RANGER 7, THE FIRST CLOSE-UP MOON'S PHOTOGRAPHS

Today, The Grandma has been reading about Ranger 7, the NASA space probe, that sent back the first close-up photographs of the moon, with images 1,000 times clearer than anything ever seen from earth-bound telescopes, on a day like today in 1964.

Ranger 7 was the first NASA space probe to successfully transmit close-up images of the lunar surface back to Earth.

It was also the first completely successful flight of the Ranger program. Launched on July 28, 1964, Ranger 7 was designed to achieve a lunar-impact trajectory and to transmit high-resolution photographs of the lunar surface during the final minutes of flight up to impact.

The spacecraft carried six television vidicon cameras -two wide-angle (channel F, cameras A and B) and four narrow-angle (channel P)- to accomplish these objectives. The cameras were arranged in two separate chains, or channels, each self-contained with separate power supplies, timers, and transmitters so as to afford the greatest reliability and probability of obtaining high-quality video pictures.

Ranger 7 transmitted over 4,300 photographs during the final 17 minutes of its flight. After 68.6 hours of flight, the spacecraft impacted between Mare Nubium and Oceanus Procellarum. This landing site was later named Mare Cognitum. The velocity at impact was 2.61 kilometers per second, and the performance of the spacecraft exceeded hopes. No other experiments were carried on the spacecraft.

Although NASA had attempted to put a positive spin on Ranger 6 on the grounds that everything except the camera system had worked well, William J. Coughlin, editor of the publication Missiles and Rockets, called it a one hundred percent failure and JPL's record thus far was a disgrace. The mission had not been a complete failure, but Coughlin was not alone in his opinion that Jet Propulsion Laboratory in Pasadena, California, a nonprofit laboratory and extension of the California Institute of Technology (Caltech), was a soft academic environment without the drive or ambition needed to make the missions succeed. He considered Ranger a loser and for a while, anyone at NASA involved in the Ranger program tried to conceal it. It was also being said that sending probes up for the sole purpose of returning images was pointless and accomplished nothing that Apollo could not also achieve.

On July 6, Ranger 7 completed its ground testing and was stacked atop the booster. On July 9, a NASA committee met and deemed the booster and spacecraft fully ready for launch, which was targeted for the 27th.

The first countdown on July 27 failed due to a defective battery in the Atlas and a problem with the ground guidance equipment. The next day, all went smoothly and Ranger 7 lifted off from LC-12 at 12:50 PM EST. The weather was clear and cloudless on this launch and Atlas staging was observed by tracking cameras. The expected propellant cloud enveloped the booster, but no anomalous events occurred this time. Thirty minutes after liftoff, the Agena restarted to boost Ranger 7 on a trajectory towards the Moon.

The flight trajectory for Ranger 7 was quite accurate, but a short midcourse correction was carried out early on the morning of July 29 to ensure impact in the Sea of Storms instead of the far side of the Moon. The warmup period for the TV cameras would be performed earlier and made shorter than on Ranger 6. Out of fear of jeopardizing the mission, ground controllers decided that the probe's orientation was acceptable enough and they would not risk maneuvering with the attitude control thrusters to get into a better angle. At 6:09 AM PDT, the first video imagery reached Earth.

Ranger 7 reached the Moon on July 31. The F-channel began its one-minute warm-up 18 minutes before impact. The first image was taken at 13:08:45 UT at an altitude of 2,110 kilometers. Transmission of 4,308 photographs of excellent quality occurred over the final 17 minutes of flight. The final image taken before impact has a resolution of 0.5 metres.

The spacecraft encountered the lunar surface in direct motion along a hyperbolic trajectory, with an incoming asymptotic direction at an angle of -5.57° from the lunar equator. The orbit plane was inclined 26.84° to the lunar equator. After 68.6 hours of flight, Ranger 7 impacted in an area between Mare Nubium and Oceanus Procellarum (subsequently named Mare Cognitum) at 10.6340°S 20.6771°W.

The impact site is listed as 10.63 S, 20.66 W in the initial report Ranger 7 Photographs of the Moon. Impact occurred at 13:25:48.82 UT at a velocity of 2.62 km/s. The spacecraft performance was excellent and the success of the mission finally brought a turnaround in NASA's fortunes after the endless string of lunar probe failures since 1958.

Ranger 7 is credited for beginning the peanut tradition at NASA command stations. On the success of Ranger 7, someone in the control room was noticed eating peanuts. Since 1964, control rooms ceremonially open a container of peanuts for luck and tradition.

More information: NASA

We are probably nearing the limit 

of all we can know about astronomy.

Simon Newcomb