Letter | Published:

Interaction of West Ford Needles with the Earth's Magnetosphere and their Life-time

Naturevolume 192page1061 (1961) | Download Citation



THE life-time of the copper needles which were to be placed in orbit for the West Ford experiment is a matter of great concern. It is generally believed that the pressure of solar radiation (not drag) will bring the needles down in about seven years provided they are launched into a ‘resonant’ orbit (for example, a polar orbit at altitude 3,800 km.); for a good description of the resonance effect, see I. I. Shapiro and H. M. Jones1. These authors also show that if the semi-major axis of the orbit is changed by more than 150 km., the resonance would be destroyed and the life-time greatly increased.

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  1. 1

    Shapiro, I. I., and Jones, H. M., Science, 134, 973 (1961).

  2. 2

    Singer, S. F., Nature, 192, 303 (1961).

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    • S. F. SINGER

    Present address: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California


  1. Physics Department, University of Maryland, College Park, Maryland

    • S. F. SINGER


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