UPSC CIVIL SERVICES EXAMINATION

PRELIMS 2019 SPECIAL

LECTURE 13

MCQs – STATIC – SCIENCE

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CLASSIFICATION OF ORBITS

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CENTRIC CLASSIFICATION

INCLINATION CLASSIFICATION

SYNCHRONICITY CLASSFICATION

ALTITUDE CLASSIFICATION

CLASSIFICATION CRITERIA

1. Galactocentric2. Heliocentric3. Geocentric4. Selenocentric

INCLINED NON-INCLINED

1. Polar2. Polar Sun-

Synchronous

1. Equatorial2. Near Equatorial

1. Low Earth2. Medium Earth3. High Earth

1. Geosynchronous Orbit

2. Geostationary orbit3. Graveyard Orbit4. Sun synchronous

Orbit5. Geo Synchronous

Transfer Orbit

Types of Orbits

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Galactocentric Orbit: A galactocentric orbit is an orbit that goes around the center of a galaxy. Our solar systemfollows this type of orbit around the Milky Way.

1

Heliocentric Orbit: A heliocentric orbit is one that goes around the sun. All the planets in our solar system, alongwith all the asteroids in the Asteroid Belt and all comets, follow this kind of orbit.

2

Geocentric Orbit: A geocentric orbit is one that goes around the Earth. Our moon follows a geocentric orbit, andso do most manmade satellites. The Moon is Earth's only natural satellite.

3

There are three major types of geocentric orbits: low-Earth orbit (LEO), medium-Earth orbit (MEO), andgeostationary orbit.

4

Selenocentric Orbit: Also called as Lunar Orbit i.e. the orbit around the Earth’s Moon.5

Types of Orbits

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Inclined Orbit: A satellite is said to occupy an inclined orbit around Earth if the orbit exhibits an angle other than0° to the equatorial plane.

1

Polar Orbit: A polar orbit has an inclination of 90 degrees passing over the poles of the planet on each pass. Thesetypes of orbits are often used for earth observation and weather services.

2

Polar Sun Synchronous Orbit: It is a nearly polar orbit around a planet, in which the satellite passes over anygiven point of the planet's surface at the same local mean solar time. It is therefore sun synchronous.

3

TYPES OF ORBIT

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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.

1

Equatorial Orbit: A satellite in equatorial orbit flies along the line of the Earth's equator.2

Equatorial orbits can be useful for satellites observing tropical weather patterns, as they can monitor cloudconditions around the globe. These Orbits are usually medium or low orbits.

4

To get into equatorial orbit, a satellite must be launched from a place on Earth close to the equator. NASA oftenlaunches satellites aboard an Ariane rocket into equatorial orbit from French Guyana.

3

Near Equatorial Orbit: It is an orbit that lies close to the equatorial plane of the object orbited. It does not lieexactly on the equatorial. Its inclination with respect to equatorial plane is nearly zero but not exactly zero.

5

TYPES OF ORBIT

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Synchronous Orbit: An orbit whose period is a rational multiple of the average rotational period of the bodybeing orbited and in the same direction of rotation as that body

1

Geostationary Orbit: It is a circular orbit that is exactly in the plane of equator on the earth. A satellite moving ina geostationary orbit has its angular velocity is equal to the angular velocity of the Earth (appears stationary)

2

There is only one geostationary orbit.3

TYPES OF ORBIT

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Most communications satellites in use today for commercial purposes are placed in the geostationary orbit,because one satellite can cover almost 1/3 of Earth’s surface, offering a reach far more extensive than what anyterrestrial network can achieve.

1

The height of the geostationary orbit is 35,786 kilometers above earth. In Geostationary Orbit, the satellite moveswith an orbital speed of 11,068 km per hours.

2

TYPES OF ORBIT

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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.

1

Because the satellite orbits at the same speed that the Earth is turning, the satellite seems to stay in place over asingle longitude, though it may drift north to south i.e. it does not appear exactly stationary

2

Sun synchronous Orbit: A sun-synchronous orbit is one that lies in a plane that maintains a fixed angle withrespect to the Earth-sun direction.

4

It is NOT circular orbit. It is NOT in equatorial plane but is inclined. There can be many geosynchronous orbits.3

TYPES OF ORBIT

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Geosynchronous Transfer Orbit is an elliptical orbit used to transfer between two circular orbits of different radiiin the same plane—used to reach geosynchronous or geostationary orbit using high-thrust chemical engines.

1

Graveyard Orbit: A graveyard orbit, also called a junk orbit or disposal orbit, is an orbit that lies away fromcommon operational orbits. One significant graveyard orbit is a supersynchronous orbit well abovegeosynchronous orbit. Satellites are typically moved into such orbits at the end of their operational life to reducethe probability of colliding with operational spacecraft and generating space debris.

2

TYPES OF ORBIT

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Low Earth

Orbit

Medium Earth

Orbit

High Earth

Orbit

It lies at an altitude of about 100-2000km.

A typical LEO satellite takes one and half hour to orbit the Earth

The International Space Station is in a LEO that 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 place a satellite in a LEO

MEO operates at about 8,000-20,000 km above the Earth (lower than GEO Orbit)

Their higher altitude as compared to LEO needs fewer satellites to provide coverage for communications

Orbits above thealtitude of 20,000km

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

QUESTION 1

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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

QUESTION 2

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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

QUESTION 3

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Q. Match the following

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

QUESTION 4

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A – Heliocentric 1 - The orbit that goes around the center of a galaxy

B –

Selenocentric

2 - The orbit wherein the motion of satellite is in same

direction as the rotation of the centric object

C -

Galactocentric

3 - The orbit that goes around the Sun.

D – Prograde

Orbit

4 - The orbit around the Earth’s Moon

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

QUESTION 5

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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

DO IT YOURSELF

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