Editing Mariner 3 (section)

==Background==
[[File:Mariner_3_or_4_diagram.jpg|thumb|Mariner 3 and 4 diagram]]
[[File:JPL mariner test model.jpg|thumb|This photo shows Mariner C-2 configured for system tests in May 1964]]
[[Mariner 2]] had been a modified [[Ranger program|Ranger lunar probe]], however Mariner 3 used a new, larger bus with four solar panels, a TV camera, and additional instrumentation. Because of the greater mass, the new [[RM-81 Agena#Agena-D|Agena D]] stage would be used instead of the [[RM-81 Agena#Agena-B|Agena B]]. Mariner 3 also utilized a new, larger fiberglass payload fairing. Of the two Atlas-Agena pads at Cape Canaveral, [[Cape Canaveral Launch Complex 13|LC-13]] became available first following the launch of an Air Force Vela satellite in July 1964. Atlas vehicle 289D was erected on the pad on August 17, with the backup Mariner probe and booster (Atlas 288D) erected on LC-12 on September 28.