As you read this, Halley's Comet is streaking its way toward our fair planet. Although we won't be able to see it without telescopes until later in the year, you can find out more about the cosmic snowball this weekend at the Air and Space Museum. "Comet Quest" in the Albert Einstein planetarium is a multi-media (mostly films and slides) depiction of the life-cycle and habits of comets, the myths surrounding them and how past visits by Halley's Comet have affected us earthlings. "Comet Quest" is shown every 40 minutes from 10:50 to 6:50 daily. Admission is $1.50, 75 cents for those under 16, over 60 and for students with ID.

While you're at the museum, take a gander at the 40 winning designs from the Great International Paper Airplane Contest. The paper flying machines were selected from more than 5,000 entries and will be on display through January 1986. Air and Space is open from 10 to 7:30 daily through Labor Day. It's at Sixth Street and Independence Avenue SW. If you're taking Metrorail, exit from the Blue, Orange or Yellow lines at the L'Enfant Plaza station. Call 357-2700; free.