From my understanding, by having two satellites emit a signal simultaneously (carrying atomic clocks to achieve it), a ground device could measure the difference in times of arrival to determine its own position on the axis parallel to the line between the two satellites. With three or more satellites, the ground device would determine its own position on two axes.
Firstly: Is there a way to achieve something similar with a single satellite (even if less accurate), and has it been done? Could a single satellite send the same signal from opposite ends of its own structure and achieve a similar effect (one axis localization), or does the tiny distance between two sides of a satellite mean that the difference in arrival time would be too small to measure?
Secondly: Would a CubeSat GPS network make sense, or is the size constraint a dealbreaker for the required energy/weight constraint? Could a simpler version be created that would make sense? I haven't found previous implementations of such networks :/
I hope these questions are not too dumb, I appreciate any knowledge or pointers to learning resources if the questions cannot really be answered without more background.