
At the opening of Season 5, Pierre Chang was viewed filming an Orientation film for The Arrow Station and, even though his speech was half-finished, we probably learned as much about this place as we’re ever likely to.

“Hello, I’m Dr. Marvin Candle, and this is the Orientation film for Station Number Two, the Arrow. Given your specific area of expertise, you should find it no surprise that this station’s primary purpose is to develop defensive strategies and gather intelligence on the Island’s hostile indigenous population. . .”
Strangely, Pierre Chang uses the same fake name (Marvin Candle) as he used for making The Swan Orientation film. He is, also, wearing a Dharma coat with The Swan logo upon it. I’ll come back to this because much can be speculated about this matter.
Before the speculation the facts.
The Arrow is, as Pierre Chang was beginning to explain, designed to be used as an offensive and intelligence-gathering facility in the battle against ‘the hostiles’. The very name ‘Arrow’ itself is derived from it being an actual weapon, implicitly an aerial attack weapon. Did they actually fire weapons from this station? Missiles and suchlike? Hard to say, though I am inclined to think not.
Goodwin remarked, “It looks like some sort of storage facility.”

Of course, Goodwin was an Other-in-disguise amongst the tail-survivors ranks, but it’s difficult to figure he was lying. The Arrow looked like a Station that could store various materials, walled-in from practically all sides and tucked away from view. As a base to launch weapons from it doesn’t appear suitable so I can surmise that it was used as a storage area for Dharma’s serious weaponry.
If they had rockets to launch, my bet would be they stored the rockets there but launched them from somewhere else. (It would actually make sense – Dharma would not want to give ‘the hostiles’ any indication about where they kept their heavy-duty firepower so attacks would be better staged away from it.)
In this sense The Swan and The Arrow would appear to share the same characteristic: they were Dharma Stations The Others didn’t know anything about until after the crash of Oceanic 815. This actually brings me back to the matter of Pierre Chang referring to himself as Marvin Candle and wearing a Swan logo lab coat for The Arrow Orientation film.

A niggling question has always been, Why does Pierre Chang use aliases in the Orientation films? Previously we could assume it was to do with keeping his real identity secret but, really, that doesn’t seem to be a particularly crucial element. He wanders and lives freely by his real name within The Barracks, his identity is not kept under wraps to Dharma people. So what if it was something else? What if his pseudonyms were actually a form of code?
Consider that for The Swan and The Arrow Orientation films Pierre uses the pseudonym ‘Marvin Candle’. These are both top secret Stations, intended to be kept secret from The Others. Could it be the name ‘Marvin Candle’ is indicative to the ‘secrecy level’ of the Station in question? For the relatively less secret Pearl Station, Pierre uses the name ‘Mark Wickmund’, perhaps indicating a lower security level of name?

It doesn’t feel massively pertinent why a change of name should be used as a code in this way, but then it doesn’t feel massively pertinent why Pierre Chang elects to use different names at all. The fact that he does, and uses the same name twice for different films, does suggest to me some form of rationale behind the naming convention – a ‘security level’ is a reasonable conclusion.
Of course, Dharma and ‘the hostiles’ existed with a form of truce for a few years but the building of The Swan was in direct conflict with that agreement. If The Swan site was discovered that would immediately spell conflict, and The Arrow existed purely on the basis of such conflict – thus a clear link between Swan and Arrow is generated.

Perhaps The Arrow existed primarily due to The Swan construction. (Note Chang was filming The Arrow Orientation around the time The Swan was being built.) The two Stations are bound together. Those that know about one will know about the other. If they see Pierre Chang in The Swan Orientation they may see him in The Arrow film too – and therefore for consistency he uses the same name: ‘Marvin Candle’. As no actual scientific work takes place in The Arrow, Pierre Chang wears a lab coat with a Swan logo. More and more, through these fragments of information, a picture starts to emerge. We have a coherent and logical explanation for the use of the same name and the same logo of The Swan as it recurred for The Arrow.
Someone who actually did wear an Arrow logo on his Dharma gear was Horace Goodspeed.

When Horace met young Ben on the pier, he was wearing a Dharma jumpsuit with the Arrow logo, and when adult Ben closed Horace’s eyes after he had died, he was still wearing a jumpsuit with the Arrow logo. Whilst we have since seen that Horace was pretty much running Dharma’s people, he was indelibly associated with The Arrow Station. It’s rather curious that for a secret Station the logo was brandished and sported rather brazenly. But then Pierre Chang waltzed around with The Swan logo emblazoned on his clothing and that was supposed to be top secret, too.
In the Dharma Initiative, they don’t hide the fact that there are certain elements kept secret. You may know the logo, but if you don’t have clearance you wouldn’t have known anything about The Arrow or The Swan!

In terms of the original intended use of The Arrow, then, I believe we have a reasonably good idea of what it was all about. Yet there are a few points of interest worth picking up as they further correlations with The Swan. As we saw in Season 2, when the tail-enders found The Arrow they also discovered a box that contained a Bible, a glass eye and a radio.
There's popular belief that the glass eye belonged to Mikhail. Just because the socket beneath Mikhail's eyepatch was revealed as healed over during Through The Looking Glass it doesn't mean the glass eye couldn't have been his, but to suggest anything further would be pure conjecture (and not my concern here).

The Bible, however, was found to contain a missing piece of film from The Swan Orientation. The missing piece showed ‘Marvin Candle’ warning that use of the computer in The Swan for communication purposes was strictly prohibited. Arguably this piece of film was taken to encourage later occupants of The Swan to use the computer for communication, but we know it was Radzinsky that cut it out and probably moved it.

Desmond: “Why are there missing parts?”
Inman: “Radzinsky made some edits.”
Radzinsky, as we know, remained in The Swan Station and worked on his Blast Door Map. One of the notations on the Blast Door Map, relating to The Arrow, was ‘I think we’re on the same wavelength’. It’s a strange notation, really, but then what else was in the box in The Arrow? A two-way radio!

A two-way radio! The same wavelength! Using these pieces of information, let me just throw out one last piece of conjecture. The Purge happened, and Radzinsky had hunkered down in The Swan Station, pressing the button. The Others didn’t know of The Swan, and so he remained undetected. He started making his Blast Door Map and maybe, somehow, he got the idea that someone else had survived in The Arrow. ‘I think we’re on the same wavelength’, he noted, perhaps as a result of tinkering with his own radio and maybe picking up signals from the other side of the Island.
Who could that other survivor have been? Why, Kelvin Inman! The military man brought in to the Dharma Initiative! Where better to post such a man than at the defense base Arrow Station? Radzinsky gets in touch, perhaps guides him over to The Swan, and the rest we know. . .

It’s fanciful, I know, but it’s an appealing little untold story that works well enough. However, in terms of the hard and fast facts about The Arrow I believe we have enough information, scrappy and fragmented as it is, to arrive at a reasonable understanding of its function within Dharma as I have relayed here. I trust you’re on the same wavelength!