Ranger 6

Ranger 6

Ranger 6
Mission type	Lunar impactor
Operator	NASA
COSPAR ID	1964-007A
SATCAT №	747
Mission duration	65.5 hours
Spacecraft properties
Manufacturer	Jet Propulsion Laboratory
Launch mass	381 kilograms (840 lb)
Start of mission
Launch date	January 30, 1964, 15:49:00 (1964-01-30UTC15:49Z) UTC
Rocket	Atlas LV-3 Agena-B
Launch site	Cape Canaveral LC-12
Lunar impactor
Impact date	February 2, 1964, 09:24:32 (1964-02-02UTC09:24:33Z) UTC
Impact site

Ranger 6 was a lunar probe in the Ranger program, a robotic spacecraft series launched by NASA in the early and mid-1960s to obtain the first close-up images of the Moon's surface. It was designed to achieve a lunar-impact trajectory and to transmit high-resolution photographs of the lunar surface during the final minutes of flight up to impact. 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 self-contained with separate power supplies, timers, and transmitters so as to afford the greatest reliability and probability of obtaining high-quality television pictures. No other experiments were carried on the spacecraft. Due to a failure of the camera system, no images were returned.

Spacecraft design

Rangers 6, 7, 8, and 9 were called 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 gyros, 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.

Communications were through the quasiomnidirectional low-gain antenna and the parabolic high-gain antenna. Transmitters aboard the spacecraft included a 60 W TV channel F at 959.52 MHz, a 60 W TV channel P at 960.05 MHz, and a 3 W 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 high-gain antenna. Sufficient video bandwidth was provided to allow for rapid framing sequences of both narrow- and wide-angle television pictures.

Mission profile

Ranger 6 was launched into an Earth parking orbit and injected on a lunar trajectory by a second Agena burn. The midcourse trajectory correction was accomplished early in the flight by ground control. On February 2, 1964, 65.5 hours after launch, Ranger 6 impacted the Moon on the eastern edge of Mare Tranquillitatis (Sea of Tranquility). The orientation of the spacecraft to the surface during descent was correct, but no video signal was received and no camera data obtained. A review board determined the most likely cause of failure was due to an arc-over in the TV power system when it inadvertently turned on for 67 seconds approximately 2 minutes after launch during the period of booster-engine separation.

This fourth American attempt at lunar impact was the closest success. The spacecraft, the first Block III type vehicle with a suite of six TV cameras, was sterilized to avoid contaminating the lunar surface. The series would also serve as a test bed for future interplanetary spacecraft by deploying systems (such as solar panels) that could be used for more ambitious missions. The Block III spacecraft carried a 173-kilogram TV unit (replacing the impact capsule carried on the Block II Ranger spacecraft). The six cameras included two full-scan and four partial-scan cameras. Ranger 6 flew to the Moon successfully and impacted precisely on schedule at 09:24:32 UT on 2 February. Unfortunately, the power supply for the TV camera package had short-circuited three days previously during Atlas booster separation and left the system inoperable. The cameras were to have transmitted high-resolution photos of the lunar approach from 1,448 kilometers to 6.4 kilometers range in support of Project Apollo. Impact coordinates were 9°24' north latitude and 21°30' east longitude.

See also

• Ranger program
• Timeline of Solar System exploration
• List of artificial objects on the Moon

External links

• Lunar impact: A history of Project Ranger (PDF) 1977