Why do spacecraft transmit only photos, not videos?

Images transmitted by spacecraft: interplanetary stations, rovers, probes, delight many people. Of course, first of all, the images are intended for analysis by scientists - a specialist can carry out a detailed study of a region or object from photographs. There are already tens of thousands of photos of the cosmos, planets, and the devices themselves on the Web.

But why not a video? After all, it would be interesting to watch a watch movie where Pluto was shown, for example (the station New Horizons has already woken up). But no, there are only photos, and the video will not appear in the near future (except for animated videos). This is due to three main reasons.

The explanation is given by the example of the Curiosity rover. This is one of the most advanced devices currently located outside the Earth, on another planet.
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Reason 1. Very narrow data channel.

Despite all the perfection of the design of the rover, information to Earth (directly) comes at a speed of 500-3200 bits per second. This is much less than the old dialup.

The rover can transmit data at a faster rate to the orbital satellite of Mars. Here you can transfer about 31 MB of data per day. In this case, the orbital satellite itself takes pictures of the surface of Mars, plus analyzes a large amount of information. Accordingly, the satellite also has a lot of data to transmit. And the data transmission channel from the orbital satellite to the Earth is also narrow. By the way, data from spacecraft to Earth are transmitted via the Deep Space Network (see the load on various channels here ).


Here you can see which of the ground antennas are involved, and which device is now transmitting data

And how much will science give a low-quality video of 31 MB? Hardly more than a series of relatively high-quality images, which, if desired, can be put together in an animated sequence.

The second reason - the lack of suitable equipment on the devices.

On the same Curiosity, not to mention other devices, there is simply no suitable equipment capable of shooting video. When designing the rover, scientists planned to place a high-quality camera with zoom, stereoscopic "vision" and other buns. But NASA's budget savings did not allow this. By placing a lower-quality functional camera, the administrators of science managed to save $ 1.5 million (this is 0.1% of the total project budget).



Stereoscopic pictures can be taken, but the functionality of the camera is very limited. For example, you cannot zoom in or out - there is no zoom.

On other space vehicles, cameras are also not suitable for receiving video, and the channel for data transmission is even narrower than that of the Mars rovers.

The same “animations” are not so easy to do either, because for this you need to shoot the terrain consistently, each time with a slight change of focus. Accordingly, we obtain a huge amount of data that must be transmitted to Earth. And this is impossible, since the width of the communication channel is limited (see above). And besides Curiosity, there are other rovers, if we talk only about Mars. The rover sends information to Earth once a day.

If you change the information carrier from radio waves to laser, then perhaps scientists will be able to get much more information per unit of time than they do now.



The third reason is the low scientific value of the video.

Yes, look at how the Earth goes back on Mars in real time would be great. But this is entertainment for the average person. And the scientific value of the video is much lower (in this case) than the value of high-resolution quality photos.

In the photo you can see a lot of things, including the structure of rocks, or the shape of the comet's nucleus. Considering the video for this purpose is pointless.

By the way, there are several cameras on the ISS that transmit HD video in real time. Astronauts from the ISS transmit video. But this is rather an exception, since not so long ago the ISS received a very wide channel of communication with the Earth. And transmitting data from Earth’s orbit is one thing, and from Mars’s orbit or, moreover, Pluto is another matter.