The Emergency Security Gorn, or ESG Mark-1 for short, was a sophisticated holographic program used aboard Starfleet's first Emergency Medical Vessel in the latter part of the 24th century. The ESG Mark-1 was an Emergency Security Hologram based on the Gorn species. The Doctor, one of its developers, espoused that the ESG Mark-1 had proven to be a fierce hand-to-hand combatant during tests. Unlike the Gorn species, the ESG sported a tail, which the Mark-1 also utilized in combat. These holograms spoke flawless Federation Standard. (VOY novel: Unworthy)
The ESG Mark-1 was a variation of the Emergency Security Hologram developed by Doctor Lewis Zimmerman and the Doctor with the assistance of Lieutenant Reginald Barclay on Jupiter Station. The ESH was based on the success of the Emergency Medical Hologram programs. The ESH, including the ESG Mark-1, were subsequently tested on Jupiter Station before being assigned to the USS Galen, which also pioneered a number of other advanced holographic staff, including upgraded EMH staff and holographic engineers.
In May 2381, the Galen was assigned to Project Full Circle and, shortly in to the expedition the Doctor and Lieutenant Barclay suggested that the ESH's should be tested. When Clarissa Glenn, the ship's commander, questioned the necessity of this, they explained that the matrices used in creating the ESH's had been based on some of the more feared species that the Federation had encountered, including the Klingons and the Hirogen something which the non-holographic crew members would not be used to.
Following a scuffle in the holographic research lab, an ESG Mark-1 carried an injured Barclay to sickbay and reported how he and a Klingon ESH had found him there. The ESG's scans of the lieutenant suggested a mild concussion to the occipital lobe. The Doctor dismissed them when he commenced treatment. (VOY novel: Unworthy)