Early in this journal I posted something I judged to be a poem ("Harrison's Pocket Principles") and got a comment saying that it wasn't a poem at all. Yesterday I posted something I judged to be a poem so deliberately awful that it couldn't possibly be judged otherwise ("The Martian Dog"), and got back a comment disagreeing. There is clearly the issue of defining "a poem," to start with, then the issue of defining "a science fiction poem" to narrow the field, and then the issue of determining -- ideally, in some rigorous fashion that would be useful to a "professional writers organization" like SFWA -- whether a poem is good or bad. And there seems to be precious little in the way of a consensus.
I don't expect you to agree with or approve of my own proposals in this regard, but I'm willing to post them as a springboard for discussion -- saving the question of how we determine whether a poem is good or bad for a separate post.
Defining a poem
In the linguistics textbook I did with John Grinder long long ago, the generative stylistics chapter defined a poem as having at least these three defining characteristics:
1. The presence of deviation from the rules of ordinary non-literary language
2. The presence of deliberate patterning on one or more levels of language
3. Resistance to change -- to such a degree that any change will either ruin the poem or cause it to become some other poem
I can provide examples of each of those if you'd like to see them -- but not now, since I don't want this post to be overly long. I've seen no reason to change the definition; it seems to me that it still holds.
Defining a science fiction poem
As editor of the Science Fiction Poetry Association's newsletter, I defined the science fiction poem (as opposed to "speculative poem" or "fantasy poem" or "horror poem") as a poem that has (a) a science component and (b) a narrative component. That's a definition that you can actually apply, but it was wildly unpopular with the membership. I still define sf poetry that way, but I stepped down from the editor's slot because it was manifestly unfair for me to judge submissions by a standard that almost nobody else in the field supported. For purposes of discussion, however, the definition at least exists.
[Note: There's more information about these matters in the Science Fiction Poetry Handbook that I wrote for the Science Fiction Poetry Association, due out this March. You can see the cover, editorial description, and so on by going to http://www.genremall.com/poetry.htm