Justification for launching from French Guiana which is

Justification for launching from French Guiana which
is near to equator

As
we all know near the equator, the surface of the Earth is traveling faster. If
we look at two spots from pole to pole, one spot on the equator and the other is
halfway to the pole, so each will make a complete revolution in 24 hours in a
loop. But since the Earth’s shape is round, and the widest point is at the
equator the spot on the equator would have to cover more miles in that twenty
four hours. That means that the land is moving faster at the equator than any
other place on the surface of the Earth.

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 The land at the equator is moving 1670 km per
hour whereas land halfway to the pole is only moving 1180 km per hour, so this
gives us an advantage by launching from the equator the spacecraft travels almost
500 km/hour faster once it is launched.

Hohman-transfer orbit

The
transfer process to the final orbit will be perform by using a Hohman Transfer
orbit. The parking orbit (200-300 Km) of the satellite will be a lower circular
orbit. This maneuver is used to perform a transfer between two circular orbits
of different radii in the same plane. Two engine impulses will be used as seen
in figure below.

The
orbit transfer process from the lower circular orbit occurs by firing the first
impulse in the perigee section of the Earth to transfer it to the elliptical
orbit where it moves to the elliptical orbit where it performs the second
impulse that will transfer the satellite from its elliptical orbit to the
higher circular orbit.

 

 

In
GEO position. Orbit maneuvers are necessary in order to decrease inclination or
move the satellite in emergency scenarios this movements will be perform by
delta-burns. After operations and completion of the mission the satellite will
use the remaing fuel to deorbit or to move itself to the “disposal orbit”.
Since a GEO orbit satellite is quite expensive to recover we deorbit it around
the earth and burn it in the atmosphere. That requires delta-v to move the
satellite into a graveyard orbit is about 11 m/s.

 

 

Environment

Due
to the satellites location it is exposed to environmental effects such as high
radiation. The satellite has to be protected from this effects, satellite
design engineer has to take in to account the space weather and environment,
with the use of radiation models we can determine how the satellite will be
affected to space weather. Cahoy study states that a satellite’s radiation
exposure may vary depending on its orbit. For instance, some orbits are more
dangerous than others; engineers needs to select components and materials that
can survive and operate in such environments

Cahoy
and Lohmeyer discovered that many amplifiers where affected during times of
high-energy electron activity, a phenomenon that occurs during the solar cycle,
in which the sun’s activity fluctuates over a period of 11 years. The high-energy
electrons flux is higher during the declining phase of the solar cycle. Taking
into account all these various effects our satellite has to be designed in order
to operate under such harsh conditions for a long time.

Payloads

Satellite
has to receive all the buoys’ data and retransmit it in real time to the
nearest ground station in our case it can be the Santiago de Chile’s. In order
to do that a repeater is needed on the satellite working at two frequencies for
uplink and downlink.

The
total latency will be the sum of the free-path (250ms), the computational delay
of the satellite and the time response of the ground stations. Its latency
depends mainly on the distance to the orbit and the ground equipment which can
be assumed as an instantaneous system.

Having
the sensors on the buoys the resolution is maximum and power consumption of the
satellite is just needed to operate the radio equipment, which can be obtained
via solar panels.

Additionally,
buoys need energy which can be obtained by batteries and solar panels. As the
lifetime of the mission is high (7 years) the need of alternative power sources
is needed for the “Tsunameter” or may use different type of sensors attached to
buoys. We have checked that for a GEO and a buoy would be enough to cover in
real time.

For meteorological purposes, we
would need to include a camera on the visible and the infrared spectrum and a
High-resolution visible HRV imaging of half of the Earth’s disc and altimeter.

 

Operation

Detection
of tsunamis by DART systems

The
detection of tsunamis is carried out by the Deep-ocean Assessment and Reporting
of Tsunami (DART) solution. DART systems consist of an anchored seafloor bottom
pressure recorder (BPR) and a companion moored surface buoy for real-time
communications. Sensors that measure the pressure at fixed points on the
seafloor in a quiet environment of the deep waters.

When
tsunami occurs, the change in pressure is observed on the seafloor and detected
by the sensors. An acoustic link transmits data from the BPR on the seafloor to
the surface buoy. The BPR collects temperature and pressure at 15-second
intervals. The pressure values are corrected for temperature effects and the
pressure is converted to an estimated sea-surface height (height of the ocean
surface above the seafloor) by using a constant 670 mm Hg.

The
system has two data reporting modes, standard and event. The system operates
routinely in standard mode, in which
four spot values (of the 15-s data) at 15-minute intervals of the estimated sea
surface height are reported at scheduled transmission times the initial few
minutes, followed by 1-minute averages.

Event mode messages also contain
the time of the initial occurrence of the event. The system returns to standard
transmission after 4 hours of 1-minute real-time transmissions if no further
events are detected.

Underwater-to-surface data transmission

This
is realized by using mooring cable. In this system, data from sensor is transmitted
to the surface by applying a signal to the internal winding of a cable coupler.
This induces a signal in the single-turn secondary winding formed by the
mooring cable passing through the coupler. The signal is retrieved at the
surface by a similar configuration. This inductive modem technology provides a
convenient, economical, and reliable solution while still maintaining
flexibility.

 

Ground stations

The
TSUSAT system will use two ground stations located in South America, the main
station will work in Santiago, downloading the data collected by the
geostationary satellite. An algorithm for detecting variations in measurements
that could be potentially dangerous might be implemented in near real time in
order to have enough time to alert at the related institutions. A backup ground
station located in Lima can be used in case that the main station has a
technical disruption.

The
subsystems will be redundant being able to use different combinations of them,
just in case if one of them stops working due to technical disruptions. This
configurations will be selected by setting different modes from ground control.

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