In fairness, these sensor dishes are being used to emit and/or detect "trans-light" signals, as opposed to the signals on the electromagnetic spectrum present-day radar operates with. So this might be what they have to look like in order to work in-universe. Or something.
Also, I appreciate how Shapeways has allowed a certain degree of finesse in how special sensors are placed on a given ship - not least how the Tholians make a point of using hexagonal types
on their scout ships.
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Typically, when a given empire encounters another for the first time, Tactical Intelligence (be it from a ship's own fire control suite, and/or the use of a scout channel assigned to this purpose) is part of a broader spectrum of data being gathered by both sides and (if one or both sides survive the encounter) being reported back to their respective admiralties.
If both sides operate more or less "in the open", such as the United Federation of Planets and the Klingon Empire, there are a variety of signals intelligence, espionage, and/or (in peacetime) diplomatic and cultural exchanges which can be pursued. Of course, operating "in the open" is not the same as being "open" in terms of
what is being exchanged; the UFP is much more comfortable sharing certain aspects of itself in comparison to how the Klingons speak of their own empire.
Then you have factions which, to various degrees, tend to operate "in secret". Be it a star empire which is liable to obscure the deployment of their ships (such as the Romulan use of the cloaking device) yet which still needs to operate at least part of their empire "in the open" (as even the Romulans need to maintain a network of bases and patrol ships in order to scan their territory for potential threats). Or be it a "pirate" faction which, for obvious reasons, wants to hide both the movement of their ships and the locations of the bases needed to support them; see the Orions (even those without access to cloaks) or the High Pirate Bands of M81. Those factions
can be talked with, should they wish to engage in conversation: whether it's the negotiation of a new treaty between the Klingon and Romulan empires, or perhaps the signing of a mercenary contract with a given Orion negotiating agent.
But what do you do if even such options as those aren't on the table?
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The beginnings of this problem from an Alpha Octant perspective was in the mid-to-late Y160s, when hitherto-unknown "
Intruders" were first encountered by the various star fleets. Or rather, the first instances in which an Alpha ship survived to report such encounters took place.
One of the very earliest such encounters was dramatized in
Captain's Log #25. A Federation police cutter close to the Federation-Klingon border was destroyed by an unknown type of alien vessel; when a Star Fleet destroyer leader, a squadron of Klingon frigates, plus an Orion salvage cruiser converged on its last known location, the intruder appeared with
a collection of smaller ships in tow.
This and other battles fought against Intruders elsewhere led to a series of startling discoveries. For one thing, these new aliens did not use shields; they instead appeared to use some sort of panels capable of absorbing energy from incoming weapons fire. These panels appeared to be hemispheric, as opposed to the six-sided shields used by most types of Alpha Octant starship. Remarkably, while opposing ships could not beam through such panels, the Intruders themselves could beam through them - making hit-and-run raids (via robotic boarding parties) and transporter bomb operations more dangerous prospects.
But that wasn't all their transporters were good for. Indeed, it appeared that the larger "Motherships" could beam the smaller "satellite ships" in their entirety and deploy them out into open space, or directly onto a planetary surface - and/or to retrieve them via transporter also! As to how these hangar bays actually function, it was unclear if the satellite ships were being fit "snugly" (as opposed to the leeway Seltorian ships have when docked inside the bays of a Hive or Nest Ship), or - to borrow a term from a different science fiction universe - if the Motherships' hangar bays are somehow "bigger on the inside".
Further, while they appeared to use a "medium-caliber" weapon more or less akin to a phaser-2, their heavy weapons appeared to be a weaponization of tractor beam technology to a remarkable degree, in that they could be used to "shake" a target to pieces. Fortunately, the tractor-repulsor beams on the satellite ships appeared to have only half of the strength of those on the Motherships.
Most remarkable of all was a system which enabled the operating ship to displace certain types of object from one location of space to another - or, in the most extreme of circumstances, into the molten core of a nearby planet! However, it appeared that only certain types of unit could be so displaced; for example, bases with active positional stabilizers could not be affected by this system. Further, it appeared that no more than two ships were able to use their displacement devices at once, limiting the number of Motherships and satellite ships that were encountered accordingly.
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Throughout the General War, the number of encounters with these intruders increased, along with the range of Mothership and satellite ship types being recorded.
A light cruiser equivalent was given the Federation class designation of
Conquistador; the original small satellite ship (designated the Viper) was followed by medium and heavy types, listed by Star Fleet as the
Cobra and
Mamba respectively. Cobra- and Mamba-sized satellite ship types were observed with displacement devices of their own; the first was referred to as the Reconnaissance Cobra, and the second type as the
Python. Most worryingly, near the end of the General War, a larger and more powerful Mothership type was encountered: this was designated as the
Dominator. And while conjectural fighters and Adder PFs were drawn up and programed into the simulators at Star Fleet Academy (as seen in
Star Fleet Battles Module C3A), the only attrition units observed in use by these aliens were a series of Interceptor-esque
mobile weapons platforms.
Yet still there was not much to go on, save for the data being recorded by the encountering ships' fire control suites and active special sensors. These intruders made no attempt to open communications; left no definitive clues as to their origins, or even their very identity as a species; and (since their ships tended to violently explode when destroyed, due to cascades from the power being stored in those absorber panels) left little in the way of wreckage for Alpha Octant engineers to study.
They did, however, begin to leave clues as to their ultimate intentions. Approximately mid-way through the General War, they adopted a more aggressive posture, attacking Alpha Octant ships on sight. As dramatized in
Captain's Log #27, a Dominator launched an attack on the Federation colony of Rimworld during the era of the ISC Pacification. And while the Usurper was otherwise engaged in the War of Return, a dramatic attempt to invade the WYN Cluster was carried out. Fortunately for the WYNs, power absorber panels don't appear to mix well with the WYN radiation shell, though the exact nature of these interactions has yet to be spelled out in
SFB terms. In any case, the wreck of an invading Dominator was salvaged as a war trophy and tourist attraction; through the study of this wreck, the WYNs found evidence that the ship had come all the way from M31: the Andromeda Galaxy.
Thus, by the time the first wave of large-scale attacks broke out against the ISC's Pacification cordons in Y188, these aliens were being referred to as the
Andromedan Invaders.