By Sanjay Jahagirdar
On September 24, Indian Space Research Organization (ISRO) will be on the verge of accomplishing a spectacular space mission, insertion of Mangalyan (orbiter) in the Mars orbit. Of the total fifty-one missions to the red planet undertaken by different countries, only twenty-one have been successful. For every Indian, this moment should be as crucial as Sunil Gawaskar breaking Sir Don Bradman’s record. Recall how the entire country celebrated this feat. Should we then not be equally proud of ISRO’s the scientific and technological endeavour? At the very least we should be aware of this mission.
ISRO started space exploration from scratch beginning with the development of rockets. Scientists would themselves carry small test rockets on their bicycle-carriers to distant launching pads.
Today, ISRO has successfully placed artificial satellites in polar and geosynchronous orbits, it has indigenously built both the launch vehicle and satellite which map every inch of the earth either for terrestrial, meteorological, geological data or for communication purpose, it has developed the technology to carry six to seven satellites at-a-time and now provides this facility to other countries as well, and finally it planned and implemented the mission to moon and mars for which spaceships Chandrayan and Mangalyan were developed.
ABOUT THE MARS ORBITER MISSION
ISRO’s Mars Orbiter mission involves placing a satellite within the orbit of planet Mar under the influence of the planet’s gravity.
The spacecraft orbiting Mars will have periapsis (closet distance from Mars) of 365.3 km and apoapsis (farthest distance from the Mars) of 80,000 km.
Insertion of Mars Orbiter will happen on September 24, 2014 at 02.34.
OBJECTIVES OF THE MISSION
Technological objectives include design and realisation of a Mars orbiter with a capability to survive and perform Earth bound manoeuvres, maintain a cruise phase of 300 days of travelling a distance of 149,597,891 km, and Mars orbit insertion/capture and on-orbit phase around Mars.
Scientific objectives involve research purpose exploration of Mars surface features, morphology, mineralogy and Martian atmosphere by indigenous scientific instruments.
FACING THE MISSION
As seen from Mars, the orbiter is in a hyperbolic trajectory at a distance of 573,473 km from the surface. At the point of periapsis, the velocity of the orbiter should be reduced from 22 km/sec to a mere 1.6 km/sec. This is known as imparting delta v retro, which is not as simple as applying breaks or cutting off fuel supply!
Sensors – accelerometers – will be used to measure decremented velocity. The Japanese failed in this type of manoeuvring and eventually their space ship was trapped in the sun’s orbit. To reduce the velocity of the orbiter thrust has to be given in the opposite direction for which the LE 440N engine has been employed, which will start after 299 days of hibernation.
All these tasks are to be remotely performed from the ISRO station at Bangalore while the orbiter will be at an astonishing distance of 225,000,000 km, eclipsed behind the red planet.
THE TECHNOLOGY THAT WENT
INTO THE MISSION
To impart 11.2 km/sec escape velocity to the rocket, ISRO has indigenously built a workhorse known as the Polar Satellite Launch Vehicle (PSLV).
A liquid engine of 440 N thrust is used for orbit raising and insertion in Martian orbit. The power required for such kind of manoeuvring is provided by 852 kg of fuel stored in a 390-litre tank.
The orbiter craft requires three solar panels (size 1800 X 1400 mm) to compensate for the lower solar irradiance as Mars is further away from the sun.
For the purpose of giving instructions to the orbiter, a high-gain antenna of 2.2 meter diameter reflector has been mounted and communication falls in the S-band. The antenna is used to transmit/receive telemetry, tracking and commanding (TTC) and data to/from the Indian Deep Space Network.
The most striking design feature of the orbiter is that the craft troubleshoots itself in contingency situations as the large distance does not permit real time intervention.
THE POLAR SATELLITE
The Polar Satellite Launch Vehicle is capable of launching 1600 kg satellite(s) in sun-synchronous polar orbit of 620 km and 1050 kg satellite in geo-synchronous transfer orbit.
In standard configuration it measures 44.4 meters in height (about 15 storeys high) with a lift off weight of 295 tonnes, equivalent roughly to weight of a hundred adult Asian elephants.
PSLV has four stages that use solid and liquid propulsion systems alternately. The first stage uses one of the largest solid propellant boosters in the world and carries 139 tonnes of propellant. (We, Indians are usually curious about the mileage of a bike or car. Well, PSLV has a mileage of, hold your breath, about 1075 km per kg of fuel! )
PSLV’s track record is excellent. It has repeatedly proved its reliability and versatility by launching 70 satellites/spacecrafts (30 Indian and 40 foreign satellites) into a variety of orbits so far.
Let this manmade celestial event achievement of ISRO be a source of inspiration to the billions of Indians.
For ISRO sky is not the limit!
By Sanjay Jahagirdar