early in the tpm tracking program when the

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Unformatted text preview: uot; is shown as a bold vertical line. The area under the probability curve to the left of the bold vertical line represents the probability that the spacecraft's injected mass will be less than or equal to the launch vehicle's payload capability. If injected mass is a TPM being tracked using the risk management method, this probability could be plotted in a display similar to Figure 22(c). If this probability were nearly one, then the project manager might consider adding more objectives to the mission in order to take advantage of the "large margin" that appears to exist. In the above figure, however, the probability is significantly less than one. Here, the project manager might consider descoping the project, for example by removing an instrument or otherwise changing mission objectives. The project manager could also solve the problem by requesting a larger launch vehicle! cation"). A new planned profile was then established to track the TPM over the remaining time of the TPM tracking program. The margin management method of assessing is illustrated for the same example in Figure 22(b). The replanning at time t occurred when the TPM fell significantly below the margin requirement. The new higher allocation for the TPM resulted in a higher margin requirement, but it also immediately placed the margin in excess of that requirement. Both of these methods recognize that the final value of the TPM being tracked is uncertain throughout most of Phases C and D. The margin management method attempts to deal with this implicitly by establishing a margin requirement that reduces the chances of the final value exceeding its allocation to a low number, for example five percent or less. A third method of reporting and assessing deals with this risk explicitly. The risk management method is illustrated for the same example in Figure 22(c). The replanning at time t occurred when the probability of the final TPM value being less than the allocation fell precipitously into the red alert zone. The new higher allocation for the TPM resulted...
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