Deployed Instrument Monocular Localization on the InSight Mars Lander

The primary purpose of the InSight Instrument Deployment System (IDS) on the Mars InSight Lander, which landed in November 2018, was to deploy three payloads: a seismometer (SEIS), a heat flow probe (HP3), and a wind and thermal shield (WTS), to the Martian surface. The system consists of the Instrument Deployment Arm (IDA), Instrument Deployment Camera (IDC) on the forearm of the IDA, and the Instrument Context Camera (ICC). A core functionality of the IDS that was critical to the success of the deployments was the ability to use only the single camera on the arm and monocular localization methods to calculate the poses of each of the instruments before and after deployment. Given that the ICC has a fisheye lens and was located under the lander, relatively far from the deployment sites, only the IDC was useful for quantitative localization. Knowledge of the exact pose of each instrument was critical for any activity that involved interacting with the instruments, such as the deployment of the WTS over SEIS to protect the instrument and reduce environmental noise. Additionally, knowledge of the instrument poses was necessary to meet the mission's science objectives, used to accept the instrument deployment sites, and to create noise models used to help scientists interpret the instrument data. While the technology was employed on this mission to allow for stereo data to be captured by moving the single camera over a known baseline, physical arm constraints, operational constraints, and a desire for independent verification necessitated robust methods of monocular localization. Two different methods of monocular localization were developed and employed for the deployment phase of the mission. Fiducial localization which used precisely measured, round single point fiducials along with more robust AprilTag fiducials that provide 5 points as well as an independent orientation from each fiducial. Along with quantitative analysis, grapple localization was developed to confirm the localization by physically lining up the IDA grapple with the hook on each instrument. This paper will discuss the motivation, implementation, and execution of each monocular localization technique employed by the IDS. Additionally, it will detail the results and error sources identified throughout the mission using downlinked images and measurements from the InSight lander and InSight Testbed.