Today it seems that whenever one of NASA’s missions to worlds beyond our own encounters a potentially mission ending problem, teams of talented engineers and scientists inevitably find an innovative way to resolve the issue allowing the mission to continue. Of course, this is not always true and heartbreaking failures do still occur. Unfortunately, such mission ending failures seemed to be more the norm than the exception during the early years of the Space Age as we learned the difficult lessons needed to design, build and operate spacecraft as well as properly manage such complex enterprises.

NASA’s Surveyor robotic lunar landing program of the 1960s was a prime example. Despite their best efforts gleaned from lessons learned over the previous decade from various programs, two of the first four Surveyor missions failed to meet their objectives (see “Surveyor 2: Things Don’t Always Go As Planned” and “Surveyor 4: The Impact of a Low Probability Event”). The tally for this program could have hit three failures with the Surveyor 5 mission when it encountered what would normally have been considered a mission-ending malfunction. Instead, ground controllers were able to snatch the mission from the jaws of failure in what must be one of the more brilliant recovery efforts of the opening decade of the Space Age.


The Surveyor Spacecraft

Work began on NASA’s Surveyor program in May 1960 under the responsibility of Caltech’s Jet Propulsion Laboratory (JPL) in Pasadena, California (for details on the early history and development of Surveyor, see “Surveyor 1: America’s First Lunar Landing”). Built by Hughes Aircraft Company (whose space division is now part of Boeing), Surveyor was arguably the most advanced lunar spacecraft of its day. The basic 2.4-meter tall structure consisted of a simple 27-kilogram tetrahedral frame made of tubular aluminum alloy members. In each of the three lower corners was a landing leg equipped with an aircraft-style shock absorber and a footpad of crushable honeycomb aluminum. The total span of the legs, once deployed, was 4.3 meters. Rising from the apex of the frame was a mast upon which was mounted a gimballed planar high-gain antenna and a solar panel supplying up to 85 watts of electrical power to the lander’s rechargeable silver-zinc batteries. From the footpads to the top of its mast, Surveyor stood three meters tall.

Diagram showing the major components of the Surveyor 5 spacecraft. Click on image to enlarge. (NASA)

Buried inside the spacecraft’s frame was a Morton Thiokol-built 91-centimeter diameter TE-M-364 solid propellant rocket motor that would provide between 35.5 to 44.5 kilonewtons of thrust, depending on the motor’s temperature at ignition. This 656-kilogram motor, which would later be used as the third stage in various Delta launch vehicles models flown in the 1970s and as the final “kick stage” for the Pioneer and Voyager missions to the outer planets, would be used to negate most of Surveyor’s motion towards the Moon as the lander approached the lunar surface.

Diagram of the Thiokol TE-M-364 rocket motor used to slow the descending Surveyor spacecraft. Click on image to enlarge. (NASA)

Surveyor also carried a second propulsion system for midcourse corrections and attitude control during the main retrorocket burn as well as for the final descent. This system consisted of three vernier engines fueled by monomethylhydrazine hydrate with MON-10 (a mixture of 90% nitrogen tetroxide and 10% nitric acid) serving as the oxidizer. These engines could be throttled by command of the spacecraft’s flight control subsystem producing between 130 and 460 newtons of thrust each. Yaw, pitch, and descent rate were controlled by selective throttling of the engines while roll was controlled by swiveling a single gimballed vernier. During the trans-lunar coast, Surveyor’s attitude was controlled by a set of six nitrogen gas jets, each providing 270 millinewtons of thrust.

All the temperature sensitive electronics were carried in two thermal boxes mounted to the frame. These compartments were covered with 75 layers of aluminized Mylar insulation and the tops were covered by mirrored glass thermal regulators. Compartment A, which maintained it internal temperature between +4° and +52° C, carried a redundant set of receivers and ten-watt radio transmitters, the batteries, their charge regulators, and some auxiliary equipment. The second box, Compartment B, was designed to maintain the temperature between -15° and +52° C. This compartment carried the computer “brains” of the spacecraft which controlled all aspects of the lander’s operation using a total of just 256 commands. Mounted elsewhere on the frame were star sensors, a pair of radar systems for landing, low-gain antennas, propellant, and helium pressurization tanks.

Diagram detailing the components of the first Block I Surveyor landers as viewed from above. Click on image to enlarge. (NASA

The first “Block I” Surveyors were considered “engineering models” for more advanced “Block II” versions of the lander which had been proposed. Most of its instrumentation were engineering sensors such as strain gauges, accelerometers, rate gyros, temperature sensors, and so on to be used to make more than two hundred measurements of the spacecraft’s performance and condition. While not specifically designed for investigating the lunar environment, many of these measurements could be used to determine some of its basic properties including surface mechanical properties and its temperature.

Diagram showing the major components of the camera Surveyor used to image its surroundings after landing. Click on image to enlarge. (NASA)

The only true scientific instrument carried by the initial batch of what would be seven Block I Surveyors was a slow-scan television camera. The camera was mounted in a 1.65-meter tall mast attached to the spacecraft’s framework. The camera pointed up into a movable mirror that allowed the camera to view 360° of azimuth and from 60° below to 50° above the normal plane of the camera. The 7.6-kilogram camera package was canted at a 16° angle to offer a clear view of the surface between two of the footpads out to the lunar horizon 2½ kilometers away. The camera was fitted with a 25 to 100 mm zoom lens that offered a field of view of between 25.3° and 6.4°.  The aperture could be set between f/4 and f/22 and the lens could be focused from 1.2 meters to infinity.  A shutter was also included so that various integration times could be used to obtain the ideal exposure.  While the nominal exposure time was 150 milliseconds, exposures as long as about thirty minutes could be accommodated.  The typical resolution of the camera was one millimeter at a distance of four meters. By combining a series of images taken in a stepwise fashion at various azimuth and elevation angles, panoramic mosaics of the spacecraft and the surrounding terrain could be created.

A schematic diagram of the Surveyor television camera. Click on image to enlarge. (NASA)

The camera was also fitted with a filter wheel containing clear and three color filters. With the aid of calibration targets mounted at various points of the spacecraft, pictures taken through red, green, and blue spectral filters could be reconstructed back on Earth to yield full-color views of the lunar surface. The camera could only operate in real time via remote control from Earth using a total of 25 commands. The primary means of transmitting images was through the high-gain antenna. Using this powerful antenna, an image would be broken up into 600 scan lines and transmitted back to Earth in 3.6 seconds. The use of the less powerful low-gain antennas, which served as a backup, would permit an image to be broken up into 200 lines and would require 61.8 seconds to transmit.


The Surveyor E Mission

With the cancellation of the more advanced Block II Surveyor missions on December 13, 1966 which would have explored the lunar surface with a wider array of instruments, program officials decided to incorporate some of the Block II science payloads already completing development on the remaining five approved engineering flights of the more limited Block I spacecraft. The third and fourth Block I Surveyor flights were selected to carry a remote controlled mechanical arm formally known as the Soil Mechanics Surface Sampler or SMSS (see “Surveyor 3: Touching the Face of the Moon”).

The major components of Surveyor’s Alpha Scattering Experiment. Click on image to enlarge. (NASA)

For the fifth Surveyor mission, designated Surveyor E before launch, the SMSS was replaced with a new instrument known as the Alpha Scattering Experiment designed to measure the concentration of various elements in the lunar soil. The 13-kilogram instrument consisted of three major components: a sensor head, a deployment mechanism and a thermally controlled electronics compartment. The sensor head consisted of a 17.1 by 16.5 by 13.3 centimeter high box on a plate with a diameter of 30.5 centimeters which would sit on the lunar surface once deployed. The sensor head was mounted on the spacecraft during flight and would be lowered to the lunar surface upon ground command by a nylon cord wrapped around a geared cylinder which would unwind under the action of lunar gravity in a series of controlled steps.

Diagram illustrating the steps to deploy the Alpha Scattering Experiment sensor head. Click on image to enlarge. (NASA)

Once deployed on the lunar surface, a set of six small radiation sources composed of the artificial element, curium-242 with a half life of just 160 days, would bombard a small part of the lunar surface with alpha particles (essentially nuclei of helium-4 consisting of a pair of each of protons and neutrons) that would penetrate only about 25 micrometers into the lunar surface. A pair of alpha particle detectors located adjacent to the curium-242 sources would be used to detect the energy and number of alpha particles scattered by the lunar surface allowing the concentrations of elements heavier than lithium to be determined.

A schematic diagram of the sensor head for the Alpha Scattering Experiment. Click on image to enlarge. (NASA)

Four other detectors included inside of the sensor head would measure the energy and number of protons that were emitted by the lunar surface as a result of interactions with the alpha particles. These sensors would allow the concentration of boron, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine and potassium to be assessed. While stowed on the lander, the alpha particle and proton detectors in the sensor head were calibrated using small amounts of einsteinium-252 on the mounting platform. By measuring the concentration of elements present in the lunar surface, scientists could estimate what types of rocks made up the lunar surface.

The spacecraft for the Surveyor E mission, SC-5, also included a pair of metal bars (one magnetic and the other nonmagnetic) attached to one of the footpads just like its unsuccessful predecessor, Surveyor 4 (see “Surveyor 4: The Impact of a Low Probability Event”). Observations of these 5.1 by 1.3 by 0.3 centimeter thick bars by the television camera would allow scientists to determine the magnetic properties of the lunar soil. As in earlier missions, SC-5 included a pair of small mirrors mounted on one of the landing legs. Unlike the earlier flat mirrors, the mirrors on SC-5 were convex to provide a wider field of view and one of them was repositioned to provide a clearer view of the underside of the Surveyor lander allowing an assessment of how the lander’s vernier engines disturbed the lunar soil. The launch mass of SC-5 for the Surveyor E mission was 1,005 kilograms. After it had jettisoned its spent retrorocket and consumed all of its propellants during descent, the spacecraft would have a mass of just 279 kilograms upon landing.

This diagram shows the placement of two metal bars on the landing pad of Surveyor E to be used to assess the magnetic properties of the lunar soil. Click on image to enlarge. (NASA)

Surveyor’s launch vehicle was one of NASA’s most advanced rockets called the Atlas-Centaur. The Centaur upper stage used liquid hydrogen and liquid oxygen (LOX) as propellants – the first rocket stage to do so. This combination provided up to half again as much thrust than a like mass of conventional propellants then in use. Unlike the earlier versions of the Atlas-Centaur which employed a modified Atlas D ICBM for its first stage, AC-13 to be used to launch the Surveyor E mission was the first to employ the improved SLV-3C model of the Atlas. In this version of the Atlas, the propellant tanks were stretched by 1.3 meters to increase the propellant load by 8% to 123 metric tons and lengthen the burn time by ten seconds. The thrust of the improved MA-5 propulsion system was also increased by about 2% to provide a total liftoff thrust of 1,756 kilonewtons. With a total height of 35.7 meters and a liftoff mass of 146 metric tons, the new Atlas-Centaur was now capable of launching up to about 1,135 kilograms towards the Moon on a Surveyor-type mission or about 68 kilograms more than the earlier Atlas-Centaur models.

Diagram showing the major components of the Atlas-Centaur SLV-3C used to launch the later Surveyor missions. Click on image to enlarge. (NASA)

In order to maximize its payload and launch widow flexibility, the Atlas-Centaur was designed to first place its payload into a low parking orbit. The pair of RL-10 engines powering the Centaur would then reignite at the proper injection point to send the Surveyor lander on its way to the Moon. Due to problems with the development of the Centaur and its in-orbit restart capability, the initial two Surveyor missions were forced to use direct ascent trajectories to the Moon which required only a single burn of the RL-10 engines. With the successful test flight of AC-9 on October 26, 1966 where the Centaur finally demonstrated its in-orbit restart capability by sending a dynamic model of a Surveyor lander, designated SD-4, into a simulated lunar trajectory, the way was finally clear for the technique to be used in future Surveyor missions starting with Surveyor 3.

Diagram illustrating Surveyor’s lunar trajectory options. Click on image to enlarge. (NASA)

Unlike the later Apollo lunar landing missions, Surveyor was designed to make a direct descent to the lunar surface from its translunar trajectory about 65 hours after launch with no intermediate stop in lunar orbit. Since Surveyor was designed with the capability of landing on the Moon with an approach trajectory substantially off of the local vertical, most of the lunar hemisphere facing Earth was accessible to Surveyor. Early flights, however, were limited to the equatorial mare regions of what was called the “Apollo landing zone” which appeared to be the safest landing sites based on orbital photography. It was intended that the initial Surveyor missions would provide ground truth data on these proposed sites to support the upcoming Apollo lunar landing missions.

Diagram showing the major events in Surveyor’s descent to the lunar surface. Click on image to enlarge. (NASA)

Like the earlier four Surveyor missions, the objectives of the Surveyor E mission were chosen to support the upcoming Apollo lunar landings. The primary objectives were to land in the equatorial Apollo landing zone east of the Moon’s prime meridian in Mare Tranquillatatis and obtain postlanding television images of the lunar surface. This would be the most easterly landing attempted so far in the Surveyor program and would require the spacecraft to perform a large gravity turn as it approached the lunar surface as much as about 47° to the local vertical – much larger than the 6° and 25° approaches of the earlier Surveyor 1 and 3 missions, respectively. The landing site chosen was at 24° E and 1° N about 39 kilometers north of the crater Molke and 58 kilometers southwest of where NASA’s Ranger 8 mission intentionally impacted 2½ years earlier (see “50 Years Ago Today: The Launch of Ranger 8”). Secondary objectives included using the Alpha Scattering Experiment to determine the composition of the lunar surface, conduct a vernier engine erosion experiment and obtain information on the bearing strength, radar reflectivity and thermal properties of the lunar surface.

Map of the Moon showing the Apollo Landing Zone and the location of the Surveyor 1, 3 and 5 landing sites. Click on image to enlarge. (NASA)


Getting Off the Ground

In order to meet the postlanding lighting requirements at the selected site as well as satisfy other mission and launch constraints, the Surveyor E mission had a six day launch period running from September 8 to 13, 1967. The launch window on September 8 ran from 3:39 AM to 5:29 AM EDT. Daily launch windows of about 1½ to just over two hours in length started later on each successive day. Landing was scheduled to occur about 65 hours after liftoff with the exact transit time dictated by the date and time of launch.

This schematic illustrates the effects of the various constraints on the launch windows of the Surveyor E mission for launch between September 8 and 13, 1967. Times are in GMT. Click on image to enlarge. (NASA)

Preparations for the Surveyor E mission began on April 17, 1967 immediately following the successful launch of Surveyor 3 from Pad B of Launch Complex 36 (LC-36B) at Cape Kennedy (which reverted back to its original name of Cape Canaveral in 1973). In order to accommodate the newer SLV-3C Atlas-Centaur, the facilities at LC-36B had to be modified as launch preparations for Surveyor 4 were conducted in parallel at the neighboring LC-36A starting on May 3. Modifications included relocating the service tower levels, replacement of the launcher system and changes to the launch control system followed by a thorough checkout.

SC-5 with all of its appendages stowed shown being prepared for the Surveyor E mission. (NASA)

The first piece of mission hardware to arrive at Cape Kennedy was Surveyor SC-5 on June 28, 1967. The booster for the mission, designated Atlas 5901C, arrived at the Cape on June 30 and was erected on the pad at LC-36B on July 3. On the same day, the Centaur arrived followed by the nose fairing and the interstage adapter two days later. On July 6, the Centaur was added to the stack completing the on-pad assembly of AC-13.

A view of AC-13 on the pad being prepared to launch the Surveyor 5 mission. (NASA)

Following inspection and initial verification testing of SC-5, the spacecraft was temporarily fitted with a dummy retrorocket as well as test instrumentation and mated to its adapter on July 25. Encapsulated in its nose fairing, SC-5 was mated to AC-13 on July 28 for the beginning of prelaunch testing. Following the completion of the AC-13/SC-5 Joint Flight Acceptance Composite Test on July 31, the spacecraft was removed from the launch vehicle to start final preparations for its flight. The encapsulated SC-5 was mated to AC-13 on September 1 as the launch vehicle was completing its Composite Readiness Test. A problem was found with the propellant utilization system in Atlas 5901C which was swapped out on September 2 with the system from Atlas 5902C which was already at the Cape being prepared for the upcoming Surveyor F mission.

The final spacecraft readiness test began at 3:03 PM EDT on September 7, 1967 at the countdown time of T-680 minutes and was completed at 8:14 PM. The countdown proceeded smoothly until T-9 minutes 49 seconds when an indicator light in the blockhouse went out intermittently suggesting a possible problem with the launch vehicle stabilization pressure. A preplanned ten-minute hold at T-5 minutes was extended by 18 minutes until it was determined that everything was fine. The countdown restarted at 3:52 AM EDT on September 8 with liftoff finally taking place 3:57:01.257 AM EDT (07:57:01.257 GMT).

The launch of Surveyor 5 from LC-36B at Cape Kennedy on September 8, 1967. (NASA)

The new Atlas SLV-3C performed well and shutdown its sustainer engine just two seconds earlier than planned at 246.3 seconds after launch. Following a 329-second first burn of the Centaur’s pair of RL-10 engines (about nine seconds longer than planned), the Centaur and its payload were in a temporary 157.4 by 164.3 kilometer parking orbit with an inclination of 29.8°. After coasting for 402.5 seconds, the Centaur’s engines reignited this time for 114.2 seconds to send what was now designated Surveyor 5 into a 167.6 by 549,654 kilometer geocentric orbit towards the Moon. About 62 seconds later, Surveyor 5 separated from the spent Centaur stage and prepare for independent flight. Five seconds later, the Centaur turned and used its own hydrogen peroxide thrusters and the venting of its residual cryogenic propellants in a retromaneuver which moved the spent stage safely away from Surveyor 5 and placed it into a new 168.5 by 346,337 kilometer orbit which would miss the Moon by about 40,000 kilometers at about 12:40 GMT on September 11.


Disaster Averted

After separating from its spent Centaur upper stage, Surveyor 5 dutifully deployed its various appendages and started searching for its first attitude reference, the Sun, which it located 32 minutes after liftoff. A minute later, Surveyor made two-way contact with Earth-bound tracking stations. About six and a half hours after launch Surveyor 5 locked its star sensor onto Canopus at 14:28 GMT settling into its proper cruise attitude. Checkout of the spacecraft systems indicated all was going well.

Tracking of the receding Surveyor 5 showed that it would miss its intended target point on the Moon by only 46 kilometers. Surveyor 5 was commanded to turn and at 01:45:02 GMT on September 9, it fired its trio of vernier engines for 14.29 seconds to change its velocity by 14.0 meters per second. This delta-v not only cancelled out the aiming error but also modified the approach trajectory to optimize the descent conditions unto the lunar surface.

This diagram illustrates the typical sequence of events for Surveyor to perform a midcourse correction. Click on image to enlarge. (NASA)

After this midcourse correction burn, however, it was discovered that the helium pressurant for the vernier engines’ propellant tanks was leaking into space. In the eighteen hours since launch, the pressure in the helium tank had dropped from 35,850 kilopascals (kPa) to only 20,680 kPa. This gas was needed to force the propellants out of their tanks and into the engines. When the pressure in the propellant tanks fell below 3,790 kPa, the verniers would no longer work and Surveyor would be unable to land.

Engineers quickly determined that the cause of the leak was a faulty regulator valve and that the helium was leaking directly into the propellant tanks. These tanks’ pressure relief valves would then bleed off excess gas once the pressure reached 5,690 kPa. In an effort to get the faulty regulator valve to reseat itself properly, ground controllers fired the vernier engines for ten seconds starting at 02:12:02 GMT and again for 23 seconds at 02:39:50 GMT. Neither of these burns had the intended effect and the helium pressurant continued to leak slowly past the regulator valve. At 04:18:48 GMT, the vernier engines were fired for 12 seconds and then again immediately afterwards for a pair of short half-second bursts in a last attempt to fix the valve as well as move the spacecraft back towards its intended aim point. Again, the suspect valve continued to leak.

A schematic diagram of Surveyors vernier propulsion system. The helium pressure regulator just below the helium tank at the top of the diagram failed causing the gas leak. Click on image to enlarge. (NASA)

With the mission in jeopardy, engineers began to examine their options to salvage the Surveyor 5 mission. One option, which was quickly rejected, was to fire the retrorocket while the verniers still worked to place Surveyor 5 into a highly elliptical orbit around Earth in order to gather at least some engineering data from the mission. Instead, calculations and tests performed on Earth with the SC-6 spacecraft being prepared for the Surveyor F mission had shown that a lunar landing was still possible with a modified fast-descent profile with key commands radioed to the spacecraft in real time. If the retrorocket was fired 12.33 seconds later than normal, just enough helium would be left to quickly reach the surface, which would now be only 1,400 meters away instead of about 9,140 meters at burnout during the normal descent sequence. Split second timing was absolutely essential for this to work. A one-second delay in retrorocket burnout, which was possible given the state of solid rocket technology in 1967, or a slightly out-of-nominal performance by any combination of key systems could result in a crash.

This schematic diagram shows the major milestones of the Surveyor 5 voyage to the Moon. Click on image to enlarge. (NASA)

At 08:24:02 GMT, ground controllers fired the vernier engines for 33.0 seconds for a delta-v of 32.4 meters per second. Not only did this firing slightly alter the course of Surveyor 5, the burning of the 12.2 kilograms of propellant lightened the spacecraft and left just enough propellant remaining in the tanks as well as adequate helium gas in the propulsion system to optimize the length of the vernier engine burn. One last course correction burn of 5.45 seconds starting at 23:31:00 with a delta-v of 5.3 meters per second set Surveyor 5 back on course. About fifteen hours later on September 10, the helium leak stopped as predicted when the pressure inside of the spacecraft’s propulsion system stabilized at about 5,690 kPa.

A plot showing how the helium pressure decreased over time with key engine burns indicated. Click on image to enlarge. (NASA)

With the new landing sequence loaded on a tape recorder to be transmitted to Surveyor 5 in real time, the probe approached the lunar surface on September 11. As the lander’s slant range hit the 96.5-kilometer mark at 00:44:37.85 GMT, the tape was started 141.41 seconds before the predicted landing time. The normal retrorocket ignition altitude of 83.5 kilometers was passed and Surveyor continued to accelerate towards the lunar surface. At 00:44:50.19 GMT the vernier engines were started at an altitude of 45.7 kilometers followed 1.07 seconds later by the ignition of the TE-M-364 solid propellant retrorocket. Two seconds before the retrorocket thrust tailed off to zero, the explosive bolts holding the retrorocket in place were blown early by ground command in order to activate the landing radar and allow it to lock onto the approaching surface a precious few seconds early. The retrorocket was then held in place by its own thrust for the remainder of the burn.

Burnout of the retrorocket occurred just 0.31 seconds earlier than predicted at an altitude of 1,265 meters with Surveyor 5 descending at a speed of only 25 meters per second instead of the 152 meter per second expected during a normal descent. With the vernier engines already throttled up to full thrust, control of the descent was passed to the onboard computer control system at 00:45:41.16 GMT. Surveyor 5 automatically shutdown its engines as intended at an altitude of four meters and contacted the lunar surface at 00:46:44.284 GMT at a speed of 4.3 meters per second skidding about a meter sideways before coming to rest. Surveyor 5 was safely down on the lunar surface at 1.50°N, 23.19° E or about 32 kilometers northwest of its pre-midcourse aim point. This large error was mainly due to the trajectory uncertainties resulting from the limited tracking time between the multiple burns of the vernier engines during the trip to the Moon. Upon touchdown, the propellant tank pressure was 3,830 kPa or only 40 kPa above the safe minimum operation limit.


Operations on the Lunar Surface

About an hour and 18 minutes after landing, Surveyor 5 started returning the first 18 high-quality 200-line television images via its low gain antennas before the spacecraft was configured to begin transmission of higher resolution 600-line images. After some difficulty, the first batch of 142 600-line images were received to reveal that Surveyor 5 had come to rest inside of a rimless 9 by 12-meter crater on a slope of about 20°. It was the resulting tilt of the spacecraft which made it difficult to get Surveyor’s high gain antenna properly aligned to transmit images and other data.

The first 200-line television image returned by Surveyor 5 after it has successfully landed showing part of the spacecraft and the lunar surface. (NASA)

About 11½ hours after landing, commands were sent to deploy and partially lower the sensor head of the Alpha Scattering Experiment towards the lunar surface in order to obtain background radiation data. At 15:36:03 GMT on landing day, the sensor head was finally lowered the rest of the way to the lunar surface to begin collecting data. A total of 83 hours of readings were accumulated during the first lunar day of operations allowing scientists to get their first look at the composition of the surface of another world. The mix of elements present in the lunar soil was dominated by oxygen, silicon and aluminum and was consistent with that of terrestrial basalt – the most common rock type on Earth which covers most of the ocean basins and is found in many terrestrial volcanic structures. Images of the pair of bars on one of Surveyor’s landing pads showed that soil preferentially stuck to the magnetic bar instead of the non-magnetic one suggesting the presence of a magnetic component in the lunar soil. These findings were confirmed with the return of the first samples of the lunar surface from the Apollo 11 mission which landed about 25 kilometers to the southeast of Surveyor 5 two years later.

The sensor head of the Alpha Scattering Experiment shown deployed on the lunar surface. (NASA)

At 05:38 GMT on September 13 (about 53 hours after landing), the vernier engines were fired for 0.55 seconds to see how they might erode the lunar surface. Television images showed no dust cloud was produced by the firing and only three or four out of five observed clods of soil near the lander’s engines had moved. While the attitude of the spacecraft had changed slightly as a result of the firing, the sensor head of the Alpha Scatter Experiment had moved about ten centimeters after about 18 hours of measurements had been taken in its original location. This allowed another 65 hours of readings to be accumulated in a slightly different location.

Footpad #2 of Surveyor 5 showing how the effects of its one-meter skid upon landing on the lunar surface. (NASA)

During local high Sun, operations on the lunar surface were curtailed because of high spacecraft temperatures. The unexpected tilt of Surveyor 5 had increased solar heating on key parts of the spacecraft. Minimizing use of heat-producing equipment as well as using the mast-mounted solar panel and high gain antenna to shade critical components helped to keep the temperatures down. Afterwards, the spacecraft resumed normal operations collecting images and other data after losing about 28 hours of operation time. Although the focus, zoom and color filter controls on the camera became inoperative, television images were still obtained using a fixed-focus mode.

A mosaic of television images showing the Surveyor 5 landing site and the lengthening shadow of the spacecraft. The curved horizon is an artifact caused by the combined tilt of the television camera and spacecraft. Click on image to enlarge. (NASA)

In order to improve the chances of Surveyor 5 surviving the long lunar night, operations near the end of the first lunar day were carefully planned to ensure that the battery was fully charged at sunset which occurred at 10:56 GMT on September 24, 1967. Preceding this event, a preplanned sequence of television images were returned to observe the progression of shadows across the lunar surface. After sunset, the camera was used to observe the solar corona as well take three images the spacecraft and lunar surface illuminated by Earthshine. A total of 18,006 television images had been returned during this first lunar day of operation.

A television image showing the Sun’s corona above the tilted lunar horizon as it appeared after local sunset. This five-minute exposure was taken on September 24, 1967 at 13:20:03 GMT with the position and size of the Sun indicated by the white disk. (NASA)

About four hours after sunset, the solar panels and high gain antenna were repositioned in anticipation of restarting operations the next lunar day. Low-level operations of the spacecraft continued into the lunar night to obtain more lunar thermal measurements. Due to the limited battery capacity, ground controllers finally commanded Surveyor 5 to shutdown at 06:36 GMT on September 29, 1967.

After hibernating for 16 days, commands were sent to reactivate Surveyor 5 at 08:07 GMT on October 15 after the spacecraft had several days to warm up in the sunlight. The spacecraft responded immediately although some of its systems had degraded during the long lunar night with surface temperature dipping to an estimated -150° C. Despite the decrease in image quality caused by a video preamplifier problem, Surveyor’s television camera managed to return 1,048 more pictures during the second lunar day. Another 22 hours of data from the Alpha Scattering Experiment was also returned although detector noise issues degraded data quality. On October 18, Surveyor 5 observed a total eclipse of the Sun by the Earth (i.e. a lunar eclipse as viewed from the perspective of the Earth) allowing valuable data on the thermal properties of the lunar surface to be acquired. The spacecraft was shutdown for a second time on November 1 about 200 hours after local sunset.

Plot showing how the brightness temperature of the lunar surface changed during an eclipse on October 18, 1967. Click on image to enlarge. (NASA)

While attempts to recontact Surveyor 5 during its third lunar day were unsuccessful, ground controllers did hear from the spacecraft on the fourth lunar day. It managed to return another 64 200-line images before it was last heard from at 04:30 GMT on December 17, 1967. And so ended the highly successful mission of Surveyor 5 which had been recovered from what would surely have been another disappointing failure by the ingenuity of the people who built and operated this innovative robotic spacecraft. Just two more Surveyor missions remained before NASA would start sending astronauts to our nearest celestial neighbor.


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Related Reading

For more articles on NASA’s Surveyor program, check out Drew Ex Machina’s Surveyor Program page.


General References

Raymond N. Watts, Jr., “How Surveyor 5 Was Saved”, Sky & Telescope, Vol. 34, No. 5, pp 305-307, November 1967

Fifth Surveyor Soft-lander Due for Launch, NASA Press Release 67-227, August 31, 1967

Surveyor V Flight Performance Final Report, SSD 68189-5, Hughes Aircraft Company, November 1967

Surveyor V A Preliminary Report, SP-163, NASA, December 1967

Surveyor V Mission Report Part I. Mission Description and Performance, Technical Report 32-1246, JPL, March 15, 1968

Flight Performance of Atlas-Centaur AC-13, AC-14, AC-15 in Support of the Surveyor Lunar Landing Program, TM X-1844, NASA Lewis Research Center, February 1970