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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.[1] 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.[2]

Ranger 8

Ranger 8
Mission type	Lunar impactor
Operator	NASA
COSPAR ID	1965-010A
SATCAT no.	1086
Mission duration	65 hours
Spacecraft properties
Manufacturer	Jet Propulsion Laboratory
Launch mass	367 kilograms (809 lb)
Dimensions	1.52 m × 2.51 m (5.0 ft × 8.2 ft)
Power	200 W
Start of mission
Launch date	February 17, 1965, 17:05:00 (1965-02-17UTC17:05Z) UTC
Rocket	Atlas LV-3 Agena-B 196D/AA13
Launch site	Cape Canaveral LC-12
Lunar impactor
Impact date	February 20, 1965, 09:57:36.756 (1965-02-20UTC09:57:37Z) UTC
Impact site	02.6377°N 24.7881°E / 02.6377; 24.7881 (Mare Tranquillitatis)
Instruments Vidicon Television Cameras
Ranger ← Ranger 7 Ranger 9 →

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.[2]

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.[2]

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.[3] The cameras were arranged in two separate chains, or channels; each was self-contained with separate power supplies, timers, and transmitters, to afford the greatest reliability and probability of obtaining high-quality television pictures. No other experiments were carried on the spacecraft.[2]

Communications

Communications were through the quasiomnidirectional low-gain antenna and the parabolic high-gain antenna. Transmitters aboard the spacecraft included a 60-watt television channel F at 959.52 MHz, a 60-watt television channel P at 960.05 MHz, and a 3-watt transponder channel 8 at 960.58 MHz. The telecommunications equipment converted the composite video signal from the camera transmitters into a radio-frequency 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.[2]

Mission profile

The Atlas 196D and Agena B 6006 boosters performed nominally, injecting the Agena and Ranger 8 into an Earth parking orbit at 185 km altitude after launch. Fourteen minutes later a 90-second burn of the Agena put the spacecraft into lunar transfer trajectory, and several minutes later the Ranger and Agena separated. The Ranger solar panels were deployed, attitude control activated, and spacecraft transmissions switched from the omniantenna to the high-gain antenna by 21:30 UT. On February 18, at a distance of 160,000 km from Earth, the planned mid-course maneuver took place, involving reorientation and a 59-second rocket burn. During the 27-minute maneuver, spacecraft transmitter power dropped severely, so that lock was lost on all telemetry channels. This continued intermittently until the rocket burn ended, at which time power returned to normal. The telemetry dropout had no serious effects on the mission. A planned terminal sequence to point the cameras more in the direction of flight just before reaching the Moon was cancelled to allow the cameras to cover a greater area of the Moon's surface.[2]

Ranger 8 reached the Moon on February 20, 1965.[4] The first image was taken at 9:34:32 UT at an altitude of 2510 km. Transmission of 7,137 photographs[4] of good quality occurred over the final 23 minutes of flight. The final image taken before impact has a resolution of 1.5 meters. The spacecraft encountered the lunar surface in a direct hyperbolic trajectory, with incoming asymptotic direction at an angle of −13.6 degrees from the lunar equator. The orbit plane was inclined 16.5 degrees to the lunar equator. After 64.9 hours of flight, impact occurred at 09:57:36.756 UT on February 20, 1965, in Mare Tranquillitatis at approximately 2.67° N, 24.65° E. (The impact site is listed as about 2.72° N, 24.61° E in the initial report "Ranger 8 Photographs of the Moon".) Impact velocity was slightly less than 2.68 km/s, approximately 6,000 mph. The spacecraft performance was excellent.[2]

The impact crater of Ranger 8, approximately 13.5 m wide, was later photographed by Lunar Orbiter 4.[5]

See also

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

References

 This article incorporates public domain material from Ranger 8. National Aeronautics and Space Administration.

External links

• Lunar impact: A history of Project Ranger (PDF), R. Cargill Hall, 1977
• Photographs from Ranger 8
• Video from Ranger 8

 This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.

На других языках

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[de] Ranger 8

Ranger 8 war eine Raumsonde der US-amerikanischen Raumfahrtagentur NASA. Sie war die achte Sonde im Rahmen des Ranger-Programms zur Erforschung des Mondes. Sie war wie Ranger 6 und Ranger 7 im Block-III-Design gebaut und wog 367 Kilogramm. Wie die vorhergehenden Missionen sollte sie in den letzten Minuten vor dem Aufschlag Bilder der Mondoberfläche machen und zur Erde übermitteln.

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- [en] Ranger 8

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[ru] Рейнджер-8

Рейнджер-8 (англ. Ranger 8) — американская автоматическая межпланетная станция, запущенная 17 февраля 1965 года по программе «Рейнджер». В общей сложности аппарат имел 6 телевизионных камер. Целью полёта Рейнджера-8 было передача чётких фотографий лунной поверхности в последние минуты полёта перед столкновением. Никаких других экспериментов программой полёта не подразумевалось.[2]

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