They did a few things differently. Because their thrust was relatively limited, they made several short burns at perigee to raise their apogee in successive stages. Essentially, it was more efficient to fire their engine several times very close to perigee in 5-10 minute bursts, than make one long 30 minute burn.
Secondly, there was never any stage where they circularized their orbit, as one would do with a Hohmann. Rather, they kept burning at perigee until they escaped earth. Picture a an ellipse growing more and more eccentric until it becomes open at one end.
Also note that they never burned at apogee. The point wasn't to raise apogee so they could escape at apogee, but to increase velocity at perigee until they could reach escape velocity with a 20 minute burn on their last orbit.
Secondly, there was never any stage where they circularized their orbit, as one would do with a Hohmann. Rather, they kept burning at perigee until they escaped earth. Picture a an ellipse growing more and more eccentric until it becomes open at one end.
Also note that they never burned at apogee. The point wasn't to raise apogee so they could escape at apogee, but to increase velocity at perigee until they could reach escape velocity with a 20 minute burn on their last orbit.
http://www.isro.org/mars/mission-profile.aspx