The RC-135s are special versions of the
C-135 cargo plane (Boeing 707). The fleet has consistently
proved of great value, both as a strategic reconnaissance tool
during peacetime and as a more tactical asset during times of
tension. The fleet consists of:
RC-135U 'Combat Sent'
Two aircraft are designated RC-135U "Combat Sent"
and are characterized by cheek fairings and additional fairings
in the chin, boomer, wingtip, tail cone and fin-top positions.
Until 1991 they were fitted with "towel rail" antennas
above the cheek fairings, but these have been removed. The
RC-135Us are believed to have special purposes within the SIGINT
fleet, and may also be used to trial new equipment.
RC-135V/W 'Rivet Joint'
Eight aircraft are designated RC-135V "Rivet Joint,"
Six are the essentially similar to the RC-135W variant. These are
the workhorses of the SIGINT fleet and are distinguished by
having extended "thimble" noses and large plate
aerials under the center-section. External differences between
the two variants are restricted to a lengthened cheek fairing on
the W-model, which also lacks auxiliary air intakes on its
RC-135S 'Cobra Ball'
An altogether more specialized role is
undertaken by three RC-135S "Cobra Ball"
aircraft which normally operate from Shemya Island, Alaska. In
addition to "thimble" noses, electronic receivers
mounted in cheek fairings and a teardrop-shaped fairing on the
aft fuselage, these also have large circular windows in the
fuselage for the photography of foreign ballistic-missile tests
at long range. The intelligence equipment includes multiple
infrared telescopes and is known as the Real Time Optical System
(RTOS). These aircraft allow the U.S. to monitor every reentry
vehicle flown from Russian test ranges, to determine the
capabilities of each Russian missile, new or old.