The optical fire control system consisted of two 10.5-metre rangefinders installed atop the forward superstructure and on the aft command post. Each of them was mounted on a trainable, gyro-stabilized, armoured post. Both rangefinders directed the main as well as the secondary battery fire. Additionally, each gun turret had its own 10.5-metre rangefinder which allowed for a complete autonomy in case the contact with the fire control post was severed. All the data was transmitted to the fire control centre located under the armoured deck in compartment XIV. It was connected with the main command post through a special communication shaft. In service, after conclusion of Operation “Berlin”, the rangefinder was removed from turret “A” and its remaining openings were closed, since it had been constantly flooded by splashes of water. The main and secondary battery were also supported by a 6-metre rangefinder installed on the forward fire control post. The anti-aircraft fire was directed by four 4-metre SL-6 rangefinders installed in gyro-stabilized dome-shaped posts. Target data was transmitted to one of the rooms in the fire control central. From there it was sent directly to individual guns. Portable 1.25-metre base rangefinders used by the light anti-aircraft battery supplemented the optical equipment. In October 1939 the Gneisenau received FuMO 22 radar. Its antenna was installed on the armoured rangefinder post located atop the forward superstructure. While being stationed in Brest, in the summer of 1941 the ship received new FuMo 27 and FuMO 21 radar equipment. Moreover, at the turn of 1941/1942, both Scharnhorst class battleships were equipped with FuMB “Timor” and “Sumatra” antennas that were capable of detecting operating enemy radar devices.
When the Gneisenau entered service, she was equipped with two 14.60-metre catapults. The first one was installed on an 8-metre tower located behind the aft superstructure. Admittedly, it could be trained full 360°, but the ability to launch a floatplane was reduced to ¼ and ranged from 80 to 90 degrees. The second catapult was installed on the roof of turret “C”, but it was removed in February 1940. The battleship was initially supposed to carry 4 floatplanes, but since the hangar space was insufficient, she could theoretically embark 3 planes, but in reality only 2 could be carried including one on the catapult. In the middle of 1939 Arado Ar 196 A-1 of the 1st Bordfliegerstaffel 196 were embarked on board the battleship. They were later replaced by the A-3 variant. The small hangar located near the catapult was removed in 1939. Only in the autumn of 1940, a new hangar was constructed in that section, which allowed for the floatplanes to be launched directly from within. Two lattice hoisting cranes located on the sides of the hangar and one boom installed at the side of turret “C” were used for operating floatplanes.
In January 1939 the battleship underwent her first refit in Deutsche Werke shipyard in Kiel. The previous clipper bow was replaced with the new stem. Moreover, a funnel cap was installed to better facilitate the flow of exhaust fumes. In May 1939 the bow hawse pipes were modified and the stem was rebuilt into the so-called “Atlantic bow”. The funnel cap was also slightly altered and the radio topmast (Funkstenge) installed on the rangefinder located atop the forward superstructure was replaced by a larger one. The smaller built on hangar was removed. Further modifications were introduced in October 1939 including the installation of radar equipment with FuMO 22 mattress antenna installed atop the forward 10.5-metre rangefinder. While the ship was dry-docked, in December 1939, the admiral’s bridge of the forward superstructure was enclosed and she also received the degaussing cable installation (MES). In February 1940 the catapult installed atop turret “C” was removed at the Kriegsmarine Werf shipyard in Wilhelmshaven. At the end of 1940, a single Flakvierling C/35 cannon mount was installed on board the battleship for artillery test purposes and since January 14, 1941, all 20 mm MG C/30 cannons were being replaced by the new MG C/38 mounts. Also, a Flakvierling C/35 mount was installed on a platform behind the funnel. In the summer of 1941, while the battleship was stationed at Brest, FuMO 27 radar was installed atop the aft rangefinder. During the installation of a new hangar amidship, the Flakvierling platform was removed and the mount itself was installed on a platform atop the hangar. Before the beginning of Operation “Cerberus” the existing anti-aircraft armament was reinforced. The admiral’s bridge was also rebuilt by shortening its wings by half.
