Use of Statistical Process Control in Deep Space Network Operations
James A. Hodder, Jet Propulsion Laboratory, California Institute of Technology
Source:
trs.jpl.nasa.gov
The material was prepared by the scientific director of the AQT Center
Sergey P. Grigoryev
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This report describes how the Deep Space Mission System (DSMS) Operations Program Office at JPL uses Statistical Process Control (SPC) methodology to monitor performance and evaluate process improvement initiatives in the Deep Space Network (DSN) of the National Aeronautics and Space Administration (NASA).
Background information is provided on how subjective parameters have previously been used to evaluate the performance of the Deep Space Network (DSN), and how these evaluations led to unproductive results because changes in monthly parameters were not clearly understood. Analysis of some parameters explains how Shewhart Statistical Process Control (SPC) charts are now used to determine whether monthly values reflect a significant change in productivity due to special causes, or whether the changes are natural, being in a statistically controlled state under the influence of general causes of variation. Operational definitions for interpreting control charts using rules are given. Western Electric . Shows several examples of how Shewhart control charts are used to determine the effectiveness of NASA's improvement process.
Statistical Process Control (SPC) provides the information needed to evaluate process capability, which is also discussed in the article. This information is important for making decisions about what to do to improve data collection and delivery systems. Information is also provided on how SPC was implemented in the Deep Space Network (DSN) at a modest cost, using the existing problem reporting system and historical planning information. The methodology described in this report can be used to meet the requirements of Section 8 of the ISO Q9001-2000 Quality Systems Standard, Process Monitoring and Measurement.
The examples also show that Statistical Process Control (SPC) can be used in both service and manufacturing environments.
The research described in this article was conducted at the Jet Propulsion Laboratory (JPL), California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).