Kuiper belt constraint from Pioneer 10

We extract information from the failure of small objects to cause detectable damage to Pioneer 10, which has been inside the Kuiper Belt for a decade, Belt objects too small for telescope detection and too large for IR emission visibility are addressed, This is a size range with few other potential techniques, short of a new space mission, for direct detection, Results, based on an 8-inch radius propellant tank, are bounds of about 1/10th of an Earth mass on low-mass, low-density objects, Implications of Poynting-Robertson drag and ISM erosion, and potential improvements to the bounds, are discussed. (C) 1998 Academic Press.