I've always wondered about the cameras in the space probes, especially in the Voyagers.

1) What kind of cameras do they have? Digital? (Electronic - what kind of sensor and megapixel count?) Analog? (Do they develop the film and then scan it, as Luna 3?)

2) How do they transmit information to NASA?

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    $\begingroup$ Note "Analog" doesn't need to mean "chemical film" - there's the thing of analog TV camera, as used in early TV broadcasts, sending analog scanlines instead of digital pixels. $\endgroup$ – SF. Oct 13 '17 at 15:51

Definitely digital. There's no way to develop the film out there and they would have run out long before they finished the mission.

Cameras - There are several camera on-board the Voyager spacecraft. Here is a link to the Instruments page on the Voyager website. This site provides diagrams of the optical elements of each of the cameras, but it doesn't seem to provide specific specifications on the detectors. On NASA's Planetary Data System website, there are detailed specifications on each camera. Links to those pages are provided below.

Data was stored on a digital tape drive and then played back during transmission periods. During the planetary encounters, data was accumulated much faster than it could be relayed back to Earth. Images were downloaded as fast as possible, but mostly the data built up on the tape drive and was then played back over the long interplanetary stretches.

As for getting the data back, it was transmitted back to Earth and received by NASA's Deep Space network of radio dishes placed around the world specifically to receive transmissions from the various space probes out in the solar system. The rates are very low by todays standards, but this is late 1960s and early 1970s technology.

Voyager telemetry operates at these transmission rates

  • 7200, 1400 bit/s tape recorder playbacks
  • 600 bit/s real-time fields, particles, and waves; full UVS; engineering
  • 160 bit/s real-time fields, particles, and waves; UVS subset; engineering
  • 40 bit/s real-time engineering data, no science data.

So the best transmission rate is 7.2 kilobits per second.

Here is a link to the official Voyager website.

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    $\begingroup$ Actually some of the earliest Earth satellites did use silver-based photography, did develop the images with chemicals, and then scanned them electronically. $\endgroup$ – Geoff Gaherty Jun 13 '11 at 3:37
  • $\begingroup$ @Geoff Gaherty: Luna 3 $\endgroup$ – Andres Jun 13 '11 at 16:22
  • $\begingroup$ Thank you—I knew I'd read it somewhere. I love mid-20th century technology! $\endgroup$ – Geoff Gaherty Jun 13 '11 at 21:40
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    $\begingroup$ Those are the camera for the much newer Cassini spacecraft. Voyager was launched in 1977 when CCDs were tiny lab curiosities. Voyager1 used vidicon 'tube' cameras pds-rings.seti.org/voyager/iss/inst_cat_na1.html#inst_info $\endgroup$ – Martin Beckett Jun 23 '12 at 16:27

The cameras from Voyagers are described here.

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Voyager's optical camera was digital, with a camera tube similar to TV cameras of the period. The initial analog signal was converted to a digital format that had a resolution of 800 x 800 pixels and transmitted back to NASA. CCDs were not used.

https://www.quora.com/Does-the-Voyager-spacecraft-have-digital-cameras https://www.quora.com/What-are-the-specs-for-the-optical-cameras-on-Voyager-I-and-Voyager-II

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