Here's a little history and explanation for those interested...

In reality, three models of the Ultra Probe were were built for the episode by Martin Bower. One was built at 2.5 feet in length, which is about 1/96th scale (it's the one you see docking with the alien ship) and one at five feet in length, done to the scale of 1/48. This large model was only used for a few "fly by" shots. The third model was actually only a partial model of the nose cone and front body section and was built to the scale of 1/24th. This is the model you see when the command module detaches from the main body.

The original studio models were built by Bower and therefore, like many film props, were very crude compared to what one would expect in a display model. Also, the detailing varied considerably between the different sizes. Therefore it would have, for example, been pointless to exactly copy all the "kit bashing" used, since the detailing varied so considerably. The original models, although they looked great for the few seconds you see them on film and harshly lit. were, in all honesty, not terribly desirable in the context of a display model.  Even some "key" proportions varied between the three original models, so it's arguably open to a lot of interpretation which way is correct to build an "accurate" replica.

Many people propose that, usually correctly, that the only way to build an accurate replica of a studio model is to copy the exact size, shape and detailing of the size of model you're replicating. I usually agree with that philosophy, but in this particular case of the Ultra Probe, I decided that some artistic interpretation was in order. I wanted to make a model of the SHIP, not a specific studio model per se. So I deliberately took great liberties with the kit bashing, but did  maintain exact overall shape and proportions when possible. Other improvements were made over the originals, such as more realistic turned aluminum engine bells (on the tail and the command module) instead of silver painted plastic parts which were used on the originals.

Decals were made by JBOT to my specifications.