Aditya-L1 and Space Science Missions: Notes and MCQs

The correct answer is D, 1984. Wing Commander Rakesh Sharma flew in April 1984 aboard the Soviet spacecraft Soyuz T-11 as part of a joint programme between the Soviet Union and India, and spent about eight days aboard the Salyut 7 space station. He thus became the first Indian to travel into space. He is remembered for his reply when the Prime Minister asked how India looked from up there, and he was awarded the Ashoka Chakra.

Options A, B and C give 1981, 1982 and 1983, all near years placed there to see whether the date is firmly held. Fix the year by tying it to two other facts of the same decade: India launched its own satellite Aryabhata in 1975 and put Rohini in orbit with an Indian rocket in 1980, and Rakesh Sharma flew four years after that. The second Indian origin astronauts, Kalpana Chawla and Sunita Williams, flew with the American programme much later.

The correct answer is B, Gaganyaan. Gaganyaan is the programme under which the Indian Space Research Organisation is preparing to send Indian astronauts into a low orbit around the Earth in a crew module of its own and bring them back safely. The programme includes uncrewed test flights, a crew escape system and a human rated launch vehicle. Its first flight test of the crew escape system, called TV-D1, took place in October 2023.

Option A, Mangalyaan, is the Mars Orbiter Mission, an uncrewed spacecraft that reached Mars orbit in 2014. Option C, Chandrayaan-2, was an uncrewed Moon mission of 2019 with an orbiter, a lander and a rover. Option D, Aditya-L1, is the solar observatory launched in 2023 to a halo orbit around the Lagrange point L1. None of the three carries a crew, so only Gaganyaan can be the human spaceflight programme.

The correct answer is B, STUDSAT. STUDSAT, short for Student Satellite, was the first pico satellite built in India. A pico satellite is one that weighs under about one kilogram, and STUDSAT weighed less than that. It was built by students of engineering colleges in Bengaluru and Hyderabad and was launched in 2010 by a PSLV flight as an auxiliary payload, carrying a small camera for imaging the Earth.

Option A, INSAT, is not a single satellite but the Indian National Satellite System, a family of heavy communication satellites in geostationary orbit. Option C, GSAT-4, was an experimental communication satellite that was lost when its launch vehicle failed in 2010. Option D, ANUSAT, was built by Anna University and launched in 2009, but it was a micro satellite of about forty kilograms, not a pico satellite, which is exactly the distinction the question is testing.

The correct answer is B, to measure the vertical temperature profile of the lunar regolith. ChaSTE was carried on the Vikram lander of Chandrayaan-3. It has a probe fitted with a set of temperature sensors, which was pushed into the lunar soil to a depth of about ten centimetres near the south polar region. From its readings scientists can see how heat moves through the top layer of the Moon, which tells them about the thermal properties of the soil at a place never measured before.

Option A, the geological composition, was the task of the two instruments on the Pragyan rover, which used alpha particles and a laser to find the elements in the soil. Option C is wrong because the Moon has only an extremely thin envelope of gas rather than an atmosphere with measurable pressure of the usual kind. Option D, the magnetic field, was not the aim of ChaSTE; the lander instead carried instruments to record moonquakes and to study the plasma near the surface.

The correct answer is B, Sindhu Netra Satellite. Sindhu Netra was developed by the Defence Research and Development Organisation and was placed in orbit in February 2021 by the PSLV-C51 flight, the same flight whose main payload was the Amazonia-1 satellite of Brazil. The satellite is meant to watch shipping in the Indian Ocean Region and to help identify warships and merchant vessels moving through those waters, which supports maritime awareness for the armed forces.

Option A, the Satish Dhawan Satellite, was also aboard the same PSLV-C51 flight, but it was a small satellite built by a private Indian team and is not a surveillance satellite. Options C and D, Sindhu Durga and Sri Shakti, are invented names that sound plausible beside the correct one. Remember the pairing of PSLV-C51 with Amazonia-1 as its main payload and Sindhu Netra among the rideshare satellites.

The correct answer is B, PSLV-C57. Aditya-L1 was launched on 2 September 2023 from the Satish Dhawan Space Centre at Sriharikota by the PSLV-C57 flight, which used the most powerful version of the Polar Satellite Launch Vehicle. The spacecraft was first placed in an orbit around the Earth, raised that orbit in steps, and then left for the Lagrange point L1, where it was inserted into a halo orbit in January 2024.

Option A, the GSLV Mk II, is used mainly for communication satellites going to geostationary transfer orbit. Option C, LVM3-M4, is the vehicle that launched Chandrayaan-3 in July 2023, and candidates often mix the two missions of the same year. Option D, the SSLV, is the small satellite launch vehicle meant for light payloads into low orbits. Tie the pair firmly in memory: LVM3 for Chandrayaan-3, PSLV for Aditya-L1.

The correct answer is B, L1, about 15 lakh kilometres. The Lagrange point L1 of the Sun and the Earth lies between the two bodies, roughly 1.5 million or fifteen lakh kilometres from the Earth. At that point the gravitational pulls of the Sun and the Earth combine with the motion of the spacecraft so that it keeps station with the Earth. A spacecraft there can watch the Sun without any interruption from an eclipse or from the night side of the Earth, which is why Aditya-L1 was sent there.

Option A names L2, which lies on the far side of the Earth from the Sun at a similar distance and holds the James Webb Space Telescope. Option C gives the distance of the Moon from the Earth, about 3.84 lakh kilometres, which is far too close. Option D gives roughly the distance of the Earth from the Sun and a different Lagrange point altogether. Remember that L1 is about one hundredth of the way to the Sun.

The correct answer is B, VELC. The Visible Emission Line Coronagraph is the largest and the principal instrument aboard Aditya-L1. A coronagraph creates an artificial eclipse inside the instrument by covering the bright disc of the Sun, so that the faint outer atmosphere called the corona becomes visible. VELC can observe the corona close to the solar surface and study how coronal mass ejections begin, which is the key to understanding space weather.

Option A, SUIT, is the Solar Ultraviolet Imaging Telescope, which photographs the Sun in ultraviolet light and studies the layers below the corona. Option C, HEL1OS, is the high energy X-ray spectrometer that records the hard X-rays of solar flares. Option D, ASPEX, is the particle experiment that samples the solar wind arriving at the spacecraft. All four are genuine payloads of the mission, so the question turns on which one is the chief instrument.

The correct answer is B, 23 August 2023. The Vikram lander of Chandrayaan-3 touched down near the south polar region of the Moon on 23 August 2023, making India the fourth country to achieve a soft landing on the Moon and the first to do so near the lunar south pole. The Pragyan rover then rolled out and worked through one lunar day. The landing site was named Shiv Shakti Point and 23 August is now observed in India as National Space Day.

Option A, 14 July 2023, is the launch date of Chandrayaan-3 aboard the LVM3-M4 vehicle. Option C, 2 September 2023, is the launch date of Aditya-L1, the solar mission that followed soon after. Option D, 6 January 2024, is the date on which Aditya-L1 was inserted into its halo orbit around the Lagrange point L1. All three are real dates from the same period, which is what makes the question tricky.

The correct answer is C, 2014. The Mars Orbiter Mission was launched on 5 November 2013 by a PSLV and reached the orbit of Mars on 24 September 2014. With that, India became the first country in the world to reach Mars at its first attempt, and the Indian Space Research Organisation became the fourth agency to reach the planet after those of the Soviet Union, the United States and Europe. The mission carried five instruments, among them a methane sensor and a colour camera, and it was built at a remarkably low cost.

Option A, 2008, is the year of Chandrayaan-1, the first Indian Moon mission. Option B, 2013, is the launch year of the Mars mission itself, not the year it arrived, and that gap of about ten months is what the question is testing. Option D, 2019, is the year of Chandrayaan-2. Separating the launch year from the arrival year is the habit to build here.

The correct answer is B, Aryabhata. Aryabhata was the first satellite built by India and it was launched on 19 April 1975 from a Soviet launch site, since India had no launch vehicle of its own at the time. It was named after the ancient Indian astronomer and mathematician, and it carried experiments in X-ray astronomy, solar physics and the study of the ionosphere. It marks the beginning of the Indian satellite programme.

Option A, Bhaskara, was an experimental earth observation satellite launched later, in 1979. Option C, Rohini, refers to the series of which RS-1 became the first satellite placed in orbit by an Indian launch vehicle, the SLV-3, on 18 July 1980. Option D, APPLE, was the Ariane Passenger Payload Experiment of 1981, the first Indian experimental communication satellite in geostationary orbit. Keep the order Aryabhata, Bhaskara, Rohini, APPLE in mind.