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> The Lunar Orbiters never returned to Earth with the imagery. Instead, the Orbiter developed the 70mm film (yes film) and then raster scanned the negatives wit

> The Lunar Orbiters never returned to Earth with the imagery. Instead, the Orbiter developed the 70mm film (yes film) and then raster scanned the negatives with a 5 micron spot (200 lines/mm resolution) and beamed the data back to Earth using lossless analog compression, which was yet to actually be patented by anyone. Absolutely incredible! The level of complexity involved involved in space flight, along with the tight tolerances, continually impresses me when I consider the relative success of these missions.

skunkworker 8y ago
Amazing that they could get this from the stored tapes. http://www.worldofindie.co.uk/wp-content/uploads/2018/05/earthise.old_.new_.hi_.jpg http://www.worldofindie.co.uk/wp-content/uploads/2018/05/ear...
pjc50 8y ago
> lossless analog compression Are there any details of this? Some of the documents imply it's simply FM modulated, no different from passing a tightly-focused B&W TV camera over the film.
- ithkuil 8y ago
  What does lossless mean in the context of analog processing?
  - blattimwind 8y ago
    It means you combine things (because it's handy or whatever) in a manner that loses essentially no information. Normally this would just be some kind of modulation. The salient difference being losing information due to technical limitations (SNR, distortion, bandwidth limits) versus designing the system to remove information (lossy). Contrast: lossy analog compression, e.g. colour TV.
    - namibj 8y ago
      Specifically, PAL-style color subsampling which is more or less YUV 422. They could have fixed it other ways, but they decided to incorporate a quartz glass prism and piezo transducers to realize a 1-scanline physical delay, which they then used to do the analog variant of XORing each line with the one before.
- Implicated 8y ago
  > It used a method called vestigial sideband where a precise (1hz) people lot tone was used as a means to allow the stripping away of one half the waveform and then using that tone on the other end to reconstitute the missing side band. It is still used in communications today. Quoted from Dennis Wingo, co-founder of the Lunar Orbiter Image Recovery Project, who has been commenting on the linked article.
  - biggieshellz 8y ago
    "people lot tone" -> "pilot tone", I think.
  - deleted 8y ago
    [deleted]
  - acqq 8y ago
    The description appears to be something more similar to the "reduced-carrier single-sideband." There's long history behind the variants of sideband modulation: https://en.wikipedia.org/wiki/Single-sideband_modulation https://en.wikipedia.org/wiki/Single-sideband_modulation In the same article, vestigal sideband is reported as used around that time for modems: https://en.wikipedia.org/wiki/Single-sideband_modulation#Vestigial_sideband_(VSB) https://en.wikipedia.org/wiki/Single-sideband_modulation#Ves...

skunkworker 8y ago

Amazing that they could get this from the stored tapes. http://www.worldofindie.co.uk/wp-content/uploads/2018/05/earthise.old_.new_.hi_.jpg http://www.worldofindie.co.uk/wp-content/uploads/2018/05/ear...

pjc50 8y ago

> lossless analog compression Are there any details of this? Some of the documents imply it's simply FM modulated, no different from passing a tightly-focused B&W TV camera over the film.

ithkuil 8y ago
What does lossless mean in the context of analog processing?
- blattimwind 8y ago
  It means you combine things (because it's handy or whatever) in a manner that loses essentially no information. Normally this would just be some kind of modulation. The salient difference being losing information due to technical limitations (SNR, distortion, bandwidth limits) versus designing the system to remove information (lossy). Contrast: lossy analog compression, e.g. colour TV.
  - namibj 8y ago
    Specifically, PAL-style color subsampling which is more or less YUV 422. They could have fixed it other ways, but they decided to incorporate a quartz glass prism and piezo transducers to realize a 1-scanline physical delay, which they then used to do the analog variant of XORing each line with the one before.
Implicated 8y ago
> It used a method called vestigial sideband where a precise (1hz) people lot tone was used as a means to allow the stripping away of one half the waveform and then using that tone on the other end to reconstitute the missing side band. It is still used in communications today. Quoted from Dennis Wingo, co-founder of the Lunar Orbiter Image Recovery Project, who has been commenting on the linked article.
- biggieshellz 8y ago
  "people lot tone" -> "pilot tone", I think.
- deleted 8y ago
  [deleted]
- acqq 8y ago
  The description appears to be something more similar to the "reduced-carrier single-sideband." There's long history behind the variants of sideband modulation: https://en.wikipedia.org/wiki/Single-sideband_modulation https://en.wikipedia.org/wiki/Single-sideband_modulation In the same article, vestigal sideband is reported as used around that time for modems: https://en.wikipedia.org/wiki/Single-sideband_modulation#Vestigial_sideband_(VSB) https://en.wikipedia.org/wiki/Single-sideband_modulation#Ves...