Horsepower
From Betamountain.org
Summary
Doc and Niko are drawn to a planet in the empty zone by a mysterious psychic force. The natives of the world believe Voyager to be a god called Hopi who will help them survive the radical weather changes. It turns out the Queen has a weather control device station on the planet.
Cel
A batch of animation cels appeared in a recent eBay auction and the majority appear to come from Horsepower.
There are only a few episodes with Doc and Niko wearing hats, and Niko with shoulder strap is even rare. Dave Morris has a cel description at ComicArtFans.com has a description of "Nico and Doc, on a non-matching background."