Vulcan's Forge II

OK."...cabochons..." are shaped and polished gemstones so Poul Anderson's use of the term to describe spacecraft observed from the Mercurian surface in "Vulcan's Forge" (Space Folk, New York, 1989) is metaphorical.

This Vulcan is not a planet between Mercury and the sun but "...an asteroid sufficiently close to the sun that its metallic body is molten..." (p. 37), kind of a mini-Satan's World.

As such, it warrants close scientific observation:

"...it may yield information about solar weather and other processes over a long timespan. Details are impossible to retrieve from afar. Direct investigation is necessary." (ibid.)

Fortunately, there is already a base on Mercury. A scout ship controlled internally by a consciousness-level computer and externally by a man who will remain at the base but with a radio time lag are sent to Mercury, having previously explored the outer Solar System. Then the scout approaches Vulcan and establishes orbit around it.

So close to the sun, Vulcan is "'...precessing and nutating at high rates.'" (p. 45) Not processing or mutating, precessing and nutating: changing the orientation of its axial rotation and swaying in that direction. This generates magnetism that causes problems for the scout.

However, what makes the story is not merely the technicalities but the human dimension. When the controller's wife and partner, now dead, had remotely controlled the scout in an emergency on Titan, her personality had entered the data bank and computer program. Thus, it is possible that what remains of her suffers as the software is damaged - so he gives her peace by wiping the program at the expense of losing the data from Vulcan.