Two satellites revolve around a planet in coplanar circular orbits in anticlockwise direction. Their period of revolutions are 1 hour and 8 hours respectively. The radius of the orbit of nearer satellite is $2 \times 10 ^ { 3 } \mathrm {~km}$. The angular speed of the farther satellite as observed from the nearer satellite at the instant when both the satellites are closest is $\frac { \pi } { x } \mathrm { rad } \mathrm { h} ^ { - 1 }$, where $x$ is $\_\_\_\_$.