Posts Tagged ‘Mars Orbiter’

Moment of truth approaches for India’s Mars Orbiter Mission

November 28, 2013

When everything is for the first time,achievements are incremental and there are very many critical “moments of truth” to meet and overcome. But now comes a very large “moment of truth” as ISRO prepares to inject the Mars Orbiter spacecraft into its Trans Mars Trajectory.

India’s Mars Orbiter (Mangalyaan) is currently in its final orbit around the earth and is scheduled to fire its 440 Newton liquid engine at 0049 hours IST on Sunday morning ( 1919 GMT Saturday 30th November).  It entered its final Earth orbit yesterday which has an orbital period of 5575 minutes (just under 4 days) and it should be approaching apogee later tonight (early hours of Friday morning) and the next engine burn will take place at perigee. Currently apogee is about 193,000 km from earth and perigee is around 350km.

The spacecraft must first be manoeuvred into the right attitude using its thrusters for the firing of its main engine which must then be fired to impart the correct change of velocity (delta-vee). Both, an incorrect attitude and/or an incorrect delta-vee are potential sources of error. Three mid-course corrections are planned  (the first on December 11th) but the margin of error allowable is still extremely small. Too low a velocity change could leave the craft in earth orbit or put it into a heliocentric orbit which does not get close enough to Mars. Too high a delta-vee would also put the craft into a heliocentric orbit which would eventually decay into the sun. I believe there is no chance of achieving a velocity high enough to escape the sun. And even if the velocity change is correct but the direction is too far in error then just another orbital path around the sun would result.

NDTV:“The trans-Mars injection- we are planning to depart on December 1, 2013 early hours of 00:49 hours IST and we are going to burn a liquid engine for duration of roughly 23 minutes which will impart an incremental velocity of 648 metres per second consuming a fuel of 198 kgs,” ISRO Scientific Secretary V Koteswara Rao told reporters in Bangalore.

K. Radhakrishnan, ISRO Chairman. (For the) trans-Mars injection and its insertion into the Martian orbit, the firing of the liquid engine is done in a closed loop mode. Here, a precision accelerometer is used to estimate the incremental velocity added as the liquid engine burns and when the accelerometer gives a feedback that the required incremental velocity added to the spacecraft has been achieved, the burning of the liquid engine is automatically terminated. So, minor variations in the performance of the liquid engine will not matter because we are cutting off its burning based on the delta-v that is achieved. That is why we call it closed loop of firing. … The spacecraft’s propulsion system, i.e., the 440 Newton liquid engine, will complete its first phase of operations on December 1. It has to be re-started for its operation on September 24 (2014).

MOM Trans Mars Injection ISRO

MOM Trans Mars Injection ISRO

ISRO: This voyage is achieved by a combination of navigation and propulsion technologies, governed by the gravity of Sun and Mars, and assisted by the 440 N Liquid engine. Further fine tuning of the trajectory is achieved using the Attitude and Orbit Control Thrusters during the Trajectory Correction maneuvers planned en route.

… on December 11, we plan to have one small firing for mid-course correction of the spacecraft. There may be one more mid-course correction during the helio-centric phase, and subsequently, a fortnight before the spacecraft’s arrival near Mars, there will be one more mid-course correction. So there will be three mid-course corrections between December 1, 2013 and September 24, 2014. 

Mangalyaan is eventually to be placed into a Martian orbit, with a periapsis height of 365 km, apoapsis height of 80,000 km and an orbital period of about 77 hours.

So on Saturday I shall have as many of my fingers crossed as I can manage. I suspect there will be many others doing the same across India.

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India’s frugal Mars orbiter mission completes 3rd burn in earth orbit

November 9, 2013

There has been some criticism  (within and outside India) from the usual suspects about the frugally-engineered, Indian, Mangalyaan Mars Orbiter mission as “being too expensive” for a developing country like India. I tend to discount these voices which merely continue the long, retrograde and shameful tradition of the Luddites. Some of these voices are of those who would like humankind to return to the trees. Others are of those who feel threatened by the idea of “backward nations” moving into space.

Reaching Mars is not that easy. More missions have failed than have succeeded. The full list of Mars missions is here. There are many crucial steps left for the Mangalyaan mission to achieve and success is far from assured.

TOI: India’s Mars Rover Mission (MOM) named ‘Mangalyaan’ is the 42nd mission aimed at understanding Mars. Out of the 41 missions so far, 25 have been declared failures and only 16 have been a success. Even the latest Phobos-Grunt/Yinghuo-1 launched by Russia/China was a failure as it got stranded in the earth’s orbit. 

Close on the heels of ‘Mangalyaan’ being sent into space by India, the United States (US) is also gearing up for the MAVEN mission to be launched on November 18, 2013. The mission is intended to be a step towards ‘unravelling the planetary puzzle about Mars’. The US is also gearing up for the Mars Rover 2020 mission to understand ‘Martian atmosphere’.

Underlying all missions is the vision of Mars one day being inhabited by humans. And that vision transcends the petty and mean criticism of those who can only see a “glass half empty”.

Last night the 3rd of five rocket burns was completed to lift the earth orbit of Mangalyaan from 40,186 km to 71,636 km (apogee). The fourth and fifth burns are planned for November 11th and 16th to raise the apogee to 100,000 km and then to 192,000 km. The 6th burn will be to leave Earth’s orbit and  insert the spacecraft into a trajectory towards Mars. The Trans-Mars injection is expected around 12.42 AM on December 1st.

ISRO: The third orbit raising manoeuvre of Mars Orbiter Spacecraft, starting at 02:10:43 hrs(IST) on Nov 09, 2013, with a burn time of 707 seconds has been successfully completed. The observed change in Apogee is from 40186km to 71636km.

ISRO’s Mission Profile.

The Launch Vehicle – PSLV-C25 will inject the Spacecraft into an Elliptical Parking Orbit with a perigee of 250 km and an apogee of 23,500 km. With six Liquid Engine firing, the spacecraft is gradually maneuvered into a hyperbolic trajectory with which it escapes from the Earth’s Sphere of Influence (SOI) and arrives at the Mars Sphere of Influence. When spacecraft reaches nearest point of Mars (Peri-apsis), it is maneuvered in to an elliptical orbit around Mars by firing the Liquid Engine. The spacecraft then moves around the Mars in an orbit with Peri-apsis of 366 km and Apo-apsis of about 80000 km. 

The mission consists of following three phases:

1. Geo Centric Phase
The spacecraft is injected into an Elliptic Parking Orbit by the launcher. With six main engine burns, the spacecraft is gradually maneuvered into a departure hyperbolic trajectory with which it escapes from the Earth’s Sphere of Influence (SOI) with Earth’s orbital velocity + V boost. The SOI of earth ends at 918347 km from the surface of the earth beyond which the perturbing force on the orbiter is mainly due to 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 leaves Earth in a direction tangential to Earth’s orbit and encounters Mars tangentially to its orbit. The flight path is roughly one half of an ellipse around sun. Eventually it will intersect the orbit of Mars at the exact moment 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 44o. Such an arrangement recur periodically at intervals of about 780 days. Minimum energy opportunities for Earth-Mars occur in November 2013, January 2016, May 2018 etc. 

3. Martian Phase
The spacecraft arrives at the Mars Sphere of Influence (around 573473 km from the surface of Mars) in a hyperbolic trajectory. At the time the spacecraft reaches the closest approach to Mars (Periapsis), it is captured into planned orbit around mars by imparting ∆V retro which is called the Mars Orbit Insertion (MOI) manoeuvre. The Earth-Mars trajectory is shown in the above figure. ISRO plans to launch the Mars Orbiter Mission during the November 2013 window utilizing minimum energy transfer opportunity.


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