On November 5 2013, the Indian Space Research Organization (ISRO) made history by launching Mars Orbiter Mission (MOM) or Mangalyaan on its first interplanetary mission to Mars. Mangalyaan entered the Martian orbit on 24 September 2014 and ISRO became the fourth Space agency to achieve this feat and Bharat became the first Asian nation to reach the Martian orbit. The MOM probe lifted-off from the first launch pad at Satish Dhawan Space Centre using a Polar Satellite Launch vehicle (PSLV) rocket and reached the Mars orbit after 298 days. The mission is a "technology demonstrator" project to develop the technologies for designing, planning, management, and operations of an interplanetary mission. The spacecraft is currently being monitored from the Spacecraft Control Centre at ISRO Telemetry, Tracking and Command Network (ISTRAC) in Bengaluru with support from the Indian Deep Space Network (IDSN) antennae at Bengaluru, Karnataka.

The Probe

The spacecraft was based on the modified I-1 K structure which is similar to the Chandrayaan-1, with specific modifications for Mars. The electric Power is provided by the solar array which powers a 36Ah Lithium-ion battery and the propulsion system is a liquid fuel engine which was used for orbit raising and insertion into mars orbit. The space probe has been configured to carry out observation of physical features of mars and carry out limited study of Martian atmosphere with following five payloads: Mars Color Camera (MCC), Thermal Infrared Imaging Spectrometer (TIS), and Methane Sensor for Mars (MSM), Mars Exospheric Neutral Composition Analyzer (MENCA), and Lyman Alpha Photometer (LAP).

The Launch

ISRO originally planned to launch Mangalyaan with its GSLV (Geosynchronous Satellite Launch Vehicle), but GSLV failed twice in 2010. The launch of MOM would be delayed for 3 years if ISRO wanted to use the GSLV as the cryogenic engine still had problems. So ISRO went with its workhorse, the PSLV C25 since it was not powerful enough to place MOM on a direct-to-Mars trajectory, the spacecraft was launched into a highly elliptical Earth orbit and used its own thrusters to place itself on a trans-Mars trajectory.

The Trajectory to Mars

1.Geo Centric Phase

After the orbiter was put into an elliptical parking orbit, the spacecraft was gradually maneuvered into a departure hyperbolic trajectory through six main engine perigee burns. Perigee is the point in an orbit of a moon or a satellite where it comes closest to the Earth. Earth’s Sphere of Influence ends at 918347 km from the surface of the earth beyond which the gravitational force on the orbiter is mainly due to the Sun.

A total of six burns were completed while the spacecraft remained in Earth’s orbit. The seventh burn conducted on 30 November inserted MOM into a heliocentric orbit for its transit to Mars. A heliocentric orbit (also called circumsolar orbit) is an orbit around the center of the Solar System, which is usually located within or very near the surface of the Sun. One primary concern is how to get the spacecraft to Mars, on the least amount of fuel. ISRO uses a method of travel called a Hohmann Transfer Orbit – or a Minimum Energy Transfer Orbit – to send a spacecraft from Earth to Mars with the least amount of fuel possible.

2. Helio Centric Phase:

The spacecraft left Earth in a direction tangential to Earth’s orbit and encountered Mars tangentially to its orbit. The flight path is roughly one half of an ellipse around the sun. The probe travelled a distance of 780,000,000 kilometers (480,000,000 miles) to reach Mars. The orbiter underwent 3 trajectory correction maneuvers to ensure it enters into Mars orbit around the sun at the exact time when mars is there too.

This trajectory becomes possible with certain allowances when the relative position of Earth, Mars and Sun form an angle of approximately 44°. Such an arrangement recurs periodically at intervals of about 780 days. Minimum energy opportunities for Earth-Mars occurred in November 2013, January 2016, May2018 etc.

3.The Martian Phase:

The spacecraft arrived at the Mars Sphere of Influence (around 573473 km from the surface of Mars) in a hyperbolic trajectory. At that time the spacecraft reached the closest approach to Mars (Periapsis), it was captured into the planned orbit around mars by firing the main engine thruster which is called the Mars Orbit Insertion (MOI).

The biggest challenge for the mission was during the flight from Earth’s Sphere of influence to the Mars Sphere of Influence, the liquid fueled rockets were completely shut off and there was no guarantee that the apogee motor would fire after its long journey to mars through cold vacuum of space. Due to ISRO’s ingenuity the 440-newton liquid apogee motor was successfully test fired on 22 September 2014, 41 hours before the Mars orbit insertion. The Earth-Mars trajectory is shown in the figure below.

Impact of Mangalyaan:

At the end of the orbit insertion, Mangalyaan was left with 40kg of fuel on board, which was much more than the 20kg of fuel required for completing its 6 month mission. On 24 March 2015, MOM completed its planned six-month mission in orbit around Mars. ISRO extended the mission by an additional six months; the spacecraft has 37 kg (82 lb.) of propellant remaining and all five of its scientific instruments are working properly. The orbiter can reportedly continue orbiting Mars for several years with its remaining propellant.

MOM has captured plenty of images of Mars through the Mars Color camera (MCC); the first one was captured on 28th September 2014. MOM has completed over 7 years around Mars, capturing over 980 images through the MCC, sending over 2 TB of imaging data, and all of its instruments functioning normally. On 24th September 2015 ISRO released a Mars Atlas, a 120 page scientific Atlas with all the information that MOM collected over its first year in orbit.

The Mangalyaan team won the 2015 Space Pioneer award in the science and engineering category awarded by the National Space Society of USA. NSS said the award was given as ISRO successfully executed a Mars mission in its first attempt; and the spacecraft is in an elliptical orbit with a high apoapsis where, with its high resolution camera, it is taking full-disk color imagery of Mars. Very few full disk images have ever been taken in the past, mostly on approach to the planet, as most imaging is done looking straight down in mapping mode. These images will aid planetary scientists in the future.

ISRO plans to develop and launch a Mangalyaan-2 mission with a greater scientific payload and get closer to mars to collect more data for future manned missions to Mars.