Imaging and photometry of comet C/1999 S4 (LINEAR) before perihelion and after breakup

We analyzed photometric measurements and images of comet C/LINEAR before pe rihelion and after its breakup. Results from our photometry data include a lower limit of 0.44 kilometer for the radius of the nucleus before breakup, and a determination that it was depleted in carbon-chain molecules relativ e to most other comets. Our imaging and modeling results, which include a c onstraint on the rotational state of the nucleus, indicate that the disinte gration likely started on 18 or 19 July 2000. The total mass delectable in the dust tail after the breakup was 3 x 10(8) kilograms, comparable to one of the fragments in the Hubble Space Telescope images; we therefore infer t hat most of the comet's original mass is hidden in remnants between 1 milli meter and 50 meters in diameter.