Constraint Editor

The HCI group worked with lead mission scientists and engineers to design Constraint Editor, a tool to support the transfer of scientific intent through the critical command uplink process for the Mars Exploration Rovers '03 mission.

Twin Remote-Controlled Scientists

Acting as robotic geologists, two six-wheeled rovers are scheduled to land in early 2004 on opposite sides of Mars to search for evidence of water or a history of water on the planet. Each Mars Exploration Rover’s planned mission lifetime is ninety sols (Martian days) and it can perform several hours worth of activity per day (e.g., taking panoramic images or driving). Each Martian day, commands will be uploaded to the rovers. Due to limited data capacity and significant lag between command issuance and data return, the science discovery and planning process is highly time-pressured. The mission science and engineering teams have 18 earth hours to analyze the data received, use the analysis in deciding the science plan for the following day, and encode the science activities as a sequence of commands for transmission to the rover.

Expressing Intent from Shift to Shift

Having analyzed the previous day’s data and created a set of high level requests for activities to be done by the rover the following day, the scientists go off shift as the engineering team is coming on shift. The engineers need to generate a sequence of commands that are consistent with scientific intent in order for that data collected to be scientifically useful. For example, three images must be done an hour apart to measure atmospheric change over time. Without all three images in that time frame, the data will not be useful to the scientists.

Speaking the Language of an Automated Planner

The lead scientist for the day works with a mission engineer to encode scientific intent using a tool called Constraint Editor. For example, specifying that one activity must come before or after another or at a particular time of day. These constraints are strictly enforced by a scheduling tool called MAPGEN that the engineers use later in the process. However, entering constraints without omissions or errors is very difficult. The MAPGEN team asked the Human-Computer Interaction (HCI) team in the Human Factors Research and Technology Division at Ames to design the Constraint Editor to support the efficient and accurate capture of scientific intent through the mission critical uplink process.

A True Paradigm Shift

The HCI team worked with lead mission scientists and engineers to design Constraint Editor. As the HCI team understood the problem, they realized scientists could not keep the large number of constraints (often 100+) in their heads. Successful execution of the task required a representation of constrained activities, activities not yet constrained, and a real-time view of the state and correctness of the developing plan. The HCI team iterated with JPL through several prototypes of the tool. Concurrently, the HCI team provided mission scientists and engineers training on the tool and concept of constraint-based planning. The HCI team worked with JPL to transform the mindset of experienced scientists and engineers from the familiar method of hand sequenced plans to a method involving automated constraint satisfaction. The combination of the HCI design and focused training has led to the successful adoption of constraint-based planning and of the tool for the Mars Exploration Rovers 2003 Mission.