Chandrayaan-3 lands on Moon: A much-needed guide to space lingo

It is celebration time for India as the Chandrayaan-3 spacecraft has successfully landed on the Moon today (23 August). Scripting history, India has become the first country to soft land on the south pole of the lunar surface and the fourth nation to safely land a robotic probe on the Earth’s only natural satellite.This proud moment was summed up by Indian Space Research Organisation (ISRO) chief S Somanath declaration: “India is on the Moon”. The ambitious lunar journey that began on 14 July has reached a historic moment more than a month later.As the world watches India’s success, let’s understand some key terms related to India’s Moon mission.Chandrayaan-3India’s third lunar mission is called Chandrayaan-3. It is the name of the spacecraft that was launched by the Launch Vehicle Mark-III (LVM-3) rocket towards the Moon. India’s heaviest rocket put the over 3000-kilogramme spacecraft into a 170 x 36,500 km elliptic Earth parking orbit. The craft consisted of two parts — the propulsion and the Lander module.Moon’s south poleAccording to the American space agency NASA, the Moon's south pole is full of "mystery, science and intrigue". The region has a difficult terrain – full of craters and deep trenches. Some of the areas in the south polar region have not received sunlight for billions of years, leading to temperatures plummeting to as low as minus 230 degree Celsius. As reports have confirmed the presence of water ice in some of the shadowed craters, the Moon’s south pole has renewed interest for countries across the world.Soft landingA soft landing entails a safe landing of a spacecraft without sustaining any significant damage to itself or its payloads. Amitabha Ghosh, a scientist for NASA’s Rover mission to Mars, told Indian Express, “Imagine a spacecraft hurtling through space, at 10 times the speed of an airplane, having to nearly come to a standstill in order to land gently on the Earth — all in a matter of a few minutes and, more importantly, without any human intervention. This, in a nutshell, is a soft landing.”Chandrayaan-3's soft landing on the Moon today has paved the way for India's emergence as a space power.[caption id="attachment_13030462" align="alignnone" width="640"]

An illustration showing the soft landing of ISRO's 'Chandrayaan-3' on the lunar surface. PTI File Photo[/caption]Propulsion moduleThe main job of Chandrayaan-3’s propulsion module was to carry the lander and rover from the Earth into the Moon’s orbit. However, this does not mean it is not serving any purpose after the lander module separated from it on 17 August. The propulsion module, which has more than 150kg of fuel left, will continue its path on the lunar orbit for possibly years. Its payload, Spectro-polarimetry of HAbitable Planet Earth (SHAPE), will study spectral and polarimetric measurements of Earth from the lunar orbit.LanderA lander is a strong vehicle designed to land on a celestial body, such as a planet or Moon. Chandrayaan-3’s lander is named Vikram and has four payloads or scientific instruments for lunar exploration. It does not have wheels but legs – or stilts – that vertically touch down on the lunar surface to mark a successful and safe landing.The Vikram lander touched down on the lunar surface at around 6:04 pm.RoverA rover is a small robotic vehicle designed for exploring the surface of a planet or Moon. Chandrayaan-3’s rover is called Pragyan, which is Sanskrit for "wisdom". After the lander’s touchdown on the Moon’s south pole, the six-wheeled rover – which was in Vikram’s belly – will slide out and move on the lunar surface to carry out scientific experiments.

PayloadsAccording to ISRO, a payload is a scientific or technological instrument aboard a satellite to perform specific functions after landing on the celestial body. It refers to those instruments that are “dedicated to producing mission data and then relaying that data back to Earth”, as per the European Space Agency (ESA).Chandrayaan-3’s lander and rover, which have a life of one lunar day or 14 Earth days, have a total of six payloads to carry out experiments on the Moon’s south pole. The propulsion module has one payload which will examine the Earth’s atmosphere from its current lunar orbit.ALSO READ: Why Chandrayaan 3's success matters to the United StatesLunar dustLunar dust, a component of regolith, is present on the surface of the Moon. Regolith is loose, unconsolidated rock and dust present on the Earth, Moon, and other celestial bodies. Lunar dust makes the landing of spacecraft more difficult. As per NASA, “The presence of dust, even in very small quantities, can have a significant effect on temperature control and optical performance of hardware on the lunar surface.” This dust can cling to surfaces and easily enter the human body through the respiratory system due to its small particles.Throttleable engineChandrayaan-3’s lander has only four throttleable engines for powered descent. Once this phase began, the Vikram lander used its thrusters to initiate a touchdown on the lunar surface. “The lander’s four engines are used to reduce the velocity and there are also eight small engines to control the direction of the descent. The engines are throttleable and the thrust can be varied from 800 Newton to a lower value. It can keep the lander hovering on the Moon’s gravity,” ISRO chairman Somanath was quoted as saying by Indian Express.With inputs from agencies