Wednesday, 15 April 2009

Heroic data recovery story: 40-year old lunar orbital data

Thanks to Andrew Treloar for the heads up on a wonderful data recovery story. Andrew’s link was to a Slashdot article; there’s not a lot of information there. After a bit of searching around, I found a longer version of the story from last November at CollectSpace, and an interesting discussion on WattsUpWithThat (dated 1 April, which is why I emphasised the November date!).

Roughly the story is that NASA has been sitting on a collection of some 1500 2” analogue tapes which captured high resolution images taken by the Lunar Orbiter mission in 1964 that preceded the Moon landings. The aim of this program was to identify sites for the landings. Although NASA only used low resolution versions of the images (including the famous “Earth Rise” image, see Wikipedia article), the high resolution images were recorded onto the tapes by special Ampex FR-900 instrumentation recorders. Many years later, the archivist concerned refused to throw the tapes out. And eventually even found 3 non-functioning drives, which she stored in her garage, until news of the story leaked out to some interested people, including at least one retired Ampex engineer. Since then, with a little funding from NASA, and some space in an old McDonalds at NASA Ames, they have been attempting to refurbish the drives, and have managed to get at least two images off the tapes. If they can find more manuals and parts, they hope eventually to read all the tapes.

There’s lots that is interesting here. I particularly liked the response to this question from a reader: “What’s being done about the tape itself? You can’t just pull it out of the tins and thread it up.” Dennis Wingo, the main engineer involved replied:
“You know, amazingly enough that is exactly what we do. I am continually amazed that this works as I used to run a TV studio in LA where we could not do that even 20 years ago, but we have had an amazingly small number of tapes that even produce head clogs. We have run some tapes as many as 20-30 times in doing testing. Absolutely amazing to us.

I heard a story, that seems plausable but not sure about it really. It turns out that in 1975 all of the vendors changed the formula for the adhesive that holds the iron particles to the tape back. The new formulation had problems with moisture and over time degraded significantly.

However, the tape before 1975 that did not have this problem was made with a different mixture that included WHALE OIL, I kid you not. I don’t know if this is true […].”
One commenter had a major set of suggestions on how to deal with the stream if all they had was the analogue signal. Dennis responded, in part:
“We are using PCIe digitizers on a Mac Pro workstation to capture our data so we are able to get high data rate captures up to 180 megasamples per second.

We can do a lot with that but we would have to do a LOT of digital post processing including doing the demodulation in the digital domain, which is NOT going to be easy. Much easier to do in hardware, especially since we have spent the money doing so.”
Hey, that'se a hardware engineer talking! I guess it means he’s optimistic to be able to make and keep the drives alive long enough to digitise the entire set, rather than trying any more radical software solutions.

Data recovery from > 40 years ago, anyone? It is heroic, but let’s not be frightened!

1 comment:

  1. Nowadays, a number of advanced technologies are available worldwide for data recovery purposes.


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