Mapping the Moon

Digital photography in an analog age.

Moon Map With Jim

Lunar Farside One

Prologue

Sputnik The space age began on October 4, 1957, when Soviet rocket scientists successfully inserted a 23" diameter artificial satellite into low Earth orbit. It was a propaganda coup, a shock to the American public, who feared that the Soviet achievement indicated that they had leapfrogged ahead of the US in the military use of space. The "Missile Gap," immediately became a feature of subsequent political discourse.

Sputnik ceased transmitting its trumphant little beeps in a few weeks, when its batteries died. A few months later it fell to Earth, a victim of atmospheric drag, but its place in history is secure

Eisenhower President Eisenhower viewed military involvement in civilian activities with suspicion. He was determined that space exploration, and the use of space for scientific purposes, should be separate, as far as possible, from the development of weapons of war. He was also mindful of the propaganda potential for the Soviets if the US space effort appeared going in that direction. The Soviets had no such sensitivity; they were not bashful about the fact that their space effort was directed toward achieving military superiority

A new agency, The National Aeronautics and Space Administration, was created on October 1, 1958. America already had an agency for aeronautics, The National Advisory Committee for Aeronautics. It was created on March 13, 1915, to promote and advance development of atmospheric flight. When NASA came into existence, all personnel and projects of NACA were transferred to the new agency, and NACA ceased to exist. Going forward, all matters concerning travel, exploration, or research above the Earth's surface would belong to NASA/.

Kennedy The election of 1960 brought a new president to the White House, and a new direction and greater urgency to American efforts in space. President Eisenhower's strict separation between military and civilian efforts in the development of space hardware relaxed a bit as NASA found that developing their own launch vehicles was impractical. A few months after President Kennedy's inauguration, he addressed a joint session of Congress on May 5, 1951. In his speech he announced his intentiion for the United States to put an American citizen on the moon by the end of the decade. Congress responded enthusiastically, and qjuickly passed the necessary enabling legislation. The Apollo project was born. In the end, it took eight years and 400,000 people to reach the president's goal. American citizens were the first in human history to walk on the surface of the Moon, but only after a long, steep, climb.

Vanguard No one ever said it would be easy, but the Soviets did their best to make it look that way. On April 12, 1961, Yuri Gagarin became the first human to travel in space, completing a single pass around the Earth. The first American in space was Alan Shepard, who flew a little over a month later.

Before the Mercury project, there were Vanguard and Explorer, 'civilian' scientific research projects. The Naval Research Laboratory team had originally planned to be the first to put a satellite in orbit. Their schedule was not very aggressive, and Sputnik 2 was in orbit before they made their first launch attempt. Shown live on nationwide television on December 6, 1961, the Vanguard rose about four feet off the pad, its engines shut off, it desceneded to the pad, and exploded. The payload satellite was destroyed.

The Army Ballistic Missile Aency had been working wih the Jupiter-C missile with promising results. A fourth stage was added to the Jupiter-C to carry the Explorer satellite, built by the Jet Propulsion Laboratory in California. The modified Jupiter was known as Juno. Launched on January 31, 1958, it was a complete success. The first sattelite designed to collect data about near-Earth space, Explorer disclosed the existence of concentric spheres of charged particles which surround the planet and provide a measure of protection from cosmic radiation. Furthermore, Explorer 1 is up there today, Eath's oldest man-made celestial companion.

Worker bees

Following the success of Explorer, launching of satellites was left to the scientific communiy, based on their needs from time to time. When the number of experiments ready to go to space justified the launch cost, they flew. The main line of work was preparation for going to he Moon. To this end, the Mercury Project flew 20 uncrewed missions between the first Explorer and the first crewed, sub-orbital flight. The first American astronaut was Alan Shepard, carried aloft in Mercury capsule "Freedom 7" on May 5, 1961. The flight lasted 15 minutes and 28 seconds. Astronaut Virgil Grissom was next, on July 21, 1961, in "Liberty Bell 7."

Astronaut John Glenn was the first American to orbit the Earth. On February 20, 1962, His ship, "Friendship 7," lifted off for a planned 7-orbit flight. He circled the Earth three times before problems with the capsule's heat shield made it necessary to terminate the flight and return to Earth. Cosmonauts Gagarin (once) and Titov (one day) had preceded him, Gagarin in 1961. In all, three American astronauts and two Soviet cosmonauts made orbital flights in 1962. Highlights of 1963 were the flight of Valentina Tereshkova, the first woman in space, in "Chalka (Seagull)," on June 16, and the start of the Lunar Orbiter Project.

The first flight with passengers was the only notable event in space in 1964. Those on board were Cosmonauts Vladimir Komarov, the pilot, Konstantin Feoktitsov, an author of books on technology, and Bolris Yegorov, a physician and expert on problems with the sense of balance.

Cosmonauts Boris Belyavyev and Pavel Leonev kicked off 1965 by missing their landing zone, landing in a remote part of the Ural mountains on their return from the first spacewalk, which had been performed by Leonov. They spent two days lost in the mountains before they were found. That was the last Soviet flight for that year. In the US, that same month saw the start of the Gemini Program, with Astronauts Grissom and Young making the first tandem flight.

1966 was busy, with Gemini fligts 6 through 12, learning to space walk, to use tools in space, and to dock with another vehicle. After three years of development, Lunar Orbiter 1, the first of six planned flights, was launched on August 10, 1966, followed by another flight in the same year, and three more in 1967. The spcecraft and it's photographic subsystem worked so well, the sixth flight was cancelled.

As a direct consequence of the flight of Lunar Orbiter 1, I ceased being a spectator of the space race, and became one of NASA's thousands of anonymous worker bees. In the years since I was one, they made a movie about three of them, and one of them, determined lady named Nancy Evans, spent forty years and a lot of her own money, doing what I'm describing here over again, with better tools, and much better results. Her labor of love was called the Lunar Orbiter Image Recovery Project. You can find it on NASA'a web site under LOIRP>

Worker bees

The scriptures tell us that Hiram of Tyre built the temple of Solomon. In several places he is described as doing this, or that, or something else. Hiram was a widow's son who became the King of Tyre. It is doubtful that, as king, he ever got his hands dirty. The job took many years. There must have been hundreds of people we have never heard of working on it at one time or another. So it is with the American Space effort.

Of the 400,000 people involved, 399,750, give or take a few dozen, are people you never heard of, the worker bees that keep the hive alive. "Busy as a bee," doesn't refer to the Queen. The film, Hidden Figures, put a spotlight on three of those worker bees who performed essential tasks, and were forgotten for half a century. What follows is the tale of a few other worker bees, likewise unknown for many years, who only escaped obscurity because a friend, Glenn Oscarson, invited me to tell the story to the Salt Lake Astronomical Society as part of their celebration of the 50th anniversery of the first Moon landing.

Earthrise

The pictures from the Lunar Orbiter were intended to be used to make contour maps of potential landing sites on the moon. As an historic artifact, the picture above is p[riceless. As a photograph, it's terrible. For it's intended purpose, it's useless. Much useful information about the Moon was being accumulated by on-going Orbiter flights, but no better images could be produced, using the equipment available to the people who had to have them.

It was unthinkable to ask an Astronaut to land, blind, on a surface whose irregularity was obvious from 380,000 miles away. The Ural mountains are one thing. The Moon is another. Maps had to be available, or there would be no Moon landing.

Boeing and Kodak did a wonderful job when they designed and built the Lunar Orbiters. Placed in orbit around the Moon, their performance was all they could have asked for, and more. Then, here on Earth, something went horrbly wrong. The Orbiters kept flying, returning a great volume of priceless information which could be obtained no other way, while NASA went hunting for someone who could spin straw into gold.

The Adventure Begins

The first stop on the tour was the Aeronautical Chart and Infomation Center in St. Louis, Missouri. They said it looked impossibe, but maybe the aero reconnaissance people could do it, or knew some folks who could. The next stop was Wright-Paterson AFB, to talk to the people responsible for getting every possible bit of useful information out of an aerial photograph. They frquently had to work with irrreplaceable images obtained in adverse conditions. They said it looked difficult, but not impossble, and sent them up the street to one of their contractors, a small company called Data Corporation.

Data Corporation, in Beavercreek, Ohio, was located a few miles from W-P AFB, and specialized in optics, purpose-built electronics, and field support for anything involving reconnainnsnce and or surveillance. Data Corp had recently acquired a new IBM 360/40 computer for another USAF contract which could, possibly, be used for NASA's work while that project got up to speed. The piece de resistance, however, to the people from NASA, was the Data Corp Microdensitometer, which had recently been completed, and which was ideally suited to the task at hand.

NASA put the question to Data's executives, "Can you do it?" Jack Finley, the VP of engineering, gathered a number of us in a conference room, showed us what we had to start with, and what we had to end up with. We all sat there, staring at the board. Finally, I said to Richard, "If you had a giant matrix, with a place for every pixel in the finished image in it's ideal location, and another giant matrix with a place for every pixel where the Micro-D finds it in the pile of filmstrips, do you think you could drag all the pixels into their proper places?" Richard said he could. I turned to Davey and asked, "Can you keep track of all the pieces of two four-million-byte images while you move them in and out of the computer's quarter-million-byte memory without losing, anything while Richard keeps mvimg them around?" He said it would be slow, but he could do it. Jack said to me, "I'll tell them we can do it. You're in charge,"

In 1963 NASA selected Boeing to build the Lunar Orbiter spacecraft and to manage the Lunar Orbiter program. The overall plan is described in Boeing's report to NASA, here. Boeing, in turn, selected Kodak to provide the Photographic Subsystem, described in exhaustive detail in Kodak's report to Boeing, here. The Phtographic Subsystem was based on reconnaissance cameras that had been in use for years in U-2 and SR-71 spy planes. The film transport, developing, storage, scanning, and transmitting sections were new, but had been tested extensively on the ground and approved before the first Orbiter flight.

For the most part, the plan was carried out to perfectiion. The first few Lunar Orbiter missions returned enough useable data that subsequent Orbiters could be redirected to photograph a number of areas of the Moon of lesser interest, including the far side, shown in the photo at the top of this page. None of that 'usable' data was, unfortunately, uasble for making a photomosaic, as was originally intended.

Twenty years later, Nancy Evans, the custodian of the Lunar Orbiter tapes, with Mark Nelson, obtained surplus FR-900 tape drives, intending to recover the images from the tapes. Lack of funds dellayed the Lunar Orbiter Image Recovery Project (LOIRP) for decades. Finally, in 2007, NASA released beautifully reconstructed Orbiter images, 42 years too late.

The images produced by the ground reconstruction system had several errors. Some are obvious in the iconic picture of Earth as seen from the Moon, Earthrise, taken by a Lunar Orbiter. Others are more subtle. Taken together, there was no possibility that the images could be used as-is for making contour maps.

Getting Help

The folks at NASA enlisted the help of the Air Force's expert cartographers at the Aeronnautical Chart and Information center in St. Louis, MO, to make maps from the 35mm film strips they had. ACIC had been making maps from aerial photographs sincee the cameras were carried aloft in baloons. ACIC recommended talking with the USAF photoreconnaissance people at Wright-Paterson AFB in Ohio to see if they could enhance the images. They, in turn, pointed out that Data Corporatiion, in nearby Beavercreek, OH, were the only ones they knew of where the equipment needed and the people with the skill to use it existed.

When NASA came to Data Corporation for help, what they had was a handfull of 35mm film strips and a compilation of material about the Lunar Orbiter Camera and the physical properties of the Moon. Jack Finley, Data's VP of Engineering, gathered a few of us in a conference room and described the problem in broad terms. On the plus side, the Orbiter camera clamped the film in place during exposure; the glass plate that clamped the film during exposure had fiducial marks etched into it at 1 cm intervals in both directions, and the edges of each scan overlapped the next by 0.005". On the minus side were a dozen or so challenges, some of which were immediately evident, and some which we discovered as the work went on.

Jack ended his presentation by asking us if anyone had any idea how what we had could be turned into what NASA wanted. After a long silence I asked Richard Pratt if he thought it was possible to create a virtual image of the assembled frame in computer memory, and a real image containing the pixels we could get from the film strips, and perform a transformation to move pixels from the real to he virtual frame, dragging the fiducial marks from their actual location on the films to their ideal locations in the virtual frame, carrying the adjacent image pixels with them. Richrd thought it could be done. I asked Davey Behane if he could shoehorn two six-million-pixel images into our computer's 256 KiloByte memory. Richard and Davey began an animated conversation about how both tasks could be done in a machine too small for either. As they began to sound like they were in agreement, Jack called a halt, assigned me to run the project, and we were off and running.

Step One: Tiger by the tail; What have I got us into?

One of the reasons the Air Force recon group recommended Data Corp for the job was the Data Corporation Microdensitometer. As part of on-going work on improving the quality of information that could be extracted from aerial reconnaissance imagery, Data Corporation had developed a microdensitometer with exceptional accuracy, both in positioning the film and in measurement of image density. The Micro-D was capable of resolving picture elements as small as a thousandth of a miillimeter, and measuring photographic density as great as 4.0. The high spatial resolution made it necesary to house the machine in a clean room, since common dust particles are much larger than the pixels being measured. Measuring the density of pixels that size put stringent limits on the light source being used to illuninate them, both in intensity and stability. The extremel;y low intenity of the light reaching the detector likewise required extreme sensitivity and power suppply stability. Without the Micro-D, the project could not have been considered.

Bob Boone, shown here with the Micro-D, and Bob Troidl, two of Data's photscientists, used the Micro-D to scan the film strips corrsponding to a high-resolution frame from the Orbiter camera, producing a set of large digital files. Davey set about writing code to handle the resulting volume of data as expeditiously as possible, while Richard worked on superimposing the overlaping pixels from adjacent strips and locating the images of fiducial marks in the assembled raw image. Three challenges met and overcome.

CRT displays were rare in those days. The one I had seen on the Illiac at school was actually a memory device. A clever student had figured out how to program the machine so the bit pattern in memory appeared on the face of the tube as a waving flag, but showing real images was not possible. The standard user input device was a teletype, and output was paper tape. Our computer had a line printer, but it printed characters, not pixels. It was common for programmers with time on their hands to use a printer to reproduce works of art by overprinting various combinations of characters. The Mona Lisa was a popular subject. Overprinting slowed the output rate considerably, but prinnting art was wasting time anyway. At first, we tried printing Moon Map pages that way, but getting a good black was almost impossible, and even the best black dot we could print had a while border. People can't read scrunched-together print, so printers don't print it. I took up the printer challenge.

Richard and Davey had managed to create a system to move the two images in and out of memory piecemeal, and to print individual film strips. Each strip was printed as two and about two thirds strips of 14" wide computer paper, 20' or so long. Three more challenges; two we expected, and one we didn't. We expected geometric distortion. The fiducial marks were displaced from their ideal locations. We expected density errors. It turned out that there was a systematc variation asross the width of each strip, basicall W-shaped,darker at the edges and the middle, lighter in other areas. The unexpected problem was gel spots. The film in the Orbiter Camera was developed by pressing a chemical-soaked web against it for a time and then separating the two webs. Ocassionally a small blob of material from the developer web would stick to the film.

When the systematic errors were fixed, it was decided that the effort required to fix the gel spots would not be invested unless a spot appeared in a critical location in the assembled image. We printed a complete frame for the first time. It took forever, it was gray-on-gray instead of black on white, but at least it looked like a moonscape. I had to come up with a better way to print

The publishing industry struggled with printing continuous-tone images for years. line drawings were easy. Etching and engraving were well established techniques. Sheets of Ben Day dotscould be used to print areas in color, but not with any detail. Half tone screens were invented in the 1860s. The screen, placed over the image, broke it up into dots. The engraving plate, reveicing more light from one dot, would be eaten away more deeply in the etch bath, and vice versa. In this way a continuous-tone image became a half-tone image. I decide we neede a half-tone print train for our printer. After all, we knew exactly what size dor we needed for every single pixel.

you were IBM, a modified Selectric typwriter. Bulk output was produced on a line printer, in our case, an IBM 1403N1 printer. It printed 132-character lines at the rate of 1000 lines per minute. You could print graphics by leaving off the line feed at the end of a line and over-printing. Dark pixels were made by printins M, W, and X on top of one another, lighter ones by an asterisk or a period. It sorta worked, but over-printing once cut the speed in half, and twice made it a third. The other problem was that each character on the print train perforce had a white border. Without the border, reading printer output would be impossible. With it, printing any solid black area was impossible. For a long time we just had to live with it.

Overprinted Pixels

A problem that was obious from the start was systematic errors in density across the image strips. Image pixels were darker near the edges and in the middle, and lighter everywhere else. Part of this came from scanning a flat furface with a beam coming fron a point source. The edges get less light. Some of this can be compensated for by varying the strength of the scanning beam as it sweeps across the strip. The rest is taken care of by scanning in narrow strips and having the light source as far as possible from the film. Of course, we had no control over this, but knowing how it happened was helpful in figuring out how to deal with it. Later on, this had to be revisited, but at this stage it was good enough to allow us to make some progress.

Seeing our progress took much more time and effort than we thought it would.

The biggest part of the problem was, simply, the size of the image and the speed of the computer. They combined to slow progress to a crawl. Each time we made a change, it took an hour or more to create and print a test strip. Then we had to paste the sheets of printout together and hang them on the wall before we could see what we had done. Fortunately, we had a big anough workspace that we could hang a strip and stand far enough away to see our output as a picture, not as a collection of spots. Two inches on the original Orbiter image was about twenty feet on the wall.

Getting from digitized strips to printed strips on the wall took several weeks. From there to deliverable images took quite a bit longer. A substantial part of the time was spent in mathematical manipulation. The purpose of the project was to help select a landing site. For this, a simple picture was not enough. A single picture tells nothing about the contour of the area shown. In the normal course of aerial mapping the area of interest is photographed twice, from two different positions, so a sterographic image can be created, from which elevation information can be derived. The Lunar Orbiter mission included attempts at stereo photography, but the combined images were not good enough to be useful.