Altair III
Altair III is the third planet in the Altair system, orbiting the star named Altair.
When the USS Hood visited this system, Lieutenant Commander William Riker stopped Captain Robert DeSoto from transporting to the surface of Altair III with an away team, because he deemed the action as too dangerous, inappropriate for a commanding officer. (TNG: "Encounter at Farpoint", "The Pegasus")
At the beginning of the episode , in the ship's briefing room, Picard discusses with Riker during an incident on the planet Altair III, when he refused to let Captain Robert DeSoto of the USS Hood beam down, seeing that a captain's life could be in danger. Picard asks him if he intends to back down from that policy. Riker confidently says "No, sir." Then, Captain Picard formally welcomes Riker on board the Enterprise and shakes his hand.