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Pushpender Singh Gusain
Mangalyaan, Indian Mars Orbiter Mission
'Any space mission is complex, we work like surgeons, totally focussed on the job' Dr. K Radhakrishan, chairman, ISRO
The Mangalyaan, also known as Mars Orbiter Mission (MOM), India’s first interplanetary mission is well on its way to Mars at the rate of 370 lakh km a day. The orbiter crossed half way distance to Mars along the designated hyperbolic trajectory around sun on April 09, 2014. It will approach its destination on September 24, 2014 after streaking through space for about ten and half months and covering a distance of 68 crore km. Since MOM will orbit Mars and not land on it, hence the name orbiter.
The orbiter left Earth's sphere of influence on December 4, 2013 making India the fourth country in the world and the first Asian nation to accomplish such a feat. Of the 51 missions launched to Mars across the world so far, 27 have failed. If Mangalyaan manages to reach Mars orbit in its maiden flight, it will be a great achievement.
Work on the Mars mission was initiated back in 2010 and the project was approved by government of India in August 2012. ISRO had just 15 months at hand to design, develop, assemble and test the spacecraft to use the impending 20 days long interplanetary launch window (a time period during which a particular vehicle must be launched in order to reach its intended target) available for Mars between 28th October and 19th November, 2013. The launch window recurs once every 26 months for Mars.
It goes to the credit of ISRO that the entire Mars mission was executed within a short period of 15 months. It shows the dedication and technical expertise of the people associated with the project. With the launch of Mangalyaan, Indian space programme has come a long way from its first sounding rocket, carrying scientific instruments that took off from Thumba, the spaceport near Thiruvananthapuram on November 21, 1963.
The total approved cost for Mangalyaan project is Rs 450 crore with the rocket costing Rs 110 crore, orbiter about Rs 150 crore and the balance spent on beefing up the ground support and tracking system.
Originally the Mars Mission was scheduled for launch on October 28, 2013. But the launch was postponed as the tracking ships could not reach at their required locations in time due to bad weather in Pacific Ocean and it was rescheduled for November 5, 2013.
As per Dr K Radhakrisnan, Chairman ISRO, the mission has two objectives. The first is to test and extend ISRO’s technological capabilities. The second one is to extend acquired scientific knowledge to solve the various problems of India.
The Mars spacecraft is largely based on the Chandrayaan-1 Moon Orbiter with specific improvements and upgrades required for the mission. It weighs 1,337 kg that includes a payload mass of 15 kg and a fuel load of 852 kg.
The spacecraft has a single deployable solar array. It will produce 840 Watts of electrical power in Mars orbit which is fed to different units and payloads and also charges a 36-Amp-hour battery for night passes.
For its orbit raising and other maneuvers, Mangalyaan has a bipropellant propulsion system with 780 liters of propellant. The Propulsion System is centered around 440-Newton Liquid Engine (NLE) that provides 440 Newton thrust. Similarly, a propulsive Attitude control system in Mangalyaan is used for attitude or orientation control with the help of eight 22-Newton thrusters.
Attitude and navigation data is provided by two star trackers and gyros as well as a coarse Sun sensor. Attitude data is also provided by an Inertial Reference Unit and Accelerometer Package. It has a 2.2-meter diameter High Gain Antenna that is used for data downlink and command uplink. Science data and spacecraft telemetry is stored in two 16Gb Solid State Recorders for downlink during regular communications sessions. Low and Medium Gain Antennas are used for low-bandwidth communications such as command uplink and systems telemetry downlink.
The spacecraft has five payloads (scientific instruments) to explore the mars and its atmosphere:
1. Lyman Alpha Photometer - to measure relative abundance of Deuterium & Hydrogen in the atmosphere. Measurement of Deuterium to Hydrogen ratio can throw some light about the loss process of water in the evolutionary history of Mars atmosphere.
2. Martian Exospheric Neutral Composition Analyzer – is a mass spectrometer to study the atmosphere. The core objective is to study the exospheric neutral density and composition at altitudes as low as 372 km above the Martian surface. Studying the Martian exosphere will provide valuable data on the present conditions as well as atmospheric loss phenomena.
3. Methane Sensor for Mars – is designed to detect and identify the source of methane in the atmosphere of Mars.
4. Thermal Infrared Imaging System – measures thermal emission and can be used both during day and night. It will map the surface composition and mineralogy of the planet.
5. Mars Color Camera – provides images and information about the surface features and composition of Mars surface. The camera provides images with 50 by 50 km frame size and a resolution of 25 meters per pixel when the orbiter is closest to Mars and a wide field of view of 8,000 by 8,000 km when farthest from it.
Launch & Transfer into Trans-Martian Trajectory
Mangalyaan was placed into an elliptical orbit of earth with apogee (closest distance of the orbiter from earth) of 247 km, perigee (farthest distance of the orbiter from earth) of 23,567 km and at an inclination of 19.2 degrees by Polar Satellite Launch Vehicle from Satish Dhawan Space Centre, Sriharikota on November 5, 2013 at 14:38 hrs.
The rocket took a 44 minute ascent to place the MOM in the orbit and then orbiter used its own propulsion system to move into Trans-Martian Trajectory with the help of a series of six orbit raising maneuver. Trans-Martian Trajectory is the path that the orbiter will follow to Mars after it is boosted out of the earth orbit.
Orbiter raised its apogee from the initial 23,567 km to 1,92,870 km with the five maneuvers. This apogee meant that the orbiter was ready to leave the orbit of the earth and embark on its journey to Mars. It just required a push and that was to be given by Trans-Martian Injection maneuver scheduled for December 1, 2013. A trans-Mars injection is a propulsive maneuver that puts the vehicle onto its Trans Martian Trajectory.
All the orbit raising maneuvers except the forth one went on smoothly and achieved the intended result. The orbiter experienced a problem during its fourth orbit-raising maneuver. The Newton liquid Engine burn did not achieve the planned change in velocity and left the spacecraft in a lower-than-planned orbit. The team of ISRO scientists cracked the issue and fourth supplementary orbit raising maneuver was carried out November 12, 2013.
The Trans-Martian Injection maneuver on December 01, 2013 provided the necessary thrust to the spacecraft to move from earth’s orbit to a helio-centric Orbit (an orbit that takes the spacecraft from one planet to another planet) towards Mars. The Trans-Martian Injection was targeted to occur at the optimal time within the interplanetary launch window that allows the most efficient transfer of spacecraft to Mars in terms of fuel expenditure.
Flying in helio-centric orbit, Mangalyaan is set for the trip to Mars that will take about 300 days. During this period ground stations will keep on reviewing the telemetry data received from the spacecraft along with a number of periodic on board instruments testing activities to ensure their field operational readiness.
Trajectory Correction Maneuver
The spacecraft is regularly being tracked by ground stations to determine its precise trajectory. Any deviation from the planned path is to be rectified by a series of Trajectory Correction Maneuvers (TCM).
The first TCM was done on December 11, 2013 with the help of 22 Newton thrusters. The second TCM scheduled for April 8, 2014 has been skipped as spacecraft was right on the track. The final TCM is planned on September 14, ten days before the transfer of orbiter into Mars orbit to set up the accurate flight path for the critical operation.
Mangalyaan in Mars Orbit
While approaching the sphere of influence of Mars in September 2014, Mangalyaan will eventually intersect Mars orbit at the exact moment while Mars is there too. The moment orbiter approaches the closest distance to Mars (periapsis), 440 Newton Liquid Engine will fire to slow down the spacecraft to enable it to be pulled by Maritan gravity into a planned orbit. This action is named Mars Orbit Insertion (MOI) maneuver and is very crucial. Since the Liquid Apogee Motor is being operated for MOI operation almost after a gap of ten months, its reliability is very important. Should the MOI burn not start on time or achieve the required change in velocity, Mangalyaan would be lost in its orbit around the sun.
Ones in the Mars orbit, the spacecraft targets an operational orbit of 365.3km by 80,000 km with an inclination of 150 degrees and duration of 76.72 hours from where it will study the various aspects of Mars and its atmosphere with the help of five instruments. The MOM mission in Mars orbit is open-ended and is expected to last about 160 days.
On April 9, 2014, the radio distance between the Spacecraft and the Earth was 39 million km. A signal from the Earth to the Spacecraft and back to Earth took 4 minutes and 15 seconds. The signal time will stretch to 20 minutes one way as and when the orbiter approaches Mars orbit.
Communications during the Mangalyaan mission are supported by India’s Deep Space Network Ground Stations while coverage for critical mission events such as Mars Orbit Insertion is supported by NASA’s global Deep Space Network.