Polar Projection of Northern Hemisphere

[Ryan Ollerenshaw]

I am currently only able to display my data that is to the right of the 
northern pole i think down to the equator.  I want to be  able to 
project my data in a polar projection that shows the entire northern 
hemisphere but i am not sure what it is that i am doing wrong.

I am using the following extent and projection in my MapFile

EXTENT -4000000 -3000000 4000000 3000000

PROJECTION
"proj=ortho"
"lat_0=90"
END


Any help would be much appreciated.