This is REQUIN (SSR-481) in January of 1952, while operating off the US east coast. The boat is camouflaged in Measure SS 17 F, the postwar version of Measure 32/9SS-B ("the dark gray job").
The disastrous wartime experience off Okinawa reinforced the need for survivable radar picket ships; this requirement gave rise to Project MIGRAINE and the conversion of existing fleet-type subs into radar picket submarines (SSR). REQUIN was modified in the fall of 1946 to bring the boat up to MIGRAINE I standard: this series of modifications added an air search radar and height finder on the main deck aft, but this configuration was found to be problematic. The MIGRAINE II program attempted to resolve these issues by elevating the radars where possible. REQUIN was further modified in 1948 to near-MIGRAINE II standard.
The MIGRAINE II modifications for REQUIN relocated the big SR-2 air search radar from the main deck to a tall pedestal on the fairwater, replacing the 40mm Bofors in this position. This refit also added a snorkel, with the induction/exhaust just aft of the periscope shears. REQUIN retains the original SV-1 air search radar, with SS surface search radar on a small mast ahead of the periscopes. The no.1 periscope has been fitted with the ST range-only radar. The WFA sonar transducer is mounted abeam the forward planes, and the JT trainable passive sonar head remains in its original position. Aft, the YE-2 homing beacon is mounted on a small pedestal, and the SV-2 heightfinder is right aft. This radar suffered from water intrusion in this position, and on later MIGRAINE II boats it was relocated to a tall pedestal aft of the SR-2. The small mast ahead of the YE-2 is an air early warning antenna. Note wire antennas for the TCZ and TCS radios strung between small masts fore and aft of the SV-2, and the large outgrowth of whip antennas.
The MIGRAINE mods removed the 5" guns as weight compensation. Aft, all four torpedo tubes were demilitarized and the aft torpedo room converted to a rudimentary CIC and electronics spare parts store room. Forward, the upper two torpedo tubes were converted to storage lockers, but the bottom four tubes remained in use.
REQUIN would serve in this configuration until her conversion to the "Fleet Snorkel" standard in August 1959, before being converted into a museum ship in 1972.