I've just read John Scalzi's newly-published story "Slow Time Between Stars", and I was reminded of a similar story which I read 30 or more years ago but I can't now remember the title.
The story concerns an uncrewed, AI-powered - but not particularly intelligent - ship which is constructed in Earth orbit and launched towards the stars in something of a hurry. A few years into the voyage, communication from Earth ceases and the ship notices the Sun briefly becoming brighter, then fading.
It continues on for thousands of years before it arrives at its destination solar system, at which point it realises that it can no longer remember what its mission was supposed to be: over time, cosmic radiation has eroded its memory banks. It nevertheless chooses a planet which is similar to Earth, and lands. On introspection it discovers a frozen block of water inside itself, which it warms slightly; the temperature change causes some instructions to be released, which tell it to warm a small tank and inject a cell into it. The story ends with it understanding that further instructions would be provided in nine months' time.
I thought I might have read this in Brian Aldiss's anthology Space Opera, but none of the titles seem a match.
