ISRO created history on September 24, 2014, when the Indian spacecraft called Mangalyaan reached Mars orbit on its first attempt. This mission made India the first Asian nation to enter the Martian atmosphere and the only nation to accomplish so on its first attempt. Globally, India became the fourth country to do so, after previous missions carried out by the Soviet Space Program, NASA and the European Space Agency. Interestingly, Japan and China also made efforts to reach Mars in 1998 and 2011, respectively, but were unsuccessful.
Figure 1: India's Mars Orbiter Mission i.e. Mangalyaan
What is Mangalyaan:
Mangalyaan, a Hindi term for Mars Craft, is India's satellite that has been orbiting Mars since 24 September 2014. It was launched by the Indian Space Research Organization (ISRO) on 5 November 2013 from the first launch pad at the Center Satish Dhawan Space located in Sriharikota, Andhra Pradesh. It was lifted off using a PSLV C25 rocket in the country's first interplanetary mission. After spending a month in Earth orbit, it reached Trans-Mars injection on November 30, 2013, and finally entered Martian orbit on September 24, 2014.
The Mangalyaan mission is a project designed primarily to demonstrate India's capability in interplanetary exploration. Secondly, it aims to develop technologies to explore the Red Planet and collect vital information about it with the help of the 5 instruments listed below.
Methane Sensor for Mars (MSM): The MSM was designed to measure CH4 in the Martian atmosphere and map its sources.
Mars Exospheric Neutral Composition Analyzer (MENCA): It analyzes the neutral composition of particles in the range of 1-300 amu (atomic mass unit) with unit mass resolution. It performs five observations per orbit, with each observation taking one hour.
Infrared thermal imaging spectrometer (TIS): It maps the surface composition and mineralogy behind Mars, along with atmospheric CO2 and turbidity.
Mars Color Camera (MCC): Each time data is acquired from the MSM and TIS, this camera captures images informing the characteristics and composition of the Martian surface.
Mangalyaan Cost
Figure 2: Cost comparison of Mangalyaan and Maven (Source: NASA and ISRO)
ISRO managed to place Mangalyaan in the Martian orbit at a total cost of just Rs 450 million, which at the time was equivalent to around 73 million dollars. Today, this amount would translate into around 66 million dollars. This amount was just a fraction of what other countries spent on similar missions, making Mangalyaan the least expensive interplanetary mission ever. Considering that the longest distance between Mars and Earth is 400 million km, the cost of this expedition is approximately INR 11 per kilometer. This is cheaper than a rickshaw ride in Mumbai.
Talking about NASA and the European Space Agency, they incurred a cost of 671 million dollars and 200 million dollars respectively. It is interesting to note that even the Hollywood film Gravity was made with a total budget of 100 million dollars.
According to Mr K Radhakrishnan, former Chairman of ISRO, this low cost was attributed to several factors such as a modular approach, few soil tests and long working durations (18-20 hours) for the scientists.
Physics behind the launch of Mangalyaan
Figure 3: Launch of Mangalyaan by ISRO
• Mangalyaan weighs around 1,350 kg, which is roughly equivalent to the weight of a small car. One of the most important aspects of the mission was detecting the presence of methane and measuring the rate of loss of atmospheric gases into outer space, which could later be used to collect data on the planet's history.
• The spacecraft was launched by India's PSLV C25 rocket, using alternative solid and liquid propulsion in four stages. When igniting solid fuel, the thrust could not be regulated, but for liquid fuel, the engine could be turned off or on. The orbiter separated from the PSLV C25 rocket and entered Earth's elliptical orbit.
• Now, as the orbiter moved away from the Earth, the speed decreased and as it approached the Earth, the speed increased due to the gravitational pull of the Earth. This meant that the engine only needed to be fired for a short period, i.e. when the orbiter was close or the speed was high. This increased the orbit as well as the speed while using the least amount of fuel. After the 6 main engines were burned out, it managed to gain escape velocity and left Earth's sphere of influence.
To understand the meaning of escape velocity and sphere of influence , let's discuss the phenomenon briefly. As we know, the Sun is much larger than any of the planets and therefore its gravitational force dominates the solar system. Therefore, a planet's gravity is only stronger when an object is closer to that planet. This region around the planet is called that planet's sphere of influence and the speed required to leave this sphere is known as escape velocity.
• When Mars is in the correct position, the orbiter has left Earth in a direction that is tangential to Earth's orbit. So to put the orbiter on a trajectory that gets it to Mars is conveniently called a trans-Mars injection. As we know, Newton's first law of motion states that an object continues in motion unless acted upon by an external force. Applying the same rule here, the fuel was forced to burn just to define the trajectory and this process is called Trajectory Correction Maneuver.
• Another factor that determined MOM's entry into the Martian orbit was the angle between Earth, Mars and the Sun, which needs to be approximately 44 degrees. This condition occurs in the time interval of 780 days, implying that if the mission had not been able to send the satellite on that specific date, it would have been postponed to January 2016 and later to May 2018 and so on.
Figure 4: Mars Transfer Trajectory
• The shortest distance between Earth and Mars is 54.6 million, which means that an extremely large amount of fuel is needed to cover this distance. Scientists had to opt for the shortest route and then slow it down to match the planet's speed. This was only possible through an elliptical orbit of about 680 million km, which forms a tangent to Mars and Earth's orbit around the Sun. This type of transfer of a satellite/spacecraft from one orbit to another is called of Hohmann Transfer.
Figure 5: Diagram representing Mangalyaan's projected path
• The orbiter's speed was detected in the same way that drivers' speed is detected on highways. Radio waves were sent to the orbiter to establish communication with Earth. Each time the orbiter moved further away, each wave had to travel a greater distance and, therefore, the distance between them, i.e. the wavelength, increased. This change in wavelength helped in calculating the orbiter's velocity, also known as the Doppler Effect.
Mangalyaan-2
Soon after the success of MOM, ISRO made an announcement on October 28, 2014 about Mangalyaan 2, which will be an interplanetary follow-up mission. In addition to the orbiter, it is likely to include a Lander and a Rover. Furthermore, this time it will be jointly built by India and France. The two countries signed a letter of intent for ISRO and CNES to build the spacecraft together by 2020.
ISRO has planned to use GSLV III FOR Chandrayaan 2 (Moon mission) by 2018 and later for Mangalyaan (Mars mission) by 2020. According to some reports, the second iteration of Mangalyaan will be 7 times heavier than the first and will focus on more intense exploration of Mars with an improved set of equipment.
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