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3 hours ago
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On July 14th, 1965, the Mariner 4 spacecraft flew by Mars, the first to ever reach the planet successfully. In the scientific data it recorded, it took 21 pictures, similar space probes built for the moon or earth would usually transmit image data back in a analog format of continuous scan-lines (similar to a TV broadcast). But for clarity across interplanetary distances, This probe had to record and transmit its data back in a digital format.
The clearest image from Mariner 4, with pixels visible
Image data from this was transmitted back as a series of bits, with a 6 bit number per pixel. Weirdly enough, the highest number (63, 0b111111) represented black whilst 0 represented white, the opposite of how its represented today.
The first image from Mariner 4, white parts showing gaps in transmission and highlighting pixel boundaries.
These pixels would be transmitted continuously to send a 200x200 image.
From here, these pixels would be recorded as dots on a tape, this tape would be scanned to imprint the image onto film, and finer restoration work would be done to perfect the picture. This is an example of an early dot-matrix image printer.
Now, with modern computers and image formats, this data format does not have to be imprinted onto tape to be viewed, converting this to raw RGB data is fairly easy, and from there, you can convert that to png/jpg/etc using tools like XPM or farbfeld (which is just 16-bit ARGB). The only hard part of this process is that Mariner 4 image data works with 6 bit pixels, which means that you have to work with chunks of 4 pixels (3 bytes) at a time.
Doing bit the manipulation needed to pack the image data efficiently, any 200x200 image can be converted and viewed as if it came from the antenna of a 1960’s space probe.
- Appointment on the Moon by Richard S. Lewis - Information in the chapter “No Hiding Place” was the inspiration for this article.
- My converter for this format: mar4-ff
