Initial predictions about the longe

Initial predictions about the longevity of the STARFISH debris ranged from the overly optimistic of some months to the more realistic of a few years. Studies conducted in the late 1960s [1, 2, 3, 4] attempted to define the rate of decay with varying results. An in-depth evaluation performed in 1970-71 [5] using data from the 1963-38C satellite and covering the time span from September 1963 to December 1968, identified three distinct regions within the inner zone domain populated by the artificial electrons and established that their decay lifetime x (in days) could best be presented as a complex function of three variables: magnetic shell parameter L (in Earth radii), field strength B (in gauss), and energy E (in MeV), as shown in Figure 1 for E = 0.28 MeV electrons. A more thorough approach a year later produced a model of the STARFISH flux for epoch September 1964 [6], based on data from several spacecraft (OGO-1, OGO-3, OGO-5, OV3-3, and 1963-38C). That model distinguished between artificial and natural electrons and provided the artificial flux as a function of equatorial pitch angle, energy, and L value. The decay times for this flux were determined by two separate methods, which were combined to yield average values that are appropriate for the evaluation of the long-term loss process of the artificials. A threshold-energy vs L-value map for decay cutoff times is presented in Figure 2