When NASA's Mariner 4 Mission flew by past Mars in 1965, it sent many close-up pictures of the Martian landscape. It looked like a scene from a sci-fi movie. But today it is becoming a promising reality, as India's maiden Mars Orbiter Mission (MOM) is due to reach the red planet in just two months from now. After the success of India’s Chandrayaan Mission, scientists at Indian Space Research Organisation (ISRO) thought the next logical step was to go to Mars. The project got an approval from the Government of India in 2012 and it was decided that the Mission to Mars will be launched in October next year. Due to some technical glitches, the MOM finally took off on November 5, 2013. Sitting on PSLV-C25 transport vehicle, the mission to Mars started its journey from Satish Dhawan Space Centre at Sriharikota in Andhra Pradesh. It is scheduled to reach Mars in September this year. Not an easy mission Interplanetary travel is not as simple as travelling between New Delhi and Mumbai. A number of failed attempts by NASA, the erstwhile Soviet Union and the European Space Agency (ESA) to successfully land on Mars indicate the complexity of the task. There are many factors that need to be taken into account while planning such a mission. To begin with, the distance between Earth and Mars is huge. At its closest Mars is about 50 million Kilometres away from Earth and at the furthest it is 400 million kilometres away. The next problem is that the two planets are continuously moving around the Sun. Complex calculations need to be made to precisely predict how to reach the destination at the right time. To travel such long distances a large amount of fuel is required. Since the fuel itself has a lot of weight and it is very expensive, scientists need other lighter and cheaper alternatives. Gravity, the Mission’s fuel In our daily lives we never consider gravity as a fuel but space scientists almost exclusively depend on it for missions beyond our atmosphere. In agriculture, it is common to see how a farmer ties a small stone to a rope, swings it around and throws it far away into his field to scare away the birds. Space scientists use the same technique to send probes from one planet to another. In the farmer's case it is his arm that is the source of fuel.
In a scientist's case it is the gravity of one celestial body or the other which provides the necessary energy to make the probe move. In a mission to Mars, gravity of three celestial bodies is utilized. In the first phase gravity of Earth provides the speed to begin the journey. In the next phase the gravity of Sun is used to further increase the speed and turn the probe towards Mars. In the last phase the gravity of Mars is utilized to complete the mission and to enter into its orbit. When MOM was launched in 2013 it went around earth for around 25 days. The probe gained speed using the Earth's gravity as its fuel. Later, the engines on MOM gave a gentle tug to the probe to leave the influence of Earth's gravity and to enter a trajectory around sun. It was as if our farmer (Earth) had thrown the stone (MOM) toward the influence of Sun. The mission currently is in the Helio centric or Sun centric trajectory. The probe will travel a distance of roughly 780 million kilometres before it enters the orbit of Mars. Most of this journey is done by just using the gravity as a force to move the probe. Course correction is done by burning the engines as and when required. There are four planned course corrections in this mission. The next course corrections will happen in August and September as the probe comes near Mars. ISRO, if successful, will become the fourth agency to enter into the orbit of another planet after Soviet Space Program, NASA, and the European Space Agency. The American, Mars Atmosphere and Volatile Evolution (MAVEN) mission which was also launched in November 2013 is expected to reach Mars at around the same time as MOM. Remarkably, the Indian MOM costs less than one tenth the American mission. It is interesting to note that no nation has ever been able to enter the planet's orbit in its first try. If MOM successfully enters into an orbit around Mars it will set new precedents in the Indian space efforts. Even if the mission is unable to do it, ISRO will have a lot to learn. Many terabytes of data will come out of this mission and will be very helpful in many future interplanetary missions. The fate of this ambitious mission will only be known on or around September 24, 2014 when the MOM is scheduled to enter the orbit of the Red Planet, till then we can keep our finger crossed and pride ourselves as a nation making great strides in space sciences. The writer is the General Secretary of the Amateur Astronomers Association at Nehru Planetarium, New Delhi