This is a guest contribution from Santosh Deshmukh.
Mission Objectives –
Primary Objective – Technological Demonstration of capability of taking an Operative Spacecraft to Mars and successfully injecting it in the Martian Orbit.
Secondary Objective – To collect Scientific Data of Mars’s atmosphere using 5 on board Scientific Instruments and to analyse and study it.
The main Instruments being Mars Colour Camera and Methane Sensor.
Pre development Major Challenges.
- Tiny Budget.
Budget of 450 Crores was approved by the Government of India on 03-Aug-2012 for development of Mars Orbiter Mission Satellite and its 5 Scientific Instruments, its Launcher (Home grown PSLV Rocket) and the Communication Support required from NASA’s Deep Space & ISRO’s Deep Space Network ground stations for round the clock communication with the Satellite. This budget was extremely low considering the volume of the mission requirements. To accommodate all the requirements of the mission in such a small budget was itself a big challenge for the Space Agency.
- Short time for Development & Testing.
The budget was approved by Government of India on 03-Aug-2012. There was a Mars Launch Window between 28-October-2013 to 08-November-2013. If this window would have been missed due to whatever reason, then the next Launch Window was available only in 2016. To achieve the 2013 window of Launch, The Space Agency needed to work at a rapid pace of development as they had only 1 year and few months for planning, design, development & testing of the entire Mission. It demanded the staff working on this project to work even for 16 hours a day and 7 days a week to be able to complete this project within the timeline. I have gone through interviews of some of the ladies staff in many newspaper articles, who were working on this project and said that they have worked round the clock & many a times even during weekends to complete this Project in time.
- Restriction of the Spacecraft Weight.
Keeping the weight of the Spacecraft under 1.4 tons was also a major challenge for the Space Agency, as the rocket carrying the Spacecraft was not powerful enough to carry more weight. The Spacecraft needed to carry 850 Kg of fuel with it, which was required for several maneuver’s around the Earth, during the transit from Earth to Mars and during the Insertion of Mars Orbit once it reaches Mars. So, 1400 Kg – 850 Kg (Fuel) = 550 Kgs. Thus the Space Agency required to build the rest of the Spacecraft components & Engine including the Scientific Instruments at a maximum weight of 550 Kg which was again a daunting task for the Space Agency.
Post Launch Challenges.
- Giving Power to Spacecraft to escape Earth’s Sphere of Influence.
India had capability to launch 1.5 ton Spacecraft to a Sun Synchronous Orbit (A highly Elliptical Orbit around Earth) using its home grown PSLV rocket. But the Mars Orbiter Mission Spacecraft needed huge power to break free from the gravitation influence of the Earth in order to move towards Mars. This could have been obtained only by following two approaches.
Either the rocket which is launching the Spacecraft had enough power to push the Spacecraft out of the Earth’s Sphere of Influence,
To maneuver the Spacecraft around Earth by a sling shot method (using Earth’s gravity) in order to gather enough momentum to move out of the Earth’s Sphere of Influence.
India, didn’t have the Powerful Rocket to directly push the Spacecraft out of the gravitational influence of Earth. So the first approach mentioned above was not possible and ruled out. Only the second one was possible. But maneuvering the Spacecraft around the Earth for a slingshot was also not that easy and it needed series of precise & accurate Orbit raising maneuvers. This task was till date only a theoretically possible one, and no other country was successful in achieving it practically.
- Inserting the Spacecraft precisely in Mars Transfer Trajectory.
After series of 5 to 6 Orbit raising maneuvers’, inserting the Spacecraft in precise trajectory to Mars was the major milestone. This task also needed pin point accuracy as an error in calculations as small as 0.001% could have lead the Spacecraft to miss the Mars by a huge margin & the mission into failure.
- Tracking the Spacecraft 24×7.
After the Spacecraft was injected into the Mars Transfer Trajectory, the Spacecraft begun its 780 million miles journey to Mars. It crossed the Earth’s Sphere of Influence in 8 days and kept on moving in its trajectory path. During this journey, the major challenge was tracking the Spacecraft 24×7. ISRO’s Deep Space Network have ground stations in several countries but they are not enough to track the Spacecraft 24×7 as due to Earth’s rotation, the Spacecraft visibility of each ground station was only for few hours. So ISRO joined hands with NASA’s Deep Space Network for tracking the Spacecraft from their network when the Spacecraft was not visible at ISRO’s Deep Space Network ground station visibility. As you may know NASA’s Deep Space Network has 3 main ground stations across the globe with powerful Antenna. Madrid, Canberra & Goldstone are those 3 ground stations which have 24×7 visibility of any Deep Space Network operations at any point of time. So, it became possible for ISRO to get the telemetry and tracking data of the spacecraft 24×7 during the entire journey and even as on today.
- Determining whether the path of the Spacecraft is correct or it needed any correction.
During 780 million miles journey, monitoring the Spacecraft path precisely and determining if the existing path is correct or it required correction was also one of the major challenges. From the telemetry and tracking data, it required several complex calculations to come to conclusion whether the existing path of the Spacecraft is correct or it needed some correction in order to reach Mars. If any of the calculations goes wrong, the Mars could have been missed by the Spacecraft. The complexity of this calculations can be demonstrated by this example. Imagine that you are playing golf and you need to shot a ball into a hole which is moving continuously at a rate of 5 mtrs/sec. That is you need to aim for a target which is moving continuously at a fixed rate. That difficult it was to determine whether the Spacecraft which is moving towards Mars (Which is also moving in its Orbit around Sun) is in correct path or not.
From the data, if the Spacecraft was found to be deviating from the correct path, then it needed trajectory correction maneuver. This was done by firing its Engine and reorienting the Spacecraft in precise direction. This was also the most tough task and many things could have gone wrong in such correction maneuvers as well.
- Awaking the Main Engine after 10 Months of sleep.
The 780 million mile journey to Mars was 10 months journey. But during this journey, the Spacecraft was not required to burn its Main Engine as it had already gathered momentum (Velocity required) for reaching Mars. So the Main Engine of the Spacecraft was in idle state during the 10 month long journey to Mars. But once it started approaching the Mars, the Spacecraft was required to be slowed down from its cruising speed of 30 Km/sec to 5 Km/sec in order to be able to capture it by Mars’s gravity so that it will Orbit the Mars. This slowdown was possible only if the Main Engine is fired for 25 to 30 minutes in opposite direction of the motion of the Spacecraft.
Awaking the Spacecraft’s main Engine after 10 month’s of sleep was a major challenge as fuel lines of the Engine were vulnerable to corrosion during the idle state and due to vacuum conditions of Space. To overcome this, provision was made for redundant fuel line in the Engine so that even if the primary fuel line is not working the secondary one should work and supply fuel to main Engine during the Mars Orbit Insertion firing.
- Commanding the Spacecraft for Mars Orbit Insertion.
During the Mars Orbit Insertion, the Spacecraft was behind Mars. i.e. Mars was between the Spacecraft and Earth. So, the real time communication with the Spacecraft was not possible as the signals from Earth could not reach the Spacecraft when it was behind the Mars. So, the Mars Orbit Insertion commands were required to be given to the Spacecraft well in advance with time tagging. And the on board computer would execute them precisely as per the time tagged in the command. This was also a major challenge as even a small error in time tagging the commands would have led to the unsuccessful Mars Orbit Insertion.
Post Mars Orbit Insertion Challenges.
1] Maneuvering the Spacecraft to a Safe Orbit for Comet Siding Spring Pass near Mars in October 2014.
Even after the successful insertion into the Martian Orbit on 24–September-2014, the Space Agency could not relax for many days. The next immediate challenge for the Space Agency was maneuvering the Spacecraft to a safe altitude in order to avoid any possible collision with the Comet Siding Spring. The Comet Siding spring’s closest approach to Mars was on 19-Oct-2014. At the closest approach to Mars, the Comet was expected to come within 82,000 miles (132,000 Kms) from Mars. The Comet had a long tail too, so even if the Comet dust would have reached Mars’s Orbit, it would have created a potential damage to the Spacecraft in Orbit there. Thus it became very essential to maneuver the Spacecraft to a different Orbit and also maintain safe distance from the Comet and its dust till they are completely passed from the Mars’s Sphere of Influence.
The Spacecraft had to be maneuvered to be behind the other side of the Mars when the Comet was scheduled to pass from the side of the Mars. This was a critical maneuver the Spacecraft was needed to be behind the other side even when the dust shower was expected for 100 minutes during the Comet pass by.
Though the Comet Siding Spring’s closest approach to Mars was a threat to Spacecraft and it needed maneuver to protect the Spacecraft from the collision of Comet or its dust, it was a unique opportunity for learning about the Comet and it was once in life time celestial event too.
2] Providing Autonomy to the Spacecraft during Solar Congestion Period of 15 days (June 8 to 22).
Another major challenge faced by the Space Agency was in June-2015 when the Solar Congestion was scheduled for the period of 15 days from June 8 to June 22, 2015. The Solar Congestion takes place when the Sun comes in straight line between Mars and Earth. So during this time, the signals sent from Earth cannot reach Mars as they get lost by Sun’s energy. In short, during this period no communication becomes possible between Earth and Mars. So the Spacecraft Orbiting the Mars required to be given complete Autonomy for taking decisions independently for any contingency that possibly may occur in order to survive during that period. For this, the Spacecraft’s on board computer was commanded well in advance to be able to handle all the routine work and take decisions independently during the Solar Congestion Period.29