Chandrayaan II launched on 22 July, Monday from Sriharikota

After the much-acclaimed mission of orbiting the Moon with the Chandrayaan I, the Indian Space Research Organisation (ISRO) is busy with its follow up mission called Chandrayaan II. The launch vehicle is on course to the lunar south pole, carrying an orbiter, a lander named Vikram and a rover called Pragyan.

The mission will see the lander and rover module of the spacecraft make a soft landing near the unexplored south pole of the lunar surface 48 days from now. They will operate there for 14 days, carry out experiments and collect data samples for further assessment.

But why 48 days? Why isn’t it faster? Well, that’s because Chandrayaan-2 is powered by the GSLV MK-III, which is a relatively inexpensive, low-power engine that can lift only 8,000 Kg into low-earth orbit (LEO) and half that weight into higher orbits.

Compared to this, SpaceX’s Falcon 9 can carry nearly 23,000 Kg, while the Saturn-V rocket of the Apollo mission that took Neil Armstrong to the Moon, could haul a massive 118,000 Kg to LEO.

In layperson terms, that’s like riding to the Moon on a Hero Splendor (which gives great mileage) compared to a Suzuki Hayabusa.

Time Taken for Other Missions to Reach the Moon

China’s Chang’e 1: Four days, 12 hours 
NASA Apollo 11: Four days
Russia’s Luna 15: Four days

Chandrayaan-2 will spend the next 23 days circling around the earth, incrementally raising its orbit, before starting its journey for over seven days to enter an orbit around the Moon.

We need to understand that the Apollo missions were also designed to carry astronauts, while Chandrayaan-2 is a smaller, uncrewed mission, looking to enter the dark side of the Moon, where none have landed so far.

Post the entry into the initial orbit, the duty of managing and tracking Chandrayaan-2 is now with the ISRO Telemetry, Tracking and Command (ISTRAC) centre in Bangalore, as highlighted in this Times of India report.

Over the next 62 days (48 for the journey and 14 days after the rover lands on the Moon), ISTRAC will be guiding the spacecraft to Moon, help it land and unload the rover. For this, ISTRAC will be using ground stations across different parts of the world.

How the GSLV MK-III plans to succeed in its mission

The same report also specified that if Chandrayaan-2 had launched without a glitch on 15 July, it would have reached lunar orbit in 22 days and gone around the moon for 28 days.

But as per the new schedule, since its launch on 22 July, the module comprising of the lander and the rover will remain in the 100 km x 100 km orbit for 13 days.

When Science Precedes Technology

ISRO had to overcome tremendous challenges to build the GSLV MK-III launch vehicle, which has taken decades of scientific and technological groundwork.

ISRO Chairman K Sivan, as quoted in this Indian Express report, said that for this mission, the performance of the GSLV-MK-III has been increased by 15 percent compared to the previous missions.

But even that pales in front of the capability of other rockets that have attempted to reach the Moon, as we’ve mentioned above.

GSLV MK III has been built by the engineers at ISRO. 

This places heavy emphasis on the Chandrayaan II (GSLV-MK-III) to opt for a conservative route to complete its mission. Which means, instead of pushing the GSLV-MK-III full throttle, ISRO is guiding the spacecraft to take multiple orbits, to get closer to the Moon, which is called the Oberth effect.

With each orbit, the spacecraft moves away from the gravitational pull of the Earth and finally enter the Moon’s orbit, after which the spacecraft can start its unloading cycle of the lander and the rover.