After drawing attention on Monday (16), the WC-135 Constant Phoenix jet of the US Air Force (USAF) is back on the Brazilian coast. At the time of writing, the “nuclear sniffer” flies along the northeast, near Rio Grande do Norte, over the ocean. 

Again, the aircraft number 64-14836 departed from Luis Muñoz International Airport, which serves the capital of Puerto Rico, San Juan. Operating under radio code MILLR36 (the same as the last occasion), the WC-135R took off from the Caribbean island at 09:43 am according to data from the air tracking website Flightradar24. The plane also performed an in-flight refueling with a KC-10 Extender tanker, code SKATR15.

And there's the tanker support for MILLR36.

KC-10A Extender # AE0221 as SKATR15 looks to be heading for a linkup with WC-135R Constant Phoenix #AE048D north of South America. Last time, the Constant Phoenix took on 90k of fuel for it's long mission around South America. https://t.co/3mPaZ53sRu pic.twitter.com/6Rs2EzaOFe

— TheIntelFrog (@TheIntelFrog) January 20, 2023

The flight of the nuclear sniffer can be tracked by clicking here or by the plugin below. 

For the time being, the reasons for this second operation of the WC-135R near the country are still unknown. Yesterday the USAF responded to questions from a North American portal, stating that the flight from earlier this week was a “baseline” collection mission.

The objective is to carry out a sampling of particles from the atmospheric air “to establish what atmospheric radiation levels should be like under normal conditions”. In other words, a calibration of the military aircraft's systems. 

Nuclear Sniffer

Based on the KC-135R Stratotanker tanker platform, this Boeing WC-135R was delivered to the US Air Force in June last year, replacing older versions of the model. 

Nicknamed Nuclear/Nuke Sniffer (Nuclear Sniffer), the jet is the result of the Constant Phoenix program, originated in 1947. The first WC-135 entered into operation in 1965, replacing the WB-50 (a version of the B-29 bomber) with the 55th Meteorological Reconnaissance Squadron. 

The aircraft's mission is quite specific: to detect radioactive particles present in the atmosphere. The USAF says the WC-135 “supports national level customers by collecting particulate and gaseous effluents and debris from accessible regions of the atmosphere in support of the 1963 Limited Nuclear Test Ban Treaty.” That's why his presence always draws attention wherever he goes.