The Solar Ray, also known as the Solar Ray System, was a massive laser cannon constructed by the Principality of Zeon near the end of the One Year War. It appeared as the Principality of Zeon's final weapon to intercept the incoming Federation fleet during the Earth Federation Forces' Operation Star One.
The Solar Ray was converted from one of the space colonies of Side 3, Banchi 3 Mahal. Due to the modification of the space colony, it functions as a laser cannon with a diameter of 6.5 km. The interior of the modified colony was mirrored in aluminum (shipped from Zeon's European base), and equipped with an electric field generator using the system of an artificial sun. A critical semi-permeable membrane with a diameter of 6.5 km was set on both sides, and powerful cooling systems were installed in various places, as well as rocket motors for aiming the weapon. It was filled with an atmosphere of 80% helium, 15% nitrogen, and 5% carbon dioxide for laser oscillation, and almost all of the Principality of Zeon's power sets were used for firing.
Since the critical semi-permeable membrane and polarizing mirror were only in the practical prototype stage, they could only be used once, and even if that problem was overcome, each launch would consume Zeon's total power for several hours, and cooling after irradiation would take at least a week.
On December 22nd, U.C. 0079, under the order of Gihren Zabi, the Principality of Zeon began forcefully evicting the residents of Mahal, the third colony of Side 3. Solar panels from other colonies were sent to Mahal, and countless worker ships and mobile suits began converting the colony into a superweapon capable of annihilating half of the Earth Federation space fleet attacking A Baoa Qu.
Several days before the Battle of A Baoa Qu on December 31st, the Principality government placed an order to limit the use of electricity in order to power the Solar Ray. However, during this time, Sovereign Degwin Sodo Zabi secretly contacted General Revil of the Earth Federation Forces to arrange for peace talks. On December 30th, 20:20, his flagship, the Great Degwin, made contact with the Revil fleet. Considering his father's actions to be a threat to Zeon, Gihren ordered the Solar Ray to be fired at Gel Dorva, one of three preset launch axes.
At 21:05, under the command of technical officer Asakura, the Solar Ray was fired. The resulting laser reached its target - the Great Degwin and the Federation main fleet - in three seconds, vaporizing the Great Degwin, Revil's flagship Phoebe, and a third of the entire Federation attack force. The transport carrying the Solar System, which was planned to be used during the attack on A Baoa Qu, was also destroyed. The laser beam was bright enough to be visible from Earth's equator.
Due to technical limitations, the Solar Ray was unable to be fired again for at least a week. As the war came to an end soon after, it was never fired again. Its fate after the end of the war is unknown, but the technology behind it was acquired by the Earth Federation Forces and used to construct the Gryps II colony laser.
- In the TV series, the Solar Ray was referred to as the "Solar System" several times. All later sources, such as the compilation movie, used the name "Solar Ray" to differentiate it from the Federation's Solar System.
- The power output at the time of launch is mentioned as "8,500 gigawatts per hour" in the TV version episode 41, and as "85 million gigawatts per second" in the theatrical version of "Mobile Suit Gundam III: Encounters in Space".