In that year, the crew of the Antares transferred a young man, Charles Evans, who had been stranded on the planet Thasus for fourteen years and possessed psychokinetic powers, to the USS Enterprise, so he could be transported to Colony Alpha 5 to be reunited with his closest living relatives.
On stardate 1535.8, the Antares was destroyed when young Charlie used his psychokinetic powers to make a baffle plate on the shield of the ship's energy pile "go away." Charlie did not seem to understand the seriousness of his actions, saying simply that the baffle plate had been warped, and that the Antares would have blown up anyway. (TOS: "Charlie X")
According to the Star Trek Encyclopedia (4th ed., vol. 1, p. 31), the Antares was named after Antares, a star in the constellation Scorpius (the Scorpion) and one of the brightest stars as seen from Earth.
In the episode, the ship was given four different descriptions: 1) cargo vessel, 2) transport ship, 3) science-probe vessel, and 4) survey ship. The fourth edition of the Star Trek Encyclopedia described the Antares as a science vessel (vol. 1, p. 31) or as a transport (vol. 1, p. 367).
At first, however, the Antares was a trading ship. In a memo (dated 15 April 1966) from Robert Justman to Gene Roddenberry regarding the initial story outline of "Charlie X" (then called "Charlie Is God"), Justman advised, "I would suggest we eliminate the trading vessel in the story." He later referred to the Antares as a "trading vessel" twice in a memo he wrote John D.F. Black about the episode's revised story outline (the memo was dated 11 May 1966, by which time the installment had been renamed "Charlie X"). In the same memo, Justman asked, "Is it necessary that we see this vessel?"
The final draft script of "Charlie X" (dated 5 July 1966) made it clear that the Antares was indeed intended to be depicted on screen. When first established in the stage directions from that script, the craft was described, in comparison to the Enterprise, as a "much smaller survey ship." However, the scripted stage directions also referred to it as a transport. Additionally, in an ultimately unused line of dialogue from the same draft of the script, the Antares was said to have been on "a geological probe" of Thasus when it discovered Charles Evans.
The Star Trek Concordance (3rd ed. p. 278), by Bjo Trimble, had an original design illustration from Brian Pimenta of the Antares, with registry number NCC-717. In the Star Trek Encyclopedia (3rd ed., p. 470), though, a registry number of NCC-501 was given to the Antares, based on conjecture by Michael Okuda.
The Antares was one of the ships that the team who worked on the remastered version of Star Trek: The Original Series wanted to feature, if doing so would be possible. (Star Trek: The Official Starships Collection issue 63, p. 12) For that project, Mike Okuda used his earlier-conceived registry number of NCC-501 in the remastered edition of "Charlie X". In this remastering, the Antares is essentially depicted as a CG model of a type of robot grain ship visible in TAS: "More Tribbles, More Troubles", with an addition of a "crew module." Commented Okuda, "I can't recall whose idea it was to use the grain ship from The Animated Series. It might have been mine, or it might have been Dave Rossi's." (Star Trek: The Official Starships Collection issue 63, p. 12)
The process of adapting the robot grain ship as the design of the Antares began with Mike Okuda spending "a couple of days" on examining the layout of the grain ship. He then looked online for any blueprints of the vessel. Though Okuda found some blueprints he regarded as "very fine," none of them seemed to match how he imagined the craft's appearance. "So I did a 3D drawing of what my interpretation of that ship looked like," he continued, "and turned it over to Niel Wray (visual effects supervisor for Remastered TOS). The key to making it happen was that the blueprints had to be ready if Neil decided there was time to do it." (Star Trek: The Official Starships Collection issue 63, pp. 12-13)
Building the actual CG model of the Antares was a case of trial and error, but the creative staff of Remastered TOS knew there wasn't a lot of time to perfect the model. "The Antares ship was really a last minute add, even though it was planned ahead, so I simply said to Neil to use the same basic textures as the Enterprise," Mike Okuda remembered. "It has a little more relief to the surface texture, but unless somebody was very dissatisfied with it, we were pretty much going with Neil's first guess. I gave them the markings, but Neil used the same basic textures that were used to create subtle relief on the Enterprise's hull, but exaggerated them a bit." Despite the Antares being added late in the process, everyone involved was happy with the results. (Star Trek: The Official Starships Collection issue 63, p. 13)
The prefix "USS" was never applied to the Antares in on-screen dialogue nor appeared on the ship's hull.  Nonetheless, both StarTrek.com and the Star Trek Encyclopedia (4th ed., Vol. 1 A-L, p. 31) listed this ship as USS Antares. 
Additionally, in all editions of the Star Trek Encyclopedia, the Antares was referred to, in a list of Federation starships, as the prototype ship of the Antares-class starship, with the USS Hermes also stated to be of this class. 
According to an article at StarTrek.com, the Antares insignia was the Spacecraft Duty insignia. This insignia was worn by personnel assigned to an auxiliary spacecraft in Starfleet's Merchant Marine Corps. 
An Oberth-class science vessel, also named USS Antares, was part of the Star Trek: Orion Rendezvous planetarium show, produced in 1992 and authorized by Paramount Pictures in conjunction with the Star Trek: Federation Science exhibit. The ship was commanded by Captain Katryana DiChario, and left Neptune Station on a mission to explore a recently discovered, artificially constructed wormhole interstellar transit system that had "jump points" throughout the Milky Way Galaxy at real-life scientific phenomena, such as the Orion Nebula, the Crab Nebula, a flare star, etc. Geordi La Forge was a temporary crewmember during the expedition, along with a group of Starfleet cadets (the audience).
- USS Antares (NCC-501) at Memory Beta, the wiki for licensed Star Trek works
- Antares at Memory Omega, the wiki for licensed Star Trek books, audiobooks, and comics
- Antares-class at the Advanced Starship Design Bureau – includes a fan-made reconstruction of Brian Pimenta's illustration, from Star Trek Concordance, of this ship