SMALL-COMET ATMOSPHERIC HOLES ARE INSTRUMENT NOISE

Frank and Sigwarth claim that dark pixel clusters observed by the VIS Earth Camera are atmospheric holes created by small comets. We have ex amined their catalog, which contains about 700,000 of these ''atmosphe ric holes''. for consistency with this small-comet hypothesis and with instrument noise. A geometrical requirement of the small-comet hypoth esis is that the number of pixels in a typical cluster must vary by a factor >100 with spacecraft altitude because of the inverse-square law of the apparent cluster area versus distance. We find no systematic v ariation of cluster size with spacecraft altitude. The Iowa catalog da ta are consistent with instrument noise because neither the size distr ibution nor the event rate of dark pixel clusters depend on altitude. At altitudes outside of the radiation belts during the one day of avai lable raw data, more than 75% of the dark pixel clusters result from t he process that Frank and Sigwarth employ to remove bright pixels caus ed by energetic particles. This data processing also causes additional meaningless dark pixel clusters to occur in the dark sky or over the dark Earth.