If everything goes as planned, this December, the Bengaluru-based Team Indus will become the first private firm in the world to land a spacecraft on the moon.

The company is now just a step away from building the flight model that will be flown on-board a PSLV from Sriharikota spaceport.

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"We have built a qualification model of the spacecraft, which will undergo rigorous testing at Isro's test facility in August second week. The next step will be building the flight model, which will be flown," said Sheelika Ravishankar, in-charge of the firm's marketing.

The company is one of the five finalists in the Google Lunar X Prize competition that seeks teams to successfully land a 90% private-funded spacecraft on the moon, travel 500m on its surface and transmit images and videos back to earth.

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Guided by two dozen retired Isro scientists, a team of more than 100 have designed and developed the 600kg spacecraft and a 6kg rover.

Besides carrying their own rover ECA or Ek Chhoti si Asha (a small hope), the spacecraft will also carry a rover built by the competing Japanese team — a student-built cubesat that will orbit the earth for 90 days and instruments that will conduct eight student-built experiments. The craft will also carry cameras for the French space agency CNES.

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Explaining the lunar mission, Rahul Narayan said once the spacecraft gets separated from the launch vehicle — about 15 minutes after takeoff — it will circle the earth twice, each time raising its altitude. On board engines will then be fired to reach the trans-lunar injection, a trajectory leading to the moon.

From there, the spacecraft will begin a five-day journey covering about 3.8 lakh km from earth to the moon. About 120km from the moon, the engines will be shut and fired again to get to a lower orbit where it will remain stationary for four days. At the crack of dawn, the spacecraft will make its descent.

"We will land on Mare Imbrium, a crater the size of Europe. Russia and China had landed there," he said.

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The trickiest part in the entire mission is the landing. As the spacecraft maneuvers and reduces its velocity from 1.3km per sec to 0km per sec while landing, it also has to simultaneously correct its altitude, select a landing area and avoid obstacles.

With expertise from Isro gone into making the spacecraft, Narayan said he sees a 93% probability of making a precise landing on the lunar surface. Isro has also planned its second lunar mission Chandrayaan-2 in the first quarter of 2018.