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Activation model

Beyond the suggestion in the q6 model results, we have additional evidence for activation. This representation leads to the suggestion that we can parameterize the background as a function of coordinates. In the world map shown, any satellite track through a given earth latitude and longitude can have only two histories, and the two histories are separated by whether the z-velocity is positive or negative. A simpler representation is to recast the coordinates into earth longitude at which the satellite crosses the equator going north and orbit phase relative to equator crossings. The activation model attempts to parameterize the extra background component as a function of these two parameters. This is equivalent to assuming that the effect of the SAA is aproximately constant for each passs; the validity of this assumption will be addressed later as more experience is gained with applying the model over a wide range of mission times.

As currently implemented, the activation model is evaluated during the orbits where activation is considered important by first applying the particle based model to the data, and then parameterizing the activation model in terms of the two coordinates BKGD_THETA and BKGD_PHI. This approach results in no predicted activation component for about half of the orbits. The adequacy of this approach is being studied.

We will try to demonstrate the estimated activation component for the occulted observations of NGC 4151 during IOC soon.



Keith Jahoda
Wed Nov 27 15:54:02 EST 1996