Stop, drop and roll — Chandrayaan 2 prepares to enter the Moon's orbit tomorrow

• Chandrayaan 2 is going to attempt entry into Moon’s orbit tomorrow.
• The spacecraft will have to slow down and reorient itself in order to be pulled by the Moon’s gravity.
• If Chandrayaan 2 does not slow down adequately, it will simply fly past the Moon.

Chandrayaan 2 has been orbiting the Earth for 29 days and it’s finally going to enter the Moon’s orbit tomorrow morning.

The success of the switch over depends on how fast the spacecraft’s going when it hits the intersection.

The plan is for the spacecraft’s onboard propulsion system to slow down the spacecraft so that the Moon’s gravity can pull it in Indian Space Research Organisation (ISRO) Chairman K Sivan who spoke to TOI.

If the spacecraft is going too fast, it’s going to miss its point of entry and simply fly past the moon.

Even after managing to slow down and reorient itself successfully, Chandrayaan 2 will have only completed 60% of its journey.

The tale of two orbits

The Moon and the Earth, both, have a ‘sphere of influence’, which is the extent of their gravitational fields.

The Earth’s sphere of influence — also called the Earth’s Hill Sphere — extends to 1.5 million kilometers.

And, the Moon’s sphere of influence, which lies within the Hill Sphere, extends to 65,000 kilometers.

In the past 29 days, Chandrayaan 2 was in Earth’s orbit — gaining speed and looping outwards in order to get closer to the Moon’s sphere of influence.

Tomorrow, Chandrayaan 2 will be around 150 kilometers away from the lunar orbit, which is when it plans to reorient itself and break free from Earth’s gravitational pull.

Going forward

Once Chandrayaan 2 successfully turns itself towards the Moon, the spacecraft will have to make five more maneuvers before it finally tries to land on the lunar surface.

After the last maneuver takes place on 1 September, the Vikram lander will separate from the main module and make a power descent to attempt a soft landing.

In order to assess the landing site before touchdown — and make sure there aren’t any obstacles in the way — cameras on board the lander as well as the orbiter will send back real-time data. In the past, Sivan has expressed how the 15 minutes prior to touchdown will be the 15 most terrifying moments for ISRO.

Landing on the Moon is no small feat but the Chandrayaan 2 attempting to land near the South Pole — one of the most cratered regions of the Moon — checking the landing site for hindrances is all the more important.

See also:
Here’s why it’s going to take 7 weeks for Chandrayaan 2 to reach the Moon

India's second moon mission Chandrayaan 2 that will cost ₹10 billion will break new records

Chandrayaan 2 will give India bragging rights even if it doesn’t find water