I have never seen an explanation for the two mirror like things at the center of the Pancam bar

You can see them in this picture:
http://upload.wikimedia.org/wikipedia/comm...ra_PIA05187.jpg

What are they used for?

I don't know, but the're not mirrors, you can see the ruler reflected in them in that image and the refection is quite distorted.

I'm guessing they are reflective for thermal reasons, in which case they are probably electronics boxes of some sort.

And why are they placed at slightly different positions?

I think that is because they are opposite ways up, the one on the left has a connector on the top, the other one has one on the bottom. When these are taken it consideration they are effectively in the same position. I think the reason they they are opposite ways up is because they have side connectors to the navcams.

Looking again at the picture you sent, they must be the control for the navcams, only the CCD is inside the camera and you couldn't read the raw data out of them and all the way down the PMA into the WEB. Look at the far ends of the bar, the pancams have a similar shiny box too.

James

They're the pancam and navcam electronics boxes. They contain circuitry for the cameras. There's one for each of the four Hazcams as well, and the MI ( it's on the end of the IDD, we saw a cool picture taken by a Hazcam, of itself, reflected in the MI's electronics box once) and the DC (it's on the empty lander)

You can see the two Navcam ones in the middle there ( one is 'upsidedown' compared to the other ) and the Pancam ones are at 90 degrees to them, tucked in at each end.

Lots of pictures like this one...


Here ->
http://marswatch.astro.cornell.edu/pancam_...ng_testing.html

Doug

Ahh-Ha! That surely is it. Nice find, Doug. I knew there had to be a page somewhere with construction images, but I couldn't find it. As jamescanvin noted, they almost had to be electronic boxes for the cams.