UPSC Prelims Practice Questions — From moon’s far side, a satellite to look for the first radio signal
Q1. Consider the following statements comparing India's PRATUSH programme with the earlier SARAS 3 experiment:
1. SARAS 3 made its observations from a radiometer floating on water bodies in Karnataka, whereas PRATUSH is conceived as a space-based radiometer.
2. PRATUSH is planned in two phases, with the first phase in an orbit around the Earth and the second phase as a lunar orbiter.
3. SARAS 3 confirmed the cosmic dawn absorption signal earlier reported by the EDGES experiment, which PRATUSH is now intended to characterise in greater detail.
Which of the statements given above is/are correct?
- SARAS 3 made its observations from a radiometer floating on water bodies in Karnataka, whereas PRATUSH is conceived as a space-based radiometer.
- PRATUSH is planned in two phases, with the first phase in an orbit around the Earth and the second phase as a lunar orbiter.
- SARAS 3 confirmed the cosmic dawn absorption signal earlier reported by the EDGES experiment, which PRATUSH is now intended to characterise in greater detail.
- A. 1 and 3 only
- B. 2 and 3 only
- C. 1 and 2 only
- D. 1, 2 and 3
Q2. PRATUSH (Probing ReionizATion of the Universe using Signal from Hydrogen) is being developed by which one of the following?
- A. The National Centre for Radio Astrophysics, an autonomous centre of the Tata Institute of Fundamental Research at Pune
- B. The Physical Research Laboratory, a unit of the Department of Space of the Government of India at Ahmedabad
- C. The Raman Research Institute, an autonomous institute funded by the Department of Science and Technology at Bengaluru
- D. The Indian Institute of Astrophysics, an autonomous institute funded by the Ministry of Earth Sciences at Bengaluru
Q3. The 21-cm line of neutral hydrogen, which these lunar experiments are designed to detect, originates in which one of the following?
- A. The recombination of free electrons with protons to form neutral hydrogen atoms in the cooling early universe
- B. The hyperfine transition between the aligned and anti-aligned spin states of the electron and proton in ground-state hydrogen
- C. The fall of an electron from the second to the first energy level of the hydrogen atom, called the Lyman-alpha transition
- D. The rotational transition of molecular hydrogen within cold interstellar clouds shielded from ultraviolet radiation
Q4. With reference to the 21-cm hydrogen line and its use in probing the early universe, consider the following statements:
1. Its rest-frame frequency is about 1420 MHz, corresponding to a wavelength of about 21 cm.
2. It is an intrinsically strong, permitted transition, which is why it can be readily detected from individual hydrogen atoms.
3. Radiation at these wavelengths can pass through interstellar dust clouds that are opaque to visible light.
4. Because the signal from the early universe is redshifted, the Dark Ages must be observed at frequencies well above 1420 MHz.
Which of the statements given above is/are NOT correct?
- Its rest-frame frequency is about 1420 MHz, corresponding to a wavelength of about 21 cm.
- It is an intrinsically strong, permitted transition, which is why it can be readily detected from individual hydrogen atoms.
- Radiation at these wavelengths can pass through interstellar dust clouds that are opaque to visible light.
- Because the signal from the early universe is redshifted, the Dark Ages must be observed at frequencies well above 1420 MHz.
- A. 1 and 3
- B. 2 and 4
- C. 2, 3 and 4
- D. 4 only
Q5. Consider the following as reasons advanced for placing a redshifted 21-cm experiment on or above the far side of the Moon:
1. The Moon's synchronous rotation keeps one hemisphere permanently turned away from the Earth, screening it from terrestrial transmissions.
2. The Moon lacks a substantial ionosphere, permitting observations below about 30–40 MHz that are unavailable to ground-based telescopes.
3. The far side remains permanently in darkness, so solar radio emission never reaches it.
4. The Earth's ionosphere refracts and distorts low-frequency radio waves, corrupting such measurements made from the ground.
Which of the above is/are correctly identified?
- The Moon's synchronous rotation keeps one hemisphere permanently turned away from the Earth, screening it from terrestrial transmissions.
- The Moon lacks a substantial ionosphere, permitting observations below about 30–40 MHz that are unavailable to ground-based telescopes.
- The far side remains permanently in darkness, so solar radio emission never reaches it.
- The Earth's ionosphere refracts and distorts low-frequency radio waves, corrupting such measurements made from the ground.
- A. 1 and 2 only
- B. 2, 3 and 4
- C. 1, 2 and 4
- D. 1 and 4 only
Q6. Which one of the following is described by the Department of Science and Technology as the most radio-quiet location in the inner Solar System for low-frequency observations?
- A. The Earth–Moon L2 halo orbit region used for relay communication spacecraft
- B. The high-altitude Antarctic plateau, where atmospheric water vapour is minimal
- C. A geostationary orbit at about 36,000 km, the highest altitude examined for such work
- D. The far side of the Moon
Q7. The CosmoCube lunar satellite mission, whose design was reported in Nature Astronomy, is led by a radio astronomy and cosmology team based at which one of the following universities?
- A. Arizona State University, United States of America
- B. University of Cambridge, United Kingdom
- C. University of Colorado Boulder, United States of America
- D. Radboud University Nijmegen, the Netherlands
Q8. Which one of the following best describes the largest window of interference-free observation available to CosmoCube during its operation in lunar orbit?
- A. It stays permanently screened from the Earth's radio emission throughout its mission, because the Moon always blocks the line of sight to the Earth
- B. It is screened for the entire duration of the lunar night, and all of its scientific observations are necessarily confined to that period
- C. It is screened for roughly 40 minutes in each orbit of about two hours, while it passes behind the Moon
- D. It is screened only while it passes over the near side, where a dedicated relay satellite maintains a continuous data link
Q9. Which one of the following correctly describes the origin and present funding of the Raman Research Institute?
- A. Founded in 1948 by C.V. Raman with private funds, reorganised in 1972, and funded since then by the Council of Scientific and Industrial Research
- B. Set up in 1971 as a national laboratory of the Department of Atomic Energy, and administered at present by the Atomic Energy Commission
- C. Established as a constituent department of the Indian Institute of Science, Bengaluru, and funded at present by the Ministry of Education
- D. Founded in 1948 by C.V. Raman with private funds, reorganised in 1972, and funded since then by the Department of Science and Technology
Q10. STARFIRE, the algorithm developed at the Raman Research Institute to estimate terrestrial radio-frequency interference in orbits around the Earth, drew on FM transmitter databases of how many countries?
- A. Four
- B. Five
- C. Six
- D. Eight
Q11. The 2018 report of a flattened absorption profile centred at 78 MHz in the sky-averaged radio spectrum, interpreted as the imprint of the first stars, came from which one of the following experiments?
- A. EDGES
- B. SARAS 3
- C. LOFAR
- D. LEDA