|Ranger 6, 7, 8, 9 - |
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After a series of failures with the more ambitious early Ranger spacecraft, the design was simplified and the lander was deleted. The last Rangers successfully returned a series of high resolution images of the lunar surface before being destroyed when crashing into the surface. The spacecraft carried six television vidicon cameras, 2 wide angle (channel F, cameras A and B) and 4 narrow angle (channel P). 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 video pictures. No other experiments were carried. These ‘Block 3’ versions of the Ranger 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.
The payload included: (1) the six-camera television subsystem; (2) power supplies; (3) telemetry; (4) an Earth-controlled command system; (5) timing; orientation, and temperature-control devices; and, (6) a small rocket system for midcourse trajectory correction. Two solar panel wings, each 73.9 cm wide by 153.7 cm 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 4 jet-vane vector control. Orientation and attitude control about 3 axes was enabled by 12 nitrogen gas jets coupled to a system of 3 gyros, 4 primary Sun sensors, 2 secondary Sun sensors, and an Earth sensor. Power was supplied by 9792 Si 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-hr 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-hr 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.
Total Mass: 364 kg. Electric system: 0.14 total average kW.
NASA announced that planned Ranger launchings would be increased from five to nine. These additional spacecraft would be equipped with six high-resolution television cameras. They would be programmed to begin operating at about 800 miles above the lunar surface and continue until moments before the spacecraft crash-landed. The final pictures would record features no more than eight inches across. About 1,600 photographs were expected from each spacecraft, which would no longer carry previously planned instrumented capsules. The objective of these spacecraft now was to provide information on the lunar surface in support of the manned lunar landing mission.
NASA announced that five additional Ranger spacecraft would be added to the lunar exploration program, raising the total to 14 to be launched through 1964.
NASA announced that Ranger VI would be used for intensive reliability tests. Resultant improvements would be incorporated into subsequent spacecraft (numbers VII-IX), delaying the launchings of those vehicles by "several months." The revised schedule was based on recommendations by a Board of Inquiry headed by Cdr. Albert J. Kelley (USN), Director of Electronics and Control in the NASA Office of Advanced Research and Technology. The Kelley board, appointed by NASA Space Sciences Director Homer E. Newell after the Ranger V flight, consisted of officials from NASA Headquarters, five NASA Centers, and Bellcomm, Inc. The board concluded that increased reliability could be achieved through spacecraft design and construction modifications and by more rigorous testing and checkout.
NASA canceled five Ranger flights (numbers 10 through 14) designed to take high-resolution photographs of the lunar surface before impact. (Five Rangers had thus far been launched.) OSS Associate Administrator Homer E. Newell stated that NASA would depend on the remaining four Rangers, the Lunar Orbiters, and the Surveyors for information about the lunar surface. Cancellation of the flights promised to save $90 million.
Impacted Moon but TV camera malfunctioned. A 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). No camera data were obtained, probably because of failure due to an arc-over in the TV power system when it inadvertently turned on during the period of booster-engine separation.
First successful Ranger; returned 4,308 photos before lunar impact. The Atlas- Agena B inserted the Agena and Ranger into a 192 km altitude Earth parking orbit. Half an hour after launch a second burn of the Agena engine injected the spacecraft into a lunar intercept trajectory. After separation from the Agena, the solar panels were deployed, attitude control activated, and spacecraft transmissions switched from the omniantenna to the high-gain antenna. The next day the planned mid-course maneuver was successfully initiated at 10:27 GMT. The only anomaly during flight was a brief loss of two-way lock on the spacecraft by the DSIF tracking station at Cape Kennedy following launch.
Ranger 7 reached the Moon on 31 July. The F-channel began its one minute warm up 18 minutes before impact. The first image was taken at 13:08:45 GMT at an altitude of 2110 km. Transmission of 4,308 photographs of excellent quality occurred over the final 17 minutes of flight. The final image taken before impact had a resolution of 0.5 meters. The spacecraft encountered the lunar surface in direct motion along a hyperbolic trajectory, with an incoming asymptotic direction at an angle of -5.57 degrees from the lunar equator. The orbit plane was inclined 26.84 degrees to the lunar equator. After 68.6 hours of flight, Ranger 7 impacted in an area between Mare Nubium and Oceanus Procellarum (subsequently named Mare Cognitum) at approximately 10.35 S latitude, 339.42 E longitude. Impact occurred at 13:25:48.82 GMT at a velocity of 2.62 km/s.
Dr. William H. Pickering, Director of Jet Propulsion Laboratory, commented on the importance of Ranger VII in locating possible lunar landing sites.
Returned 7137 photos before lunar impact. The Atlas- Agena B booster injected the Agena and Ranger 8 into an Earth parking orbit at 185 km altitude 7 minutes 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 omni-directional antenna to the high-gain antenna by 21:30 GMT. On 18 February at a distance of 160,000 km from Earth the planned mid-course manoeuvre took place, involving reorientation and a 59 second rocket burn. During the 27 minute manoeuvre, spacecraft transmitter power dropped severely, so that lock was lost on all telemetry channels. This continued intermittently until the rocket burn, 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.
Ranger 8 reached the Moon on 20 February 1965. The first image was taken at 9:34:32 GMT at an altitude of 2510 km. Transmission of 7,137 photographs 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 GMT on 20 February 1965 in Mare Tranquillitatis at approximately 2.67 degrees N, 24.65 degrees E. Impact velocity was slightly less than 2.68 km/s.
Newton W. Cunningham, NASA's Ranger Program Manager, notified Apollo Program Manager Samuel C. Phillips that the Ranger investigators and Jet Propulsion Laboratory Ranger Project Office had submitted their unanimous choice of targets for the Ranger IX mission. The first two days of the launch windows were omitted from the plan; Day III: Crater Alphonsus; Day IV: Crater Copernicus; Day V: Crater Kepler; Day VI: Crater Aristarchus; Day VII: near Crater Grimaldi.
NASA's Office of Manned Space Flight agreed with Days IV-VII, but recommended a smooth highland area for Day I, a highland basin area for Day II, and the Flammarion highland basin for Day III.
Ranger 9, last of the series, returned 5814 images before lunar impact. The target was Alphonsus, a large crater about 12 degrees south of the lunar equator. The probe was timed to arrive when lighting conditions would be at their best. The Atlas- Agena B booster injected the Agena and Ranger 9 into an Earth parking orbit at 185 km altitude. A 90 second Agena 2nd burn put the spacecraft into lunar transfer trajectory. This was followed by the separation of the Agena and Ranger. The initial trajectory was highly accurate; uncorrected, the craft would have landed only 650 km north of Alphonsus. 70 minutes after launch the command was given to deploy solar panels, activate attitude control, and switch from the omni-directional antenna to the high-gain antenna. The accuracy of the initial trajectory enabled delay of the planned mid-course correction from 22 March to 23 March when the manoeuvre was initiated at 12:03 GMT. After orientation, a 31 second rocket burn at 12:30 GMT, and reorientation, the manoeuvre was completed at 13:30 GMT. Ranger 9 reached the Moon on 24 March 1965. At 13:31 GMT a terminal manoeuvre was executed to orient the spacecraft so the cameras were more in line with the flight direction to improve the resolution of the pictures. Twenty minutes before impact the one-minute camera system warm-up began. The first image was taken at 13:49:41 at an altitude of 2363 km. Transmission of 5,814 good contrast photographs was made during the final 19 minutes of flight. The final image taken before impact has a resolution of 0.3 meters. The spacecraft encountered the lunar surface with an incoming asymptotic direction at an angle of -5.6 degrees from the lunar equator. The orbit plane was inclined 15.6 degrees to the lunar equator. After 64.5 hours of flight, impact occurred at 14:08:19.994 GMT at approximately 12.83 S latitude, 357.63 E longitude in the crater Alphonsus. Impact velocity was 2.67 km/s. Millions of Americans followed the spacecraft's descent via real time television coverage provided to the three networks of many of the F-channel images (primarily camera B but also some camera A pictures) were provided for this flight.
The pictures showed the rim and floor of the crater in fine detail: in those just prior to impact, objects less than a foot in size were discernible.
A panel of scientists presented some preliminary conclusions from Ranger IX at a press conference that same afternoon. Crater rims and ridges inside the walls, they believed, were harder and smoother than the moon's dusty plains, and therefore were considered likely sites for future manned landings. Generally, the panel was dubious about landing on crater floors however. Apparently, the floors were solidified volcanic material incapable of supporting a spacecraft. Investigators believed several types of craters were seen that were of nonmeteoric origin. These findings reinforced arguments that the moon at one time had experienced volcanic activity. Later the images were shown to the press as a continuous-motion movie, leading astronaut Wally Schirra to yell ‘bail out you fool!’ just before the final frame.
Jet Propulsion Laboratory scientists W. L. Sjogren and D. W. Trask reported that as a result of Ranger VI and Ranger VII tracking data, Deep Space Instrumentation Facility station locations could be determined to within 10 m (10.9 yds) in the radial direction normal to the earth's spin axis. Differences in the longitude between stations could be calculated to within 20 m (21.9 yds). The moon's radius had been found to be 3 km (l.86 mi) less than was thought, and knowledge of its mass had been improved by an order of magnitude.