from what i could tell, you couldnt tell just what ship that he jumped out of... so he could have already landed on earth and just jumped from somethin else after he got the upgrade. besides at the end of halo 2 it sure seems that master chief beat sgt. johnson and the arbiter to earth, because he was in transit while they were fightin the chieftain. but in halo 3 they were there on earth before he crash landed... so lookin at master chief almost killin the arbiter in h3, then thats the point where they finally regrouped... master chief should have already been on earth..
im pretty sure that i read somewhere that his armor gets upgraded between each of the games. IE Mark V armor during Halo:CE, Mark V.5 during Halo2, and then the legendary Mark VI armor during Halo3. I think the Mark V.5 armor was when he got a partial upgrade to VI, but they didnt have the time or the resources or something to do the complete upgrade.