Radiometric orbit determination activities in support of navigating Deep Space 1 to Comet BorrellyAfter several months of planning, development and testing, new software was uploaded that allowed Deep Space 1 to restore celestial inertia reference and begin thrusting towards an encounter with comet Borrelly. The new mission plan would have to work within the constraints of the new software as well as minimize use of the dwindling supply of hydrazine, the fuel needed to maintain the spacecraft attitude.