From the outset in the design of the Convair B-58 Hustler, the unique fuel/weapons pod carried underneath the sleek bomber was to be only one of a family of systems that were to be pod mounted as well- rather than have to develop different versions for different roles, different pods for different roles would be carried by "stock" B-58s. Some proposals were for air-launched ballistic missiles, others were for reconnaissance systems with cameras housed in the pod. There was even a proposal for a passenger-carrying pod. But many of these ideas never came to be.
But one system that did get flight tested was for an airborne side-looking radar that would allow a B-58 to get detailed radar imagery from stand-off distances. The first system to be built was the pod-mounted Hughes AN/APQ-69 radar system which first flew on a B-58 on 24 December 1959. The AN/APQ-69 was one of the largest airborne radar antennas ever flown with a 50-foot long antenna that took up all of a long square-section pod carried by the Hustler. Twenty-five test flights were made with the radar and it had a 10 foot resolution from 50 miles which was quite good for the technology of the day. However, the size and weight of the pod restricted the B-58 to subsonic flight and as the radar took up the entire pod, it couldn't be used to carry additional fuel as the fuel/weapons pods used by the SAC alert Hustlers. As such, the B-58 carrying the AN/APQ-69 was limited to only 3 hours' flying time, making it of limited usefulness. In addition, the bow wave from the blunt nosed pod hampered nose gear retraction and a 0.5G pushover after takeoff was necessary to "help" the nose gear retract.
A more advanced radar pod flew in 1961, this time it was a Goodyear AN/APS-73 radar- this time it was a SAR (synthetic aperture radar) which allowed for a smaller antenna but a more detailed radar picture and it was used in a pod that had the same cross-section as the MB-1 fuel/weapons pod already in use- this allowed the B-58 to use nearly all of its performance envelope and the pod could also carry a sizeable amount of fuel.
The AN/APS-73 was housed in a black fiberglass nose section of the pod with the aft 2/3 of the pod carrying fuel. There were two X-band rotating antennas in the pod nose that rotated on an axis that ran longitudinally the length of the pod. The radar range was about 80 miles and was flight tested under the code name Project Quick Check. While the system never went into production, it was used operationally on one flight during the Cuban Missile Crisis- a single B-58 flight carrying the AN/APS-73 was made to survey targets of interest on the island, making it the first and only flight of a B-58 Hustler into hostile airspace.
That particular aircraft, 55-0668, also was the same aircraft that flight tested the earlier Hughes radar pod. It survived the scrapping of the Hustler fleet in 1970 and is now on display at the Lone Star Flight Museum in Galveston, Texas.
Source: Convair B-58 Hustler: The World's First Supersonic Bomber by Jay Miller. Midland Publishing/Aerofax, 1997, p81-86.
