Q31) Which are the frequency bands used by satellite to connect with Ground Stations or Earth Stations with the help of VSATs ?
Answer:
- Following bands are used by satellite for different applications.
- L band : 1 to 2 GHz
- S band : 2 to 4 GHz
- C band : 4 to 8 GHz
- X band : 8 to 12 GHz
- Ku band : 12 to 18 GHz
- K band : 18 to 26.5 GHz
- Ka band : 26 to 40 GHz
Q32) What is the frequency range of Ku band ? What are its applications ?
Answer: Frequency Band: 12-18GHz.
It is used in Direct to Home (DTH) services.
Q33) Explain the range of Ka Band.
Answer: Ka-Band: The range of frequencies that are available for use by satellite communication systems at around 30GHz for the uplink and 20GHz for downlink. This band is used in particular for satellite internet services and regional broadcasting.
Q34) Why we prefer ku band over c band ?
Answer: Ku-band is preferred for cases where there is a limited area for installation, because a smaller dish size is needed and it is easy to install. From a commercial point of view, Ku-band is better for satellite applications that need smaller bandwidth, as the equipment is cheaper than C-band.
Q35) What are types of orbits based on the angle of inclination ?
Answer:
- There are four types of orbits based on the angle of inclination.
- Angle of inclination is either zero degrees or 180 degrees.
Polar orbit: - Angle of inclination is 90 degrees.
Prograde orbit: - Angle of inclination lies between zero and 90 degrees.
Retrograde orbit: - Angle of inclination lies between 90 and 180 degrees.
Equatorial orbit:
Q36) Why is link budget calculated ?
Answer: it is calculated to know the reduction in received power caused by losses at transmission and reception.
eq: [Pr]=[EIRP] +[G]-[losses]
Q37) What are types of losses in satellite communication ?
Answer:
Q38) What are the 6 orbital elements ?
Answer:
Q39) What is semi-major axis and semi-minor axis ?
Answer:
- Semi-major axis:
- In ellipse, the semi-major axis is the longest diameter through the center and foci
- Semi-major axis:
- In ellipse, the semi-minor axis is the shortest diameter through the center and perpedicular to semi-major axis.
Q40) What is the Eccentricity ?
Answer:
- The value of Eccentricity (e) fixes the shape of satellite’s orbit.
- e = c / a
- For ellipse, It ranges in between 0 and 1.
- e = 0 for a circle
Eccentricity(e): distance from the centre of the ellipse to one focus / semimajor axis
Q41) What is argument of perigee (ω) ?
Answer: Argument og perigee is the angle between the ascending node and perigee, measured in the orbital plane
Q42) What is right ascension of the ascending node (Ω) ?
Answer:
- The ascending node is the point where the satellite crosses the equatorial plane going north. Ω is the right ascension of this point. In practice, it is the right ascension of the intersection of the orbital plane with the equatorial plane.
Q43) What is Inclination ?
Answer: The angle between orbital plane and earth’s equatorial plane is known as inclination (i).
Q44) Why we do not use 22GHz and 63GHz frequency for ionospheric satellite communication ?
Answer: Two components in ionosphere are responsible for majority of signal absorption. ie. Oxygen and Water.
Water absorption takes frequencies 22GHz and around 63GHz are absorbed by Oxygen.
Hence use of such frequencies are avoid in ionospheric and satellite communication.
Q45) Define Eclipse.
Answer: The total or [partial obscuring of one celestial body by another. The events that most affect satellites are eclipses of the sun by the earth or the moon., which deprives the satellite of its usual source of power and causes it to cool down rapidly because it is no longer heated by the sun. The satellites are designed to cope with such extreme events. Normally there is no effect on the commuication services provided by the satellite during eclipse.
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