Enterprise was always in HD so no extra effort or money needed there, the visual effects were rendered at HD from the start.
Millimeter magazine March 2002 issue article titled: "Effective HD Effects"
Ron Moore Enterprise's visual-effects supervisor tells of the show being mastered in 24p HD format. He hoped the team would be in a position to build a pipeline by next season [season 2] to post a show entirely within a 24p HD pipeline.
'Initially however, the HD requirement came before there was any logisitical or financial possibility of ramping up all the show's visual-effects facilities to work exclusively in the 24p world.'
"The obvious problem is paying for it," says Moore. "The cool thing is Paramount is letting us create a high-def master and is airing the show letterbox. The disappointment right now, is that the visual effects are still up-rezzed. Occasionally, we will create an element in HD. This shot has a lot of aliasing and other artifacts we can see at 601 standard def
[ITU-R Recommendation BT.601, more commonly known by the abbreviations Rec. 601 or BT.601 (or its former name, CCIR 601,)
The Rec. 601 signal can be regarded as if it is a digitally encoded analog component video signal.]
so I went back to the CG house and they gave it to me in high-def. We'll find a way to put it directly onto the final [online] tape, which is a much better way to go. Unfortunately, it isn't feasible to do that with all our shots right now."
Season 1 the visual effects were mostly rendered in standard definition and uprezzed to HD.
if you wish to continue a discussion of remastering 'Enterprise' for HD syndication and Blu-ray please go here to this most relevant thread:
'Star Trek: Enterprise seasons Blu-ray spec. features wishlist'
If you wish to continue discussion of TNG series remastering be my guest.