Outpost 4
Outpost 4 was an outpost constructed a mile deep on an asteroid of almost solid iron by Starfleet in 2160. This outpost was one of seven Earth Outpost Stations located on the Federation side of the Romulan Neutral Zone in Sector Z-6 of the Beta Quadrant. The outpost's protective shield was made of cast rodinium. ().

History 
The outpost was under the command of Commander Hansen Al-Salah by 2259. Under a retrofit directive, the  and the  delivered state-of-the-art matter synthesizers and a set of fully automated mining craft to Outpost 4. ()

That same year, the location of this outpost was labeled on a stellar cartography chart that was seen on the 's ready room viewscreen. () 

In 2266, Outpost 4 came under attack by an unknown starship that was later discovered to be Romulan Bird-of-Prey. Although protected by full deflectors, the outpost was hit by a powerful high-energy plasma torpedo that completely blew out the outpost's deflector shield, as well as taking out its phasers and killing its weapons crew. The second attack by the plasma torpedo hit the outpost, unprotected, resulting in the base's disintegration. 

During the Neutral Zone Incursion, the location of Outpost 4 was labeled on a map of Sector Z-6 that was displayed on the bridge viewscreen of the . (, production art)

Between 2266 and 2366, this outpost had been replaced. The location of the new Outpost 4 was labeled on a tactical intelligence analysis star chart. This outpost received a warning from Starfleet Command about an alleged Romulan base on Nelvana III. (, okudagram)

Background 
This outpost's quadrant of origin is inferred based on the location of Sigma Nelvanas system, in the vicinity of sister outposts 3 and 5 to 6, as seen in the star charts appearing in the  episode  and in the  episode .

In the Star Trek: Star Charts (p. 66), the location of 23 Earth outposts were depicted on a map of the Beta Quadrant. Outposts 1 to 8 were mentioned in dialogue or were seen on the Z-6 Sector map in  and Outpost 23 was mentioned in dialogue in . Outpost 4 was constructed in an area of space that been contested over during the Romulan War Theater of Operations (2156-2160).

Apocrypha 

The October spread of the Star Trek: Ships of the Line (2017) calendar titled "Duel of the Flagships" depicted the Enterprise and a Romulan Bird-of-Prey in battle over Outpost 4, by D.M. Phoenix.

External link 
 

de:Erdaußenstation 4
fr:Avant-poste terrien 4
ja:第4前哨基地
nl:Buitenpost 4
Outpost 04
Outpost 04