UPSC CIVIL SERVICES EXAMINATION PRELIMS 2019 SPECIAL MCQs – STATIC – SCIENCE LECTURE 13
www.civilstap.com CLASSIFICATION OF ORBITS
CLASSIFICATION CRITERIA
CENTRIC INCLINATION SYNCHRONICITY ALTITUDE CLASSIFICATION CLASSIFICATION CLASSFICATION CLASSIFICATION
1. Galactocentric 1. Geosynchronous 1. Low Earth 2. Heliocentric Orbit 2. Medium Earth 3. Geocentric INCLINED NON-INCLINED 2. Geostationary orbit 3. High Earth 4. Selenocentric 3. Graveyard Orbit 1. Polar 1. Equatorial 4. Sun synchronous 2. Polar Sun- 2. Near Equatorial Orbit Synchronous 5. Geo Synchronous Transfer Orbit
www.civilstap.com Types of Orbits
1 Galactocentric Orbit: A galactocentric orbit is an orbit that goes around the center of a galaxy. Our solar system follows this type of orbit around the Milky Way.
2 Heliocentric Orbit: A heliocentric orbit is one that goes around the sun. All the planets in our solar system, along with all the asteroids in the Asteroid Belt and all comets, follow this kind of orbit.
3 Geocentric Orbit: A geocentric orbit is one that goes around the Earth. Our moon follows a geocentric orbit, and so do most manmade satellites. The Moon is Earth's only natural satellite.
4 There are three major types of geocentric orbits: low-Earth orbit (LEO), medium-Earth orbit (MEO), and geostationary orbit.
5 Selenocentric Orbit: Also called as Lunar Orbit i.e. the orbit around the Earth’s Moon.
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1 Inclined Orbit: A satellite is said to occupy an inclined orbit around Earth if the orbit exhibits an angle other than 0° to the equatorial plane.
2 Polar Orbit: A polar orbit has an inclination of 90 degrees passing over the poles of the planet on each pass. These types of orbits are often used for earth observation and weather services.
3 Polar Sun Synchronous Orbit: It is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. It is therefore sun synchronous.
www.civilstap.com TYPES OF ORBIT
1 Non Inclined Orbit: A non-inclined orbit is an orbit coplanar with a plane of reference. The orbital inclination is 0° for prograde orbits, and π (180°) for retrograde ones.
2 Equatorial Orbit: A satellite in equatorial orbit flies along the line of the Earth's equator.
3 To get into equatorial orbit, a satellite must be launched from a place on Earth close to the equator. NASA often launches satellites aboard an Ariane rocket into equatorial orbit from French Guyana.
4 Equatorial orbits can be useful for satellites observing tropical weather patterns, as they can monitor cloud conditions around the globe. These Orbits are usually medium or low orbits.
5 Near Equatorial Orbit: It is an orbit that lies close to the equatorial plane of the object orbited. It does not lie exactly on the equatorial. Its inclination with respect to equatorial plane is nearly zero but not exactly zero.
www.civilstap.com TYPES OF ORBIT
1 Synchronous Orbit: An orbit whose period is a rational multiple of the average rotational period of the body being orbited and in the same direction of rotation as that body
2 Geostationary Orbit: It is a circular orbit that is exactly in the plane of equator on the earth. A satellite moving in a geostationary orbit has its angular velocity is equal to the angular velocity of the Earth (appears stationary)
3 There is only one geostationary orbit.
www.civilstap.com TYPES OF ORBIT
Most communications satellites in use today for commercial purposes are placed in the geostationary orbit, 1 because one satellite can cover almost 1/3 of Earth’s surface, offering a reach far more extensive than what any terrestrial network can achieve.
2 The height of the geostationary orbit is 35,786 kilometers above earth. In Geostationary Orbit, the satellite moves with an orbital speed of 11,068 km per hours.
www.civilstap.com TYPES OF ORBIT
1 Geosynchronous Orbits: A satellite revolving in a geosynchronous orbit has its period equal to one sidereal day. However, such an orbit is neither equatorial nor circular.
2 Because the satellite orbits at the same speed that the Earth is turning, the satellite seems to stay in place over a single longitude, though it may drift north to south i.e. it does not appear exactly stationary
3 It is NOT circular orbit. It is NOT in equatorial plane but is inclined. There can be many geosynchronous orbits.
4 Sun synchronous Orbit: A sun-synchronous orbit is one that lies in a plane that maintains a fixed angle with respect to the Earth-sun direction.
www.civilstap.com TYPES OF ORBIT
1 Geosynchronous Transfer Orbit is an elliptical orbit used to transfer between two circular orbits of different radii in the same plane—used to reach geosynchronous or geostationary orbit using high-thrust chemical engines.
2 Graveyard Orbit: A graveyard orbit, also called a junk orbit or disposal orbit, is an orbit that lies away from common operational orbits. One significant graveyard orbit is a supersynchronous orbit well above geosynchronous orbit. Satellites are typically moved into such orbits at the end of their operational life to reduce the probability of colliding with operational spacecraft and generating space debris.
www.civilstap.com TYPES OF ORBIT
Low Earth Medium Earth High Earth Orbit Orbit Orbit
. It lies at an altitude of . Orbits above the about 100-2000km. . MEO operates at about 8,000-20,000 altitude of 20,000km . A typical LEO satellite takes km above the Earth (lower than GEO one and half hour to orbit Orbit) the Earth . Their higher altitude as compared to . The International Space LEO needs fewer satellites to provide Station is in a LEO that coverage for communications varies from 320km to 400km above the Earth’s surface . The transmission delay associated with LEO system is the lowest of all . It requires less energy to www.civilstap.com place a satellite in a LEO QUESTION 1
Q. Consider the following statements regarding geosynchronous orbits: 1) The satellite seems to stay in place over a single longitude 2) A person on any point on Earth, will always see a satellite in this Orbit Stationary with respect to his position Which of the above is/are correct? a) 1 only b) 2 only c) Both are correct d) None is correct Answer : a
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Q. Consider the following statements regarding Geostationary Orbit: 1) It is geo synchronous in nature 2) It has an angle of 1800 with the equatorial plane of the earth 3) There can only be one geostationary orbit Which of the above is/are correct? a) 3 only b) 1 and 3 only c) All of the above d) None of the above Answer : b
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Q. Consider the following statements regarding Geostationary Satellites: 1) The height of a Geostationary Orbit is nearly 11,068 km from the surface of the Earth 2) The satellite in a Geostationary Orbit moves with a speed of nearly 35,786km per hour Which of the above is/are incorrect? a) 1 only b) 2 only c) Both 1 and 2 d) None of the above Answer : c
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Q. Match the following
A – Heliocentric 1 - The orbit that goes around the center of a galaxy B – 2 - The orbit wherein the motion of satellite is in same Selenocentric direction as the rotation of the centric object C - 3 - The orbit that goes around the Sun. Galactocentric D – Prograde 4 - The orbit around the Earth’s Moon Orbit Select the correct code: a) A-1; B-3; C-4; D-2 b) A-3; B-4; C-1; D-2 c) A-4; B-3; C-1; D-2 d) A-3; B-2; C-1; D-4 Answer : b www.civilstap.com QUESTION 5
Q. Which of the following statements are correct: 1) A communication satellite placed in a geostationary orbit can cover almost half of the Earth’s Surface 2) Minimum three communication satellites placed in a geostationary orbit can cover entire Earth. Select the correct code: a) 1 only b) 2 only c) Both the statements are correct d) None of the statements are correct Answer : b
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Q. If you travel by road from Delhi to Shillong, what is the minimum number of States within India through which you can travel, excluding the origin and the destination? Select the correct option a) 4 b) 5 c) 6 d) 7
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