# Approximately how much fuel will ISRO Mars Orbiter have available when it enter Mars' orbit?

मंगलयान (Maṅgalayāna) is due to launch on November 05, 2013 AD of the Gregorian Calendar at 1436H (GMT+0530). Wikipedia writes to say

The November 2013 launch will place the Mars Orbiter Mission into Earth orbit, then six engine firings will raise that orbit to one with an apogee of 215,000 km and a perigee of 600 km, where it will remain for about 25 days. A final firing in 30 November 2013 will send MOM onto an interplanetary trajectory.

The same article goes on to write

The spacecraft's dry mass is planned to be 500 kg, and it will carry 850 kg of propellant and oxidiser.

I'm no rocket-man; what fraction of the 850KG is expected to be consumed during the course of transfer, and correction burn? Put another way, how much fuel will remain available to enter Mars' orbit?

According to Wikipedia, "At the end of the orbit insertion, MOM was left with 40 kg (88 lb) of fuel as against the 20 kg (44 lb) that was thought necessary for the six-month life span." (see https://en.m.wikipedia.org/wiki/Mars_Orbiter_Mission)

• This begs the follow-up question - how could the estimates be off by 100%? Any takers? Commented Nov 6, 2014 at 6:00
• Everyone - MOM needed only two of the anticipated four mid-course correction burns, thus there was more fuel available after Mars Orbit Insertion. Commented Nov 6, 2014 at 6:51
• I went through the article awhile back (+: it's still a huge difference from 44lbs to 88 lbs. Commented Nov 6, 2014 at 8:26
• Everyone - Compared to the 810Kg already expended, 40Kg vs 20Kg does not strike me as huge ... Commented Nov 6, 2014 at 22:57
• I may be wrong ; the impression I had was that a correction burn is a relatively short-duration burn. Anyway, it's a bonus to have that extra fuel on board. I wonder how much of it they used to get behind the Warlord away from Siding Spring ... and whether some extra propellant was planned for the Siding Spring encounter. Commented Nov 7, 2014 at 17:38