approx. 240m (Including antenna, based on the size of the airlocks and necessary deck height in the "arms")
Print orientation for Detail Plastic:
Update Feb. '21:
New, more detailed model. Size increased.
The Regula One lab in "Star Trek II" was a re-dress of the Orbital Office Complex from "ST: The Motion Picture". For that, the model was flipped and most of the smaller pods were removed. Instead, an "observatory" was added to one of the larger pods. The miniature also appeared in several episodes of TNG and DS9 to depict other space stations and starbases. This model has the same size as the Orbital Office Complex in my shop for which i determined the size according to the various airlocks around the station. They need to be the same size (about 2m in diameter) as on the TMP Constitution Refit, so that Travel Pods and the Vulcan Surak Shuttle can actually dock with them. This size also allows to fit a narrow corridor into the "arms" holding the pods, so that the crew can walk in them without having to duck. However, some of these stations in TNG might be intended to be much larger, although the model wasn't altered to reflect this (E.g. window sizes). The same applies to the last modification of the model to depict lager starbases in DS9 (E.g. Starbase 375). For that the four large tubes and the smaller pod on the side with the "observatory" were removed but the outer appearance does not correspond to the shown size against starships like the Defiant, Miranda or even Galaxy Classes next to the station.
If you need this in another material, size, or quantity, send me a message. I will try to make it as you need. Be sure to read my comments below my shop page first.