The process of setting down Chandrayaan 2 on the Moon is very complex

After nearly 30 days of space travel, India's moonshot Chandrayaan 2 is nearing its target. In a make-or-break effort, the Indian space agency ISRO will manoeuvre the spacecraft into the lunar orbit between 8:30 to 9:30 am today.

This is one of the most tricky operations in the mission because if the satellite approaches the Moon at a higher-than-expected velocity it will bounce off it and get lost in deep space. But If it approaches at a slow velocity, the Moon's gravity will pull the Chandrayaan 2 and it might crash into the surface.

The approach velocity has to be just right and the altitude over the Moon rather precise for the operation to go off as planned. Even a small error can kill the mission.

With a few hundred kilometres to the Moon, the satellite will be re-oriented and slowed down by just the right amount so that the Moon can capture the spacecraft and bring Chandrayaan 2 in its embrace. After coasting in the lunar orbit for about a fortnight, the big Moon landing is scheduled for September 7.

The process of setting down Chandrayaan 2 on the Moon is very complex since it blasted off at a velocity of 39,240 kilometres per hour, which is almost 30 times the speed at which sound travels through air. ISRO chairman Dr K Sivan said, "One can imagine even a small error can make Chandrayaan 2 miss its rendezvous with the Moon."

The former director of the ISRO satellite centre Dr M Annadurai, who was the head of India's first Moon mission Chandrayaan 1, described the complexity of the ongoing operation saying, "It is like a gentleman with a rose in hand proposing to a lady who is dancing at a stunning speed of 3,600 kilometres per hour (almost five times the speed of an airplane), and not next door, but at a distance of 3.84 lakh kilometres away. If the couple have to meet, then the precision and accuracy is of utmost importance."

India's most ambitious space mission to date, Chandrayaan 2 had lifted off from India's spaceport at Sriharikota in Andhra Pradesh on July 22. The lift-off was successful in its second attempt, a week after it was aborted just under an hour from its launch due to a technical glitch.

The mission stands out because of its low cost, with just about Rs 1,000 crore spent - a much smaller price tag compared to similar missions by other countries.

If successful, the mission will make India the fourth country to soft land a rover on the lunar surface after Russia, US and China. The last nation to attempt a soft landing on the Moon, Israel, failed in its earlier this year.

After shooting off into space, the spacecraft's orbit was "progressively increased five times" between July 23 and August 6. It was then flung towards the Moon, at a distance of 3.84 lakh kilometres away.

After 13 days in a Moon-bound orbit, the spacecraft will engage Vikram, a 1.4-tonne lander, which will in turn set the 27-kilogramme rover Pragyan down on a high plain between two craters on the lunar south pole, where no country has gone so far, according to the ISRO.

After the landing, the rover carry out experiments on Moon's surface for one lunar day, which is equal to 14 earth days. The mission life of the lander is also one lunar day, while the orbiter will continue its mission for a year.

The Chandrayaan 2 mission aims to expand the knowledge about the Moon, leading to a better understanding of its origin and evolution.