The single line comes from the trajectory of the spacecraft as it flies through the focus point, reading one pixel at a time. Stopping and rastering is not poss

The single line comes from the trajectory of the spacecraft as it flies through the focus point, reading one pixel at a time. Stopping and rastering is not possible and not close to possible with current technology. Of course, you still want a raster grid, but you have to obtain the grid by sending a swarm of different spacecraft. They each collect a line as they fly through the focus point, and then you can assemble the lines into a grid.