and a deployable Sun-shade on the aft of the spacecraft for thermal control. The UV Photometer was originally supposed to fly on Mariner 4 and would have been mounted to its TV Camera scan platform. However, it was removed (allowing it to be flown on Mariner 5) and swapped out for a thermal/inertial mass simulator late in the assembly of Mariner 4 as it was discovered to create electrical arcing problems that would have jeopardized the TV Camera. Prior to the choice of Venus as the target proposals had been made to send it to either the comet 7P/Pons–Winnecke or 10P/Tempel. Launch Liftoff took place on June 14, 1967, from Cape Canaveral Air Force Station Launch Complex 12 on Atlas vehicle 5401. Booster performance was normal through the Atlas portion of the launch and the first Agena burn, with all systems operating at the proper level. During the second Agena burn, abnormal fluctuations in the engine chamber pressure occurred, however they did not preclude successful interplanetary injection. There had been several occurrences of this behavior on previous NASA and Air Force launches and a program was initiated to correct it which led to a redesign of the Agena turbopump gearbox. Venus flyby Mariner 5 flew by Venus on October 19 1967 at an altitude of . With more sensitive instruments than its predecessor Mariner 2, Mariner 5 was able to shed new light on the hot, cloud-covered planet and on conditions in interplanetary space. Radio occultation data from Mariner 5 helped to understand the temperature and pressure data returned by the Venera 4 lander, which arrived at Venus shortly before it. The Venera 4 and Mariner 5 data was subsequently analysed together under a combined Soviet–American working group of COSPAR in 1969, an organization of early space cooperation. With the data of these missions, it was clear that Venus had a very hot surface and an atmosphere even denser than expected. The operations of Mariner 5 ended in November 1967 and it is now defunct in a heliocentric orbit. Further communication attempts Further communication attempts were tried, in a joint spacecraft solar wind / solar magnetic fields investigation with Mariner 4, back in communication with Earth after being out of telemetry for about a year or more around superior conjunction. During the experiment, both spacecraft were going to be on the same idealized magnetic field spiral carried out from the