Ranger 8 - Spacecraft Design

Spacecraft Design

Rangers 6, 7, 8, and 9 were called the Block 3 versions of the Ranger spacecraft. 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 which held the TV 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 quasiomnidirectional 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 9792 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 nine 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.

Communications were through the quasiomnidirectional low-gain antenna and the parabolic high-gain antenna. Transmitters aboard the spacecraft included a 60 watt TV channel F at 959.52 MHz, a 60 watt TV channel P at 960.05 MHz, and a three watt transponder channel 8 at 960.58 MHz. The telecommunications equipment converted the composite video signal from the camera transmitters into an RF signal for subsequent transmission through the spacecraft's high-gain antenna. Sufficient video bandwidth was provided to allow for rapid framing sequences of both narrow- and wide-angle television pictures.