Space

ISRO to Launch Chandrayaan 2 on July 15, Moon Landing by September 7

Sivan said at the conference that the period when the lander will attempt to descend on the lunar surface will encompass "the most terrifying moments" for the organisation.

In a press conference on June 12, K. Sivan, the chairman of the Indian Space Research Organisation, presented new details of its upcoming Chandrayaan 2 mission to the Moon. Perhaps the most notable announcement was that the mission now has a confirmed launch time: 2:51 am on July 15.

While the launch itself will be subject to weather conditions on that day, the announcement hopefully means the delays and deadline postponements are finally at end. The mission cost ISRO Rs 603 crore from start to finish.

Sivan said 60% of this went to industries and universities around the country that worked on the mission.

Chandrayaan 2 is expected to be the most complex the organisation has undertaken till date. Sivan said at the conference that the period when the lander will attempt to descend on the lunar surface will encompass “the most terrifying moments” for the organisation.

On July 15, a GSLV Mk III rocket carrying the Chandrayaan 2 stack of instruments will take off from the organisation’s space port in Sriharikota. The whole setup is expected to weigh 3.877 kg; the orbiter will weigh 2,379 kg, the lander 1,471 kg and the rover, 27 kg.

Fifteen minutes later, the Chandrayaan 2 stack will be placed in a highly elliptical orbit around Earth. Over the next 16 days, its orbit will be raised through five ‘burns’. Then, Chandrayaan 2 will perform a translunar injection burn and then travel for five days towards the Moon, covering a distance of 380,000 km, and eventually entering into an elliptical orbit around the natural satellite.

Once there, a series of orbit-lowering burns will bring the stack into a more circular orbit in which it revolves around the Moon once every 24 Earth-hours, a situation it will maintain for four days. In this period, the lander will separate from the Chandrayaan 2 stack and enter into a lower orbit. It is named Vikram for Vikram Sarabhai, the organisation’s founder. Once there, scientists and engineers will check the lander’s health and performance, before commencing the most thrilling phase of the whole mission.

In this phase, set to happen on September 6 or 7 this year, the lander will slowly descend to a designated spot near the Moon’s south pole over 15 minutes. The spot is located between the craters Manzinus C and Simpelius N. Four hours after it has safely touched down, the lander doors will open to release India’s first lunar rover onto the Moon’s surface.

The planned sequence of events on September 6-7 on the Moon, as displayed on the new Chandrayaan 2 page on ISRO's website. Source: ISRO

The planned sequence of events on September 6-7 on the Moon, as displayed on the new Chandrayaan 2 page on ISRO’s website. Source: ISRO

The Chandrayaan 2 launch has cost Rs 375 crore. During the conference, Sivan thanked industry and academia for their contributions to the programme. Nearly 80% of the organisation’s expenditure on the Mk III launcher was incurred by industry, he said.

The total mission cost is thus Rs 978 crore, up from the Rs 800 crore reported in 2018. At that time, the breakdown was Rs 600 crore for the stack and Rs 200 crore for the launcher. When the mission had originally been approved in 2008, the cost was Rs 425 crore, excluding the launch costs and cost of the lander. This was because the mission was originally envisaged as a partnership with Russia, which would provide the lander. However, Russia pulled out in 2013 and ISRO agreed to build the lander itself.

Once the rover is out – its exit timed to the dawn of a new day on the Moon – it will communicate with Earth directly because it will have line of sight, as will the orbiter. The rover is named Pragyan (Sanskrit for ‘wisdom’) and will move very slowly – at 1 cm/s – and traverse the lunar surface for a distance of 500 m (expected to take 2 days and 22 hours at this speed).

According to Sivan, the lander and rover will have a lifetime of 14 Earth days, or one lunar day, while the orbiter is expected to remain operational for a year. This limitation is most likely because temperatures on the part of the Moon where Pragyan will move around are expected to swing between -120º C and -160º C. The rover also sports a solar panel to recharge the batteries. So when it sleeps at night and wakes up in the morning, it will need the lithium-ion batteries on board to switch on and function properly. A study published in June 2018 found that these batteries can function for at most 14 days at -160º C.

For the mission, Chandrayaan 2’s payload will have 14 instruments. The orbiter will carry eight, the lander three and the rover two. Sivan had said in May this year that the stack would also carry a “passive experiment from NASA”, the 14th.

All together, the instruments will study the chemical composition of the lunar surface up to a depth of few tens of metres, its thermal characteristics, surface plasma, distribution of minerals, the lunar exosphere, quakes on the Moon, etc.. The NASA experiment is reportedly a small retroreflector that will help measure the distance between Earth and the Moon with greater precision.

ISRO had launched in Chandrayaan 1 – a simpler mission that included just the lunar orbiter – in October 2008, at a cost of a little over Rs 380 crore. The mission was designed to last for two years but failed after 10 months. It carried 11 instruments in all, of which five were Indian.

A month after launch, it shot an impact probe onto the lunar surface and kicked up some soil, which was then chemically analysed. This mission’s most significant finding was the presence of water molecules in the lunar soil.

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