LEO PNT with Nano Satellites
What is the New Space for GNSS?
Joshua Critchley-Marrows
7th Cis-lunar PNT Conference
28th May 2024

PNT TodayPNT is ﬁrmly embedded into modern society today, including transportation, communications, ﬁnance and energy.
In fact, so ﬁrmly embedded is its value, in the US, a loss to GNSS will cost the economy $1 billion (¥130 billion) per day(NIST study).

Transportation

Communications
Aviation
Maritime

Time,

Maps

PoStationo,Psit
ione
Tim

Broadcast Tower

onisitCommunication
NetworkSmartphone

Rail金融ネットワーク

GNSS

送電網mTieTime

Internet Banking

Power Plant
Hydroelectric

Nuclear

EnergyFinancialATM

参考：内閣官房HP、デジタル田園都市国家構想実現会議第13回（令和5年6月2日）資料
https://www.cas.go.jp/jp/seisaku/digital_denen/dai13/04_muraiiinn.pdf

Stock Market

2

PNT TodayThe economic value of the GNSS industry is
expected to increase greatly over the next
decade.
This is especially the case for the Asia-Paciﬁc(to share 47% of the GNSS market).

772兆円!

65兆円!

‘EUSPA GNSS Market Report 2024’, EUSPA

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PNT Under Threat

4

PNT Under Threat‘A Time and a Place for Resilience’, FrontierSI5PNT Under Threats ofeitilirabVulne
GNSSeamrtsowndmoFreamrts
to up

A Time and a Place for Resilience, FrontierSI

6

Deﬁnitions of Resilient PNTWhere it concerns issues
to PNT, and to ensure its
resilience, it is best toconsider the literature.

Commonly adopted inmilitary ﬁelds

The largest market‘Ensuring PNT resilience:
A global review of navigation
policies and roadmaps’,
University of Tokyo

To ensure the continuity
and availability

When GNSS isunavailable

7Maritime Sector is in trouble, especially...

Perhaps we should
start here?

What are the performance requirements?
Published in ‘IALA R-129 GNSS Vulnerabilities and Mitigation Measures’TargetDomains9

Our Solutions
Our micro satellites to meet various demonstration and business needs● Flexible and efficient production system● Multiple manufacturing technologies

IoT communicationsfor SDGs

Optical / IRfor SDGs

VHF antenna
for maritime DX

Lunarinfrastructure

Resilient andHigh-Precision PNT

IoTCommunicationsfor SDGs

High-resolution
optical, infrared,
spectroscopic
missions

VDES
communication,
ship monitoring

Ranging for mass
market applications

Education,advertising anddemonstration
opportunities

Advertising anddemonstration
opportunities

Adapted tohigh-spec hosted
payloads

High-precision
pointing attitudecontrol for opticalcommunication forlunar infrastructure

Scientiﬁc Education

Smart Agriculture

Disaster Prevention

Education andResearch

Hosted payload foreasy access tospace

Next AIS system(AIS+ASM+VDE)

Ship monitoring

Timingsynchronization for
criticalinfrastructure

Lunar Infrastructure Critical InfrastructureOur Solutions
Our micro satellites to meet various demonstration and business needs● Flexible and efficient production system● Multiple manufacturing technologies
But ﬁrst I want todiscuss VDES…

IoT communicationsfor SDGs

Optical / IRfor SDGs

VHF antenna
for maritime DX

Lunarinfrastructure

Resilient andHigh-Precision PNT

IoTCommunicationsfor SDGs

High-resolution
optical, infrared,
spectroscopic
missions

VDES
communication,
ship monitoring

Ranging for mass
market applications

Education,
advertising anddemonstration
opportunities

Advertising anddemonstration
opportunities

Adapted tohigh-spec hosted
payloads

High-precision
pointing attitudecontrol for opticalcommunication forlunar infrastructure

Scientiﬁc EducationSmart Agriculture

Disaster Prevention

Education andResearch

Hosted payload foreasy access tospace

Next AIS system(AIS+ASM+VDE)

Ship monitoring

Timingsynchronization for
criticalinfrastructure

Lunar Infrastructure Critical InfrastructureVDES(VHF Data Exchange System)VDES satellite constellation● Maritime Domain Awareness (MDA)● Marine environmental management● Monitoring prohibited areas● Avoidance of pirates

Maritime Authority● Identify suspicious vessels● Countermeasures against
illegal ﬁshing and smuggling● Mesh communication of ﬁshing tools,buoys, etc.
● Identiﬁcation of no signal items● Provision of weather information Buoys● Efficient port entry?

?
Suspicious ships● Proof of originof seafood● Easy communication● Identify of no signal vessels● Efficient logistics● Navigation● Support automatic operation● Efficient logistics● Big data sharing● Safety and rescue information

Fishing boats
PortGround

Vessels

Coastal area

Vessels

Offshore

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VDES(VHF Data Exchange System)

Service Area

Satellite Constellation● 50~100 Satellites

AE VDES Satellites 1st Gen.
●Size: W6U (100 x 226.3 x 366 mm)●Power: 50W●TT&C: S-band●Mission data downlink: X-band● Coverage from 60°N to 60°S
at all times

13Next Generation Marine AIS – VHF Data Exchange System
One of the most signiﬁcantchallenges to LEO PNT is theallocation of spectrum forsupporting services.

GNSSL-Band

VDES offers the opportunity
to provide a supplementary,
dedicated pseudocode on an
already ITU supported
frequency allocation, with aready market.

Reported attacks across the world on GNSS –including jamming, spooﬁng, cyber andkinetic weapons.
GNSS is at risk for maritime vessels, andensuring resilient services are essential.

Known as R-Mode, theseLEO PNT signals may operatefrom 157-162 MHz.

VDES
VHF-BandVHF would require muchlarger jamming and spooﬁng
equipment.

Could this be a ﬁrst generation LEO PNT?

Delivery of
R-Mode Services
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Challenges

Ionospheric Factor
The ionosphere is a major challenge at the VHF.
The ionospheric delay according to the atmosphericmodel of ‘P.531-15’ will cause a delay of over 100+ m –highly variable according to current atmosphericactivity.

How to remove it?
By introducing ionospheric modelling, the delay can be
reduced to approximately 30-50% for VDES.
Still, it is very poor at high ionospheric activity - above 1
km in some cases. Other methods are needed…

VDES will operate
at 157-162 MHz
Delay of 100+ m

TECU : Total Electron Content Unit
ITU-R P.531-15

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Challenges

Channel Performance
Another consideration is the channel model offered by a VDE-SAT R-Mode.
Each message could use an existing or implement a dedicated pseudocode for transmission.

We are conﬁned by the standard…
How much could be allocated?

Potential R-Mode Allocation

How to design?
What is the rate of transmission?

Only 8% of the signal bandwidth can be dedicated to delivering an R-Mode.

ITU-R M.2092-1
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Challenges

Channel Performance
Various VDES parameters have been established for each signal waveform.
Critical parameters include:● Channel bandwidth● Symbol number● Roll-off ﬁltering / cut-off● Symbol / chip rate
● Modulation● Burst length

ITU-R M.2092-1

J. Šafář, A. Grant, and M. Bransby, ‘Performance bounds for VDE-SAT R-Mode’, International Journal of Satellite
Communications and Networking, vol. 41, no. 2, pp. 134–157, 2023, doi: 10.1002/sat.1429.

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Challenges

Channel Performance
Under separate channel considerations, initially introduced by research from the UK General Lighthouse Authority,modelling of Ziv-Zakai (modiﬁcation to the Cramer-Rao Bound) can indicate potential performance.

J. Šafář, A. Grant, and M. Bransby,*Custom employs a dedicated Gold Code with a 150 kHz bandwidth signal.

‘Performance bounds for VDE-SAT
R-Mode’, International Journal of Satellite
Communications and Networking, vol. 41,

SAT-MCS-0.100, SAT_MCS-0.150 and Custom performs best - each using the highest bandwidth.

no. 2, pp. 134–157, 2023, doi:
10.1002/sat.1429.

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Challenges

A New Ephemeris
What about the navigation message?
We have proposed an extension to the traditional Kepler
parameters to account for additional orbital dynamics in LEO.
The validity interval is reduced sharply – satellite visibility time isapproximately 10 min…

GNSS derived orbit propagated to 30 min validity interval

GPS ICD: ‘IS-GPS-200N’ (2022),
US Department of Defense

Precise orbit propagated to 30 min validity interval
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VDES R-Mode Potential Performance
Scenario : Stationary ship on the ocean for 10 min.
Constellation Size : ~50 satellites
Orbit : Sun-Synchronous Orbit
Update Interval : 15 s
Frequency : 161.275 MHz
Monte-Carlo is performed over many orbital scenarios.
Performs best at polar regions because of orbit design.
Is this performance sufficient however – need to overcome the ionosphere!
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Solutions for PNT

High-Precision and Critical Applications
ArkEdge Heritage

ArkEdge FutureHigh-Precision,
Augmented PNTNavigationfor Ships

Higher SNR
More orbital
diversity
Greaterprecision

Translating
our Systemsto Deliver

Mass Market Applications
Navigation
for theMoonService
Depends on
the…
Customer

Alternative PNTGreaterresilience
Timing andnavigation
supportCritical Applications

Thank you for listening