The Terminal Tracking Camera (TTCam) imaging system on the NASA Lucy Discovery mission consists of a pair of cameras that will be used mainly as a navigation and target acquisition system for the mission’s asteroid encounters. However, a secondary science-focused function of the TTCam system is to provide wide-angle broadband images over a large range of phase angles around close approach during each asteroid flyby. The scientific data acquired by TTCam can be used for shape modeling and topographic and geologic analyses. This paper describes the pre-flight and initial in-flight calibration and characterization of the TTCams, including the development of a radiometric calibration pipeline to convert raw TTCam images into radiance and radiance factor (I/F) images, along with their uncertainties. Details are also provided here on the specific calibration algorithms, the origin and archived location of the required ancillary calibration files, and the archived sources of the raw calibration and flight data used in this analysis.

On January 6, 2019, OSIRIS-REx first observed particles ejecting from the surface of near-Earth asteroid (101955) Bennu. This ejection event was unexpected and was only captured by chance in a pair of optical navigation images taken by the OSIRIS-REx NavCam 1 imager. With this limited dataset of only two observations per ejected particle, traditional orbit determination to reconstruct the particles’ trajectories was not possible. Therefore, a new technique was developed for reconstruction of the ejection event based on some simplifying assumptions that the particles all ejected from the same location at the same time and that their velocities remained constant after ejection (a reasonable approximation for fast-moving particles given Bennu’s weak gravity). This technique was then applied to reconstruct those particle events observed by the OSIRIS-REx spacecraft at Bennu from January 2019 through June 2019 by Pelgrift et al. (2020). We present a follow-on to that work that applies the same technique to reconstruct the particle ejection events observed in the latter half of OSIRIS-REx proximity operations at Bennu, covering the time span from July 2019 through July 2020. We reconstructed 8 additional events, bringing the total number of Bennu particle ejection events reconstructed using this technique to 19. The new dataset includes the largest event observed to-date, with over 350 individual tracked particles. The new events have particle ejection velocities similar to the previous events, ranging from 5 cm/s to 1.8 m/s. In the full dataset of 19 events, we observed the same trend noted in the original work where the majority of events were estimated to have occurred at mid-latitudes and afternoon local solar times (LST). Reference: Pelgrift, J. Y., Lessac-Chenen, E. J., Adam, C. D., Leonard, J. M., Nelson, D. S., McCarthy, L., et al. (2020). Reconstruction of Bennu particle events from sparse data. Earth and Space Science. 7, e2019EA000938. https://doi.org/10.1029/2019EA000938

On October 20, 2020, NASA’s OSIRIS-REx spacecraft performed its Touch-and-Go (TAG) activity, in which it briefly contacted the surface of the asteroid Bennu and successfully collected a sample of regolith. Subsequent images of the sampling mechanism showed that thousands of small regolith particles were escaping from it, apparently in conjunction with movements of the mechanical arm and wrist joint by which the sampling mechanism is attached to the spacecraft. The escaping particles could be tracked from one image to another, and across multiple images, which allowed the OSIRIS-REx optical navigation team to detect, associate, and track particles using a combination of manual and automated techniques. The associated tracks each represent a unique particle that was further analyzed to estimate its ejection time, 3D trajectory, and velocity, as well as its photometric properties, which were used to compute its brightness, size, and mass. Compiling the aggregate photometric and physical data for all of the particles leads to an estimate of total sample mass lost during the post-TAG imaging sequences. These results further inform an understanding of the sample escape mechanisms and sample loss that occurred before the sample head was stowed in the return capsule on October 28, 2020. The material presented here is based upon work supported by NASA under Contract NNM10AA11C issued through the New Frontiers Program.