Originally posted by Ducatigaz: It's called a Senior Span/Senior Spur
Doing a little research I found that it is possibly the satellite communication pod that is called Senior Span/ Senior Spur, not the aircraft itself, and the pod can be taken off when needed. The aircraft, according to Wikipedia, is called a U-2S Senior Year, after having been re-engined with a GE F-118-101.
There are lots of interesting facts and views at
U-2S Senior Span/Spur by David W. Aungst (Testor and Cutting Edge 1/48). All collected by David W. Aungst, in support of his project of building a model of the U-2 in superscale, that is, as accurate as ever can be done.
Lots at Wikipedia, too!