UPSC Prelims Practice Questions — Navigation satellite NVS-03 is fully healthy: ISRO Chairman

Q1. With reference to India's satellite-based navigation services, consider the following statements: Which of the statements given above is/are correct?

  1. GAGAN is designed mainly to meet the accuracy and integrity requirements of civil aviation over Indian airspace.
  2. The GPS correction messages used by GAGAN receivers are broadcast by the NavIC constellation's own satellites.
  3. GAGAN's correction and integrity messages reach users through geostationary communication satellites.
  • A. 1, 2 and 3
  • B. 1 and 3 only
  • C. 1 and 2 only
  • D. 2 and 3 only

Q2. With reference to how a satellite navigation receiver determines its position, consider the following statements: Which of the statements given above are correct?

  1. The receiver infers its distance from each satellite from the signal's travel time, so an error in the satellite's clock becomes an error in the measured range.
  2. For accurate positioning the receiver must itself carry an atomic clock as stable as those on the satellites.
  3. Signals from at least four satellites are normally used because the receiver's own clock offset is solved as an unknown along with its three coordinates.
  4. Navigation satellites carry atomic frequency standards rather than ordinary oscillators because the stability of the onboard time reference limits ranging accuracy.
  • A. 1, 3 and 4 only
  • B. 1, 2, 3 and 4
  • C. 1 and 3 only
  • D. 2 and 4 only

Q3. Consider the following statements: Which of the following is correct in respect of the above statements?

  1. A navigation satellite whose onboard atomic clocks have all failed cannot provide accurate positioning service, even if its transmitters continue to work.
  2. A receiver calculates its range to a satellite from the signal's travel time, measured against the transmission time set by the satellite's clock.
  • 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

Q4. The second-generation NavIC (NVS) satellites broadcast navigation signals in the L1, L5 and S bands. In this context, consider the following statements: Which of the statements given above is/are correct?

  1. Broadcasting on two widely separated frequencies lets a receiver estimate and remove the ionospheric delay, because that delay varies with frequency.
  2. Adding an L1 signal makes NavIC easier to build into mass-market chipsets that were already designed to process L1 GPS signals.
  3. With the addition of the L1 signal, NavIC satellites become part of the GPS constellation and are controlled through its ground segment.
  • A. 1, 2 and 3
  • B. 2 and 3 only
  • C. 1 only
  • D. 1 and 2 only

Q5. Consider the following statements: Which of the following is correct in respect of the above statements?

  1. Since the NVS series added L1-band signals, NavIC can now provide positioning service worldwide, as GPS does.
  2. The coverage area of a satellite navigation system depends on the number and orbital placement of its satellites, not on the frequency band of its signals.
  • 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

Q6. NVS-03 was placed by its launch vehicle in an elliptical orbit and later reached a circular orbit after a long firing of its own engine. In this context, consider the following statements: Which of the statements given above is/are correct?

  1. Raising the highest point (apogee) of the elliptical orbit is by itself sufficient to make the orbit circular.
  2. After separation, the satellite's onboard propulsion, not the launch vehicle, completes the move to the final orbit.
  3. Release of the satellite into an elliptical orbit shows that the launch vehicle did not reach its intended orbit.
  • A. 1 and 3 only
  • B. 2 and 3 only
  • C. 2 only
  • D. 1 and 2 only

Q7. The NavIC constellation combines geostationary (GEO) and inclined geosynchronous (IGSO) satellites. With reference to these orbits, consider the following statements: Which of the statements given above is/are correct?

  1. A GEO satellite orbits in the equatorial plane and appears stationary to an observer on the ground.
  2. An IGSO satellite returns to the same point in the sky at the same time each day, although it appears to trace a figure-of-eight pattern.
  3. Every geostationary orbit is geosynchronous, but not every geosynchronous orbit is geostationary.
  • A. 1, 2 and 3
  • B. 1 only
  • C. 2 and 3 only
  • D. 1 and 3 only

Q8. NavIC places four of its satellites in inclined geosynchronous orbits instead of putting all of them in geostationary orbit. What is the main navigational advantage of this design for users in India?

  • A. Inclined satellites stay fixed above a single ground point, giving users an uninterrupted signal
  • B. Inclined satellites swing north and south daily, widening the spread of satellites seen from India
  • C. Inclined orbits have shorter periods, so each satellite passes over India several times a day
  • D. Inclined orbits keep satellites at lower altitude, shortening the signal travel time to India