74
Surveyor II
Nation: USA (31)
Objective(s): lunar soft-landing
Spacecraft: Surveyor-B
Spacecraft Mass: 995.2 kg
Mission Design and Management: NASA / JPL
Launch Vehicle: Atlas Centaur (AC-7 / Atlas D no. 194 / Centaur D)
Launch Date and Time: 20 September 1966 / 12:32:00 UT
Launch Site: Cape Kennedy / Launch Complex 36A
Scientific Instruments:
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- imaging system
Results: Surveyor II, similar in design to its predecessor, was aimed for a lunar soft-landing in Sinus Medii. During the coast to the Moon, at 05:00 UT on 21 September, one of three thrusters failed to ignite for a 9.8-second mid-course correction, and as a result, put the spacecraft into an unwanted spin. Despite as many as 39 repeated attempts to fire the recalcitrant thruster, the engine failed to ignite, and Surveyor II headed to the Moon without proper control. Just 30 seconds after retro-fire ignition at 09:34 UT on 22 September, communications ceased, and the lander crashed on to the surface of the Moon at 5° 30′ N / 12° W, just southeast of Copernicus crater.
75
Luna 12
Nation: USSR (44)
Objective(s): lunar orbit
Spacecraft: Ye-6LF (no. 102)
Spacecraft Mass: 1,640 kg
Mission Design and Management: GSMZ imeni Lavochkina
Launch Vehicle: Molniya-M + Blok L (8K78M no. N103-44, also N15000-53)
Launch Date and Time: 22 October 1966 / 08:42:26 UT
Launch Site: NIIP-5 / Site 31/6
Scientific Instruments:
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- gamma-ray spectrometer
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- RMCh-1 meteorite detector
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- SL-1 radiometer for measuring radiation near the Moon
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- RFL-F instrument for detecting x-ray fluorescence
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- Kassiopeya KYa-4 instrument for measuring intensity of longwave radio-radiation
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- US-3 spectro-photometer
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- 2 cameras (high- and low-resolution)
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- R-1 gear transmission experiment
Results: Luna 12 was launched to complete the mission that Luna 11 had failed to accomplish, i.e., take high resolution photos of the Moon's surface from lunar orbit. The propulsion system, now called S5.5A, was redesigned to account for the failure of Luna 11 but otherwise was almost identical. Luna 12 successfully reached the Moon on 25 October 1966 and entered a 103 × 1,742-kilometer orbit. About 2 hours later, the imaging system was turned on and worked for 64 minutes, returning 28 high resolution and 14 panoramic images. Film was developed, fixed, and dried automatically and scanned for transmission to Earth. The Soviet press released the first photos taken of the surface on 29 October, pictures that showed the Sea of Rains and the Aristarchus crater. Resolution was as high as 15–20 meters. No further photos were released at the time, although apparently 42 total images were obtained. After completing its main imaging mission, Luna 12 was put into a spin-stabilized roll to carry out its scientific mission which was fulfilled quite successfully—the only major failure was of the US-3 spectro-photometer. Contact was finally lost on 19 January 1967 after 302 communications sessions.
76
Lunar Orbiter II
Nation: USA (32)
Objective(s): lunar orbit
Spacecraft: LO-B (Spacecraft 5)
Spacecraft Mass: 385.6 kg
Mission Design and Management: NASA / LaRC
Launch Vehicle: Atlas Agena D (Atlas Agena D no. 18 / Atlas D no. 5802 / Agena D no. AD122/6631)
Launch Date and Time: 6 November 1966 / 23:21:00 UT
Launch Site: Cape Kennedy / Launch Complex 13
Scientific Instruments:
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- imaging system
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- micrometeoroid detectors
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- radiation dosimeters
Results: Lunar Orbiter II's mission was to photograph 13 primary and 17 secondary landings sites for the Apollo program in the northern region of the Moon's near side equatorial area. After a single mid-course correction on the way to the Moon, on 10 November 1966, the spacecraft entered a 196 × 1,850 kilometer orbit around the Moon. After 33 orbits, Lunar Orbiter II was moved to its photographic orbit with a perilune of 49.7 kilometers; on 18 November, it began its photography mission, returning excellent quality medium and high-resolution photographs, including the impact point of Ranger VIII. The spacecraft ended its photography mission on 26 November and transmission of the images was concluded by 7 December, by which time the probe had transmitted back 211 pictures of both the near side and large areas of the farside. These photos covered nearly four million km² of the lunar surface. The high-gain transmitter failed during this time, but did not significantly affect the coverage afforded by the photos. On 23 November, Lunar Orbiter II took perhaps the most memorable photo of any in the series, a spectacular shot looking across the Copernicus crater from an altitude of only 45 kilometers that vividly emphasized the three-dimensional nature of the lunar surface. On 8 December, after the main photographic mission was over, Lunar Orbiter II fired its main engine to change its orbital plane in order to provide tracking data of the Moon's gravitational field over a wider swath. Finally, on 11 October 1967, when attitude control gas was almost depleted, a retro-burn deliberately crashed the spacecraft onto the lunar surface at 4° S / 98° E on the farside to prevent communications interference on future missions.
This image was taken on 24 November 1966 by Lunar Orbiter II from an altitude of 45.7 kilometers from the lunar surface. It shows very vividly the striking topography within the crater Copernicus. Credit: NASA / LOIRP
<!-- image --> <!-- image -->Luna 13
Nation: USSR (45)
Objective(s): lunar soft-landing
Spacecraft: Ye-6M (no. 205)
Spacecraft Mass: c. 1,620 kg
Mission Design and Management: GSMZ imeni Lavochkina
Launch Vehicle: Molniya-M + Blok L (8K78M no. N103-45, also N15000-55)
Launch Date and Time: 21 December 1966 / 10:17:08 UT
Launch Site: NIIP-5 / Site 1/5
Scientific Instruments:
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- Two TV cameras
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- ID-3 instrument to measure heat stream from surface
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- GR-1 penetrometer
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- RP radiation densitometer
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- KS-17MA instrument for corpuscular radiation
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- DS-1 Yastreb instrument to register loads on landing
Results: Luna 13 became the second Soviet spacecraft to successfully soft-land on the surface of the Moon. It began its mission by entering an initial Earth orbit of 223 × 171 kilometers at 51.8° inclination. The Blok L upper stage soon fired to send the spacecraft on a trajectory to the Moon. After a routine course correction on 22 December, Luna 13 began its approach to our only natural satellite. The retro-rocket engine fired at 17:59 UT on 24 December about 70 kilometers above the surface. Within two minutes, by 18:01 UT, Luna 13 was safely on the lunar surface, having landed in the Ocean of Storms between the Krafft and Seleucus craters at 18° 52′ N / 62° 04′ W, some 440 kilometers from Luna 9. The first signal from the probe was received at 18:05:30 UT. Unlike its predecessor, the heavier Luna 13 lander (113 kilograms) carried a suite of scientific instruments in addition to the usual imaging system. A three-axis accelerometer within the pressurized frame of the lander recorded the landing forces during impact to determine the regolith structure down to a depth of 20–30 centimeters. A pair of spring-loaded booms (not carried on Luna 9) capable of extending 1.5 meters beyond the lander, was also deployed. One of these was equipped with the RP radiation densitometer for determining the composition of the lunar surface, and the other with the GR-1 penetrometer to investigate the mechanical strength of the soil. At 18:06 UT, a small solid-propellant motor fired and forced the GR-1 instrument, a 3.5-centimeter diameter titanium-tipped rod, into the lunar surface. The instrument recorded how fast and how far into the soil (4.5 centimeters) the probe penetrated, thus helping scientists gain valuable information for future landers. At the same time, the RP densitometer emitted gamma quanta from a cesium-137 sample into the soil. The resulting scattering was then recorded by three independent pickups to provide an estimate of the density of the soil, found to be about 0.8 g/cm³. In addition, four radiometers recorded infrared radiation from the surface indicating a noon temperature of 117±3°C while a radiation detector indicated that radiation levels would be less than hazardous for humans. The lander returned a total of five panoramas of the lunar surface, showing a terrain smoother than that seen by Luna 9. One of the two cameras (intended to help return stereo images) failed but this did not diminish the quality of the photographs. A fully successful mission concluded with a last communications session between 04:05 UT and 06:13 UT on 28 December when the onboard batteries were exhausted.
78
Lunar Orbiter III
Nation: USA (33)
Objective(s): lunar orbit
Spacecraft: LO-C (Spacecraft 6)
Spacecraft Mass: 385.6 kg
Mission Design and Management: NASA / LaRC
Launch Vehicle: Atlas Agena D (Atlas Agena D no. 20 / Atlas D no. 5803 / Agena D no. AD128/6632)
Launch Date and Time: 5 February 1967 / 01:17:01 UT
Launch Site: Cape Kennedy / Launch Complex 13
Scientific Instruments:
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- imaging system
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- micrometeoroid detectors
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- radiation dosimeters
Results: Lunar Orbiter III was the final Lunar Orbiter mission to study potential Apollo landing sites although its mission was focused on "site confirmation" rather than "site search." For the mission, the spacecraft's orbital inclination was increased to 21° to ensure photography both north and south of the lunar equator. Building on the stereo photography taken by Lunar Orbiter II, the third mission was focused on making two "footprints" of the same area on two successive orbits. Lunar Orbiter III was also designed to obtain precision trajectory information for defining the lunar gravitational field, measure micrometeoroid flux, and measure radiation dosage levels around the Moon. The spacecraft arrived in lunar orbit after a 9 minute 2.5 second engine burn on 8 February 1967 after a single mid-course correction. Initial orbital parameters were 210.2 × 1,801.9 kilometers at 20.93° inclination. About four days later, the spacecraft entered its operational 55 × 1,847-kilometer orbit at 20.9° inclination. At the time, Lunar Orbiter II was still in operation around the Moon, thus providing key experience for NASA's ability to track and communicate with two simultaneous spacecraft around the Moon. Lunar Orbiter III began its photographic mission on 15 February. The spacecraft exposed 211 (out of a possible 212) frames of pictures by the time that imaging concluded on 23 February. Soon, the spacecraft began to "read out" the images to the ground but this activity suddenly stopped on 4 March due to a problem with the film advance mechanism in the read-out section of the imaging system. As such, only 182 images were returned—72 others were never read out to the ground. Despite the glitch, Lunar Orbiter wholly fulfilled its original mission objectives, returning images of 15.5 million km² of the near side and 650,000 km² of the farside. One of its images showed the Surveyor II lander on the lunar surface. On 30 August 1967, ground controllers commanded the vehicle to circularize its orbit to 160 kilometers in order to simulate an Apollo trajectory. Later, on 9 October 1967, the probe was intentionally crashed onto the lunar surface at 14° 36′ N / 91° 42′ W. The photographs from the first three Lunar Orbiters allowed NASA scientists to pick eight preliminary landing sites for Apollo by early April 1967, including site 2 in the Sea of Tranquility where Apollo 11 would land and site 5 in the Ocean of Storms where Apollo 12 (and also Surveyor III) would disembark.
<!-- image -->Astronaut Alan L. Bean of Apollo 12 inspecting the remains of the Surveyor III craft in November 1969. Surveyor landed on the Moon on 20 April 1967. In the background, the Apollo 12 Lunar Module Intrepid is visible. Credit: NASA