IEEE - Aerospace and Electronic Systems - August 2022 - 14

Maximization of LEO Nanosatellite's Transmission Capacity to Multiple Ground Stations
Table 6.
Minimum, Average, Maximum Visibility Time, and Total Number of Contacts in 15 Orbits Corresponding to RAAN = 12.4
and AOP = 111.7.
Site
South Pole station
Dome-C station
Mario Zucchelli station
Atacama
White Mountain
Tenerife
Longyearbyen Airport
Total
236.01
258.01
248.01
64.00
318.01
144.00
174.01
236.01
340.01
342.01
316.01
324.01
336.01
342.01
236.01
299.26
296.76
190.01
321.01
240.01
297.57
15
8
8
2
2
2
9
46
Min. visibility time (s) Max. visibility time (s) Avg. visibility time (s) Nr. of contacts
where rS/C is the orbit semimajor axis and the only variable
of the equation, as the Earth's mean radius RE,GS
altitude hGS and minimum elevation from ground Emin
are either constrains or constants.
Figure 9 shows the visibility cone for the active pointing
telescope considering a minimum elevation detectability
of20, the FWHM main lobe of the pointing telescope,
which is equal to 0.14 for a 2-m parabolic reflector, and
the FWHM of the calibration signal from the satellite,
which is equal to 2.80. It can be deduced that without an
ADCS, the contact duration between the payload and the
radio telescope, computed as the time the TUT is contained
inside the FWHM cone, would be considered low if
compared to the time in which the satellite is visible to the
telescope. Therefore, to maximize the signal detectability,
the presence of the ADCS on board S/C is essential. The
simulations were conducted considering different combinations
ofRAAN and AOP angles, which led to a different
number of contacts by the satellite with distinct telescopes.
Orbits that did not guarantee at least one contact
with all seven radio telescopes were discarded and for the
remaining orbital configurations, the maximum, minimum,
and mean visibility time of each radio telescope
were computed considering the whole duration of the simulation
of 15 orbital periods. Figure 10 reports the mean
visibility time between the S/C and all TUTs, calculated
as the mean value of the average visibility time for every
considered combination ofRAAN and AOP angles.
It can be seen from Figure 10 that the three families of
orbits are not completely separated, but it is evident that
SET 3 ensures a set of orbits that generally have a longer
mean contact time. It is in fact evident from (10) that the
altitude of the orbit directly influences the portion of the
sky in which the satellite is visible, and therefore, to
increase the visibility time, the orbit with the greatest
14
semimajor axis should be selected. Table 4 reports the
maximum, minimum, and mean maximum values for the
visibility interval for the three sets of orbital families and
provides a numerical estimation of the relative increase in
mean visibility.
The maximum value of the mean maximum visibility
time for SET 3 orbits is found considering RAAN =
198.6 and AOP = 161.4. Table 5 reports the corresponding
results.
Figure 11 shows an overview on the number ofground
telescopes seen by the satellite during the whole duration
of the simulation considering different combinations of
angles for orbits belonging to SET 3.
It is evident that the combination of angles that provides
the maximum mean visibility time does not correspond
to the one relative to the highest number of
telescopes seen by the satellite. A high number of ground
Figure 13.
Skyplot of the satellite from the telescope in Dome-C station for
SET 3 (RAAN = 12.4 and AOP = 111.7) orbit.
IEEE A&E SYSTEMS MAGAZINE
AUGUST 2022

IEEE - Aerospace and Electronic Systems - August 2022

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