Summary of Results from the Risk Management program for the Mars Microrover Flight Experiment Robert Shishko, Ph.D. and Jacob R. Matijevic, Ph.D. Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grov'e Drive, Pasadena CA 91109 volume, mass, and power for both the microrover Abstract. On 4 July 1997, the Mars and its instrument (APXS) payload, microrover Pathfinder landed on the surface of Mars carrying interfaces with the Pathfinder spacecraft, and use of the first planetary rover, known as the Sojourner. some commercial and MiI-Spec parts. Operations Formally known as the Microrover Flight risks arose because of an unknown landed Experiment (MFEX), the Sojourner was a low cost, configuration for the lander, use of new approaches high-risk technology demonstration, in which new to command, control, and communication, and risk management techniques were tried. This paper uncertain environmental conditions. summarizes the activities and results of the effort to conduct a low-cost, yet meaningful risk This paper summarizes the activities and management program for the MFEX. The specific results of the effort to conduct a low-cost, yet activities focused on cost, performance, schedule, meaningful risk management program for the and operations risks. Just as the systems MFEX, which was originally designated as a high- engineering process was iterative and produced risk (Class D) payload. The specific objectives of successive refinements of requirements, designs, the MFEX risk management effort were: etc., so was the risk management process. Qualitative risk assessments were performed first (a) Define and implement a risk to gain some insights for refining the microrover management process tailored to design and operations concept. These then evolved the MFEX; into more quantitative analyses. Risk management (b) Develop risk-based criteria to lessons from the manager's perspective is evaluate the effectiveness of the presented for other low-cost, high-risk space risk management techniques; missions. (c) Develop data to permit evaluation. 1.1 MFEX RISK MANAGEMENT PROCESS The general risk management process The Microrover Flight Experiment followed by the MFEX is described in (NASA, (MFEX) is a small, semi-autonomous robotic 1993) and (NASA. 1995). That process consists of vehicle (better known as the Sojourner) that was four overlapping stages: risk management flown on the Mars Pathfinder (MPF) mission in planning, risk identification and characterization, 1996/97. The microrover was designed to move risk analysis, and risk mitigation and tracking. The onto the Martian surface from ramps deployed process tailored for the MFEX involved from the lander part of the Pathfinder spacecraft. performing specific activities for each of these four On the surface, it was to move away from the stages that are integrated directly into the regular lander, image the lander, place an Atpha Proton X- systems engineering process. The specific ray Spectrometer (APXS) on Martian rocks and activities focused on cost risk, performance risk. soil, and perform a variety of technology schedule risk. and operations risk. Just as the experiments. The MFEX risk management systems engineering process is iterative and activities focused on the tbllowing major risk produces successive refinements of requirements. categories: cost, schedule, performance, and designs, etc.. so is the risk management process. operations. Cost risk was considered important Qualitative risk assessments were performed first because the MFEX had a fixed budget of $25M to gain some iv,sib'hfs for refining the microrover (RY$) over its entire life cycle. Schedule risk design and operations concept. These then evolved arose because the microrover had to be integrated into more quantitative analyses. ]'he qualitative into the Mars Pathfinder spacecraft, which itself and quantitative analyses available at each decision had to meet a 1996 launch date. Performance risks point were considered by the MFEX manager in arose for a variety of reasons: design constraints on allocating MFEX reserves. Figure I shows the process for making Planning tbr risk mitigation included risk management (unshaded boxes in the figure) estimating the costs (and schedule implications) of integral to the MFEX systems engineering effort. risk mitigation actions, as well as the likelihood The following example illustrates this process flow. that the MFEX life-cycle cost would exceed the The Mars Pathfinder project defined its mission cost cap of $25M because of the identified needs for the microrover. These were to (a) deploy technical and schedule risk factors. In some science instruments and (b) image the lande_: to instances, TPM tracking provided an indication of determine its condition. Originally, the science the urgency of implementing risk mitigation plans desire was for the microrover to deploy a and actions. As problems were encountered, these seismometer, and to carry both an Alpha Proton X- assessments were used to allocate MFEX reserves. ray Spectrometer (APXS) and a neutron For example, after testing the APXS deployment spectrometer. A microrover design assessment mechanisms, the likelihood of mechanism failure indicated that a microrover that was capable of to properly position the APXS would be reassessed fitting within the MFEX cost cap was not capable and reserves allocated to cover the costs of of carrying even the lightest seismometer. providing for longer APXS operation times to make up for possible misalignment. Further, the Mars Pathfinder science budget could not support the neutron spectrometer. Timeline analyses, called Landed Mission Therefore, a capabilities assessment eliminated Operations Scenarios, were the primary tool for these two inslzuments. The requirements analysis assessing the impact of various technical risks on led to a requirements agreement between the Mars the technical mission success metric. For Pathfinder project and MFEX for a microrover example, these scenarios were used to evaluate the capable of carrying the APXS and placing it on effect of longer APXS operation times on the rocks and soil. achievement of other mission objectives, so overall technical mission success could be evaluated. With In conjunction with the requirements this information, the team leader could determine agreement, criteria were established to define whether the marginal improvement in technical MFEX technical mission success. These criteria mission success was worth the additional risk were to: (a) perform a complete set of technology mitigation costs. experiments in one soil type, (b) measure one rock with the APXS and image that rock, (c) produce The risk management activities that are one full cross- section image of the lander, and (d) described later in this report map into the unshaded do two more soil types, another APXS rock boxes in Figure I. For example, the cost risk measurement, and three more lander images if analysis box in the figure was accomplished by possible. Ninety percent technical mission success performing the Cost Uncertainty Questionnaire. was assigned to doing (a), (b), and (c), with equal Sometimes. several activities were performed in weight to each; an additional ten percent technical connection with a particular box, as was the case mission success was assigned to the extended for the technical risk assessment. mission tasks in (d). These criteria established a technical mission success metric. 1.2 RISK MANAGEMENT METRICS The requirements analysis was refined, Throughout the task, a simple risk employing tirneline analysis (Landed Mission management summary was maintained in the form Operations Scenarios) to determine what functional of a time-phased "traffic light" chart--that is, red, and performance capabilities were needed by the yellow, or green---was used to indicate the MFEX microrover in order to achieve a scientifically risk status at each discrete point in time (usually successful mission---4hat is, deploy the APXS and corresponding to significant milestones or major perform the other technology tasks described reviews). The summary, chart is reproduced here as above. As part of the ongoing successive Table I. The metrics in Table I are the classical refinement of the microrover design, technical risk ones--cost, schedule, and performance. Status was •,.assessments were made at increasing levels of determined _ith the help of some of the methods detail, and potential failures were identified. For like Technical Performance Measurement (TPM) each potential failure, risk mitigation actions were and Rec. Del Tracking. To implement these, simple developed. For example, the APXS might not be spreadsheet tools _ere developed. properly placed on the rock. The risk mitigation plan was then amended to include designing and testing prototype APXS deployment mechanisms. Miu_on I I Success Risk Mitigation _ Risk Mitigation Metnc Plans/Action I I Costs TrackingTPM ___ Re_m_e= I Figure 1--Process for Integrating Systems Engineering and Risk Management As of: DICR CDR SIM/FU ATLO LRR (7193) (2/94) (5195) (7/96) (12/96) Life-Cycle Cost G G G G G Schedule N/A N/A Y G G Technical Performance N/A G G G G System (Rover+LMRE) Mass (kg) N/A Y G G G WEB Electronics Board Volume (cm^3) N/A G G G G Average Driving Power (watts) N/A G G G G Worst Case Peak Operating Power (watts) N/A G G G G Array Electrical Energy Consumption/Sol N/A G G G G (watts/hour) Development + Ops Thermal Cycles N/A G G G G (number of cycles) UHF Data Flow (Mbits/day) N/A G G G G Data Storage - RAM (kbyte) N/A G G G G Control Memory - PROM (kbyte) NIA G G G G Operations N/A N/A N/A N/A N/A BasicMission N/A N/A N/A N/A N/A ExtendedMission N/A N/A N/A N/A N/A Codes for Table: DICR Design Implementation and Cost Review lip " N/A Not Available CDR Critical Design Review R Red SIM/FU System Integration Model/Flight Unit Y Yellow ATLO Assembly, Test, and Launch Operations G Green LRR Launch Readiness Review Table 1--Microrover Flight Experiment (MFEX) Risk Management Summary The assignment of red-yellow.green status From the workshop material and in Table I was made when appropriate criteria discussion, the landed mission operations cognizant could be devised.