m10_v_bw_o_n (1973, unnumbered photo, poss. aka fig. 3-6a)

A nice photo-mosaic of lunar images taken by Mariner 10 shortly after launch.

~8.5” x ~11”. From the estate of Eric Burgess.

From the following extract of the online version of NASA SP-424, “The Voyage of Mariner 10”. Additionally, the image, linked to below, was used in Figure 5-9:

“…Very soon after launch, the planet-viewing experiments were turned on, a first time for planetary missions. The aim was to calibrate the instruments in the well-known environment of the Earth-Moon system. The charged particle telescope was turned on within 3 hours of liftoff, the ultraviolet experiment within 7 hours, and the TV cameras shortly thereafter. First TV pictures of Earth were obtained 16 hours and 15 minutes after liftoff.

There were some problems. The two thermal strap-heaters surrounding the aluminum lens barrels of the cameras were designed to hold the camera system at a temperature of 4 to 15°C (40 to 60°F). But they failed to operate as programmed following launch. Mission controllers, watching the engineering data coming back to the Mission Operations Center, saw that the heaters were not activated. Quickly a command was sent to the spacecraft to deactivate the heaters and then to activate them by triggering the relay switch, which seemed to have stuck. Nothing happened. The telescopes continued to cool down.

There was concern that without the heaters operating the television cameras would cool down too much and affect sensitive optics so as to distort pictures of the planets and cause a degradation of camera focus. Part of the problem was caused by the screening of the spacecraft against solar heating. It was so protected by a sunshade and by surface coatings and thermal blankets that when the camera heaters failed to come on, the cameras began to cool. Engineers from JPL and Boeing studied the problem to determine how heat might pass from the rest of the spacecraft in place of that missing from the heaters. They found that the thermal insulation of the spacecraft was so good that there was no way to heat the cameras from the spacecraft itself. The fall in temperature had to be lived with. They also checked the backup spacecraft poised at Cape Kennedy in an attempt to determine what might have caused the relay to stick. Had this problem degraded the spacecraft capability to an unaccepted degree, it would have been necessary to launch the backup.

Fortunately, the cooling stabilized at an acceptable level, and the cameras did maintain their sharp focus. The lens elements and the optical tube elements were self-compensating to changes in temperature. But an ever-present danger was that the Invar rods might contract, fracturing the vidicon potting compound if the temperature fell below -40°C ( - 40°F). Project scientists halted this temperature drop by keeping the vidicons switched on to maintain some heat within the cameras. Normally the vidicons would have been rested in the cruise between the planets, but it was considered prudent to change this mode of operation and take the chance that the lifetime of the vidicons might be shortened somewhat rather than risk the cameras' becoming too cold. This [47] being done, the temperature of the cameras stabilized, at low but livable values-the vidicons were about -10°C ( + 14°F), the backs of the optics were -20°C ( - 4°F ), and the telescope fronts were about -30°C ( - 22°F).

Mariner's cameras transmitted good pictures of the Earth and the Moon despite the temperature problem. The pictures of Earth (Fig. 5-2) provided stereo photographs of clouds with revealing depth and structure. They appeared to be the clearest pictures yet received from a television camera in space. If the spacecraft returned similar-quality pictures from Venus, the project could obtain a completely unprecedented look at the brilliant clouds of that mysterious planet.

In all, Mariner 10's cameras provided a series of five Earth mosaics (Fig. 5-3) within the first few days of flight. These mosaics revealed intricate cloud patterns at about the same resolution expected during the Venus flyby. The Earth pictures could provide valuable comparisons with the Venus clouds. Earth observations also provided in-flight verification of the cameras' "veiling glare" performance, thus confirming that the preflight calculations of settings of camera exposures for Venus were correct. This was important, since Venus encounter geometry did not allow an incoming far-encounter sequence to check the exposures.

Another problem arose almost at the beginning of the flight when, on November 5, the plasma science experiment was turned on. Scientists were surprised to find that no solar wind particles were being observed. There appeared to be a good vacuum in the detectors, and the device was scanning back and forth as it should. Engineers performed a series of tests and sequences of switching commands without positive results. One possibility was that the instrument door had failed to open so that plasma could not enter the detector. Another was that the high-voltage sweep was stuck at the high end, thus permitting only a few high-energy particles to register. The operation of this experiment was, unfortunately, restricted throughout the mission, and it was concluded that the protective door had failed to open fully. However, plasma data were obtained by the scanning electron spectrometer part of the instrument, which was unaffected by the failure of the door.

As the spacecraft left Earth, the ultraviolet air glow instrument looked back at the home planet, observing the same emission regions that it expected to check later at Venus and Mercury. Lyman-alpha hydrogen emission was recorded, together with helium emission at 584 angstroms.

All subsystems of the spacecraft were performing exactly as expected. The trajectory was also very good; less than 8 m/see (27 ft/sec) of the spacecraft's total maneuvering capacity of 120 m/sec (396 ft/sec) was expected to be needed to move the Venus aiming point of the spacecraft and change the arrival time about 3 hours to bring Mariner 10 to its later pass within 1000 km (600 mi) of Mercury's surface.

Mariner 10's series of five Earth mosaics was intermixed with six mosaics of the Moon (Fig. 5-4) within the first week of flight as calibration tests for the Mercury encounter. The path of Mariner allowed images to be obtained of the north polar region of the Moon (Fig. 5-5), which, because of constraints on paths of other space vehicles, had previously been covered only obliquely. The Mariner 10 photographs provided a basis for cartographers to improve the lunar control net, the relationship of points on the lunar surface one to another in precise definitions of lunar latitude and longitude of craters and other features. The exercise in lunar cartography provided a useful prelude to applying the same techniques to map Mercury using the images to be obtained during the flyby.

Diagnostic tests were conducted on November 6, including photography of stars (Fig. 5-6) and additional tests on the Moon (Fig. 5-7). The Moon tests, as well as providing better information about how the TV system was performing, allowed scientists to evaluate the practicality of proposed measurements of the diameter of Mercury. At this stage of the mission, optical performance of the television system continued to be good even though the TV optics had not yet stabilized in temperature. As of November 7, Mariner 10 had returned almost 900 pictures to Earth. Experimenters were enthusiastic about the excellent quality. The Moon pictures recorded objects a mere 3 km (2 mi) across (Figs 5-8 and 5-9 ).

history.nasa.gov/SP-424/p53.jpg

Since the pictures to be returned from Mercury were expected to be of three times higher resolution than those of the Moon, there was good reason for excitement. At last, it seemed, mankind would have a chance to resolve those dusky markings on the innermost planet, those indistinct features that earlier astronomers had interpreted as Marslike, even erroneously with linear "canal" type features. Another test conducted was photographing the Pleiades cluster in the constellation of Taurus: a galactic cluster in the Milky Way which is visible to the unaided human eye as seven faint stars and is often called the "Seven Sisters". These stars are about 20,000 light years from the Sun and are immersed in nebulosity. A total of 84 pictures were taken, verifying the focus of the television system.”

Above at:

history.nasa.gov/SP-424/ch5.htm

Taken on: October 17, 2022

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Sets appears in: • Breaking The Bonds & Firsts • Miscellaneous more » • Mariners To Mars, Mercury & Venus « less

Groups appears in: • Space Exploration • B&W more » • Astronomy, Stars, Planets and Space • Riding with Robots on the High Frontier • Space The Final Frontier • Space stuff « less

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