Surveyor 5 essay by Hamish Lindsay

Surveyor 5

by Hamish Lindsay.

Surveyor 5.

Launched : 0757 UT (1757 AEST) Friday 8 September 1967.
Landed : 0046:42 UT (1046:42 AEST) Monday 11 September 1967.
Location : Lat: 1.461°N by Long: 23.195°E in Mare Tranquillitatus
Final LOS : Sunday 0430 UT (1430 AEST) 17 December 1967

The primary objective for this mission was to:
(1) Perform a soft landing on the Moon in Mare Tranquillitatis.
(2) To obtain post landing television pictures of the lunar surface.

The secondary objectives were to:
(1) Conduct a vernier engine erosion experiment.
(2) Determine the relative abundances of the chemical elements in the lunar soil by operation of the alpha-scattering instrument
(3) Obtain touchdown dynamics data.
(4) Obtain thermal and radar reflectivity data.

Surveyor 5 was the first lunar soft-landing spacecraft ever to obtain information about the chemical nature of the lunar surface. This was achieved through two experiments:
(1) Obtaining the gross chemical composition by an alpha particle backscattering instrument.
(2) Obtaining some magnetic characteristics of the surface material with a bar magnet.

Prime tracking station support was provided by DSS11 (Goldstone, California), DSS42 (Tidbinbilla, Australia) and DSS61 (Madrid, Spain) to provide tracking data, telemetry, video and command functions.

Additional support was provided by the Air Force Eastern Test Range during the launch phase, DSS71 (Cape Kennedy), DSS72 (Ascension Island), DSS51 (Johannesburg), the 64 metre diameter dish DSS14 (Goldstone) and DSS12 (Goldstone). All tracking and telemetry data was sent to Mission Control at the Space Flight Operations Facility (SFOF) at the Jet Propulsion Laboratory (JPL), Pasadena, California.

Launch.
Surveyor 5 was launched on an azimuth of 79.5º on 8 September 1967 at 7:57:01 UT (1757:01 AEST) from Eastern Test range launch complex 36B at Cape Kennedy on an Atlas-Centaur D SLV-3C AC13 rocket. The Centaur’s first burn placed the spacecraft into an Earth parking orbit.

Flight.
The Centaur was then restarted 6.7 minutes later, and injected Surveyor 5 into a lunar transfer trajectory. After separation from the Centaur, Surveyor 5 executed the automatic antenna, solar panel and Sun acquisition procedures, then, at 14:27:01 UT (0029:01 AEST on 9 September), the star sensor locked onto the guiding star Canopus, and the spacecraft settled down to cruise-mode.

A midcourse trajectory correction involving a 14.01 metres per second velocity correction with a 14.29 firing of the vernier engines was performed at 01:45 UT (1145 AEST) on 9 September.

Immediately following the manoeuvre, the spacecraft began losing helium pressure at an alarming rate. It was concluded that the helium pressure valve had not sealed tightly, probably due to a particle lodged in the valve seat. This caused the helium to leak into the propellant tanks, creating an over pressure which opened the relief valves to discharge the excess helium overboard. Five emergency vernier firings did not dislodge the suspected particle. It soon became apparent the loss of Helium at his rate would jeopardise a normal landing, so a new, emergency landing plan was adopted.

Early vernier engine firings were made while there was still Helium to slow the spacecraft, reduce its mass, and leave more free volume in the propellant tanks for the Helium. The burn of the main retrorocket was delayed at an altitude of 1,300 meters with a velocity of 108 kph, rather than the planned 10,700 meters at 486 kph.

Landing.
After nearly 65 hours of flight the spacecraft arrived at the Moon, but the helium leak had pressurised the vernier engines, which could have jeopardized the mission. However, an improvised braking sequence that fired the engines 42 kilometres above the surface brought the spacecraft down in 106 seconds from a height of only 1.34 kilometres. This saved the spacecraft from running out of helium, which could have shut the engines down prematurely from lack of pressure, and the vehicle would have been destroyed.

The new descent profile worked flawlessly, and Surveyor 5 arrived 4.8 metres above the lunar surface. At this point the vernier engines shut down and the spacecraft free fell. It touched down 64 hours 49 minutes 43 seconds after launch on the lunar surface on 11 September 1967 at 00:46:44 UT (1046:44 AEST) at Latitude 1.461ºN by Longitude 23.195ºE, in a 9 x 12 metre rimless crater in southwest Mare Tranquillitatis. It skidded down a 20º slope for 1.7 seconds before coming to a stop. Soil pushed onto a magnet mounted on one of the legs measured the amount of meteoritic iron in the soil as less than 1%, much less than scientists expected. Touchdown was 29 kilometres from the planned target, 35 hours after local sunrise, with the Sun 17º above the horizon.

Lunar Surface Activities.
Surveyor 5 returned 18,006 television pictures during its first lunar day, mostly through DSS11 (Goldsone) and DSS42 (Tidbinbilla). The quality of these pictures surpassed the first two landers due to the camera’s increased sensitivity and cleaner optical components after landing. They included views of the interior of the crater it had landed in, the mare surface around the crater, the stars and planets and a solar corona following local sunset.

The alpha-scattering instrument was deployed and performed the first in-situ analysis of an extraterrestrial body, returning 83 hours of data on lunar soil composition during the first lunar day. It was designed to detect the five elements expected to be especially abundant in Moon rocks (oxygen, silicon, aluminium magnesium, and sodium) and indirectly for three more (calcium, iron, and titanium). Only the upper skin of the lunar surface was analysed, finding the soil consisted of basalt, a type common on Earth, as well as establishing some history of lunar melting.

A vernier engine erosion experiment was conducted on 13 September, about 53 hours after landing, consisting of a firing of the vernier engines for 0.55 seconds while the spacecraft sat on the ground to examine the effects of high velocity exhaust gases on the lunar surface.

The spacecraft shut down on 24 September 1967, for the first lunar night. After a warm-up period in sunlight 20 days later, the spacecraft responded immediately to the first turn on command sent at 08:07 UT (1807 AEST) on 15 October, and operated until sunset of the second day on 23 October. Although the performance of the camera had deteriorated due to a video amplifier problem, an additional 1048 pictures were taken. Partial compensation was achieved for the degraded picture quality by greatly increasing the gain of the ground recorders. An additional 22 hours of alpha-scattering data was received during the second lunar day, though some detector noise posed some problems with the data reduction.

On 18 October Surveyor 5 acquired thermal data during a total eclipse of the Sun. Transmissions for the second day were received until 1 November, 1967, when shutdown for the second lunar night occurred about 200 hours after sunset.

Surveyor 5 revived after four lunar nights.

During an attempt to revive Surveyor 6 by DSS11 (Goldstone) on 14 December, a non-scheduled Surveyor 5 revival attempt was initiated. To everyone’s surprise Surveyor 5 responded immediately with good signals, even though it was in its fourth lunar day. During DSS11’s view period on 15 December, 67 pictures were received with images that were recognisable but of poor lighting quality, similar to those received during the second lunar day. Alpha Scattering and television science were also received, but were also minimal due to degradation of the systems. Surveyor 5 abruptly stopped transmitting when DSS11 commanded the spacecraft to go to high power mode. The final transmission occurred at 04:30 UT (1430 AEST) on 17 December, 1967. Pictures were transmitted during the first, second, and fourth lunar days, ending with a total of 19,118 images.

Alpha-scattering results indicated soil composition, resembling Earth basaltic rock, of 53% to 63% oxygen, 15.5% to 21.5% silicon, 10% to 16% sulphur, iron, cobalt, and nickel; 4.5% to 8.5% aluminium, and small quantities of magnesium, carbon, and sodium. The quantity of material adhering to the magnet was consistent with a mixture of pulverised basalt and 10% to 12% magnetite with no more than 1% metallic iron.

The vernier engine experiment produced minor but observable erosion of the surface.
All Surveyor 5 mission objectives were accomplished.

On 21 November 1967, Oran Nicks, Deputy Administrator for Space Science and Applications wrote,

“In the annals of space exploration a particular place must be reserved for the fifth in the Surveyor series. Regardless of the refinements in measurements of the lunar surface in the future, Surveyor 5 will be remembered as having first performed one of man’s most extraordinary technical feats; a remotely conducted analysis of the chemical constituents on an extraterrestrial body in our solar system.”

Less than two years later, Apollo 11 landed 60 kilometres away and brought back rocks with a chemistry similar to Surveyor’s analysis. Surveyor 5 landed on the oldest mare surface visited by any of the Surveyors.

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