UPSC Prelims Practice Questions — Strengthening India’s Indigenous Navigation Capabilities

Q1. With reference to the orbital architecture of a regional navigation system such as NavIC, consider the following statements: Which of the statements given above is/are correct?

1. A geostationary satellite orbits in the Earth's equatorial plane with a period equal to one sidereal day, so it appears fixed in the sky to an observer on the ground.
2. Geostationary satellites positioned at India's longitudes can serve users in the high-latitude polar regions as effectively as they serve users in India.
3. A satellite in an inclined geosynchronous orbit also has a period of one sidereal day, but its apparent position in the sky drifts north and south during the day.

• A. 1 and 3 only
• B. 1 and 2 only
• C. 1, 2 and 3
• D. 1 only

Q2. Consider the following facts about NavIC as of July 2026: only three satellites were providing positioning, navigation and timing (PNT) services; standalone positioning using NavIC alone was not possible; the NavIC timing service continued to function; and NavIC is generally used alongside other GNSS in multi-constellation receivers. Which of the following inferences can be drawn from the above?

1. A timing receiver at a fixed, precisely surveyed location could still derive accurate time from NavIC signals.
2. Users of the encrypted Restricted Service were also unable to obtain standalone positions from NavIC alone, since that service relies on the same satellites.
3. Smartphones combining NavIC with GPS and other GNSS signals were unable to compute their position during this period.
4. Restoring standalone NavIC positioning would require at least one more satellite to begin providing PNT services.

• A. 1, 2, 3 and 4
• B. 2, 3 and 4 only
• C. 1, 2 and 4 only
• D. 1 and 3 only

Q3. With reference to atomic clocks on navigation satellites, consider the following statements: Which of the statements given above is/are correct?

1. Because range is computed from a signal's travel time at the speed of light, a timing error of one microsecond would produce a range error of roughly 300 metres.
2. A navigation satellite whose atomic clock has stopped working may still be used for functions such as one-way message broadcasting.
3. Navigation satellites carry more than one atomic clock as a redundancy measure, because a satellite cannot provide usable ranging signals without a working clock.

• A. 1 only
• B. 1, 2 and 3
• C. 2 and 3 only
• D. 1 and 3 only

Q4. A satellite navigation receiver working on a single constellation needs signals from at least four satellites to compute a three-dimensional position by itself. The fourth satellite is required primarily because the receiver must:

• A. correct the ionospheric delay on each of the three measured ranges
• B. estimate its own velocity alongside its three position coordinates
• C. identify which received satellite signals are encrypted for strategic users
• D. solve for its own clock offset alongside its three position coordinates

Q5. With reference to the services and signals of NavIC, consider the following statements: Which of the statements given above is/are correct?

1. The Restricted Service is encrypted so that only authorised users can access it, whereas the Standard Positioning Service is open to civilian users.
2. Interoperability of the Standard Positioning Service with other GNSS means that NavIC satellites rebroadcast GPS signals whenever NavIC satellites are unavailable.
3. The addition of the L1 band on NVS satellites extends NavIC's service area from a regional footprint to the entire globe.

• A. 1, 2 and 3
• B. 2 and 3 only
• C. 1 only
• D. 1 and 2 only

Q6. A domestic smartphone maker wants to add NavIC support using the same GNSS chipsets it already uses for GPS and Galileo. Which feature of the second-generation NVS satellites most directly makes this easier?

• A. Transmission of navigation signals in the L1 frequency band
• B. Placement in geosynchronous rather than lower Earth orbits
• C. An indigenously developed rubidium atomic frequency standard
• D. An encrypted Restricted Service for authorised strategic users

Q7. With reference to the placement of navigation satellites into geosynchronous orbits using a transfer orbit, consider the following statements: Which of the statements given above is/are correct?

1. The launch vehicle's upper stage itself circularises the orbit at geosynchronous altitude, so the satellite does not need propulsion of its own for this purpose.
2. The burns that raise the low point of the transfer orbit to make it circular are performed near the orbit's apogee.
3. The orbit-raising failure of NVS-02 arose in the satellite's own propulsion system after the launch vehicle had already completed its job.

• A. 1 only
• B. 1 and 2 only
• C. 1, 2 and 3
• D. 2 and 3 only

Q8. Consider the following assertion: A navigation satellite stranded in its geosynchronous transfer orbit cannot serve as a normal member of a regional constellation such as NavIC. Which of the following statements support/supports the above assertion?

1. In the transfer orbit, the satellite's altitude swings from a few hundred kilometres to about 37,000 kilometres in every revolution.
2. A regional constellation depends on satellites remaining continuously above its service region, which geosynchronous orbits provide.
3. The satellite's onboard systems, including its navigation payload, stop working once orbit raising fails.
4. The satellite was launched on a GSLV rather than on a PSLV.

• A. 1, 2 and 3 only
• B. 1 and 2 only
• C. 3 and 4 only
• D. 2 and 4 only