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

• It’s going to take Chandrayaan 2, seven weeks in space before it finally attempts to land on the lunar surface.
  
• For the first 23 days of its voyage, the satellite will orbit around the Earth to build up its velocity before reaching the point that will be closest for it to enter the Moon’s orbit.
  
• Vikram, the lander, will separate from the orbiter once its on track around the Moon to ‘free fall’ towards the lunar surface before attempting a ‘soft landing’ that should take approximately 15 minutes.
  

India’s Chandrayaan 2 was successfully launched towards the Moon yesterday, but the satellite’s journey has only just begun.

“Our task is not over yet,” remarked K Sivan, the chief of the Indian Space Research Organisation (ISRO), after Chandrayaan 2 completed its launch sequence yesterday after taking off from the Satish Dhawan Space Centre (SDSC) in Sriharikota.

The satellite has to reach the Moon by September because the lander, Vikram and the rover, Pragyan, don’t have the durability to withstand the temperature of lunar nights, which can last for over two Earth weeks.

The launch vehicle dubbed ‘Bahubali’ for its size and capacity did its job of launching Chandrayaan 26,000 kms further than anticipated. Now, the satellite will have to attempt 15 maneuvers in space before it successfully lands on the Moon.

Despite the rush to reach the Moon as soon as possible, it’s going to take 7 weeks because of a simple reason — cruising speed. Bahubali has given Chandrayaan 2 the velocity to carry forward and travel the 384,000 kilometers to the Moon.

Circling the Earth to build speed

According to the mission schedule, the satellite will spend around 23 days orbiting Earth in geostationary transfer orbit (GTO). This is less than the original amount of time that Chandrayaan 2 was scheduled to spend in orbit around the Earth.

ISRO decided to cut down on the time after the launch of the satellite was delayed on July 15 due to an issue with the GSLV Mark III - M1 launch vehicle.

As it orbits the Earth, the spacecraft will continue to get faster. Once Chandrayaan 2 reaches apogee — the farthest point in orbit from Earth — combined with the satellite module’s increased velocity, the final orbit of the satellite will come close to the Moon’s orbit.

The 'free fall'

Chandrayaan 2 has three components — the lander, the orbiter and the rover. Once in position, it’s going to burn some of the excess fuel to slip into the Moon’s orbit.

Vikram, the lander, will then separate from the orbiter to reorient and ‘free fall’ towards the moon.

As Vikram comes closer the Moon’s surface, the orbiter will scan the landing site from above and Vikram scans the Moon’s South Pole on its descent.

But, in order to ‘land’ on the moon and not ‘crash’, Chandrayaan 2 needs to cushion its fall. That’s where the thrusters come in. Vikram will perform a series of deboosting procedures to in order to ‘soft land’ on the moon.

The 15 minutes that it will take to attempt the soft landing near the Moon’s South Pole are going to be the most ‘terrifying moments’ for ISRO, according to Sivan.

15 days of exploring the unexplored

Once the Vikram touches down on the Moon, it will release Pragyaan, the rover, onto the Moon. It will cover a distance of approximately 500 meters while leaving behind the Ashoka Chakra and ISRO logo imprinted wherever it wanders.

The three modules will carry out scientific observations on the Moon for 14 days, and send the data back to Earth.

See also:
India’s Chandrayaan 2 gets delayed due to a technical snag, pausing countdown at 56 mins

India's Chandrayaan 2 takes the lead ahead of America, Russia, and China as the first of many missions to the Moon's South Pole

Chandrayaan-2 mission will go where no country has ever gone before