Restoring lost lunar images after 40 years
- 05 July, 2009 22:00
Liquid nitrogen, vegetable steamers, Macintosh workstations and old, refrigerator-size tape drives. These are just some of the tools a new breed of Space Age archeologists is using to sift through the digital debris from the early days of NASA, mining the information in ways unimaginable when it was first gathered four decades ago.
At stake is data that could show Earth's risk of an asteroid strike, shed light on global warming and — perhaps — even satisfy those who think the moon landings were a hoax. The most visible of the archeologists is arguably Dennis Wingo, head of Skycorp, a small aerospace engineering firm in Alabama. He's the driving force behind the Lunar Orbiter Image Recovery Project, operating out of a decommissioned McDonald's (since dubbed McMoon's) at NASA's Ames Research Centre in Mountain View, California. The project's goal is to recover and enhance as many of the original lunar landing images as possible.
Between 1966 and 1967, five unmanned probes were sent into lunar orbit to map possible landing sites within the moon's equatorial regions at one-meter resolution and to map the rest of the surface at a resolution of 40 meters or better, Wingo explains. Those probes, known as Lunar Orbiters, sent back about 1,800 images that modern technology should be able to greatly improve.
The project's great scientific value to NASA is in enabling a comparison between the lunar surface as mapped by the Lunar Reconnaissance Orbiter, launched on June 18, with the lunar surface as it appeared 43 years ago, according to Wingo. The goal is to "get a fix on how many meteor impacts have occurred in the meantime," by catalogueing the new craters. "If we know the changes, we can establish the risk of working on the moon and even determine the small-body asteroid population of the inner solar system," Wingo says. Another valuable contribution: the ability to plot the possible risk to Earth of the impact of an asteroid. The original black-and-white images were shot on 70mm film that was automatically developed and scanned within the robot spacecraft. The signal from the scanner was sent to Earth and was then displayed as partial frames on a monitor. Each monitor image was then captured with a film camera. These pictures were put together, and then another picture was taken of the finished mosaic. Each step imposed a certain amount of image degradation. Wingo figured that if he could process the tapes of the original signals, he could improve the dynamic range of the images by a factor of four. Although this theory has proved correct, the path has been challenging. It turns out that the original two-inch tapes were available. Around 1986, NASA archivist Nancy Evans, now retired, was contacted by a federal records centre asking what to do with them. Feeling that the data should not be discarded, she persuaded the Jet Propulsion Laboratory (JPL) in California, to put them into climate-controlled storage.
However, the tapes were useless without compatible tape drives — in this case, analog Ampex FR-900 reel-to-reel units. Weighing half a ton and resembling refrigerators, the drives have not been manufactured since 1975.
She finally got a call from an Air Force base that had four of the old drives. She stored them, along with documentation and spare parts, at her home in California, There, they gathered dust for two decades.
By 2006, the tapes — still in JPL storage — fell under a new NASA edict that no planetary data should ever be destroyed, Evans explains. In an effort to preserve the drives, she submitted a white paper about the tapes and drives at a Lunar and Planetary Institute conference. After seeing it, Wingo contacted her and arranged to have the drives and tapes transported to Ames.
Then Wingo 's largely volunteer crew was able to restore two of the drives using pieces from the other two, plus off-the-shelf parts and additional components that had to be custom-made.
"We had to pay big bucks to get the bearings replaced, the motors rebuilt and rubber parts cast. We had to dip the motors in liquid nitrogen to get the bearings off," he recalls.
So far, all the tapes have proved usable. The data is read into a quad-processor Macintosh Pro workstation with 13GB of RAM and 4TB of storage.
After capture, the images are processed with Adobe Photoshop and Igor Pro analysis software from WaveMetrics. But the new plan is to move to a custom application written in C to take advantage of Mac OS X 10.6 (Snow Leopard).
With an additional $600,000 budget, Wingo hopes to have all the files processed by February, producing a moon atlas with a resolution higher than anything previously seen.However, Wingo's "deliverable" to NASA is not the images themselves, but the raw data extracted from the tapes. "They would rather have the raw data so that someone even a thousand years from now could do their own processing," he says.
The NASA edict against data destruction was issued after thespace agency's 2006 admission that it couldn't locate the original tapes of the Apollo 11 live slow-scan TV broadcast from the moon. The agency then initiated a search for the tapes, which remains ongoing, as is the internet furore the admission generated among conspiracy theorists, who believe the landings were staged.
Due to the low wattage of the transmitter on the lunar lander, they had only 500 kHz bandwidth to use for video, as opposed to the 4.5 MHz that was standard at the time for broadcast analog TV. So NASA used a slow-scan, black-and-white transmission at 10 frames per second with 320 lines per screen, Richard Nafzger, senior engineer at the Goddard Space Flight Center in Maryland, says. US broadcast TV used 30 frames per second with 525 lines per screen. The conversion was made at each ground site with a device that basically pointed a broadcast TV camera at a special monitor displaying the slow-scan image.
The slow-scan monitor had persistent phosphor to make up for the slower scan rate, and as a result the movement of the astronauts looked ghostly and jerky, he explains.
"The night we landed and did the moonwalk, that is when I became scared," he recalls. Before that point, there hadn't been as much pressure to broadcast the proceedings in real time. But after the safe landing, "they were saying that they had better be able to see this on TV, and 600 million people were watching. Something as simple as plugging a wrong patch or pushing a wrong button would mean that no one would see it," Nafzger says.
If the original tapes could be found, he estimates that they would appear three times clearer than the broadcast images.
"We have gone through landfills on the tops of mountains. I have looked through rooms the size of two or three football fields, filled with rows of shelves going up 30 feet, and we have looked on every shelf that might contain the right tapes," Nafzger says. Tapes that were suspected of being the right ones were heated for hours in dry vegetable steamers to make sure the oxide was fixed to the substrate before Nafzger's team attempted to read them.
Nafzger is currently preparing a report on the results of the search and cannot discuss them until NASA releases the report, the date of which is uncertain. "But since I am not running down the street waving a flag and shouting 'Eureka!' you can draw your own conclusions. The big picture is that there is an explanation for everything," he says.