Introduction
Unlike the previous exploration missions on the moon like the Ranger missions, Surveyor missions were planned in such a way that spacecraft would make soft lunar landings. The program was over-ambitious at first. The initial plan was that NASA would launch a Lander and an orbiter, and that it would perform several scientific experiments.
However, NASA and other stakeholders were forced to scale the scope of the program down because of a number of considerations. These include the fact that the initial plan was too costly, and the fact that the plan required sophisticated spacecraft. The main reason however, was the Apollo program.
Kennedy approved a lunar mission involving manned spacecraft, and thus Surveyor was changed from a probe to a data-collection mission that would enable human lunar landings.
The people who would operate the spacecraft in the next mission would therefore perform Science functions once they landed on the moon (Day, 2007). This paper is an in-depth analysis of NASA’s Lunar Surveyor Program that preceded the Apollo program.
Research question
The main aim of NASA’s Surveyor Program, which consisted of seven spacecraft designed for soft landing (NASA Science, 2013), was to prepare for manned lunar landings, specifically the famous crewed Apollo landings (Barton, 2010). NASA would therefore use the Surveyors to determine if the lunar surface could support the landing and re-launch of a manned spacecraft.
The Surveyor missions were famous for successfully testing soft landings on the moon, and collecting data that was used by NASA to analyze the lunar surface. These preparations were invaluable during the manned Apollo missions.
Mission requirements
Timeframe
The Surveyor program was implemented between the years 1966 and 1968, during which five NASA spacecraft successfully soft-landed on the moon. Surveyor 1, the first spacecraft in the program touched down on the lunar surface in the month of June 1966, the second was unsuccessful. It crashed in the month of October 1966 into the moon.
Surveyor 3, the third mission touched down in the month of April 1967 while the fourth mission failed in the same year. Surveyor 5, the third last touched down in the month of September 1967 while the sixth touched down in the month of November the same year. The last one touched down in January the following year (Day, 2007).
Data requirements
In order to prepare for the Apollo program adequately, it was important for the Surveyor missions to collect data, which would give information for making the Apollo missions safe and successful. Firstly, it was important to study the lunar terrain and soil composition in order to determine whether the design of the Apollo equipment was compatible with the lunar surface.
Additionally, it was vital to collect data about the length of time that spacecraft could communicate while on trajectory and after landing on the moon. NASA also needed to determine the reliability of the launcher to “inject the Surveyor spacecraft on a lunar intercept trajectory” (NASA Science, 2013, p. 1).
It was also important to collect many images and data of the surface of the moon, which would be used to, among other things, determine if the bearing strength of the moon’s surface could support manned spacecraft. This would be helpful because analysis of these images would enable NASA identify the safest lunar location for landing the Apollo missions (NASA Science, 2013).
Mission summary
Individual mission descriptions
Surveyor 1
Surveyor 1 marked the beginning of soft lunar landing of spacecraft by the U.S. It was the first of the seven spacecraft launched in the Surveyor program. NASA launched Surveyor 1 on the 30th day of May 1966 at around 14:41 UT “on an Atlas/Centaur from Complex 36-A of the Eastern Test Range directly into a lunar impact trajectory” (National Aeronautics and Space Administration, 2013, p. 1).
NASA performed a midcourse correction of the spacecraft at around 06:45 UT the following day and the spacecraft entered the lunar atmosphere approximately 63 hours after it was launched.
“At an altitude of 75.3 km and a velocity of 2612 m/s the main retrorocket, signaled by the altitude marking radar, ignited for a 40 second burn and was jettisoned at an altitude of roughly 11 km having slowed the spacecraft to 110 m/s” (National Aeronautics and Space Administration, 2013, p. 1). The spacecraft continued to descend with its vernier engines controlled by the Doppler and the altimeter radars.
At an approximate distance of 3.4 m from the surface of the moon, the engines of the spacecraft were turned off and it freely fell to the lunar surface. This landing occurred at about 3m/s on the second day of June 1966, at around 6:17 UT.
“The landing site was at 2.474 S, 43.339 W on a flat area inside a 100 km crater north of Flamsteed Crater in southwest Oceanus Procellarum” (National Aeronautics and Space Administration, 2013, p. 1).
After touching down on the lunar surface, Surveyor 1 performed engineering tests during the first hour. It then spent the rest of the lunar day initiating photography sessions. About 10,338 images were captured by the television system and relayed before the end of the lunar day of 14th June.
Surveyor 1 also collected data on the degree with which the surface of the moon could reflect radar signals, and analyzed the surface temperatures of the moon.
The spacecraft withstood its first night on the moon and returned images on July 7. Its mission was ended on the13th day of July 1966, after it had transmitted 11,240 images, due to battery voltage drop (National Aeronautics and Space Administration, 2013).
Figure 1: Surveyor 1 on the lunar surface
(Stooke, 2008, p. 1)
Surveyor 2
Surveyor 2 was launched after Surveyor 1, becoming the second soft-landing lunar exploration spacecraft launched by NASA in the Surveyor mission. It was also intended to prepare for the Apollo program, which would launch manned spacecraft. Like Surveyor 1, Surveyor 2 was intended to collect data on the degree with which the surface of the moon could reflect radar signals, and analyze the surface temperatures of the moon.
The spacecraft was planned to land in the lunar Sinus Medii area. However, one engine could not ignite mid-course making the spacecraft operate with an unbalanced thrust, which resulted in its tumbling. NASA attempted to rescue the mission but they failed and the spacecraft fell on the moon 5.5 N and 12 W, at around 03:18 UT on the 23rd day of September 1966 (National Aeronautics and Space Administration, 2013).
Surveyor 3
Surveyor 3 succeeded in making a soft landing on the moon and became the second spacecraft after Surveyor 1 to achieve this feat. Some changes were made in Surveyor 1 and Surveyor 2 spacecraft when making Surveyor 3. The latter had an extended TV-camera glare hood, a pantograph arm containing a scoop, and auxiliary mirrors giving the spacecraft an underground view.
NASA launched Surveyor 3 on the 17th day of April 1967 at around 07:05 UT “on an Atlas/Centaur from Complex 36-B of the Eastern Test Range at Kennedy’s Space Center” (National Aeronautics and Space Administration, 2013, p. 1). Despite a problem with vernier engines, the mission was successful.
The spacecraft was able to send its first photos less than one hour after it landed on the moon, and it was able to use its surface sampler after a period of two days. During the lunar day up until the 3rd day of May 1967, the Surveyor was in operation. NASA was able to operate the Surveyor’s sampler for a period totaling eighteen hours and twenty-two minutes.
During this time, the television camera was able to capture and return 6,326 pictures, and trenches of a depth of up to eighteen centimeters were dug. The spacecraft transmitted new lunar data on the structure and the strength of materials, and even recorded a solar eclipse of the moon by the earth. Thermal measurements related to the solar eclipse were also recorded.
The spacecraft transmitted the last data at around 00:04 UT on the 4th day of May 1967, and its services were closed down due to a lunar night lasting two weeks (National Aeronautics and Space Administration, 2013)..
Surveyor 4
Surveyor 4 was the fourth soft landing lunar spacecraft that was design to capture and transmit lunar photography back to the earth for determining the terrain of the surface of the moon in preparation for the Apollo manned spacecraft. The spacecraft had with it equipment like soil surface sampler, auxiliary mirrors, and television camera, a number of engineering sensors and landing legs equipped with strain gauges.
The spacecraft had successful initial phases but it malfunctioned during the terminal-descent phase. It was unable to transmit radio signals during this phase about 2.5 minutes before its landing on the 17th day of July 1967. The mission was therefore declared unsuccessful because NASA was unable to establish contact with the spacecraft, which was planned to touch down 0.4 N, 1.33 W.
The site where the spacecraft fell on the moon was never established and thus NASA scientists suspected that the spacecraft possibly exploded before it crashed on the moon (National Aeronautics and Space Administration, 2013).
Surveyor 5
This spacecraft was the third successful mission Surveyor series to achieve a soft landing on the moon. It was also the first in the Surveyor series to collect data in-situ. Its instrumentation was more or less like that of its predecessors with minor additions like a magnetic testing functionality (National Aeronautics and Space Administration, 2013).
Launched at around 07:57 UT on the 8th day of September 1967 “from Eastern Test range launch complex 36B at Cape Kennedy on an Atlas-Centaur rocket” (National Aeronautics and Space Administration, 2013, p. 1), Surveyor 5 was injected in a trajectory for lunar transfer.
On the 9th day of September, at around 01:45 UT, 14.29 seconds of vernier-engine firing corrected the trajectory of the spacecraft midcourse. The spacecraft however started experiencing helium-pressure problems and emergency landing protocols were initiated (National Aeronautics and Space Administration, 2013).
The emergency landing procedure was flawless and thus the spacecraft landed 1.461 N, 23.195 E on the moon’s surface at around 00:46 UT on the 11th day of September 1967. The landing position was approximately 29 km away from the planned touchdown position. After touching down, the spacecraft captured 18,006 pictures during the first lunar day and transmitted them to NASA.
In-situ soil analysis was also performed during the same lunar day producing data running for 83 hours. It is important to note that the in-situ analysis was the first to be performed on an extra-terrestrial body. Surveyor 5 shut down during lunar night and resumed its operations the following lunar day transmitting alpha-scattering data running for twenty-two hours and 1048 pictures.
A total solar eclipse occurred on the 18th day of October 1967, and the spacecraft acquired lunar thermal data during that time. The spacecraft continued the cycle of night shutdown and day operations until its final transmission, which occurred on the 17th day of December 1967 (National Aeronautics and Space Administration, 2013).
Surveyor 6
This was the fourth mission to achieve a soft lunar landing successfully. The spacecraft was almost similar to its predecessor, Surveyor 5. One of the main distinguishing features between this spacecraft and its predecessor were that it was composed of three auxiliary mirrors unlike the two in Surveyor 5.
Additionally, its glare hood was completely different from that of Surveyor 5 and its TV camera had polarizing filters (National Aeronautics and Space Administration, 2013).
The spacecraft was launched at around 07:39 UT on the 7th day of November 1967. It landed 0.49 N, 358.60 E on the surface of the moon at around 01:01 UT on the 10th day of November 1967 (National Aeronautics and Space Administration, 2013).
NASA fired the spacecraft’s vernier engines for a period of about 2.5 seconds at 10:32 UT on the 17th day of November, making the spacecraft to move at least 3 meters vertically and 2.4 meters horizontally.
This spacecraft hop “represented the first powered takeoff from the lunar surface and furnished new information on the effects of firing rocket engines on the Moon, allowed viewing of the original landing site, and provided a baseline for stereoscopic viewing and photogrammetric mapping of the surrounding terrain” (National Aeronautics and Space Administration, 2013, p. 1).
The spacecraft was able to record and send 30 hours of data and 29,952 photographs. The aforementioned data indicated that the surface of the moon had a bearing strength that could adequately withstand human lunar landings (National Aeronautics and Space Administration, 2013).
Surveyor 7
The last spacecraft in the Surveyor program was Surveyor 7, which became the fifth to soft-land on the surface of the moon successfully. It was designed in the same way as its predecessor, Survivor 6, although it had the most extensive payload among all the spacecraft in the program.
“It carried a television camera with polarizing filters, an alpha-scattering instrument, a surface sampler similar to that flown on Surveyor 3, bar magnets on two footpads, two horseshoe magnets on the surface scoop, and auxiliary mirrors” (National Aeronautics and Space Administration, 2013, p. 1). Three of the auxiliary mirrors were specifically for observing underneath the spacecraft.
One of the mirrors was specifically for the surface sampler providing stereoscopic views to the same. An additional seven mirrors were designated for capturing images of lunar materials that the spacecraft collected on its surface. The engineering items of the spacecraft were also enhanced (Krebs, 2013).
The launch of the seventh spacecraft in the Surveyor program occurred on the 7th day of January 1968 at around 06:30 UT. The spacecraft landed on the moon in the lunar highlands on the 10th day of January 1968 at around 01:05 UT. After touchdown, the spacecraft immediately initiated science operations. Before the end of the first day on the moon, the spacecraft had returned 20,993 images.
Problems with alpha scattering were rectified using the surface sampler and by the end of the first day on the moon, the spacecraft had transmitted 66 hours of data. After sunset, Surveyor 7 was able to take images of the solar corona, the earth, and the stars.
During the second day on the moon, 34 hours of data obtained through alpha scattering was sent as well as 45 pictures. Surveyor 7 operations ended at around 12:24 UT on the 21st day of February, terminating the operations of the Surveyor program.
Key information provided by Surveyor Missions
Surface composition
Results from Alpha-scattering showed that lunar soil composition was similar to that of the Earth’s basaltic salt. More specifically, the soil composed of “53% to 63% oxygen, 15.5% to 21.5% silicon, 10% to 16% sulphur, iron, cobalt, and nickel; 4.5% to 8.5% aluminum, and small quantities of magnesium, carbon, and sodium” National Aeronautics and Space Administration, 2013, p. 1).
The magnetism of the soil showed that the soil had up to 1% metallic iron (National Aeronautics and Space Administration, 2013).
Surrounding terrain
The terrain surrounding the landing sites of spacecraft was found to be largely similar to that of Earth’s basaltic salt. This was specifically tested by an erosion experiment that was carried out by Surveyor 5 using its vernier engines (National Aeronautics and Space Administration, 2013).
The surveyor missions reported that there was erosion on the moon, albeit minor. Contrary to information provided by earlier spacecraft models, the Surveyor program showed that the surface of the moon was rocky, hard, and less dusty.
Earlier spacecraft models had made scientists worry that the lunar surface would be having thick dust layers, which would interfere with landing by obscuring visibility. The Surveyor program therefore gave reliable data with regard to the moon’s terrain (Day, 2007).
Bearing strength
Surveyor 6 collected 30 hours of data and 29,952 photographs, whose analysis indicated that the surface of the moon had a bearing strength that could adequately withstand human lunar landings (National Aeronautics and Space Administration, 2013).
The aforementioned fact that the lunar surface underwent minor erosion was also a factor contributing to the conclusion that the bearing strength of the moon’s surface was high enough to withstand manned spacecraft landing.
Surveyor spacecraft description
Propulsion system
The Surveyor spacecraft controlled propulsion and altitude using different systems for its different phases. During the cruise phases, altitude control jets that used cold gas (nitrogen) controlled propulsion and altitude. During powered phases, vernier rocket engines that were throttlable controlled propulsion. During the final phase, terminal descent, the spacecraft used a retrorocket engine.
As the spacecraft was about to land, a radar keeping track of altitude initiated braking within the main retrorocket by firing it. Completion of firing led to jettisoning of the radar and retrorocket and activation of altimeter and Doppler radars.
The overall effect was that the autopilot took control of the vernier propulsion system making it to touch down (National Aeronautics and Space Administration, 2013).
Scientific instrumentation
The Surveyor’s main instrument was its camera that could elevate over and pan around the spacecraft. The first spacecraft was built with more than one thousand engineering sensors that included accelerometers, voltage sensors, thermometers, strain gages, and other devices. From its design, it is clear that the Surveyor did not have so many scientific functions.
Its sensors were not scientific, but engineering in nature. This affirmed the primary objective of the spacecraft, which was to establish if soft lunar landing was possible. Due to the limited scientific capability of the Surveyor spacecraft, some members within the scientific community suggested that later missions would integrate functionalities that are more scientific.
It is however important to note that only “a surface scoop that could dig a trench and expose underlying soil to the camera, and an alpha scattering experiment used to examine the composition of the soil” (Day, 2007, p. 1) were added.
Additional engineering functionalities that were part of the Surveyor spacecraft include descent guidance and control system that used a closed loop, the use of radar in determining the Lander’s velocity and altitude, and engines that could be throttled. NASA tested these systems for the first time in the challenging radiation and thermal lunar environment during the Surveyor missions.
Development history
Builder
As the construction of spacecraft in the Surveyor series was about to start, NASA was presented with four proposals for the Surveyor concept. All the proposals had their strong and weak points but NASA chose the design by Hughes Aircraft Company because it seemed to consider most technical aspects of the spacecraft (Oran, 1985).
Manufacture
Manufacture site
Different contractors manufactured various parts of the Surveyor spacecraft. For instance, Space Technology Laboratories manufactured vernier engines, Thiokol Chemical Corporation manufactured the propellant retro-rocket, and Ryan Aeronautical Company developed the Doppler radars. The final assembly was done at Hughes Aircraft Company (Oran, 1985).
Period of manufacture
It took an approximate five years from the time the Surveyor project was initiated to the time when the first Surveyor launched successfully (Oran, 1985). This was largely due to management and technical problems that were encountered as various components of the spacecraft were being manufactured.
The manufacture of vernier engines had to be transferred from Thiokol’s Reaction Motors Division to Space Technology Laboratories after it emerged that the former lacked specialized hardware (Oran, 1985).
Testing
Testing of the Surveyor spacecraft was accomplished using Earth surface simulations. Obviously, the earth’s surface is quite different from that of the moon, particularly in terms of gravity. However, such tests were vital in detecting problems that could prove costly if they were detected after the start of the program. At first, every landing component of the spacecraft was tested.
Then spacecraft controls above the earth’s surface were tested using balloons and large cranes. 1,500-foot drops were performed at White Sands, New Mexico towards the end of the testing allowing the spacecraft to control its descent as it would do on when landing on the lunar surface (Oran, 1985).
Launch vehicle
Requirements
The Surveyor program was planned such that all the spacecraft in the series would be launched on an Atlas-Centaur launch vehicle. The requirements for the program were that the launch vehicle was supposed to have the “capability of injecting 2,500 pounds into a trans-lunar trajectory from Cape Canaveral” (Fisher, 2012, p. 1).
The launch vehicle was also supposed to ensure lunar touchdown after approximately 66hours via the Goldstone tracking station (Fisher, 2012).
Description
All the spacecraft in the Surveyor program were injected into the lunar trajectories by a launch vehicle referred to as the Atlas Centaur. This launch vehicle had a payload of about 3,700 lb, a diameter of 10 ft, a gross mass of 300,000 lb and a height of about 108 ft (Kyle, 2005).
It therefore was capable of meeting the Surveyor program requirement of a launch vehicle that could launch 2,500 lb. The first time that the launch vehicle was used in a successful launch was in the 11th day of August 1965, while undergoing tests with Surveyor SD2 before the Surveyor program officially began in the year 1966.
Figure 2: Surveyor 1 being launched using the Atlas Centaur
(Kyle, 2005, p. 1)
Cost
Original bid
The contract for the Surveyor mission was given in the year 1961 to Hughes Aircraft Co. The initial contract sum was $300 million per mission totaling $2.1 billion for the seven missions (Lindroos, 1997).
Cost increases
During program implementation, additional costs were incurred. The program (comprising of seven missions) incurred additional costs amounting to USD 700 million (Lindroos, 1997).
Overall program costs
As mentioned above, the Surveyor program involved the design of up to seven lunar soft landing spacecraft that were meant to collect lunar data in preparation for the manned Apollo spacecraft program that was already approved by the U.S. President before the launch of Surveyor 1. The Surveyor program cost totaled USD 2.8 billion (National Aeronautics and Space Administration, 2013).
Summary
The success of the Surveyor program is largely attributable to the fact that NASA chose a reliable and simple architecture for the mission, which employed an incremental and pragmatic approach in solving the engineering challenges that NASA encountered during that time. NASA launched seven missions in the Surveyor program. Out of the seven, five succeeded and two failed.
Surveyor 2 experienced mechanical problems due to a fault in its engine and consequently crashed into the moon. Surveyor 4 was unable to transmit radio signals shortly before it landed and therefore the site where it crashed on the moon was never established. The other missions succeeded and collected informative data that proved invaluable during the Apollo program. The program was therefore a great success.
Conclusion
The Surveyor program consisted of seven spacecraft that were sent to the moon to act as pathfinders for the manned Apollo program. NASA contracted the Hughes Aircraft Company to make the spacecraft, which were to be launched on a launch vehicle referred to as Atlas Centaur.
Hughes Aircraft Co. in turn subcontracted other companies, including Space Technology Laboratories manufactured, Thiokol Chemical Corporation and Ryan Aeronautical Company, to manufacture various components of the spacecraft. By the time the first spacecraft was ready for launch, five years had passed amid technical and management problems.
Surveyor 1 was launched in the year 1966 while the last spacecraft was launched in 1968. Out of the seven spacecraft, two were unsuccessful and four were successful. Surveyor 2 crashed on the moon’s surface after engine fault while Surveyor 4 crashed because of a failed communication system.
Despite these two failures, the other spacecraft collected loads of data in terms of images and recordings that helped in planning for the Apollo program. The Apollo program’s success was therefore, arguably, attributable to the success of the Surveyor program. The program’s total cost was $ 2.8 billion.
Reference List
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Lindroos, M. (1997). The Cost of the Moon Race: $100 Billion to Land on the Moon. Web.
NASA Science. (2013). Missions: Surveyor. Web.
National Aeronautics and Space Administration. (2013). Surveyor 1. Web.
Oran, N. (1985). SP-480 Travelers: The Exploring Machines. Web.
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