Editing Infrared homing (section)

===German seekers===
<!-- [[WP:NFCC]] violation: [[File:He 111 - BV 143a Test (1941).jpg|thumb|right|An IR seeker known as ''Hamburg'' would have equipped the BV 143 in the anti-shipping role.]] -->
[[File:Enzian anti-aircraft missile at the Treloar Technology Centre in September 2012.JPG|thumb|right|The ''Madrid'' seeker was being developed for the [[Enzian]] surface-to-air missile.]]

The devices mentioned previously were all ''detectors'', not ''seekers''. They either produce a signal indicating the general direction of the target, or in the case of later devices, an image similar to a television image. Guidance was entirely manual by an operator looking at the image. There were a number of efforts in Germany during the war to produce a true automatic seeker system, both for anti-aircraft use as well as against ships. These devices were still in development when the war ended; although some were ready for use, there had been no work on integrating them with a missile airframe and considerable effort remained before an actual weapon would be ready for use. Nevertheless, a summer 1944 report to the [[German Air Ministry]] stated that these devices were far better developed than competing systems based on radar or acoustic methods.{{sfn|Kutzscher|1957|p=201}}

Aware of the advantages of passive IR homing, the research program started with a number of theoretical studies considering the emissions from the targets. This led to the practical discovery that the vast majority of the IR output from a piston-engine aircraft was between 3 and 4.5 micrometers. The exhaust was also a strong emitter, but cooled rapidly in the air so that it did not present a false tracking target.{{sfn|Kutzscher|1957|p=204}} Studies were also made on atmospheric attenuation, which demonstrated that air is generally more transparent to IR than visible light, although the presence of [[water vapour]] and [[carbon dioxide]] produced several sharp drops in transitivity.{{sfn|Kutzscher|1957|p=206}} Finally, they also considered the issue of background sources of IR, including reflections off clouds and similar effects, concluding this was an issue due to the way it changed very strongly across the sky.{{sfn|Kutzscher|1957|p=207}} This research suggested that an IR seeker could home on a three-engine bomber at {{convert|5|km}} with an accuracy of about {{frac|10}} degree,{{sfn|Kutzscher|1957|p=210}} making an IR seeker a very desirable device.

Kutzscher's team developed a system with the Eletroacustic Company of Kiel known as ''Hamburg'', which was being readied for installation in the [[Blohm & Voss BV 143]] [[glide bomb]] to produce an automated fire-and-forget anti-shipping missile. A more advanced version allowed the seeker to be directed off-axis by the bombardier in order to lock on to a target to the sides, without flying directly at it. However, this presented the problem that when the bomb was first released it was traveling too slowly for the aerodynamic surfaces to easily control it, and the target sometimes slipped out from the view of the seeker. A [[stabilized platform]] was being developed to address this problem. The company also developed a working IR [[proximity fuse]] by placing additional detectors pointing radially outward from the missile centerline, which triggered when the signal strength began to decrease, which it did when the missile passed the target. There was work on using a single sensor for both tasks instead of two separate ones.{{sfn|Kutzscher|1957|p=215}}

Other companies also picked up on the work by Eletroacustic and designed their own scanning methods. AEG and Kepka of Vienna used systems with two movable plates that continually scanned horizontally or vertically, and determined the location of the target by timing when the image disappeared (AEG) or reappeared (Kepka). The Kepka ''Madrid'' system had an instantaneous field of view (IFOV) of about 1.8 degrees and scanned a full 20 degree pattern. Combined with the movement of the entire seeker within the missile, it could track at angles as great as 100 degrees. Rheinmetall-Borsig and another team at AEG produced different variations on the spinning-disk system.{{sfn|Kutzscher|1957|p=216}}