I was reading some old questions about cloaking and that the Federation had agreed not to develop cloaking at the Treaty of Algeron.

However, in TNG : Who watches the Watchers the Federation is observing a pre-warp society using an observation station built into a mountain-top. (Members of the research team also wear Holosuits that make them invisible.) At one point in the episode, the 'cloak' around the observation station fails and the observation station becomes visible to the natives -- who are angry that they've been under observation for so long.

Wait? Isn't that cloaking technology? Presumably the hand-waving technology is that the observation station was hidden by a holographic projection of rocks, but to me that still seems like a 'cloak'.

Was the Federation observation outpost in violation of the Treaty of Algeron -- or did it not apply to:

  1. interactions with pre-warp societies (this makes no sense);
  2. specifically detailed only particular types of cloak (holographic projections OK; metamaterials OK; tachyon bending, not-OK);
  3. non-military applications of cloak (which would seem problematic, Hitler hid a lot of build-up to WWII as civilian production); or
  4. non-mobile cloaking?

I'm phoning the Romulan ambassador soon and would appreciate answers.

  • 4
    Yes, I'd agree with the holo-interpretation. A cloak makes stuff invisible, transparent, it looks, as if there is nothing there. To hide behind a simulated rock is something different.
    – Einer
    Commented Feb 5, 2015 at 15:01
  • 2
    I'd say: Yes. Because it would be hilariously easy to be detected: You take a torch and direct it there. If it's reflected, its not empty space. If I was a romulan, I'd say: "Go for it, dumb-ass!"
    – Einer
    Commented Feb 5, 2015 at 15:10
  • 1
    after looking at the memory alpha post it seems the federation only agreed not to do R&D on cloaking, but any captured cloak would be completely valid to use, or any existing cloaking tech would still be viable. we have examples of the fed using cloaking mines multipule times with no recourse, so i feel like it specific to new research into cloaking. -- update, it does say or use, my bad.
    – Himarm
    Commented Feb 5, 2015 at 15:12
  • 13
    I think it's important to ask exactly what both technologies do. A cloak makes a ship, station etc. invisible to the naked eye but also to sensors (usually). It was never stated on screen whether the duck blind could or could not be detected by a standard sensor sweep when the holographic rock face was working. Visibly masking something but not hiding it from sensors might not fit the text book definition of cloaking device.
    – geewhiz
    Commented Feb 5, 2015 at 15:36
  • 2
    This question seems confused. In Who Watches the Watchers, the natives did not understand the advanced technology and thought that Picard was a god. Plus, it's never stated that the research team intentionally ventured outside the holographic duck blind. In Insurrection (the movie), the "natives" are actually a post-warp society that fully understands all of the technology being used, and appear to be a bit annoyed (but non-violent and compassionate) when the research team is revealed. In this case, individual researchers did venture forth in cloaked suits of some kind.
    – Ellesedil
    Commented Feb 6, 2015 at 17:59

7 Answers 7


The script of Who Watches the Watchers is quite clear the the duckblind on Mintaka III was just a holographic projection of a rock. It's good enough to suspend disbelief on the holodeck, so it's good enough to fool some locals.

PICARD: Mister La Forge, report.
LAFORGE: We've finished replicating the parts they'll need, but what I don't understand is why a three man station would need a reactor capable of producing four point two gigawatts.
RIKER: Enough to power a small phaser bank, a subspace relay station, or
LAFORGE: A hologram generator. Oh, a duck blind. Right. They're anthropologists.


PICARD: Now, Mister La Forge.
LAFORGE [OC]: Aye, sir.
(The holographic camouflage comes down)
NURIA: What is that?
PICARD: A place where we can watch your people.

I don't recall there being holosuits that make people invisible in this episode and the script and Memory Alpha make no mention of them (Riker and Troi go to the surface in plain sight with the same props as the inhabitants surgical alterations), but more on that later.

As for whether using a holographic projector in this manner violates the Algeron treaty, we have to split the hairs of a hologram and a cloak. I think the main distinction between a cloak and a hologram is that a hologram projects an image (photons and holomatter contained by forcefields) where a cloak acts on existing ambient and active signals, bending them around the cloaked object and restoring their normal trajectory on the far side. As the Mintaka observation station is buried in the cliff, and the rock face is unmoving, it's easy to see how a cloak would be the wrong device for the job; instead of seeing an unadulterated cliff, an observer would see the inside of the artificial cave.

To imagine how a hologram would appear to an active scanner, let's consider an analogy to contemporary technology: radar. Radar is an active projection of radio waves, which are lower energy than infrared and far from the human visible spectrum. A radar dish looks for reflections of its projected waves off of objects in its sight. If we were to project a hologram of radio waves, the radar dish would pick this up immediately. This is not a cloak; it's most similar to radar jamming. If we were to project force fields that hold these radio photons in place, the projected radio waves would presumably reflect off of the 'holomatter' as it would a real device.

The human eye does not project light; we only observe reflected light. This is called passive detection. There has not been to my knowledge a humanoid lifeform introduced in Star Trek that uses active sight detection. (There are of course several earth species that use active sound detection.)

Now, there are two occasions in First Contact where standard Federation holographic projects are disrupted by seemingly simple lasers:

  1. The EMH activated as a deterrent in sick bay by Dr. Crusher flickers under a Borg eyepiece laser.
  2. The maître d' in The Big Goodbye holo novel is disrupted by Ensign Lynch, also assimilated and fitted with an eyepiece by the Borg.

The point is that holographic technology in Federation use is fairly clearly visible to technologic sensors and only concerned with blocking visible light perceived by biologic sensors, a.k.a. eyes. As the Federation makes liberal use of holographic technology with no diplomatic penalties, one can only assume that it is substantially different from and inferior to a military grade cloaking device. The Treaty of Algeron being a peace treaty, we can again only assume it was primarily concerned with military devices. Thus the Federation was not violating the treaty in Who Watches the Watchers or with any other use of hologram technology.

There are of course several occasions where the Federation makes military use of holographic projections. I think it's an episode of Voyager where they project several holographic shuttle craft decoys to attract fire from attacking Kazon ships; the Kazon are fooled presumably because of their inferior technology can't distinguish beyond the visible spectrum. I don't recall any instance where holographic projections are used to make a ship disappear. Also, there's nothing really preventing an hologram from holding and firing a weapon, with or without a mobile emitter.

However, the TNG movie Star Trek: Insurrection, used a blindingly similar introducktory hook.

A small village sits under cloudless skies, nestled in the rolling, green hills of an alien planet: home to the Ba'ku. The citizens of this village go about their days, tending to crops and livestock – performing the functions of an agrarian civilization. A beautiful woman, Anij, emerges from a crowd of her fellow Ba'ku and makes her way through the village, stopping to silently greet a man named Sojef. Both are unaware that in the calm and peace of their home, they are being watched.

On computer terminals, the activities of the Ba'ku are being monitored. Within a cloaked "duck blind" positioned high on a hill overlooking the village, Starfleet officers and their alien partners, the Son'a, spy on the Ba'ku. Through special monitors, not only can they see the goings on in the village below, but also a team of researchers, themselves cloaked in isolation suits that glow red on screen.

Source: Memory Alpha.

The Federation clearly has a penchant for observing pre-warp cultures, which makes the whole Prime Directive much easier to accidentally violate; Memory Alpha also cites the obvious assumption that the duckblinds in Who Watches the Watchers and Insurrection use the same holographic technology. Note that the Insurrection Memory Alpha article specifically references and links to cloaking technology hiding the duck blind, which I contend is an error. The reference page for cloaking device says:

A cloaking device is a form of stealth technology that uses selective bending of light (and other forms of energy) to render a starship or other object completely invisible to the electromagnetic spectrum and most sensors.

I suppose the superlative "most" sensors makes the exact definition of a cloaking device a bit fluid. However, with pre-warp (and supposedly pre-sensor) civilizations, there isn't much need to conceal things beyond the near visible spectrum. Just hope they never try to observe a planet full of sentient mantis shrimp, as I'm sure abducting and dissection of the eye qualify as 'interfering' in the eyes of the Prime Directive.

But then again, Memory Alpha also references use of "isolation suits", and falls short of calling it a full-blown cloak:

An isolation suit was a type of stealth clothing used by the Federation Starfleet in the 24th century. The suit was equipped with technology that made the person wearing it practically invisible. It was possible to see through the invisibility when a person wearing the suit was viewed through a specialized screen. The suits were linked to the "duck blind" monitoring station, in that they lost the invisibility effect when the duck blind lost it's holographic shell.

The suit itself is much closer to a cloaking device, and therefore much closer to violating the Treaty.

  1. It moves with the wearer, which is more difficult to do with a perfectly sync'ed holographic projection.
  2. It is invisible from all angles, showing an observer the perfect image of the other side of the suit.
  3. Without actually bending the light, this would require the suit to continuously observe its surroundings.
  4. Anyone who's looked at perspective based optical illusions knows that it's possible to create a near-perfect illusion for a wide range of angles. However, the illusion always has a weakness. Extending this to a hologram attempting to conceal an object, the invisibility would have to strain and warp for some observers if it were observed from enough angles simultaneously.

Revisiting the radar analogy, contemporary stealth technology works by absorbing or deflecting projected radio waves. If this were the effect of the isolation suit's 'stealth', the wearer would appear as a pitch black, humanoid shaped hole in the air. So it's clear the suit itself does not use passive stealth.

Shots from inside the Insurrection duck blind clearly show how the suits are visible to at least some light, and the 'special screen' is suggestive of an unpowered viewing window, like polarization. The red glow, on the other hand, suggests radiation (rather than reflection) of an invisible portion spectrum of light, such as infrared. Perhaps the suits were transmitting on a frequency, like a radar beacon.

Duck Blind view screen highlighting movement of 'cloaked' observer Close up of several cloaked observers in their glowing isolation suits

Memory Alpha points out that the script makes it clear the suits use a force field. This is pretty flimsy technobable, in my opinion, but here it is:

From the point of view of the rock face behind the village. Although we may not realize it yet, we are watching through a window now... slightly discolored, pulling back to see a mysterious figure in an isolation suit standing incongruously beside her, his suit glowing with a green force field. None of the Ba'ku are aware of him as he takes readings with a sophisticated sensor device built into his suit.

In conclusion, the duck blind itself, especially in Who Watches the Watchers is in no danger of violating the treaty. The isolation suits used in Insurrection are much closer to active cloaking technology. It is fairly clear from the aesthetics that these are or have become standard Federation issue suits, whether or not they were original developed or provided by the partners-turned-villains Son'a, who make liberal use of other banned technologies such as subspace weapons. The isolation suits appear to have several shortcomings that separate them from a military grade cloaking device. Whether or not these suits violate the Treaty of Algeron's prohibition against developing cloaking technology will be a matter of debate among Alpha Quandrant diplomatic scholars for some time. One can only hope that the post-Nemesis Romulan government will be forgiving.

  • I did not expect this to be the accepted answer. I have attempted to edit it to make the analysis more clear and address and incorporate the input and concerns of several commenters. Thanks everyone. (PS pun intended :-D )
    – Dacio
    Commented Feb 6, 2015 at 19:45
  • Just a side note but the suits seem to be acting like a holographic 'green screen' effect. Your quote says that they rely on the 'blind', its more likely the same tech that allows 2 people to walk away from each other in the same holodeck. Hence the suits too would be easily appear on sensors, just none of the primitives had a tri-corder. So no they too can't be classed as cloaking tech
    – Matt
    Commented Aug 10, 2017 at 19:34
  • 'Holographic green screen' seems like a contradiction to me. A green screen works by editing out a single color. A Trek hologram is a 3D projection of photons held together by force fields. It's possible to project an image into an environment, but you can't project something out of visibility – that's like trying to drain a pool by adding water. Unless you're talking about the screens in Insurrection editing back in the otherwise invisible suits, I don't see what you're getting at.
    – Dacio
    Commented Aug 14, 2017 at 23:47
  • All I meant was it seems to be a hologram projected over the suits to remove the undesired suit, although its probably not color based, (as in it tracks the suits and projects a fake image over the suits surface). That's how green screen works (removing what isn't wanted and replaces with what is - although you have to view it on a screen today, with holotech it could be done on a live scene)
    – Matt
    Commented Aug 15, 2017 at 11:18

Actually, despite appearances, the Federation is NOT using cloaking technology in this case. The Cultural Observation Post, nick-named the "duck blind" by Federation personnel, uses holographic technology to project a one-way surface over its structure. Both the duck blind itself, as well as any isolation suits worn within range, are concealed using the on-site holographic generator. Think of it as a holodeck that projects outward instead of inward.

Since the Treaty of Algeron explicitly forbids the development or use of cloaking technology alone, it does not apply. Holoprojection really only serves to hide something from the naked eye or visual surveillance - sensors or any kind of electronic mapping would still detect the concealed items or structure. This means that it would afford no advantage in combat, since any sufficiently advanced opponent would be able to detect and possibly disable the projection.

For more information regarding the Cultural Observation Post, please see the link below:


  • 5
    The federation is on thin ground here - if you holographically reproduced an image of what appears behind you to some position in front of you, you would essentially be "cloaked" - but maybe you are only "technically cloaked" if you bend light around you... Commented Feb 5, 2015 at 18:09
  • 8
    Oh, I agree. But apparently the treaty only covered the specific technology, not the concept. You'd think the Romulans would have better lawyers than that writing their treaties.
    – Omegacron
    Commented Feb 5, 2015 at 18:33
  • 17
    I think that the being able to hide from sensors part of true cloaking is really the key. If you can hide from the naked eye, but still are detectable by sensors, you're not really hidden.
    – Kai
    Commented Feb 5, 2015 at 20:57
  • Good point @Kai - I've updated to reflect that it's only visual.
    – Omegacron
    Commented Feb 5, 2015 at 21:13
  • 3
    The whole point is that it only works against such undeveloped civilizations: the Romulans wouldn't care because it's not "cloaking" just "camouflage". They certainly aren't on thin ground.
    – Jon Story
    Commented Feb 6, 2015 at 15:27

You've hit the nail on the head. While the hologram generator used by the duck-blind (to create the illusion of a solid rock face) is good enough to fool the Mintakans, it would be immediately detectable by a race with Federation-level technology such as the Romulans and therefore probably doesn't qualify as a 'cloaking device'

EXTERIOR MINTAKA THREE - DUCK BLIND - DAY : Oji is atop a bluff, finishing her reconnaissance. No luck. She returns to the duck blind rockface, touches it once more. Nothing happens. The hologram generator's doing its job; the rockface looks and feels authentic.

Although we don't have the wording of the Treaty of Algeron available to us, it's repeatedly stressed that the restriction is on the use of cloaking technology, not holographic technology.

PICARD : That's what this is all about? A cloaking device? In the Treaty of Algeron the Federation specifically agreed not to develop cloaking technology. - The Pegasus

Added to that is the fact that the Federation are using this in a benign way in a pre-warp civilisation (and presumably the results are likely being publicly shared which means that the Romulans will have access to them) and there's very little that your friend, the Romulan Ambassador can complain about.


The duck blind is not cloaking technology.

A cloaking device makes something disappear. When an object is cloaked, visible light and other emissions can pass through it (or at least appear to pass through it).

However, the duck blind uses holograms, which make something appear to be there that isn't really there; rocks in this case. In general, visible light does not pass through holograms.

Imagine trying to use the duck blind's hologram technology to hide a starship in space. You could project a facade of rocks, but not make the ship disappear. This wouldn't be legally classified as a cloak, because you wouldn't be making the ship invisible, just covering it up to appear like a different object.

  • 2
    The holosuits worn do allow the illusion of light passing through the wearer.
    – Valorum
    Commented Feb 5, 2015 at 16:26
  • 1
    @Richard: That's only in Insurrection I believe, and at that point I think we can probably surmise that times have changed what with the Romulans possibly having already joined the so-called "Federation Alliance" against the Dominion (though since Insurrection doesn't state a stardate it's hard to know whether this is really true). Commented Feb 5, 2015 at 17:29
  • @LightnessRacesinOrbit : Insurrection takes place during the Dominion War, I believe about mid-way through DS9's last season.
    – Omegacron
    Commented Feb 5, 2015 at 19:09
  • 1
    Folks were wearing holosuits in the episode that I mention.
    – RoboKaren
    Commented Feb 5, 2015 at 19:22
  • @Omegacron: Source? Insurrection doesn't state a stardate. Commented Feb 5, 2015 at 19:30

While I don't believe any printed versions of the Treaty of Algeron exist, the premise of the agreement was the Federation would agree not to research any cloaking technology which resembled the already existing technology of the Romulan Empire.

  • The treaty seems specifically bound to cloaking devices which block subspace detection and visible weapons-lock of combat oriented space vessels.

  • Since Captain Kirk had already stolen a version of that technology, any relationship with the Romulans would be predicated on the Federation NOT taking advantage of said acquisition. (See: The Enterprise Incident)

  • The Federation, playing fast and loose with the interpretations of the treaty, would go on to create a "phase-cloaking" technology, which would allow a ship to be out of phase with the existing universe AND potentially cloak a ship from being fired upon. The starship Pegasus was illegally equipped with such a device.

  • Later, we would see the Federation enter a treaty with the Romulans to allow limited use of cloaking technology onboard ships like the Defiant and in the use of the cloaked replicating mines protecting the Bajoran wormhole during the Dominion War.

  • Holographic technology used to observe alien civilizations or electromagnetic detection reduction but not visible light cloaking seem to skirt the boundary of the Treaty of Algeron, since neither of them are being used for wartime operations and likely could be detected by Romulan sensors.

  • 4
    To be fair, development of the phase cloak was not "playing fast and loose": it was in outright violation. You correctly identify that going on to actually equip a ship with such technology is also illegal, but that's only by consequence. The Treaty states that the Federation shall not develop this technology. Commented Feb 5, 2015 at 17:25
  • 1
    I called it fast and loose because the technology incorporated phasing AND cloaking. It was the addition and emphasis of the phasing aspect which was how they managed to finagle support for the technology at all. Commented Feb 5, 2015 at 22:01
  • While it's not mentioned on screen, I presume the use of cloaked mines in the Dominion War was negotiated with the Romulans similar to how they negotiated for the Defiant's cloak.
    – Schwern
    Commented Feb 5, 2015 at 23:53
  • Agreed. They were grudgingly allies during the Dominion War. Commented Feb 5, 2015 at 23:59

Just as an extension to what others have said, I think we can reasonably assume the Romulans only wanted to restrict Federation access to this particular technology that gave themselves an edge. As holographic stealth methods such as the one in question would not fool "modern" sensors, or possibly even primitive ones (the in-Universe explanation seems to be that holograms are primarily energy fields, similar to vessel's "shields", and so even our current sensor technology would likely be able to note the difference between Federation holograms and real matter).

In other words, the Federation's use of "cloaking" technology in this particular event did not present any kind of potential military use and so the Romulans could not care less what the Federation was doing with it. Remember, the Romulans were really a highly Xenophobic race who at the heart of things genuinely feared the Federation (and as we see later in the franchise, this fear may have been justified), and so their interests revolved entirely around maintaining a military edge against them. The Federation's anthropological research efforts would be pretty far outside the Romulan's interest.


You can't compare the two. OK the desired effect is the same (they can hide), to say the holographic projection is the same as a cloak is like saying hiding behind a rock is a cloak.

The Federation is forbidden from using cloaking devices, but there is no reason for them to go ridiculously over the top in their efforts to honour the treaty and refrain from using any method of concealment.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.