I’m writing some marketing materials, and they’re talking about NASA using digital photography from the moon. I wanted to fact-check that. I had thought the Apollo missions used analog signals to transmit photos.
Thanks for the help!
Also, any cites you could provide would help to justify the “nay” on that, if it is indeed “nay.” Thanks!
“Analog Signals”?
Digital Transmission of photographs, called “Facsimile” or “Fax” is a very old technology, used by newspapers to transmit photographs long before it became cheap enough for business use.
But they did famously take analog (film) cameras with them:Moon Camera, and the TV cameras they took on later flights were probably also “analog”.
TV had a common “analog” transmission method, so it is possible that the signal was not digitised for transmission. But I remember the TV transmission as being a series of still photographs, and to me that says digital encoding and transmission.
Yes: Signals modulated with analog information, such as SSTV (Slow-Scan Television, what the Apollo missions used to send video back to Earth), AM and FM radio, and NTSC, SECAM, and PAL television.
Fax machines from the era before telephones were not digital.
This is entirely incorrect. NTSC, SECAM, and PAL were all analog methods of transmitting image information. The fact they worked by sending sequences of still images doesn’t change that.
Wikipedia page on Apollo TV camera describes the TV cameras used to transmit video from the moon. Looks like they are all TV cameras with no recording capability (just broadcast).
I think the only other cameras used on Apollo were film (still) cameras.
Duckster’s citation states that digital cameras were invented after the Moon landings, so none were taken to the Moon. The OPs question is whether the analog images were transmitted to Earth in digital form. This would have required transporting an “analog to digital” converter on the landing module, and such would have been big, heavy and slow at that time. I’m guessing no, we still needed some years to develop IC technology to miniaturize this piece of equipment suitable for space travel.
Another issue is that “scientific grade” images took a very long time to transmit. Effective compression software wasn’t developed until the late '70s or early '80s.
The wiki page on Apollo 11 missing tapes is also interesting - it describes how the analog SSTV (slow-scan television) signals were displayed on SSTV monitors, and then “converted” into standard TV format for TV broadcast by pointing a TV camera at the SSTV monitor.
p.s. As an additional data point, by early 70s NASA was using digital image transmission. Here’s a description of the camera system on the Viking Mars orbiter, launched in 1975. The image from the vidicon was digitized and compressed.
Incidentally, when they went digital, that was the beginning of the end for lunar Fotomats.
Only if they don’t put digital backs on the 12 Hasselblads abandoned on the moon.
Mariner 4 which was sent to Mars in 1964 transmitted it’s images digitally, though computer that processed the data to produce actual images back on Earth was so slow that it was faster to draw it by hand. 
WireFax was analog. A voltage /current analogous to the grey-scale value was modulated and transmitted.
“RadioFax” was invented in 1924. It was binary. Binary is normally considered “digital”, unless you have a Wikipedia understanding of the words “Analog” and “Digital”. It is still used for the radio transmission of weather maps. “Fax” was based on this technology… Apollo 11 was the first moonlanding. That was 1969. Comercial Fax machines became available in the mid 60’s, and the technology was in use to transmit pictures before that.
Entirely? TV didn’t have a common analog method of transmission? I don’t remember? It wasn’t a serices of still photographs? Slow Scan doesn’t say digital encoding and tranmission to me?
NTSC, SECAM, and PAL were all analog methods of encoding pictures. None of them are actually methods of transmitting, unless you use a kinda loose definition of “transmitting”. Which I wouldn’t mention, except that claim to “entirely” seems to invite it.
In any case.the original question was about digital photography. I mentioned TV in case the original poster wanted to include SSTV in “digital photography”. I noted that TV cameras the 60’s was analog, but suggested that the images might have been digitally encoded for transmission.
Were the images digitally encode for transmission?
No, it was, and is, analog: It wasn’t binary, because it used intermediates between black and white to encode shades of gray.
To the extent this makes sense, none of it matters.
How are NTSC, SECAM, and PAL not methods of transmitting video?
Not from the moon. (This Wikipedia article is a long explanation on the analogue transmissions from the moon and converting slow-scan analogue from the moon to terrestrial analogue.)
This Wikipedia article follows the evolution of analogue TV cameras to the first digital TV cameras of the late ’90s. Nowhere is it mentioned that any digital processing by TV cameras was employed during the analogue era.
I’m guessing the question has been satisfactorily answered, but want to point out it sort of depends on how you are defining “digital photography”
I think most photographers would consider “digital photography” as basically the reverse of a “digital monitor” you have an array of pixels (although usually you have two green for each red and blue) that measure light and store data using something like a CMOS or CCD.
https://en.m.wikipedia.org/wiki/KH-11_KENNAN
Was in 1976 and is said to be “the KH-11 was the first American spy satellite to use electro-optical digital imaging, and create a real-time optical observation capability.”
Now, of course, that quote is qualified in both using “spy satellite” and “real-time”, but based on the fact that the first digital still camera was supposedly invented in 1975:
https://en.m.wikipedia.org/wiki/Charge-coupled_imaging_device
1976 seems like a pretty good date for a true digital camera to be used in space.
Methods that would/may have been used to convert an analog radio signal to digital (my guess is for error correction, but this is just a guess) aren’t really the same thing. Again depending on how you define the term.
Remember the limiting factor in digital was storage. I have the Radio-Electronics original plans for building a home computer with the 8008 (1973, IIRC). The plans included the option for adding a second bank of 256 bytes of memory.
There were various electromechanical tricks for storing large quantities of data, like recording media, rather than electronically. There were also tricks for mechanically scanning for pictures (spinning disk with holes, or in one case IIRC, the whole spacecraft rotated and used a simple photo diode sensor). the entire history of digital is wrapped up in ever-expanding capacity. In the MS-DOS days, Bill Gates is alleged to have asked why anyone needed more than 640K of RAM in a computer. Today, that isn’t enough for the screen storage to display a small picture.
Indeed - except - as you hinted - Gates denies ever having said that.
Cites the Apollo computer as being 70 pounds and apparently only ~64k of ram. While you could argue that “hey that only weighs 12 pounds (or whatever - guessing from memory) on the moon” - one could argue that if NASA was investing that much time and effort in their guidance computer - cameras wouldn’t have been equipped similarly.
Although the Apollo missions are credited for reducing the size of video cameras (I’ve seen this more than once).
