(written from a Production point of view)
What We Left Behind – Looking Back at Star Trek: Deep Space Nine is a forthcoming documentary, taking a retrospective look at Star Trek: Deep Space Nine, its impact and meaning. The documentary is produced by Ira Steven Behr and 455 Films, and directed by Adam Nimoy.
In addition to interviews with most of the Deep Space Nine main and recurring cast – with the notable exception of Avery Brooks, who Behr was unable to convince to participate but did advise Behr to not just make a talking heads film – the documentary will also include Behr, Ronald D. Moore, Robert Hewitt Wolfe, René Echevarria, and Hans Beimler breaking the story for an eighth season of the series – Behr advising the writers to "check the Trek page" for the series finale in advance. 
The documentary was first revealed by Behr during the Deep Space Nine panel at the Star Trek Las Vegas convention in August 2016. A crowd-funding campaign to complete the documentary, including additional interviews, post-production, and licensing clips from the series, was launched on 9 February 2017 and reached the goal by the next day. 
The documentary will premiere in New York, Los Angeles and London. A Blu-ray release is also planned.
Ira Steven Behr announced the documentary in 2016, but had been working for some years on the project. Behr commented: "We all went through this unbelievable experience that took seven years of our lives and now we've had all this distance from it, and it was like what does the show mean - what does the show mean to us as individuals, as people, and what does the show mean, if anything, in terms of the franchise and the culture... I had been interviewed a couple times for other docs, Trek docs, and I got really friendly with Bill Shatner and had a wonderful interview with him for the TNG doc and then Dave Zappone said, 'We can't do Shatner again, would you like to be Shatner'?". 
The documentary will be more than a series of talking heads interviews, an approach suggested by Avery Brooks to Ira Behr. This gave Behr the idea of filming in the writers room as they developed what a eighth season would be like. Behr commented: "That was an idea that I had based on a conversation with Avery, because Avery kept saying, "Don't make it talking heads only." It got me thinking, what would be something you've never seen before? There were ground rules, which was everyone had to watch the final episode of season seven, so everyone remembered where everyone was on the playing field, or at least read the Wikipedia page. We weren't going to have any cheat sheets. We are going in there with nothing for one day to see if we could get through a pilot episode of the show. And we did. Obviously, as with any show, you don't break a show in a day — and if you do, you still go back the next day and refine. This is the raw material, but it's a fascinating process. We had a fantastic time doing it. It was amazing how time slipped away and everyone was back doing their thing and interacting and arguing and getting passionate and it was really a magic day". 
Nimoy commented: "After 173 episodes, people still want more DS9, which is not unusual as fans felt the same way about TOS, which only produced 79 episodes. We’re sticking to the original vision for the documentary, but with some modifications. These things evolve over time, and the fact of the matter is DS9 evolved dramatically through seven seasons for a number of reasons, and we’re going to be looking at that, as well as what the show was about, how it changed, a focus on the characters and how they evolved over time. Then we’re going to try and take a look at what’s happened over the past 17 years since the show stopped airing. A lot of the perception of the show has changed. Accessibility to the show has changed in terms of being able to rewatch the series. We’re going to look at the show to see what are the elements that have appealed so much to fans in retrospect, and what has happened over the past 17-20 years in pop culture, and on the planet, to cause people to reassess DS9, and bring it out as one of the jewels in the crown of the Star Trek franchise. There’s just this immense popularity, due in no small part to the fact that a number of the original cast members are still out there, are still attending conventions, are still together, and there’s a lot of camaraderie and love that they’ve extended to the Star Trek family that I’ve observed from attending conventions. So while the documentary is evolving, much like the show did, we are staying true to that original concept of “What made this show so special?”" 
Possible DS9 remasteringEdit
The documentary makers have approached CBS about having footage from DS9 remastered. 
The documentary team wrote that they planned "to follow up with our intent to scan and remaster selected shots from the series for presentation for the first time in HD. While we want to reiterate that nothing’s guaranteed until we can get into details further with various departments, we’ve been empowered by our positive talks with CBS Television Studios, along with guidance from familiar faces Mike & Denise Okuda and VFX master Doug Drexler, among others".
Nimoy commented: "We’ve really expanded the scope of the project – the length of the time will expand – but it also allows us to acquire more clips from CBS from the original episode... and we are now in discussion with CBS about trying to get to the original negatives, to rescan them to give high-definition resolution to our film so that Deep Space Nine can be seen in high def for the first time. CBS is open to discussion – it’s expensive, it’s complicated, there’s a lot of logistics involved – but now that we have the financial backing to pursue this, we’re really determined to make it happen". 
Behr commented: "For many, many years – and decades, it seems – I’ve talked to people about getting DS9 in HD, discussing ways to make it happen. It’s not what I set out to do with the doc, it would be an offshoot of it. If it doesn’t happen, I’m not going to feel like, ‘Oh, damn, that was a level of success we did not reach.’ It’s a total offshoot – has to do with money [and] other things – it’s not so much a matter of the series itself, it’s just the technology of how the film was shot and how the special effects were shot back then, and the changeover. It would be nice. Just imagine: if we do get a chance to do the clips [for the doc] – I’m not talking about the series – the clips for the doc, in high def. That would be… extremely cool. Plus, it would give the fans another decade of dreaming what the whole series would look like! It would be that little taste, a lovely little taste – that first injection that leads to so many others". 
The crowdfunding for the documentary was undertaken by Indiegogo. After the first goal was successfully reached in donations, four stretch goals were announced; the first to extend the documentary from sixty minutes to ninety minutes, the second to commission an original score for the documentary and an extended writers room feature; the third to film more interviews. The fourth goal was secret at the beginning, but was revealed later as approaching CBS for original footage from the series to be remastered in high definition.
Several tongue in cheek videos were released, including one where a "Mr. F" approaches Behr with money for the documentary.
- Nana Visitor
- Terry Farrell
- Rene Auberjonois
- Armin Shimerman
- Alexander Siddig
- Colm Meaney
- Cirroc Lofton
- Michael Dorn
- Max Grodénchik
- Casey Biggs
- Jeffrey Combs
- Chase Masterson
- Andrew Robinson
- Hana Hatae
- Marc Alaimo
- Aron Eisenberg
- James Darren
- Nicole de Boer
- J.G. Hertzler
- Robert O'Reilly
- Bill Mumy