There always seems to be, what they call "The Zone of Exclusion", just east of Africa.
It's an area that for some reason, it seems, they are unable to stay in contact
with any TDRS. While watching coverage of a shuttle flight when they are doing
EVAs, they always seem to lose KU band coverage there. I know some of it has to
do with the KU not being able to look through parts of the structure of the ISS
as it gets between the line of site view to the TDRS during certain parts of an
orbit, but It doesn't seem to account for the extended loss of coverage in "The
Zone of Exclusion". I guess the real question is why is there still a zone of
exclusion if they have so many TDRS satellites in orbit. I would think by now
the entire earth would be covered. Is there some inherent reason that they just
can't overcome, that prevents them from contacting a TDRS in that area? I can't imagine what it would be.