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Science and technology have made large leaps since the beginning of the space exploration era.

We get amazing pictures from probes exploring our Solar system.

Possibly many challenges of all possible impacts and hazards have been addressed, from discoveries of new materials, new inventions, all this fed by experience drawn from numerous projects.

What are challenges* yet unsolved to build a camera capable to say shoot hi res** pictures of our Earth from the moon and radio them back to Earth beyond standard protocols? Sure the overall task is still far from trivial but the effort can't be same as earlier, or?

* In this context, a challenge is something an engineer could address without trying to override laws of physics.

** In this context, hi res means "good enough", same resolution as achieved by recent missions for example Cassini, this camera had afaik 1MP and created amazing pictures also from larger distance, like of Titan from 339000 km while distance from Earth to moon is 384400 km.

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    $\begingroup$ If you want to get hi res pictures of the Earth, the camera should be not too far away. A better camera sensor cant do anything about that, the resolution is limited by fundamental optical physics. If the diameter of the telescope used is too small, you dont get hi res. These resolution limits are known for many decades. $\endgroup$
    – Uwe
    Aug 27, 2019 at 8:31
  • $\begingroup$ thanks for adding this @Uwe; so fundamental optical physics are here a clear limit but not an unsolved challenge, in terms of the questions. $\endgroup$
    – J. Doe
    Aug 27, 2019 at 8:32
  • $\begingroup$ what do you mean by "hi-res"? are you talking 4K, or the ability to catch your neighbour sunbathing in the garden? $\endgroup$
    – user20636
    Aug 27, 2019 at 8:56
  • $\begingroup$ @JCRM so maybe your answer is, "one of the current unsolved challenges is to build a camera capable of/transmit a 4K image"? $\endgroup$
    – J. Doe
    Aug 27, 2019 at 9:07
  • $\begingroup$ I'm trying to clarify your question, @uwe's comment-answer is about what you can see with the system i.e. angular resolution, which coupled with distance gives resolution meters per pixel. However some people use resolution to talk about sensor/display size, measured in pixels. (fun fact, space cameras are often one-dimensional) $\endgroup$
    – user20636
    Aug 27, 2019 at 9:16

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Generically, the challenges are the same as any other camera, on the ground, in space, or elsewhere. Specifcally for a space camera some of the issues that need to be overcome:

  • Desired resolution - As noted in the comments above, resolution is limited by a combination of the optics and the sensor (CCD/CMOS/etc). In particular focal length, aperture size, and detector pitch all play into it. For spacecraft where mass and volume are at a premium, aperture and focal length may be limited by the size of the satellite itself.
  • Image quality - How nice a picture do you want. Metrics like signal to noise ratio and modulation transfer function (MTF) all come into play.
  • Field of view - Field of view requirements (how much to include in picture) are often in conflict with resolution requirements. No problems to solve here, but an ongoing tradeoff
  • Sensor stability - Depending on the resolution desired, the sensor will need to be very stable. This impacts attitude control of the entire spacecraft, as well as structural stability (making sure the whole satellite doesn't deform too much as it heats up and cools down)
  • Storage and data throughput - All those beautiful pictures need to be stored in memory (much like your SD camera) and downloaded over a link that has a limited data throughput. Too many pictures or very big pictures and you run out of memory or can't get them down as desired.
  • Radiation - All electronics are sensitive to the space radiation environment. Radiation effects on a sensor can lead to stuck pixels, decreased sensitivity, or completely kill your sensor. Same goes for the entire electronics chain (sensor - decoder - processor - storage - downlink).
  • Thermal environment - Some sensors, especially infrared sensors need a nice stable and cool thermal environment. That's the primary reason the JWST is at L2 - thermal stability and low temperatures for its sensors.

By the way the DSCOVR spacecraft takes some pretty amazing 1 MP to 4 MP pictures of the earth from 1,475,207 km away. Final resolution of these pictures is around 25 km/px

enter image description here

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