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Particle model

The first model is based on the instantaneous particle flux, assumed to be well measured by the housekeeping parameters Q6VxVpXeCntPcuN (N=1-5), which measures the rate of events which trigger exactly 6 of the lower level discriminators in each PCU. Background components which are created by unvetoed particle tracks or by interaction between particles and the the spacecraft or detector body should be well tracked by this rate. The rate is variable by a factor of 2.5 over the course of a single orbit, and is well correlated with latitude, magnetic rigidity, or McIlwain L.

We examine the success of this model in three bands (channel 0-40, 41-120, and 121-249 which correspond, for IOC data, to roughly 0-11 keV, 11-32 keV, and 32-65 keV). All three of these bands show short term variations (~20 minutes) which are well modelled by the particle model. These are difficult to see in the plots which cover an entire day, although the data-background_model files show less vertical spread. 4 shows 2 orbits. The 3 panels represent the data, the modle background, and the data-model. The smooth variation is largely removed.

   Figure 1
Figure 1: Channel 0-40, total count rate during occults, q6 model

   Figure 2
Figure 2: Channel 41-120, total count rate during occults, q6 model

   Figure 3
Figure 3: Channel 121-249, total count rate during occults, q6 model

   Figure 4
Figure 4: Channel 0-40, total count rate during two occults, q6 model

We also present the pulse height spectra integrated over the entire set of data shown in 1 through 3.

   Figure 5
Figure 5: Data and model, PCU 0, integrated over occults, q6 model

   Figure 6
Figure 6: Data and model, PCU 1, integrated over occults, q6 model

   Figure 7
Figure 7: Data and model, PCU 2, integrated over occults, q6 model

   Figure 8
Figure 8: Data and model, PCU 3, integrated over occults, q6 model

   Figure 9
Figure 9: Data and model, PCU 4, integrated over occults, q6 model

As currently implemented the particle based model is evaluated during orbits where the activation terms are deemed inconsequential (about half of the total).


next up previous
Next: Activation model Up: PCA Background Estimation Status Previous: Running pcabackest

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