Ranger 8 was a lunar probe in the Ranger program, a robotic spacecraft series launched by NASA in the early-to-mid-1960s to obtain the first close-up images of the Moon's surface. These pictures helped select landing sites for Apollo missions and were used for scientific study. During its 1965 mission, Ranger 8 transmitted 7,137 lunar surface photographs before it crashed into the Moon as planned. This was the second successful mission in the Ranger series, following Ranger 7. Ranger 8's design and purpose were very similar to those of Ranger 7. It had six television vidicon cameras: two full-scan and four partial-scan. Its sole purpose was to document the Moon's surface. Spacecraft design General Ranger spacecraft were originally designed, beginning in 1959, in three distinct phases called "blocks". Rangers 6, 7, 8, and 9 were the Block 3 versions. The spacecraft consisted of a hexagonal aluminum frame base 1.5 m across on which was mounted the propulsion and power units, topped by a truncated conical tower that held the television cameras. Two solar panel wings, each 739 mm wide by 1537 mm long, extended from opposite edges of the base with a full span of 4.6 m, and a pointable high-gain dish antenna was hinge mounted at one of the corners of the base away from the solar panels. A cylindrical quasi-omnidirectional antenna was seated on top of the conical tower. The overall height of the spacecraft was 3.6 m. Propulsion for the mid-course trajectory correction was provided by a 224 N thrust monopropellant hydrazine engine with four jet-vane vector control. Orientation and attitude control about three axes was enabled by twelve nitrogen gas jets coupled to a system of three gyroscopes, four primary Sun sensors, two secondary Sun sensors, and an Earth sensor. Power was supplied by 9,792 silicon solar cells contained in the two solar panels, giving a total array area of 2.3 square meters and producing 200 W. Two 1200-watt-hour AgZnO batteries rated at 26.5 V with a capacity for 9 hours of operation provided power to each of the separate communication/TV camera chains. Two 1000-watt-hour AgZnO batteries stored power for spacecraft operations. Cameras The spacecraft carried six television vidicon cameras —two wide-angle (channel F, cameras A and B) and four narrow-angle (channel P) —to accomplish these objectives. The cameras were arranged in two separate chains, or channels; each was self-contained with separate power supplies, timers, and transmitters,