2023 - onwards

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PNT to the Moon – Phases
Earth-Based GNSS
2023 - onwards

Receiver Technology1••

Use of Earth-Based GNSS
constellations for PNT inlunar missions.

High-sensitive acquisition and tracking
algorithms
Compact design (inc. power)••

In-flight FW/SW upgradability
Reliability on long missions

Missions
NASA MMS – 20152•••• Earth-to-Moon transfer• Orbital navigation andtiming

Highest operational use of GPSAcquisition and tracking ofsidelobe signals
Vehicle spinning at 3 RPM ► 4antennas
7

SpacePNT NaviMoon3 for ESA Lunar Pathfinder4
NASA-ISA LuGRE5 for Blue Ghost Mission I6

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PNT to the Moon – Phases
8LANS(Initial Services)

General Requirements•

Real-time horizontal positioning accuracy lessthan 40-50 meters at the lunar South Poleregion at any time•

Accurate orbit and clock determination•

Compliant with LunaNet standard9 to become
LNSP•

Use of Elliptical Lunar Frozen Orbits (ELFO)•S-Band signals at 2492.028MHz•BPSK Modulation

2027 - 2035

Dedicated initial lunar orbit
GNSS-like constellation toprovide South Pole surfaceand cislunar PNT services.
4• Vehicle descent, landingand ascent• South Pole lunar surface
PNTMissions
NASA LCRNS, JAXA LNSS & ESA Moonlight

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PNT to the Moon – Phases
LANS(Enhanced Services)

LunaNet9,10•2035 - onwards•

Enhanced lunar constellation(including additional SVs andlunar surface PNT beacons)
to provide full lunar coverage.

••• Full lunar surface PNT• Service integrity

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Flexible and scalable architecture for the provisionof Network, PNT and science utilization services
Infrastructure built up as mission requirements
evolveSmallSats can be providers or users
Combination of institutional and commercial nodes

Operations& Services••NASA Artemis
NASA LunaSAR within
Artemis program

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7Agenda1

PNT to the Moon - Phases

2

Simulation Challenges
2.1

Lunar Orbital Dynamics Modelling

2.4

Signal Propagation

2.2

Selenodetic Reference Systems

2.5

Multipath

2.3

Realistic Tx Antenna Patterns

2.6

Topography & Librations

3

Simulation Solutions

4

References

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8Why Simulation?
Lunar applications, either with Earth-based GNSS signals or using LANS, are pushing the requirements of GNSS technology further thanever before. Also, the diversity of these applications is likely to increase.
To successfully bring PNT to the Moon, the design of the various parts of the system, in particular GNSS receivers, must be of a highstandard that ensures reliable performance. To enable this, it is important that the product development process is based on proper testingfrom concept to production.

Advantages of Lab Simulation
Complete control over constellation and signals
Complete control over environmental conditions
Fully repeatable
No unintended interference signals or unwanted
signal effects
Easily test scenarios with constellation errors

Testing of present and future signals
Cost-effective testing in laboratory

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Simulation Challenges
Lunar Orbital Dynamics Modelling% Average Moon Gravitational Effect (vs Sun & Earth)
100%
NASA MMMS Phase I

80%

ELFOs (~9,000 – 10,000 km)

12 radii (<0.07%)

NASA MMMS Phase IIb

60%

25 radii (~0.45%)

40%
20%
0%050100150200250300350400

Distance from Earth ['000 km]
New dynamics model required to account for the uneven gravitational pull from the Moon, perturbations from other celestial bodies,different solar radiation pressure, etc.
Record-Breaking NASA Mission Advances High-Altitude GPS | NASA
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Simulation Challenges
Selenodetic Reference Systems11
Two reference frames are needed:
Body-fixed reference frame for the main body perturbation modelling and for the expression of thebroadcast navigation message, to estimate position without implementing the rotations of the inertial frame(e.g., ECEF)
Inertial reference frame for precise time resolution (including relativistic effects) and the numericalintegration of the equations of motion (e.g., ECI)

Body-Fixed Lunar Reference Systems

Lunar Inertial Reference Systems

Mean Earth Rotation (MER) – mean direction to Earth (X) andmean Lunar spin (Z): mainly used for cartography

Recommendation is to use a frame that isaligned to the Moon equator at a reference
epoch to ease integration of lunar orbits

Do not coincide
Systems differ about 1 km

Roncali12 contains a complete list of MoonCentred inertial framesPrincipal Axis (PA) – aligned with principal axis of inertial of theMoon: important for orbit propagation

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Simulation Challenges
Realistic Tx Antenna Patterns & SV Dynamics Modelling13
Limited availability of Tx antenna pattern data.
Yaw attitude representation for each SV plays an important role in the determination of the power levels received
beyond MEO orbits → Account for Z-axis rotation performed to orientate solar panels
Receiver antenna Modelling → Earth-pointing, high Gain. E.g., boresight gain of 15 dBi at L1 and 11.5 dBi at L5

14

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Simulation Challenges
Signal Propagation15

Earth-Based GNSS
Further sophistication of Earth ionospheric models required for calculating the Total Electron Count (TEC) assignals may cross ionosphere twice → Thin-shell model not sufficient for these applications.
16EXOLITHOSPHEREREG

LANS
The gas concentration in the lunar exosphere is approximately 2 ×105 𝑐𝑚 −3 during the lunar night, and 104 𝑐𝑚−3 during the lunar day.
The TEC of the exosphere is extremely low, often in the order of 0.01
TECU → Earth TEC ranges from a few to 100 TECU.
The effect of the lunar exosphere is neglectable for Earth-Based
GNSS PNT solutions. However, the consequences for lunar PNT andLANS imply the need for transmission of signals exclusively with thedirect line-of-sight, due to the lack of significant reflection anddiffraction effects.

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Simulation Challenges
Multipath17
Most of the electrical characteristics of the moon core and regolith have been directly obtained and the estimates
seem to vary.
Research values indicate that core and regolith permittivity and conductivity are similar to some ceramicmaterials.

EXOLITHOSPHERE

REGPermittivity

ConductivityCore

ε1 = 5σ1 = 5 ∗ 10−4 mhos/mRegolith

ε2 = 3σ2 = 5 ∗ 10−6 mhos/m

Opportunistic multipath measurements at the Lunar
South Pole with communications between LRO andDSN show the potential impact of multipath in SBand communication, with 0-2 kHz doppler shift andsignal delays of a few microseconds.

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Simulation Challenges
Topography18

Librations12
Earth and Moon motion that allows observers to see slightly
different parts of the Moon’s surface at different times

Longitude librations → Relative
velocity of the Moon with respect to theEarth is not constant because its orbit
is elliptical

Latitude librations → Moon’s
equator is inclined to the plane ofits orbit 6.69 degrees, generating
an apparent “nodding” motion

Diurnal librations →Rotation of the Earth causes
observers to see the Moon
from different angles

The maximum and minimum variations are approximately +8 km/-9km with both extremes occurring on the far-side of the Moon (relativeto a sphere with a radius of 1737.4 km)
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Agenda1

PNT to the Moon - Phases

2

Simulation Challenges

3

Simulation Solutions

4

3.1

System Requirements

3.2

Spirent Solutions

References

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16

Simulation Solutions
System Requirements
Scalable platform capable of simulating high-fidelity GNSS and LANS AFS (Augmented Forward Signal) RF.
Embedded solar and lunar orbital dynamics for accurate trajectory and constellation orbits generation.

Support for different lunar body-fixed and inertial reference frames.
Accurate representation of Tx antenna patterns and satellite in-orbit rotations.
Realistic Earth ionospheric modelling based on TEC calculations relative to the distance travelled by RF signals.
Statistical multipath modelling for moon’s regolith and core.
Future-proof platform that can accommodate future needs (e.g., realistic 3D environments).

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Simulation Solutions
Defining Non-SIS ICD Signals

High Dynamics
Up to 2 kHz (0.5 ms) update rate

Multi-Orbit Definition
Native support for multi-constellation RF and orbital data
input (e.g., via SP3 files)

Custom Antenna Patterns

RF Generation from I/QSpirent
GSS900019

Generate any type of in-band RF signals
from I/Q files including interference, noise
and non-SIS ICD signals
Import any I/Q file from external software
applications and generate high-fidelity RF to
test your hardware platform

User-defined Rx antenna patterns

FLEX Signal Generation
Atmospheric Modelling
Customisable atmospheric models, including
ionospheric, tropospheric and scintillation effects

Multipath

Design open and secure non-SIS ICD signals
controlling low level signal parameters suchas chip rate, modulation, frequency, codes
and navigation data

Generate synchronous RF including GNSS
and custom FLEX signals

Statistical and 3D-based multipath solutions available

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Simulation Solutions
RF GENERATION FROM I/Q

FLEX SIGNAL GENERATION

User provides I/Q file containing all satellite signal
data for individual SVs or constellations

User defines individual low-level signal
parameters prior to RF generation•Injection of various I/Q files per scenario run containing
custom waveform, interference, noise and/or non-SIS
ICD signal data•

Definition of transmitter objects associated with theI//Q files that apply the corresponding attenuation
power levels to the signals in the I/Q files based on
the distance from the transmitter to the receiverantenna

Variable Chip Rate

Variable BOC

Up to 2 signals per channel withindependent chip rate

Independent BOC selection foreach of the two signals

Navigation Data
Navigation Data
user-defined
streamModulation Types

FLEX

Non-SIS ICD Codes•

Generation of RF from I/Q data alongside existing
GNSS signals defined in SimGEN

Primary andsecondary codes

Frequency Variations
Filtering
Support for user-defined
filters

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BPSK, QPSK,etc.

Varying carrier
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19

Simulation Solutions
SimOrbit
Accurate orbital modelling tool that can be used asa reference trajectory propagator•

Create vehicle trajectories based on accurate orbital
dynamics modelling accounting for gravitational effects
and drag•

Generate constellation orbits with up to 85 satellites•Pre-canned vehicle types with fully customisable
parameters (e.g., drag coefficient, mass, cross-section
area, etc.)

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20

Agenda1

PNT to the Moon - Phases

2

Simulation Challenges

3

Simulation Solutions

4

References

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21

References
1.

Fantinato, S., Miotti, E., Boschiero, M., Bartolucci, M., Bergamin, M., Marcantonio, D., Pulliero, M., Rozzi, F., Pozzobon, O., Facchinetti, C., Musumeci, M., Ansalone, L.,
Impresario, G., D’Amore, G., Parker, J. J. K., Konitzer, L., McKim, S. A., Anderson, B., Miller, J. J., … Dovis, F. (2022). Development Challenges of a GNSS SDR Receiver forMoon Landing. 35th International Technical Meeting of the Satellite Division of the Institute of Navigation, ION GNSS+ 2022, 1, 570–595. https://doi.org/10.33012/2022.18369

2.

Winternitz, L. B., Bamford, W. A. and Price, S. R. (2017). New High-Altitude GPS Navigation Results from the Magnetospheric Multiscale Spacecraft and Simulations at LunarDistances.

3.

SpacePNT – NaviMoon. Available at: https://spacepnt.com/navimoon/

4.

Ventura, J. (n.d.). ESA Lunar Navigation Plans: Lunar Pathfinder & Moonlight.

5.

Parker, J. J. K., Dovis, F., Anderson, B., Ansalone, L., Ashman, B., Bauer, F. H., D’amore, G., Facchinetti, C., Fantinato, S., Impresario, G., Mckim, S. A., Miotti, E., Miller, J.
J., Musmeci, M., Pozzobon, O., Schlenker, L., Tuozzi, A., & Valencia, L. (n.d.). The Lunar GNSS Receiver Experiment (LuGRE).

6.

Firefly – Blue Ghost Mission I. Available at: https://fireflyspace.com/missions/blue-ghost-mission-1/

7.

ESA (2022). Moonlight Programme.

8.

Murata, M., & Iiyama, K. (2022). Lunar Navigation Satellite System (LNSS) and Its Demonstration Mission.

9.

NASA & ESA (2023). LNIS V005 LunaNet Interoperability Specification Document.

10.

NASA & ESA (2023). LSIS V1.0 Draft LunaNet Signal-In-Space Recommended Standard-Augmented Forward Signal (LSIS)

11.

Laurenti, M., Stallo, C., Bellardo, V., Marty, J. C., Giordano, P., Zoccarato, P., Schoenemann, E., Swinden, R., & Traveset, J. V. (2022). Reference Frames Analysis for Lunar
Radio Navigation System. Proceedings of the International Technical Meeting of The Institute of Navigation, ITM, 2022-January, 606–615.
https://doi.org/10.33012/2022.18170

12.

Roncoli, R. B. (2005). Lunar Constants and Models Document.

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22References
13.

Delépaut, A., Giordano, P., Ventura-Traveset, J., Blonski, D., Schönfeldt, M., Schoonejans, P., Aziz, S., & Walker, R. (2020). Use of GNSS for lunar missions and plans forlunar in-orbit development. Advances in Space Research, 66(12), 2739–2756. https://doi.org/10.1016/j.asr.2020.05.018

14.

Donaldson, J. E., Parker, J. K., Moreau, M. C. & etal., 2018. Characterization of On-Orbit GPS Transmit Antenna Patterns for Space Users. Miami, Florida, Proceedings of the
31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018), pp. 1208 -1245

15.

Manning, R. M. (2008). Long-Range Transhorizon Lunar Surface Radio Wave Propagation in the Presence of a Regolith and a Sparse Exospheric Plasma.
http://www.sti.nasa.gov

16.

Watson, C., Jayachandran, P. T., Kashcheyev, A., Themens, D. R., Langley, R. B., Marchand, R., & Yau, A. W. (2023). Radio Instrument Package for Lunar Ionospheric
Observation: A concept study. Radio Science, 58, e2023RS007666. https://doi.org/10.1029/2023RS007666

17. Sanchez, M., Rodriguez-Alvarez, N., Kahan, D., Morabito, D. D., & Elliott, H. M. (2020). Multipath Measurements at the Lunar South Pole from Opportunistic Ground-based
Observations — Part I: Experiment Concept.
18. USGS (2017). Moon Clementine Topographic Maps.
19. Spirent (2023). GSS9000 GNSS Simulator Datasheet. Available at: https://www.spirent.com/assets/u/datasheet-gss9000-series

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