by Kaye Dee

It’s been a busy month in deep space exploration, with new space probes exploring the Moon and conditions in interplanetary space, while another step forward in testing the hardware for the Apollo programme has just taken place.

Surveying the Moon

NASA may have called its lunar soft lander Surveyor 1, but its latest lunar mission, Lunar Orbiter 1, is actually surveying the Moon from orbit. It is the first of a series of Lunar Orbiter spacecraft that NASA wants to send to the Moon, with a launch planned every three months to obtain high-resolution photographs of potential Apollo landing sites. These probes will also extensively map the Moon’s surface with a resolution of 200 feet or better and study the Moon’s gravitational field as well as its radiation and micrometeoroid environments. The Boeing Missile Production Centre in Seattle is building the solar-powered spacecraft, with NASA’s Langley Research Centre managing the project.

Launched on 10 August (US time), Lunar Orbiter 1’s goals include imaging nine primary and seven secondary potential Apollo landing sites on the Earth-facing side of the Moon at medium and high resolutions, as well as photographing 11 areas on the hidden lunar far side at lower resolution. Although the spacecraft experienced a temporary failure of its navigation system (based on tracking the star Canopus) and overheated too, both these problems were resolved by the time it reached the Moon.

After a 92-hour cruise, Lunar Orbiter 1 entered an elliptical 117-by-1,160-mile orbit around the Moon, to become the first US probe to orbit our natural satellite (the USSR’s Luna 10 became the first spacecraft to orbit the Moon back in April). On 15 August, Lunar Orbiter 1 activated its 145-pound camera system and began testing it by scanning and transmitting back to Earth several pre-exposed frames of film.

A Photography Studio in Lunar Orbit

Photography is critical to the purpose and success of the Lunar Orbiter missions, and the advanced Lunar Orbiter camera system has been built by Eastman-Kodak. Rumours I heard during my recent visit to Woomera indicate that it is based on a system originally designed for a classified military satellite. Lunar Orbiter’s “camera” is actually a double instrument, using two lenses to take a wide-angle medium-resolution shot and a high-resolution image on the same film. The narrow angle, high-resolution camera has a resolution of just three feet, while the resolution of the wide-angle camera is 25 feet.

The first medium-resolution image taken by Lunar Orbiter 1, showing part of the Mare Smythii region

Once it takes a picture, Lunar Orbiter functions as a photography studio in space, developing its film onboard using a semi-dry process. The developed film is scanned in narrow strips using a photomultiplier, with the scans transmitted back to Earth. The signals are then reconverted into photos in a way that is quite fascinating. I was fortunate enough to see this process for myself while I was visiting NASA’s Island Lagoon deep space tracking station near Woomera last week. The signals representing each scanned strip are reconverted to images on film and then each strip is laid on a board, one beside the other, to build up the photograph. Once all the film strips comprising the complete frame have been received and laid out, the final image is photographed. This produces the “striped” effect seen in the pictures that NASA has already released.

Getting to Work

Lunar Orbiter acquired its first images of the Moon on 18 August, taking 16 high-resolution and four medium-resolution frames. While the medium-resolution photos were of good quality, a problem with the spacecraft’s motion compensation system caused blurring of the early high-resolution images, although this has now been resolved. A separate issue with the film developing system has also required the film to be advanced more frequently than planned, resulting in the need to take additional unplanned photographs. This has proved a bonus for mission managers, enabling them to shoot additional photographs at unusual oblique angles by temporarily reorienting the spacecraft. Perhaps these special images will produce useful perspectives that can be more fully explored on later Lunar Orbiter missions.

A medium-resolution view of the Moon's heavily-cratered far side, with the unusual crater Tsiolkovsky (with the dark interior) appearing in the top right

Initially, Lunar Orbiter concentrated on imaging the Moon's hidden side, of which we know so little, before moving on to its main task of surveying the proposed Apollo landing sites. On 20 August, the spacecraft altered its orbit to approach as close as 36 miles above the Moon’s surface, and on 25 August, it lowered its orbit still further, to 25.2 miles, to get the most detailed views of potential Apollo landing sites. This will help scientists to determine which ones will be safest for the first manned missions to the Moon.

An Historic Image

On 23 August, as Lunar Orbiter 1 emerged from behind the Moon, it captured what has to be one of the most important images so far produced in space exploration: a view of the Earth appearing to rise over the lunar horizon. This is the first time that our home planet has been photographed from so far out in space, and also the first time that the Earth and the Moon have appeared in the same picture. The hi-resolution image, seen below, is breathtaking in black and white – I just wish it could be reproduced at a larger scale here. so that you could see all the detail it provides. Just imagine how much more spectacular this view of the Earth will be when we can finally see it in colour, perhaps taken when the first Apollo astronauts orbit the Moon! 

As I write this, Lunar Orbiter has recently taken another image of the Earth from the Moon and is continuing its primary task of imaging Apollo landing sites. The spacecraft will soon run out of film and take its last photographs, although transmission of the 200 or so scanned images may not be completed until mid-September. Its photography mission may then be over, but the probe will continue to return data on radiation and micrometeoroid conditions around the Moon. Once its maneouvring fuel is almost depleted, ground controllers will command Lunar Orbiter 1 to de-orbit and crash onto the Moon. This will ensure that its presence as a dead satellite in orbit will not interfere with future Lunar Orbiter or Apollo missions.

Prelude to Apollo

While Lunar Orbiter has been assisting the Apollo programme with its work in lunar orbit, here on Earth the latest step forward in the manned lunar program has just taken place. 25 August saw the sub-orbital flight of AS-202, the second unmanned test flight of a production Block I Apollo Command and Service Module and the third for the Saturn 1B rocket.

Originally intended as the second test flight of the Saturn IB vehicle, the mission was delayed until after AS-203 because its Apollo Command and Service Module (CSM-011) was not yet ready. CSM-011 is essentially a production model capable of carrying a crew, although it was not fully fitted out and lacked the crew couches. This was the first flight of the spacecraft’s guidance and navigation system as well as the fuel cell electrical system. The flight was also designed to test the Command Module’s heat shield.

The performance of the Saturn 1B was perfect, putting the spacecraft into a ballistic trajectory. Separating from the launcher’s second stage at an altitude of 419.8 nautical miles, the CSM was pre-programmed to make four burns to test its service propulsion system (SPS). The first, and longest, burn lasted 3 minutes, 35 seconds, lifting the spacecraft apogee to 617.1 nautical miles, 874.8 nautical miles downrange. The two final burns lasted only three seconds each, designed to test the rapid restart capabilities of the engine.

The spacecraft performed a skip re-entry to shed speed. It first descended to 36 nautical miles before lifting back up to 44 nautical miles and descending again. The Command Module splashed down south-east of Wake Island, about 205 nautical miles from the target landing site, but was retrieved by the aircraft carrier USS Hornet.

The success of this flight indicates that the Block I spacecraft and Saturn IB are ready to carry a crew into orbit, so the next mission, AS-204, may well be manned. What an exciting development that will be!

Continually Pioneering

Moon missions, manned spaceflight and planetary explorers capture the attention of the public, but NASA’s Pioneer series of probes are quietly continuing to gather scientific information about the Sun and conditions in interplanetary space.

Launched on 17 August, Pioneer 7 joins its predecessor Pioneer 6, as the second of five spacecraft designed to make a long term study of the solar wind, solar magnetic field and cosmic rays. This research will contribute to the Apollo programme as well, by producing a better understanding of the radiation environment that the astronauts will encounter on the Moon, which is not protected by a magnetic field like the Earth.

NASA illustration depicting the locations in interplanetary space of the Pioneer 6, 7 and the future Pioneer 8 (Pioneer C) spacecraft 37 days after launch

Where Pioneer 6 is orbiting the Sun between the orbits of Earth and Venus, Pioneer 7 is heading 12 million miles beyond Earth’s orbit, taking up station at approximately 1.1 Astronomical Units, between the orbits of Earth and Mars. Its 140-pound package of seven scientific instruments is the same as that carried on Pioneer 6. One of these instruments, the cosmic ray anisotropy experiment, was developed by Dr. Ken McCracken, an Australian physicist interested in the hazards of space radiation to astronauts and the behaviour of cosmic rays. With professorships at both the University of Adelaide and the University of Texas, McCracken is earning himself the nickname “Sir Launchalot” for the number of instruments he has already flown on satellites, sounding rockets and high-altitude balloons!

With NASA’s Ames Research Centre as the project managers, Pioneer 7 was built by TRW and is identical to Pioneer 6. Each spin-stabilised spacecraft is cylindrical, with the main body measuring 37 inches in diameter by 35 inches high. Solar panels are mounted around the body, with a long magnetometer boom extending 82 inches long. The antenna mast is 52 inches long and the entire spacecraft weighs approximately 150 pounds. The spacecraft have a design life of six months, but Pioneer 6 has already outlived that, and there is every expectation that Pioneer 7 will exceed its design life as well.

Off the Earth

Perhaps the most fascinating aspect of this update is that all of the launches involve extraterrestrial destinations. The focus has turned from the Earth to its nearest neighbors. How far we have come in just a few years! Where might we be headed come 1970?

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