[tex]\bullet~\text{Mass of each satellite:}~m\\\\
\bullet~\text{Linear momentum of the first satellite:}\\p_1=m_1v_1=m\cdot800\Longrightarrow p_1=800m\\\\
\bullet~\text{Linear momentum of the second satellite:}~\\p_2=m_2v_2=m\cdot0\Longrightarrow p_2=0~kg\cdot m/s\\\\
\bullet~\text{Linear momentum of the connected satellites:}~\\p'=m'v'=(m_1+m_2)\cdot v'=(m+m)\cdot v'\Longrightarrow p'=2mv'\\\\
[/tex]
By the conservation the linear momentum:
[tex]p_{initial}=p_{final}\\\\
p_1+p_2=p'\\\\
800m+0=2mv'\\\\\
2mv'=800m\\\\
v'=\dfrac{800m}{2m}\\\\
\boxed{v'=400~m/s}[/tex]
The speed of the connected satellites is 400 m/s.
