GR translation: ride him a green-doped and silent hound

[Mike Jing]

V727.15-22, P741.31-38   But these heretics will be sought and the dominion
of silence will enlarge as each one goes down . . . they will all be sought
out. Each will have his personal Rocket. Stored in its target-seeker will
be the heretic’s EEG, the spikes and susurrations of heartbeat, the
ghost-blossomings of personal infrared, each Rocket will know its intended
and hunt him, ride him a green-doped and silent hound, through our World,
shining and pointed in the sky at his back, his guardian executioner
rushing in, rushing closer . . . .

What does "ride him a green-doped and silent hound" mean?  What is
"green-doped"?
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