NASA InSight: A Plan to Get the Mole Moving Again
I'm Troy Lee Hudson. I'm a member of the insight science team and the instrument systems engineer for the HP3.
Insight is a mission to study the deep interior of Mars. It has many science instruments to do this, one of which is HP3 -- A sort of planetary thermometer. A key component of HP3 is called the mole, sort of a self-hammering nail that drives its way into the ground and when we first commanded it to do this penetration, it did so beautifully, but at a certain point it stopped making forward progress.
This is a full-scale model of the HP3 support structure. The mole started out in this vertical tube and when we commanded the mole to start digging it released and started making progress millimeter by millimeter into the ground. At a certain point it began to tilt and around here approximately 10 centimeters above the surface of the ground, it stopped making progress. So, at this point we believe the mole is still partially within the support structure, pointing at about a 20-degree tilt to the southwest. It could be the case that the mole has encountered an external obstruction like a rock, but another possibility is that the soil at insight is providing us less friction than we expected and the mole needs friction to make forward progress.
JPL working along with DLR, the German space agency who provided the mole have been trying to understand what the problem is and come up with a plan of action.
We can't get a clear picture of what's happening with the mole, so we need to pick up the support structure and move it elsewhere.
We've been practicing that lift here in the test bed with models of the arm and the support structure. The lift has to be done carefully in three stages, small moves. So, we can look at the data and among other things, ensure that we're not inadvertently extracting the mole.
Once we moved the support structure and get a clear view of what's going on with the mole, we want to use the robotic arm again to help it. Our first choice is to come in with the scoop on the robotic arm and press flat on the soil above the mole. This may increase the friction at the mole giving it that extra nudge. It needs to start making progress.
This is unexplored territory. The mole is going somewhere we cannot see and have never been before to get that crucial number, the heat flow of Mars. As a scientist, I want to get that number and as an engineer I want to see the instrument we've worked on for a decade. Do the thing that was designed to do.