I’d like to relate how I was able to find those old stereo pair images from thirty years ago. As an early enthusiast of personal computers, I acquired habits of saving data “early and often”, because computers crashed and memory systems failed… frequently. And computer memory was limited, so I needed to store old data on external storage devices to make room for new projects. At the time I was working on these stereo images, the archival storage of choice was the CD-ROM, the precursor to DVDs. It was an amazing storage device, holding over 650 MEGABYTES on one disk! (Can you believe it?). After my publications and other work on the stereo constellation project was done, I copied the images, and the code that generated them, onto CD-ROM, knowing that I could restore them at any time if needed.
Twenty five years elapse, and I now find the need to restore them. As a packrat, however disorganized, I was able to find those old CD-ROMs, and connect a (now obsolete), CD drive to read them. Unfortunately, my computer did not recognize any data on the disks I inserted.
At first I thought it was a failure of the CD. The technology depends on the ablation of microscopic holes in a special thin surface material, and it is known that over time, the material can creep and diffuse to fill in the holes, corrupting the data. And my initial tests seemed to confirm it: newer CDs could be read, but the older ones failed.
It was discouraging. All that effort to create an archive of what I thought was important work was wasted; the data was no longer accessible.
But then I learned more. The reason I could not read the CD-ROMs was because they were recorded in a format that is no longer recognized and supported by modern computers. Somewhere in that 25 years, the rules for storing data had changed, and I was now beyond the “grandfather clause” of being able to read my stuff. I was further discouraged, but at least this brought back the possibility of being able to recover my ancient data.
I appealed to my fellow “distributed computer museum” curators, and sure enough, my friend Rich had a functioning computer with an old operating system that could recognize my old CDs! I have now transcribed my old files to new ones in a format that might last another decade or two. Of course, by then, the data will truly be obsolete!