Moon mission: Are Chandrayaan 3 and Luna-25 racing against each other?

With the goal of exploring the Moon’s south pole, Russia’s first lunar landing spacecraft in nearly five decades since 1976, the Luna-25, will be launched on August 11 in what has been hyped as a ‘race with India to the south pole of the Moon’. Preparations are already under way for the evacuation of a village in the far east of Russia. News reports say the locals of the Shakhtinskyi settlement in the Khabarovsk region will be relocated as they live close to where the rocket boosters are likely to fall after being separated. 

Speculation is rife in the scientific and media circles about whether Russia will beat India to become the first nation to land a rover on the Moon’s south pole. The Russian mission might closely match or even slightly precede Chandrayaan-3’s touchdown on the Moon. Space experts, however, say that beyond the apparent similarities, there is a gulf of difference between the two missions. 

Russian space agency Roscosmos has said the Luna-25 is expected to reach the Moon in just five days and spend five to seven days in lunar orbit before descending to one of its designated landing sites in one of the two possible spots near the pole. 

“The Luna-25 mission will operate on the Moon’s surface for a whole year, carrying out a wide range of observations and scientific experiments. India’s Chandrayaan-3 mission, launched on July 14, is due to land on the Moon’s south pole on August 23, nearly one and a quarter months after its takeoff from Sriharikota. The Chandrayaan-3 mission is expected to last only two weeks with its focus being on specific experiments during its limited time on the Moon. Adding up the days, Russia’s Luna-25 may get to the Moon any time between August 21 and August 23. Importantly, India’s Chandrayaan-3 is scheduled to land on the Moon’s south pole around August 23-24. But, even more importantly, Roscosmos confirmed that the two missions would not cause any problems for each other as they are aiming to land in different places,” explained space and aerospace expert Girish Linganna. 

The Luna-25 spaceship will attempt to soft-land very carefully on the Moon’s bottom part, just as Chandrayaan-3 wants to do. “Luna-25 wants to learn about the stuff on the surface of the Moon and the environment around the Moon. It will collect, and study, the rocky layer on the surface (regolith), exospheric dust and particles and the gases around the Moon (plasma). Exospheric dust and particles refer to the tiny pieces of matter found in the Moon’s atmosphere. The Luna-25 lander will study these particles for one year to learn more about their composition and origin,” added Linganna. 

The lander of Luna-25 has four legs with landing rockets and fuel tanks. Up top, there is a compartment with solar panels, communication gear, computers and most of the scientific tools. It weighs around 800 kg without fuel and is expected to have about 950 kg of fuel when it launches. The lander also has a 1.6-metre-long Lunar Robotic Arm (LRA, or Lunar Manipulator Complex) that scoops up stuff from the Moon’s surface up to a foot deep (20-30 cm). 

The robotic arm, LRA, has a scooper and a tool that can hold about 175 cubic cm of material and the tool is like a 4.7-cm-long tube with a small hole of 1.25 cm inside. The arm can move in four different ways: left and right; up and down; bend at the elbow; and twist at the wrist. The arm weighs 5.5 kg and uses the same amount of power as a regular light bulb (30W), with slightly more power available for stronger movements (50W). 

Luna-25 spacecraft will be launched from the Vostochny Cosmodrome (5,550 km east of Moscow), in Russia, on a Soyuz-2 Fregat rocket. It will first enter Earth’s orbit and then use the Fregat rocket to go into lunar transfer orbit. Once in lunar orbit, the spacecraft will fire its own engines to land on the surface. 

“The main landing site for Luna-25 is at 69.545 S, 43.544 E, north of the Boguslavsky crater. The reserve landing site is at 68.773 S and 21.21 E, south-west of the Manzini crater. Both landing sites are within 15 x 30 km landing ellipses, meaning that both of the possible landing sites for the Luna-25 lander are within an area that is 15 kilometres wide and 30 kilometres long. This gives the lander a good chance of landing safely at the desired location,” remarked Linganna. 

The spacecraft will carry a variety of scientific instruments, including a gamma-ray and neutron spectrometer, a charged particle detector, an infrared spectrometer, a mass spectrometer, a dust detector, a panoramic camera and a thermal probe. These instruments will be used to study the composition of the surface regolith, the atmosphere of the Moon, and the dust in the exosphere. 

The Luna-25 mission is expected to provide valuable data about the composition and environment of the lunar south pole—a region not well-studied earlier. This information will be important for future missions to the Moon, including those that are planning to explore the possibility of human habitation. 

In great contrast, ISRO's Chandrayaan-3 is taking several weeks to get to the bumpy surface of the Moon. “ISRO cannot send Chandrayaan-3 straight to the Moon because it does not have a strong enough rocket for that and also because India is using the most economical method to save costs. On the other hand Luna-25 is using a fast route to the Moon. First, a strong rocket puts the spacecraft into the Earth’s orbit. Then, they use a powerful engine burn called the Trans-Lunar Injection (TLI) to shoot it directly towards the Moon on a path called the Lunar Transfer Trajectory (LTT), like a speedy slingshot. This quick path gets the spacecraft to the Moon in just a few days,” Linganna told THE WEEK.