Starfleet Holograms
Following the enormous success of the Emergency Medical Holographic Program, a wide variety of Starfleet Holograms have been developed for use on starships, stations, and smaller vessels in Federation and Starfleet Auxiliary service, which can substitute for organic crewmembers on a temporary or long-term basis.
Emergency Hologram Basic Installation
Vessels equipped with holographic projectors (which includes nearly every commissioned Starfleet vessel by the 2390s) by default have a set of five emergency holograms installed, which provide organic crewmembers with support in emergency situations where their organic counterparts are incapacitated or otherwise unavailable. They are also useful in circumstances where a particular role is so rarely used on a ship that an emergency supplement is sufficient. Collectively, these programs are referred to as the Emergency Hologram Basic Installation (EHBI). Each program comes with a range of customization options, including species, personality, and gender presentation.
Emergency Medical Hologram (EMH)
The original emergency hologram, the EMH was first introduced in 2370 as a short-term medical supplement. The original version was incredibly unpopular, apart from the iteration known as The Doctor that served as Chief Medical Officer in an extended capacity during the starship Voyager's seven-year voyage from the Delta Quadrant to Sol. Later versions refined the personality and utility of the program leading up to the current EMH Mark VII, which includes personality and expertise imprints from hundreds of physicians and is capable of diagnosing most injuries and ailments without a tricorder, thanks to access to a ship's internal sensors.
Emergency Engineering Hologram (EEH)
Emergency Engineering Holograms are pre-programed with the layout and specifications of the ship they are installed on. They are useful for repairs in sections of the ship that are uninhabitable by organic beings, especially when an area has been irradiated or decompressed.
Emergency Navigation Holograms are capable of piloting the ship in the absence of an organic pilot, combining direct access to the ship's navigational sensors with personality and expertise imprints of hundreds of organic pilots that make it a much more effective and dynamic option than the main computer's autopilot functions. The ENH's functions are also stored in a different section of the main computer than the autopilot, providing redundancy in the event of damage.
Emergency Tactical Hologram (ETH)
Emergency Tactical Holograms are designed to operate a ship's weapons systems in the absence of an organic tactical officer. They are commonly used aboard auxiliary ships such as freighters, tankers, and transports which would have no need to carry an organic tactical officer, but are also part of a starship's complement of emergency holograms to provide emergency support on the bridge. An ETH is also programmed with a wide variety of strategic perspectives, which can make it a valuable advisor and counselor to a captain who needs to plan a tactical encounter.