Satellite surveillance

In connection with the increased interest in observations from space, I propose to consider what is at stake and what it is capable of. The materials of this article are mainly excerpts from this book . In the next one (if it will be) I will try to describe modern technologies based on my knowledge and experience.

The observation spacecraft (SV) usually flies in a circular orbit around its object.


In fact, this is a camera with a good lens.

This means that the person on top will be visible as a point, the tank is already about 50 points. There are no readings of newspapers and license plates from orbit (and this is generally not required).
Typical structure of the device:

For each specialist their own system is the main one. I think the main one is the traffic control system:

On past and present devices, all of this is arranged like this:

Yes, these are huge devices weighing several tons. Requiring appropriate carriers and working relatively short. Modern microelectronics can significantly reduce the size and everyone already knows about the cube-sat. Devices for communication or some tests are collected by students and even schoolchildren. But for the observation vehicles there were some fundamental limitations of space:
- it is necessary to accurately determine the orientation. As a rule, these are three or more devices.
- a fairly accurate stabilization is needed when shooting an object. You can put the power gyros, but you can not overclock them to infinity. After some time, you need to reset the kinetic moment. In a magnetic field, electromagnetic systems are already used for this, but without a field, only engines.
- more quality shooting - more focal length of the lens. On modern devices, in fact, these are telescopes.
- the transfer of large amounts of information (images) requires significant radio link capacities, especially at a distance from the Earth.
- more than about 500 watts per square meter of solar panel is not available.

That's all for now. Next, we will look at what three devices are needed for orientation, how much fuel is spent on a couple of shots and how much a square meter of solar panel weighs.