UPSC Prelims Practice Questions — Satellite radiation: blocking views

Q1. With reference to the classification of radio emissions from communication satellites used in recent radio-astronomy studies, consider the following statements: Which of the statements given above is/are correct?

  1. Electromagnetic noise from a satellite's power converters counts as an unwanted emission, because the equipment producing it supports the satellite's transmitter.
  2. Signals that a satellite's transmitter leaks outside its assigned frequency band count as unwanted emissions.
  3. Unintended radiation can be emitted even at times when a satellite's transmitter is not radiating.
  • A. 2 and 3 only
  • B. 1 and 3 only
  • C. 1, 2 and 3
  • D. 1 and 2 only

Q2. Consider the following statements: Which of the following is correct in respect of the above statements?

  1. Restricting only the frequencies and power at which satellites are licensed to transmit cannot by itself remove all the radio interference they cause to radio telescopes.
  2. Onboard components of satellites, such as power converters and computers, give off stray electromagnetic radiation that does not come from the satellite's licensed transmission chain.
  • A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
  • B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
  • C. Statement-I is correct, but Statement-II is incorrect
  • D. Statement-I is incorrect, but Statement-II is correct

Q3. Consider the following assertion: A satellite emission at about 1,613 MHz can seriously hamper the study of hydroxyl molecules in space even if every other frequency remains free of interference. Which of the following statements support/supports the above assertion?

  1. Molecules such as hydroxyl emit radio waves at their own characteristic frequencies, so studying them depends on those particular frequencies.
  2. Natural radio emissions from distant cosmic sources are extremely faint by the time they reach Earth, so a man-made signal at the same frequency can drown them out.
  3. Radio telescopes can observe hydroxyl only at night, when satellites are hidden in Earth's shadow.
  4. Satellite signals received at ground level are generally weaker than typical astronomical sources.
  • A. 2 and 3 only
  • B. 1, 2, 3 and 4
  • C. 1 and 2 only
  • D. 1, 3 and 4 only

Q4. Consider the following statements: Which of the following is correct in respect of the above statements?

  1. Emissions from communication satellites in low-earth orbit can threaten radio observations of hydroxyl molecules in space.
  2. Hydroxyl molecules occur only in Earth's upper atmosphere, through which satellite signals pass on their way to the ground.
  • A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
  • B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
  • C. Statement-I is correct, but Statement-II is incorrect
  • D. Statement-I is incorrect, but Statement-II is correct

Q5. With reference to communication satellites in low-earth orbit (LEO), consider the following statements: Which of the statements given above is/are correct?

  1. A single LEO satellite can see only a small part of Earth's surface at any one time, so continuous global service needs a very large number of satellites.
  2. Because a LEO satellite is far closer to Earth than a geostationary satellite, signals to and from it have a shorter round-trip delay.
  3. A LEO constellation meant to serve one country must still have its satellites pass over other parts of the world, as each satellite circles Earth's centre.
  • A. 2 and 3 only
  • B. 1, 2 and 3
  • C. 1 and 3 only
  • D. 1 and 2 only

Q6. With reference to direct-to-cell satellite communication, consider the following statements: Which of the statements given above is/are correct?

  1. Direct-to-cell service requires each user to install a dedicated satellite dish or terminal at the premises.
  2. Being deliberate, licensed transmissions, direct-to-cell signals are classed as intended emissions in studies of satellite interference.
  3. Because direct-to-cell signals are licensed, the transmitters producing them cannot give rise to emissions outside their assigned frequencies.
  • A. 1, 2 and 3
  • B. 1 only
  • C. 2 and 3 only
  • D. 2 only

Q7. Consider the following facts: Radio telescopes at sites in rural Australia, far from large towns, recorded radio emissions from low-earth-orbit communication satellites over roughly 376 hours of observation, and some of these signals were about 100 billion times brighter than typical astronomical sources. Which of the following inferences can be drawn from the above?

  1. Satellite interference is a problem only for observatories located in the Southern Hemisphere.
  2. Siting a radio telescope far from towns and mobile towers does not, by itself, protect it from transmitters in orbit.
  3. Within the affected frequencies, such signals can mask the faint emissions from cosmic sources.
  • A. 1 and 2 only
  • B. 2 and 3 only
  • C. 1 and 3 only
  • D. 1, 2 and 3

Q8. Consider the following facts: Radio telescopes in Australia recorded emissions from the Starlink, OneWeb and China's Guowang constellations, which are operated from different countries, and part of the radiation came from onboard electronics rather than from the satellites' transmitters. Which of the following inferences can be drawn from the above?

  1. Effective control of such interference requires coordination among the several countries under whose authority these satellites operate.
  2. Australia could end the interference at its telescopes by refusing to license these broadband services within its territory.
  3. Satellites can affect observatories in countries other than those from which the satellites are operated.
  • A. 1 and 2 only
  • B. 1, 2 and 3
  • C. 1 and 3 only
  • D. 2 and 3 only