(5) Risk Analysis Tool
A paper has been released detailing the software development and mathematical background of this tool. You can access it through ScienceDirect here or through my Publications page.
Experiences in the Texas Spacecraft Lab (TSL), and conversations with other university and low-cost CubeSat missions, show that the creation of a risk management plan specific to the set of CubeSat challenges (i.e. budget, development cycle, personnel resources) would be extremely valuable to the CubeSat community. This tool will be easily accessible to all who wish to use it. As such, using common software like Excel is ideal. Also making the tool easy to understand and use is a necessity. Based on previous research completed studying various types of cost models and their application to CubeSat missions, it was determined that a tool similar in design to existing cost models is optimal for the purposes of low-cost risk management. This tool currently includes inputs, outputs, and plots pages, where the 5x5 Likelihood-Consequence chart is displayed, as well as two pages listing the equations and coefficients chosen for each consequence and likelihood root cause. The only thing a user must do is enter their input values on the inputs page, choose their calculation option, and choose their plot options on the plots page, as the outputs pages are calculated automatically.
Existing cost model tools typically have an area for the user to input various parameters. This inputs page is considered a necessity for the development of the risk management tool in an effort to make the tool as user-friendly as possible. The mission designer simply has to input their form factor, mass, select a launch option from four choices, input their launch date, and input the months in development, integration, functional testing, environmental testing, awaiting launch, and operations. The internal calculations of the tool will then output the root cause likelihood and consequence values on the outputs page. This inputs page is shown in Figure 1. The user also has the ability to track the spacecraft risks at multiple milestones by indicating on the Options bar to which milestone the current inputs correspond. Then, the user may submit another set of inputs for a different milestone. Currently, up to three milestones may be tracked at a given time.
Figure 1 -- Risk Tool Inputs Page
Once the option to calculate the L-C values is selected, a VBA program takes the user inputs and calculates the consequence and likelihood values for each root cause based on the formulas established from the regression analysis mentioned in the Risk Estimating Relationships section to yield the outputs page shown in Figure 2. If the user had selected to track multiple milestones, the additional columns would represent the spacecraft risk status at these additional milestones. There are separate details pages which give chosen formulas and associated coefficients purely for user reference. Note that because the data for each root cause is different, the coefficients are different for every function. Once the root cause likelihood-consequence (L-C) values have been calculated, the mission risk L-C is established through a weighted average of the root cause values using the rank reciprocal method to determine the weights [see Brumbaugh & Lightsey 2013]. It is acknowledged that the rank reciprocal method is one of many weighting methods available, and future iterations of the tool may include options for the user to select a weighting method of their choice.
Figure 2 -- Risk Tool Outputs Page
The plots page shown in Figure 3 provides a quick and easy way to view the mission risks on a traditional L-C chart. The mission risk consequence is plotted on the x-axis while the likelihood is plotted on the y-axis. Simplicity and ease of use were the primary motivators for the development of this plots page. The mission risk L-C values are copied from the outputs page and displayed next to the 5x5 chart for quick reference. If the user chose to track multiple milestones, these additional mission risk values are located along the bottom of the 5x5 chart. The color of the milestone value background corresponds with the text boxes on the 5x5 chart. Additionally, interactive macro-enabled buttons allow the user to plot combinations of milestones, combinations of risks, or the ability to mix and match milestones and risks. Furthermore, the diagram is easily copied to presentations for mission status updates.
Figure 3 -- Plots Page
Here's a quick movie to show how all the pages go together and how to use the tool:
