The Robots Of Death
Japetus or Iapetus was the second moon of Saturn.
Circa 3985, there were three man-made colonies on the moon, one of which was Kaldor City. Kaldor City existed on the edge of a vast sandy desert, with the Founding Families (the initial terraformers) governing Japetus. (Legacy) However, according to all other sources, the City and the Families were in fact on the planet Kaldor. (Occam’s Razor, Crisis on Kaldor)
Japetus was one of the planets which adopted the New Astrology created by Kasterborous. (Short Trips: Zodiac[which?])
In the 30th century, Japetus was part of the Earth Empire. (So Vile a Sin) Centuries later, minerals were being sent to Io for distribution throughout the Galactic Federation. (Legacy)
In 3985, the mercenaries Lambert, Sadler, Cooper and Townsend left Japetus in stolen Federation shuttles. (Legacy)
The temple of the Lord of Time was located on Iapetus. In 2015, Iris Wildthyme held a party on the moon. (Our Tune)
Behind the scenes
The novel Legacy implies that the Robots of Death was set on Japetus, but all other sources indicate that it was located on the planet Kaldor. As pointed out in the reference book AHistory, Kaldor City is located far from Earth space and has no interstellar trade.
All DWU sources except the short story Our Tune use the spelling “Japetus”.