Neptune

Total deaths: 1,141,588

Origin of Tsunami

Neptune(After NOAA)How to issue the forecast?
Hypocenter andMagnitude~30 s

Plausible tsunami heightis extracted fromdatabase based on~３ minvarious fault planeassumption.

Tsunami forecast database (JMA)
Various fault plane are assumed for the tsunami calculation.

NeptuneExample forecast:
Neptune3 min after 2011 Tohoku earthquake (EQ)
Magnitude (M) 7.9 -> under estimated!

28 min after 2011 Tohoku EQMagnitude (M) 8.1 -> under estimated!

NeptuneEstimated magnitude after the Tohoku EQ

NeptuneActual magnitude (M9)Under estimate[S]

Initial tsunami source is required
for accurate tsunami forecast

NeptuneWhy is tsunami forecast difficult?

Neptune• It is impossible to estimate magnitude of more than 8
immediately after the large EQ.
• Fault plate slip estimated by seismic wave is notalways coincident with tsunami source.
• So far, no direct measurement of tsunami source.

Tsunami ionospheric hole

NeptuneGlobal navigation systemsatellite radio occultation(GNSS-RO) measurement canmeasure the tsunami
ionospheric hole.

Tsunami source isestimated from theionosphericelectron density
depression.
Tsunami ionospheric hole(Kamogawa et al., 2016)

Many low-earth-orbit (LEO)
satellite consternation canmeasure ionospheric electrondensity.

Method 1

Vessels crossing tsunami inform thetsunami velocity through VDES (VHF
Data Exchange System)

Neptune✓ VDES (former AIS) can obtainvessel information (location,velocity, direction etc) via satellite.
✓ When tsunami wave across thevessel, VDES includes tsunami
velocity information.
✓ Various VDES data inversely
estimate the tsunami source.

Vessel distribution identified by VDES（Vesseltracker.com）

Method 2

Propagating tsunami height measured
Neptuneby GNSS reflectrometry (GNSS-R).
GNSSLEO(CubeSat)

GNSS-R can measure
the sea height as well as
tsunami height.
Multi-point tsunami
height data provide thetsunami source throughinversion analysis.

Method 3

Summarize of operations

NeptuneInmarsat
GNSSMIS
dataCubeSat
Tsunami Ionospheric Hall Observation
Ionospheric Total Electron Count (TEC)
Occultation observation (GNSS-RO)

Tsunami Height Observation
Sea surface reflected radio
wave
GNSS-R (reflected)
Tsunami Velocity Observation
Vessel Data，VDES

tsunamipropagation

tsunamiwave
sourceTsunami Ionospheric Hole
Altitude: about 300 km
Duration: Approx. 20 min.

tsunamipropagation

Far way

Data Downlink
Ground Analysis and Warning Issuance
Tsunami HeightCubeSat

NeptuneOrbit

Non-sun-synchronous orbit(Inclination: 60 degrees)

Altitude

500 〜 700 km

LaunchMain satellite

Size

100 mm×226.3 mm×366mm

Weight7.828 kg

Communication

Uplink：S-band
Downlink：S-band
Realtime: InmarsatMission life

2.5 years

Phase control: Fading

Neptune𝑣10 = 7596.1 [m/s]Initial State
SAT10

𝑣9 = 7596.3 [m/s]}v

540.0 kmΔ =0.2 [m/s]539.5 km

SAT09
𝑣1 = 7597.9 [m/s]536.7 km
SAT01

≈22 times
6 months

Latitudinally alignment
36-degree difference

22 orbit planes

The total 220 satellites
construct spatiotemporallyuniform observation points
in space.

. Implementation plan

NeptuneMission life period

Practically 2 years

Satellite cost

$0.4 million / 1 sat.

Satellite number for constellation

220Total satellite cost

$88 million

One rocket cost

$20 million

Total rockets

22Total rocket cost$440 million

Total cost

$528 million (per 2 years)

One cable: $2 billion per 30 years.

Ocean bottom cable: $40 billion per 30 years.
(Cable will become waste 30 years later.)
Satellite cable: $9 billion per 30 years.