Fig. 11.1 Surveyor on the moon. Courtesy of NASA
J. L. Chen, How to Find the Apollo Landing Sites,
The Patrick Moore Practical Astronomy Series, DOI 10.1007/978-3-319-06456-7_11, © Springer International Publishing Switzerland 2014
NASA developed the Surveyor Program as the follow-up to the Ranger program. Ranger proved that NASA could hard crash a spacecraft into the Moon. Surveyor was NASA’s opportunity to achieve soft landings on the Moon. Additionally, NASA set scientific goals of Surveyor to gather data about the Moon’s surface, through photographs and digging scoops.
In those early days of the NASA lunar program, very little was known about the Moon’s surface. There were scientists that feared that the Moon’s surface was coated in a thick lunar dust that a lunar lander would be swallowed up and sink into the Moon’s surface. Therefore, Surveyor’s mission included experiments to test the nature of the lunar surface, including a mechanical scoop to test the firmness and granularity of the lunar soil.
As with Ranger, not all of the Surveyor missions were successful. Surveyor 2, originally targeted for Sinus Medii, or Central Bay, suffered a failure in one of its vernier rocket motors, resulting in a tumbling flight to the Moon and its crashing near the Copernicus Crater.
Surveyor 4 also crashed in its mission to Sinus Medii ( a Sinus Medii jinx?!?!). After a faultless flight to the moon, telemetry signals from the spacecraft ceased during the landing phase, about 2.5 minutes before touchdown. Contact with the spacecraft was never reestablished, and the mission failed. The engineers’ speculated that the solid fuel retro rocket exploded during the end of its scheduled burn.
In all, seven unmanned Surveyor lunar missions were launched between May 1966 and January 1968. Surveyor 1, 3, 5, 6, and 7 successfully accomplished a soft landing on the lunar surface. In addition to demonstrating the feasibility of lunar surface landings (and not disappearing into the moon dust!), the Surveyor missions obtained lunar photos, and gathered both scientific and technological information needed for the manned Apollo program. Four spacecraft, Surveyor 1, 3, 5, and 6, returned data from selected mare sites to support the Apollo program. Surveyor 7 provided data from a highland region.
Fig. 11.2 Finder chart. Courtesy of the author
Here again, as with sighting the Ranger impact sites, locating and viewing the Surveyor landing sites serves as extra credit to the backyard observer.
Fig. 11.3 LRO View of Surveyor 1. Photo courtesy of NASA and Arizona State University
All Surveyor landing sites, except for the last one, were selected primarily because they were being considered as Apollo landing sites. The landing site selected for Surveyor 1 was in the southwest part of Ocean of Storms. The spacecraft came to rest within about 15 km of the target point, on a flat surface inside a 100-km crater, one radius from the edge of a rimless 200-m crater.
Launch: 30 May, 1966. Landed: 2 June, 1966, 06:17:37 UT. Landing Site: Flamsteed P (2.45°S latitude, 316.79°E longitude)
Surveyor 1 was the first U. S. spacecraft to land softly on the Moon, proving a variety of new equipment and spacecraft design, and validating the technique for landing on the Moon. It returned a large quantity of scientific data during its first two days of operation on the lunar surface. Following its landing, the spacecraft transmitted 11,240 high-resolution television pictures back to NASA. Surveyor 1 completed its primary mission on July 14, 1966, after transmitting television pictures, data on the bearing strength of the regolith, temperatures, and radar reflectivity of the Moon. Subsequent engineering interrogations of the spacecraft were conducted through January 1967.
Fig. 11.4 Mission photo of Astronaut Conrad and Surveyor 3. Courtesy of NASA
The site selected for Surveyor 3 was in the southeast part of Ocean of Storms. The spacecraft came to rest in a subdued, rounded crater about 200 yards in diameter approximately 230 miles south of the Copernicus Crater. This site became a future landing site of an Apollo mission. As seen in Chapter 4, Apollo 12 landed within walking distance and astronauts Pete Conrad and Alan Bean visited Surveyor 3 and returned with component parts of the spacecraft for examination and study by NASA engineers.
Fig. 11.5 Mosaic taken by Surveyor 3. Courtesy of NASA
Launched: 17 April, 1967. Landed: 20 April, 1967, 00:04:53 UT. Landing Site: Ocean of Storms (2.94°S latitude, 336.66°E longitude).
The data from Surveyor 3 showed that it touched down on the lunar surface three times before the landing was completed. Surveyor 3’s engines did not shut down as intended. The spacecraft moved approximately 65 feet between the first and second touchdowns and about 36 feet between the second and third. The engines finally shut down prior to the third touchdown. A final translation movement of about 1 feet occurred following the third touchdown.
Like its predecessors, this mission carried a survey television camera, as well as other instrumentation for determining various properties of the lunar surface material. Additionally, it carried a surface sampler instrument for digging trenches, making bearing tests, and otherwise manipulating the lunar material in view of the television system. During its operation, which ended May 4, 1967, Surveyor 3 acquired a large volume of new data and took 6326 pictures. The surface sampler, during its 18 hours of operation, accumulated samples which yielded significant new information on the strength, texture, and structure of the lunar material to a depth of about a half a foot.
Fig. 11.6 Mosaic of Surveyor 5 photos showing the Surveyor landing strut and foot pad. Courtesy of NASA
The site selected for Surveyor 5 was in the southwest part of the Sea of Tranquillity. Surveyor 5 landed in a dimple-shaped, two car garage-sized rimless crater, the largest of a small chain of rimless craters. A backyard observer when sighting the Apollo 11 landing site will also have the Surveyor 5 site within the field of view.
Launch: 8 September, 1967. Landed: 11 September, 1967, 00:46:44 UT. Landing Site: Sea of Tranquility (1.41°N latitude, 23.18°E longitude).
This spacecraft was basically similar to its predecessor, except that the surface sampler was replaced by an alpha-backscatter instrument. In addition, a small bar magnet was attached to one of the footpads. Because of a critical helium regulator leak, a radically new descent profile had to be designed for the spacecraft. Surveyor 5 performed flawlessly and landed softly. Once safely on the Moon, the spacecraft functioned well and outperformed the previous missions. During its first lunar day
of operation on the Moon, 18,006 television images of exceptional quality and high scientific content were returned to Earth. On October 15, 1967, after having spent 2 weeks in the deep freeze of a lunar night, Surveyor 5 responded immediately to the first turn-on command and resumed operation, returning 1048 additional pictures and 22 hours of additional data.
The Surveyor 6 Mission
Fig. 11.7 Panoramic Lunar mosaic from Surveyor 6. Courtesy of NASA
Fig. 11.8 Panoramic Lunar mosaic 2 from Surveyor 6. Courtesy of NASA
The landing site chosen for this mission was in Sinus Medii, site of two previous Surveyor failures. The Sinus Medii curse was finally broken, with Surveyor 6 landing in the center of the Moon’s Earth-facing hemisphere. Surveyor 6 marked the last of four potential Apollo landing areas designated by the Surveyor program planners. The spacecraft landed on a nearly flat, heavily cratered mare area, about 200 yards northwest of the base of a ridge about 100 feet high.
Launch: 07 November, 1967. Landed: 10 November, 1967, 01:01:06 UT. Landing Site: Sinus Medii (0.46°N latitude, 358.63°E longitude).
The performance of Surveyor 6 on the lunar surface was virtually flawless. From touchdown until a few hours after sunset on November 24, 1967, the spacecraft transmitted 29,952 television pictures and the alpha-scattering instrument acquired 30 hours of data on the chemical composition of the lunar material.
As part of the surface mechanical properties investigation, Surveyor 6 performed a “hop” maneuver, moving 2.5 m away from its original landing area. This maneuver provided excellent views of the surface disturbances produced by the initial landing and the effects of firing rocket engines close to the lunar surface. Photography obtained after the hop contributed to the soil mechanics investigation.
On November 26, 1967, the spacecraft was placed in hibernation for the two – week lunar night. Contact with the spacecraft was resumed for a short period on December 14, 1967.
The Surveyor 7 Mission
Fig. 11.9 Panoramic Lunar mosaic from Surveyor 7. Courtesy of NASA
Surveyor 7 was the only unmanned pre-Apollo landing mission sent to an area for mainly scientific reasons. All of the previous Surveyor missions were targeted for safe mare regions. The Surveyor 7 site selection was for a highland region with a rugged, rock-strewn ejecta blanket near Tycho Crater. The spacecraft landed less than 1.5 miles from the center of the target circle, about 18 miles north of the rim of Tycho. The backyard astronomer needs merely to sight the Tycho Crater and view the north rim to view the Surveyor 7 landing site.
Launch: 07 January 1968. Landed: 10 January 1968, 01:05:36 UT. Landing Site: Tycho Crater North Rim (41.01°S latitude, 348.59°E longitude).
Despite the more hazardous terrain in the landing area, Surveyor 7 landed without incident. 20,993 television pictures were obtained during the first lunar day.
An additional 45 pictures were obtained during the second lunar day. The alphascattering instrument failed to fully deploy on its own, so the surface sampler was used to place the instrument on the surface, and enabling the device to function. The surface sampler moved the alpha-scattering instrument to two other locations for more data gathering. In addition to acquiring a wide variety of lunar surface data, Surveyor 7 also obtained pictures of Earth and performed star surveys. Laser beams from Earth were successfully detected by the television camera in a special test of laser-pointing techniques, as a proof-of-concept prelude to the Apollo LRRR experiment.
Post-sunset operations were conducted for 15 hours after local sunset at the end of the first lunar day. During these operations, additional Earth and star pictures were obtained, as were observations of the solar corona. Operation of the spacecraft was terminated 80 hours after sunset. The spacecraft was reactivated for the second lunar day on February 12, 1968, and operated until February 21, 1968.