“The Orbiter entered the final orbit of earth early Wednesday for its trans-injection into the Sun orbit Sunday at 00.49 a.m. for a nine-month journey to Mars through the interplanetary space, a senior space agency official said here.
The craft passed its penultimate perigee (closest to equator) at 07.10 a.m. Wednesday to commence its four-day final orbit around earth to leave for Mars in the wee hours of Sunday.
“A 440 Newton engine will be fired for nearly 23 minutes to sling the craft into the Sun orbit at a speed of 648 metres per second for which 190 kg of fuel will be consumed,” Indian Space Research Organisation (ISRO) scientific secretary V. Koteshwara Rao told reporters here.
Orbiter has completed its six-orbit raising manoeuvres between Nov 7 and Nov 16 and crossed an apogee (farthest from equator) of 192,915 km.
“All is going well, Orbiter will be slung into the heliocentric (Sun) orbit towards Mars for a 680-million-long coasting distance,” Rao said at the space agency’s telemetry, tracking and command network (Istrac) in the city.
The 1,337-kg Orbiter was launched Nov 5 from Sriharikota spaceport off the Bay of Bengal, about 80 km north east of Chennai, on board a 350-tonne rocket with five scientific instruments to detect Methane in the Martian atmosphere, measure the thermal emission and capture images of the red planet from its orbit at a distance of 500 km.
“The slingshot for the trans-injection will be a complex combination of navigation and propulsion technologies, governed by the gravity of Sun and Mars,” Rao said at a briefing on the Rs.450-crore mission’s next phase.
The Orbiter’s trajectory will be achieved using the attitude and orbit control thrusters during the correction manoeuvres planned enroute.
As the fourth planet from Sun and behind Earth, Mars is the second smallest celestial body in the solar system. Named after Roman god of war, it is also known as red planet due to the presence of iron oxide in abundance, giving it a reddish appearance.
Though Earth and Mars have equal period of revolution around their axis, the red planet takes 24 hours and 37 minutes to complete a revolution. Earth takes around 365 days to orbit the sun and Mars 687 days.
“The craft will be injected into the outer space in a trajectory by precisely computing 280 days in advance the position it would achieve near Mars Sep 14, 2014, which will be 500 km above its surface at that time,” Rao pointed out.
The Mars Orbiter Mission (MOM) complex at Istrac is also daily conducting checks of the main bus systems, redundant systems, failure detection, reconfiguration and its scientific instruments, including its powerful colour camera.
The camera, which has been activated, has demonstrated its functioning by taking a clear picture of the Indian sub-continent Nov 19 from a distance of 67,975 km with a 3.5 metre resolution.
During the helio sun phase, travelling at a speed of 32.5 km per second mid-course corrections will be carried, if required, Dec 11, mid-April, mid-August and Sept 14.
“The Orbiter will be inserted Sep 24 at 07:14 a.m. into the Martian orbit at 372 km periapsis (nearest to surface) and 80,000 apo-asis (farthest from surface) by firing the engine for nearly 29 minutes in the reverse direction to reduce its speed to 11,009 metres per second by consuming 24 kg fuel,” Rao pointed out.
The mission has also built-in mechanism for contingencies and redundancies have been built into the systems and the onboard autonomy to switch over from primary to stand by system.