Incoming 3rd RC-135.
One is a RC-135-S Cobra Ball (Call the Ball?)
The RC-135S Cobra Ball is a measurement and signature intelligence MASINT collector equipped with special electro-optical instruments designed to observe ballistic missile flights at long range. The Cobra Ball monitors missile-associated signals and tracks missiles during boost and re-entry phases to provide reconnaissance for treaty verification and theater ballistic missile proliferation. The aircraft are extensively modified C-135Bs.[4] The right wing and engines are traditionally painted black to reduce sun glare for tracking cameras.[21]
There are three aircraft in service and they are part of the 55th Wing, 45th Reconnaissance Squadron based at Offutt Air Force Base, Nebraska. Cobra Ball aircraft were originally assigned to Shemya and used to observe ballistic missile tests on the Kamchatka peninsula in conjunction with Cobra Dane and Cobra Judy. Two aircraft were converted for Cobra Ball in 1969 and following the loss of an aircraft in 1981 another aircraft was converted in 1983. The sole RC-135X was also converted into an RC-135S in 1995 to supplement the other aircraft.
One is a RC-135V and another is RC-135W.
The RC-135V/W is the USAF's standard airborne SIGINT platform. Missions flown by the RC-135s are designated either Burning Wind or Misty Wind.[24] Its sensor suite allows the mission crew to detect, identify and geolocate signals throughout the electromagnetic spectrum.[25] The mission crew can then forward gathered information in a variety of formats to a wide range of consumers via Rivet Joint's extensive communications suite. The crew consists of the cockpit crew, electronic warfare officers, intelligence operators, and airborne systems maintenance personnel. All Rivet Joint airframe and mission systems modifications are performed by L-3 Communications in Greenville, Texas, under the oversight of the Air Force Materiel Command.[4][25]
All RC-135s are assigned to Air Combat Command. The RC-135 is permanently based at Offutt Air Force Base, Nebraska, and operated by the 55th Wing, using various forward deployment locations worldwide.[25]
Under the "BIG SAFARI" program name, RC-135Vs were upgraded from the RC-135C "Big Team" configuration. RC-135Ws were originally delivered as C-135B transports, and most were modified from RC-135Ms. This is the only difference between the V and W variants; both carry the same mission equipment. For many years, the RC-135V/W could be identified by the four large disc-capped MUCELS antennas forward, four somewhat smaller blade antennae aft and myriad of smaller underside antennas. Baseline 8 Rivet Joints (in the 2000s) introduced the first major change to the external RC-135V/W configuration replacing the MUCELS antennas with plain blade antennas. The configuration of smaller underside antennas was also changed significantly.
one is reconnaissance, and another is electromagnetic signal plane if i'm not mistaken.