Answer
The distance between the astronaut and satellite is 42m.
Work Step by Step
According to Newtons 3rd law same force of 100N applied on both the astronaut and the satellite.
I=F$\Delta$t=m$\Delta$v
v=$\frac{F\Delta t}{m}$
Consider the astronaut, we can find there final velocity
$v=\frac{(100N)(0.5s)}{80kg}= 0.625 m/s$
Consider the satellite, we can find its final velocity
$v=\frac{(100N)(0.5s)}{640kg}= 0.078 m/s$
Relative velocity between the two,
$\Delta V= 0.625 m/s +0.078 m/s = 0.703m/s$
Final distance between two objects,
$s=v\Delta t = 0.703 m/s \times 60s = 42.18m \approx 42 m$
