Flight performance

Of the seven missions, Surveyors 2 and 4 failed. Surveyor 2 crashed into the Moon at high speed as a consequence of the failure of one of the vernier thrusters during the mid-course correction. The resulting thrust imbalance caused the spacecraft to tumble. Operations continued, however, and although the situation could not be corrected, engineering information on the functioning of the spacecraft was gained prior to impact. Surveyor 4 operated nominally until contact was lost 2.5 minutes before touchdown, as the retro engine was completing its 40 s burn. Surveyor 5 managed to recover from a helium pressurant leak in the vernier system and land successfully, as detailed in Chapter 5.

The data from Surveyor 3 showed that it touched down on the lunar surface three times before landing, because the engines did not shut down as intended. The spacecraft moved 20 m between the first and second touchdowns and about 11m between the second and third. A final translation movement of about 30 cm occurred following the third touchdown. The engines were finally shut down prior to the third touchdown. This behaviour is thought to be the result of the radar beams traversing the lip of a crater during the final part of the descent.

During surface operations of the successful missions, a total of 87,674 TV images were returned (in either 200 and 600-line modes, some with colour or polariser filters). Many of the image frames were composited together manually to form panoramas. Targets for observations apart from the lunar surface (both undisturbed and disturbed) included the Earth, laser emissions from Earth, the solar corona, Mercury, Venus and Jupiter, and stars to 6th magnitude. The SMSS instruments on Surveyors 3 and 7 performed 1898 and 4397 mechanism movements, respectively, and carried out a total of 51 bearing, trenching or impact tests. The alpha-scattering instrument was deployed and operated successfully on Surveyors 5, 6 and 7, being lowered to the ground by a winch mechanism. On Surveyor 7, the availability of the SMSS allowed it to be repositioned to examine a different location. On several of the missions, thrusters were fired to look at plume impingement and dust contamination of the spacecraft. Surveyors 1, 5 and 7 were all successful in surviving at least one lunar night to be reactivated after sunrise.

As part of the surface mechanical properties investigation, Surveyor 6 performed a 'hop' manoeuvre, moving 2.4 m away from its original landing area. This manoeuvre, the first launch and controlled movement across the lunar surface, 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.

A 'Surveyor Block II' series of missions, carrying more payload and to act as scouts and target markers for particular Apollo landing sites, was studied briefly but never implemented. Another unflown proposal included a rover.

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