(written from a Production point of view)
To Boldly Go was a ten-minute Star Trek: The Next Generation documentary produced at the behest of the American Broadcasting Company (ABC) in 1990 for their current affairs series PrimeTime Live. It was broadcast on 27 September 1990 as part of the second season of that series. The featurette was hosted by DeForest Kelley, who playfully adopted his curmudgeon alter ego character of Leonard McCoy. Kelley visited the set of The Next Generation around the time when the season four episodes "Family" and "Future Imperfect" were in production.
Apart from talking to actors and production staffers like Gates McFadden and Michael Westmore, it also featured behind-the-scenes footage, staff meetings, application of makeup, and the designing and filming of the McKinley-type studio model. Majel Barrett reprised her role as the computer voice for a short segment in the turbolift.
Produced by ABC staffers Neil Shapiro and Eric Dennis, the featurette has never been released as nor included as a special feature on any of the home video releases. Not seen for decades, it has recently resurfaced on internet websites like YouTube.
In 2012, producer Robert Meyer Burnett hinted at the possibility of the documentary being included as "value added material" (a special feature) on one of the remastered Next Generation, releases  but it was ultimately not part of the TNG Season 4 Blu-ray set when released.