As the OSIRIS-REx spacecraft descended toward the asteroid Bennu to collect a sample from the surface in the touch-and-go (TAG) procedure, many of the instruments were actively collecting observation data. We applied the process of photogrammetric control to accurately determine the position and attitude of 190 OCAMS MapCam and SamCam descent images at the time of exposure. The average image pixel resolution is 10cm (median is 7cm). The images were controlled to ground using simulated images generated from high resolution (5cm, 44cm and 88cm ground sample distance) shape models of Bennu. After least-squares adjustment, the root mean square (rms) of all image measurement residuals was 0.16 pixels. These results were applied to 581 OTES observations by interpolation over the updated ephemeris of the OCAMS MapCam and SamCam instruments using frame transformations from OCAMS to the OTES frame. Then, the surface intercept of the OTES field of view was recomputed by ray tracing the adjusted boresight look direction onto the 44cm shape model. The average of the adjusted OTES boresight surface intercepts differed from the a priori locations on the 88cm shape model by  37cm with an uncertainty less than 5cm.

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission recently returned a sample of rocks and dust collected from asteroid Bennu. We analyzed the highest-resolution thermal data obtained by the OSIRIS-REx Thermal Emission Spectrometer (OTES) to gain insight into the thermal and physical properties of the sampling site, including rocks that may have been sampled, and the immediately surrounding Hokioi Crater. After correcting the pointing of the OTES data sets, we find that OTES fortuitously observed two dark rocks moments before they were contacted by the spacecraft. We derived thermal inertias of 100–150 (±50) J m −2 K −1 s −1/2 for these two rocks—exceptionally low even compared with other previously analyzed dark rocks on Bennu (180–250 J m −2 K −1 s −1/2 ). Our simulations indicate that monolayer coatings of sand- to pebble-sized particles, as observed on one of these rocks, could significantly reduce the apparent thermal inertia and largely mask the properties of the substrate. However, the other low-thermal-inertia rock that was contacted is not obviously covered in particles. Moreover, this rock appears to have been partially crushed, and thus potentially sampled, by the spacecraft. We conclude that this rock may be highly fractured and that it should be sought in the returned sample to better understand its origin in Bennu’s parent body and the relationship between its thermal and physical properties.

Rubble-pile asteroids such as Bennu and Ryugu have boulder-covered surfaces and latitude-dependent slope distributions, signifying that mass movement of boulders could contribute significantly to the surface evolution of these small bodies. The OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) mission documented numerous locations on Bennu exhibiting evidence of such mass movements, including one contained within Bralgah Crater. This area was considered (though not used) by the mission as a candidate site for sample collection; thus, high-resolution images collected during reconnaissance of this area enabled us to resolve a smaller minimum boulder size than would be possible elsewhere. Through boulder mapping and topographic analysis, we found evidence of a pileup behind a large central boulder, a flow "wake" downhill with a relative lack of medium-sized boulders, as well as a strong orientational preference of the boulders in this area, with the long axes of the boulders pointing westward of the expected direction of motion. We performed dynamical simulations of seismic shaking using the discrete-element N-body code PKDGRAV to better constrain the conditions that may have formed the landscape. In these simulations, we were able to replicate the pileup of material uphill from the central boulder and the wake downhill from it. Comparisons with previous simulations of seismic shaking–induced mass movements show that material transport is not directly related to the shaking intensity, but instead can be maximized by dominant shaking frequencies. Simulations also showed a preferential orientation emerging, with a strong possibility for preferential orientation parallel to direction of motion. Combined with the orientational preference observed in this and other studies of Bennu's landscape, this indicates that the Coriolis effect could be a major factor in the surface evolution of Bennu and other small bodies. Finally, we estimated the impactor sizes that would instigate our simulated shaking parameters, showing that Bennu could have encountered such impactors within its near-Earth lifetime.

Changes of the Physical Properties of Cometary surfaces Introduction:This is a detailed and comprehensive photometric study on how the physical properties of surface dust cover change at different morphological location on comet 67P/ Churyumov-Gerasimenko and what mechanisms drive these changes. We examined different regolith alteration and dust transportation scenarios in different geomorphological locations and measured the properties with highest resolution sterophotoclinometry (SPC) methods possible. Method:Our technical approach would be to define different geomorphologic units in surface areas with different change level and perform mapping of wavelength-dependent photometric parameters of all units using the OSIRIS-NAC multiband imaging data as archived at PDS/SBN. We followed the procedure as in the previous similar work for 67P [1] and for other asteroids [2, 3] using other missions’ imaging and spectral data to perform photometric modeling and mapping. Once the spectrophotometric parameters and the maps are derived, we compared the differences and similarities between regions and interpret the results in the context of cometary geologic activity history. In this work, we applied a SPC method for generating global and local high-resolution shape models for describing both large scale and small-scale surface changes for multiple locations on 67P. We select our region-of-interests (ROIs) based on the surface change analysis results for further spectrophotometric studies. Then we performed a detailed modeling and mapping of the ROIs, including dramatic change like landslides, and different type of small changes. The error analysis of the modeling results follows the procedure outlined in [2, 4]. Our data products, including geometric backplanes and maps will all be archived to PDS/SBN. Surface Changes:We will report the results and analysis of the surface changes from our methods. And we will also discuss the photometry findings about the changes of the surface physical properties. Acknowledgments:This research is supported by NASA Grant #80NSSC20K1152. All data used in this study are directly downloaded from the PDS small body node. Reference:[1] Zou, X.D., et al., 2021, December. Detailed Geometry Data Study and Photometric Analysis with Rosetta/OSIRIS Images of Comet 67P/Churyumov-Gerasimenko. In AGU Fall Meeting 2021. AGU.[2] Li, J.-Y., et al., 2019. Spectrophotometric modeling and mapping of Ceres. Icarus 322, 144-167.[3] Zou, X.-D., et al., 2021. Photometry of asteroid (101955) Bennu with OVIRS on OSIRIS-REx. Icarus 358, 114183.[4] Li, J.-Y., et al., 2013. Global photometric properties of Asteroid (4) Vesta observed with Dawn Framing Camera. Icarus 226, 1252-1274.

Due to contamination on the outer optic of the NEAR-Shoemaker Multispectral Imager (MSI), all surface-resolved images of Eros acquired by MSI had wavelength-dependent degradation. The MSI team designed and imple-mented a preliminary correction for the blur during mission operations and archived the results with the original camera data. While successful for most filters, the preliminary correction had edge effect artifacts and was less effective for the 450 and 1050 nm passbands. Here we implement a new correction, based on the MSI team's original process, to improve the blur remediation for all MSI filters, particularly those at the extreme wave-lengths. The new method improves the effective resolution of the deblurred images over the preliminary remediation for all filters. Moreover, for all filters, our method preserves the 21-39% of the pixels that were lost (or obscured by artifacts) with the preliminary remediation. We apply the new method to the complete MSI dataset of resolved Eros images and archive the results for future scientific use.

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft mission characterized and collected a sample from asteroid (101955) Bennu. After the OSIRIS-REx Sample Return Capsule released to Earth’s surface in 2023 September, the spacecraft diverted into a new orbit that encounters asteroid (99942) Apophis in 2029, enabling a second mission with the same unique capabilities: OSIRIS–Apophis Explorer (APEX). On 2029 April 13, the 340 m diameter Apophis will draw within ∼32,000 km of Earth’s surface, less than 1/10 the lunar distance. Apophis will be the largest object to approach Earth this closely in recorded history. This rare planetary encounter will alter Apophis’s orbit, will subject it to tidal forces that change its spin state, and may seismically disturb its surface. APEX will distantly observe Apophis during the Earth encounter and capture its evolution in real time, revealing the consequences of an asteroid undergoing tidal disturbance by a major planet. Beginning in 2029 July, the spacecraft’s instrument suite will begin providing high-resolution data of this “stony” asteroid—advancing knowledge of these objects and their connection to meteorites. Near the mission’s end, APEX will use its thrusters to excavate regolith, a technique demonstrated at Bennu. Observations before, during, and after excavation will provide insight into the subsurface and material properties of stony asteroids. Furthermore, Apophis’s material and structure have critical implications for planetary defense.

Introduction: The Rosetta mission [1] obtained a rich set of images of comet 67P/Churyumov-Gerasimenko’s changing surface through its perihelion passage with the Narrow Angle Camera (NAC) [2]. This dataset allowed us to examine the details of the areas that shows subtle differences in their physical properties and their temporal variations. The photometric properties [3] are generally sensitive to the physical properties of a surface, such as composition, texture, porosity, roughness, and grain size; they can be markers for local alteration processes. With the help of high-resolution shape models, we can investigate the physical properties of various locations on the surface of 67P’s nucleus at various perihelion distances through photometric analysis. However, there are several obstacles we did not know of until we dived into the analyses. The changes of the surface topography: To de-convolve the regolith’s evolution we had to investigate how the surface changed during the perihelion passage of 67P. We devoted to generating a photometric dataset for this study that covers a sufficiently wide range of scattering angles that requires precise registration between images and the shape model [4]. But our previous attempts to control OSIRIS NAC images are problematic. The continuously changing nature of 67P’s surface caused bulk registration problems. Our study shows that, for about half images, a single shape model (SHAP7 [5]) is insufficient for a consistent control. The surface changes vary significantly with time and would require numerous shape models. Figure 1 Global change from pre- to post-perihelion mapped on a SPC shape model. Blue color marks where pre-perihelion surfaces are above the post-perihelion surfaces and the gray color marks the opposite case. Left and right panels are the +Z axis and –Z axis view of the shape model, respectively. Control points: When we control all the image of OSIRIS NAC to SHAP7 as ground source [6], we examined the control data quality for each dataset. Showing here RMS of the control points from processing of the PDS archived dataset M15. We found that the most common reason that causing problems in the control is either changes in the surface topography or that the image resolutions are far higher than the resolution of the shape model. Figure 2 The control points RMS for OSIRIS_NAC_M15 dataset. Indexing the irregular surface: The irregular shape of 67P made it counterintuitive to project and map the surface to a regular latitude-longitude projection system. Based on the shape model facets, we made it possible to index all the pixels by its actual location on the surface. This enables us to search and map the surface pixels directly without any ambiguous for location caused by the irregular shape. Mapping the photometric properties: We will also report our method of generating the photometric datasets and the results of our detailed photometric analysis for a few different geomorphological sites. Acknowledgments: This work is supported by NASA under Grants 80NSSC19K0421 and 80NSSC20K1152 and partially by the SSERVI16 Cooperative Agreement NNH16ZDA001N, SSERVI-TREX. References: [1] Glassmeier, K.H., Boehnhardt, H., Koschny, D., Kührt, E. and Richter, I., 2007. The Rosetta mission: flying towards the origin of the solar system. Space Science Reviews, 128(1), pp.1-21. [2] Keller, H.U., Barbieri, C., Lamy, P., Rickman, H., Rodrigo, R., Wenzel, K.P., Sierks, H., A’Hearn, M.F., Angrilli, F., Angulo, M. and Bailey, M.E., 2007. OSIRIS–The scientific camera system onboard Rosetta. Space science reviews, 128(1), pp.433-506. [3] Hapke, B., 2012. Theory of reflectance and emittance spectroscopy. Cambridge university press. [4] Zou, X.D., Becker, K.J., Li, J.Y., Gaskell, R.W., Palmer, E.E., Weirich, J.R. and Domingue, D.L., 2021, December. Detailed Geometry Data Study and Photometric Analysis with Rosetta/OSIRIS Images of Comet 67P/Churyumov-Gerasimenko. In AGU Fall Meeting 2021. AGU. [5] Preusker, F., Scholten, F., Matz, K.D., Roatsch, T., Hviid, S.F., Mottola, S., Knollenberg, J., Kührt, E., Pajola, M., Oklay, N. and Vincent, J.B., 2017. The global meter-level shape model of comet 67P/Churyumov-Gerasimenko. Astronomy & Astrophysics, 607, p.L1. [6] Zou, X.D., Li, J.Y. and Becker, K.J., 2020, March. Improving the Geometric Data of Cometary Missions. In 51st Annual Lunar and Planetary Science Conference (No. 2326, p. 2462).

The Mercury Dual Imaging System (MDIS) on the Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has provided global images of Mercury’s surface. A subset of off-nadir observations acquired at different times resulted in near-global stereo coverage and enabled the creation of local area digital elevation models (DEMs). We derived fifty-seven DEMs covering nine sites of scientific interest and tied each to a geodetic reference derived from Mercury Laser Altimeter (MLA) profiles. DEMs created as part of this study have pixel scales ranging from 78 m/px to 500 m/px, and have vertical precisions less than the DEM pixel scale. These DEMs allow detailed characterizations of key Mercurian features. We present a preliminary examination of small features called “hollows” in three DEM sites. Depth measurements from the new DEMs are consistent with previous shadow and stereo measurements.

First posted January 19, 2022 For additional information, contact: Contact Astrogeology Research Program staffAstrogeology Science CenterU.S. Geological Survey2255 N. Gemini Dr.Flagstaff, AZ 86001 This report summarizes the software and algorithms that are used to calibrate images returned by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter (MRO) spacecraft. The instrument design and data processing methods are summarized below, followed by a description of relevant calibration data and details of the calibration procedure. In this document, we describe the software that uses those coefficients and matrices to radiometrically calibrate HiRISE data. This software is included in version 3 of the Integrated Software for Imagers and Spectrometers (ISIS3), which is developed and maintained by the U.S. Geological Survey Astrogeology Science Center in Flagstaff, Ariz., for the international planetary science community via funding from the National Aeronautics and Space Administration. ISIS3 is freely available to the scientific community and can be obtained at http://isis.astrogeology.usgs.gov/index.html. Support for ISIS3 is provided at https://github.com/USGS-Astrogeology/ISIS3.

Carbonaceous asteroids, such as (101955) Bennu, preserve material from the early Solar System, including volatile compounds and organic molecules. We report spacecraft imaging and spectral data collected during and after retrieval of a sample from Bennu’s surface. The sampling event mobilized rocks and dust into a debris plume, excavating a 9-meter-long elliptical crater. This exposed material is darker, spectrally redder, and more abundant in fine particulates than the original surface. The bulk density of the displaced subsurface material was 500 to 700 kilograms per cubic meter, which is about half that of the whole asteroid. Particulates that landed on instrument optics spectrally resemble aqueously altered carbonaceous meteorites. The spacecraft stored 250 ± 101 grams of material, which will be delivered to Earth in 2023.

We present a near-global normal albedo map of asteroid (101955) Bennu, created using images from the PolyCam imager onboard the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft. PolyCam acquired high-resolution images (nadir pixel scale of similar to 6.25 cm/pixel) of the surface from the equator to mid-latitudes (similar to +/- 50 degrees) at a low phase angle (similar to 8 degrees). We applied specialized charge smear and radiometric correction to the data to compensate for image artifacts stemming from very short exposure times. We photogrammetrically controlled the images to shape model tiles with a 5-cm ground sample distance to register the images to each other and to ground. Variations in albedo on Bennu's globally dark surface (median albedo of 0.046 +/- 0.002) are associated with clusters of dark and bright boulders, as well as a much sparser population of meter-scale boulders with very high reflectances (albedo >0.10). Accordingly, Bennu has a relatively broad albedo-frequency distribution (similar to 25% full width at half maximum) with a long tail toward higher values. Owing to the distribution of the dark boulders and boulder clusters, the southern hemisphere of Bennu is darker than the northern hemisphere; this hemispheric dichotomy varies with longitude, resulting in a large-scale diagonal pattern in albedo across the full disk of Bennu.

In early 2019, NASA's OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission surveyed asteroid (101955) Bennu with a collection of instruments, including the OSIRIS-REx Camera Suite (OCAMS) PolyCam imager. Using PolyCam panchromatic images, we constructed a globally controlled basemap of Bennu at an approximate ground sample distance of 5 cm with a mean spatial accuracy of similar to 30 cm. The basemap was photometrically normalized using a Minneart phase angle correction. New mapping methods were developed to combine images of Bennu's irregular shape and extremely rough surface into a nearly seamless mosaic. Here we present the global basemap of Bennu and discuss the image processing techniques used to construct a high-resolution mosaic of an irregular small body.

Introduction: Shortly before orbit insertion around asteroid (433) Eros, the Near Earth Asteroid Rendezvous–Shoemaker (NEAR) [1] mission experienced a failed burn that ejected > 28 kg of hydrazine fuel on to the spacecraft, including the front optical surface of the Multispectral Imager (MSI). Unfortunately, this caused every surface-resolved image of Eros to have wavelength-dependent degradation of its point spread function (PSF). During the mission, the MSI team developed a preliminary remediation of the blur, utilizing post-contamination images of Canopus to model the degraded PSF [2]. This remediation was largely successful for the majority of MSI images, enabling extensive surface analysis, such as global mapping and color mapping [3,4], though images at the extreme wavelengths (450 and 1050 nm) were harder to correct. In addition, the original method necessitated cropping the images and introduced FFT edge-artifacts that reduced the usable pixel area by 21-39% [2]. We have attempted to improve this remediation by developing an alternative remediation that does not introduce cropping or FFT artifacts and adapting the PSF model to be more complex. PSF Modeling: MSI acquired > 7000 images of Canopus after contamination, using all eight filters and in nine (3x3 grid) regions on the detector. Theoretically, imaging Canopus in multiple regions offers the possibility of developing a spatially variant PSF (and therefore correction). Unfortunately, other than the central and bottom-center region, most filters had only 16-32 images per region. Some filters (2, 7, and 0) had no images in those regions. As such, we were unable to develop a spatially variant PSF that performed better than the invariant version. Nonetheless, we utilized the nearly 6000 images in the central region to model a PSF for each filter. We model the PSF as the sum of three Gaussians: responsible for the peak, shoulder, and wings of the PSF (Figure 1). We allowed the Gaussians to be radially asymmetric, as there is a clear ~25% asymmetry in the Canopus images. Figure 1. >500 images of Canopus acquired with the 950 nm filter are combined to produce a PSF measurement, shown as a horizontal cross-section (black solid line). We model that PSF with a sum of 3 Gaussians (dashed lines).

The OSIRIS-REx spacecraft encountered the asteroid (101955) Bennu on December 3, 2018, and has since acquired extensive data from the payload of scientific instruments on board. In 2019, the OSIRIS-REx team selected primary and backup sample collection sites, called Nightingale and Osprey, respectively. On October 20, 2020, OSIRIS-REx successfully collected material from Nightingale. In this work, we apply an unsupervised machine learning classification through the K-Means algorithm to spectrophotometrically characterize the surface of Bennu, and in particular Nightingale and Osprey. We first analyze a global mosaic of Bennu, from which we find four clusters scattered across the surface, reduced to three when we normalize the images at 550 nm. The three spectral clusters are associated with boulders and show significant differences in spectral slope and UV value. We do not see evidence of latitudinal non-uniformity, which suggests that Bennu's surface is well-mixed. In our higher-resolution analysis of the primary and backup sample sites, we find three representative normalized clusters, confirming an inverse correlation between reflectance and spectral slope (the darkest areas being the reddest ones) and between b' normalized reflectance and slope. Nightingale and Osprey are redder than the global surface of Bennu by more than 1 sigma from average, consistent with previous findings, with Nightingale being the reddest (S' = (-0.3 +/- 1.0) x 10(-3) percent per thousand angstroms). We see hints of a weak absorption band at 550 nm at the candidate sample sites and globally, which lends support to the proposed presence of magnetite on Bennu.

Near‐Earth asteroid (101955) Bennu is an active asteroid experiencing mass loss in the form of ejection events emitting up to hundreds of millimeter‐ to centimeter‐scale particles. The close proximity of the Origins, Spectral Interpretations, Resource Identification, and Security–Regolith Explorer spacecraft enabled monitoring of particles for a 10‐month period encompassing Bennu's perihelion and aphelion. We found 18 multiparticle ejection events, with masses ranging from near zero to hundreds of grams (or thousands with uncertainties) and translational kinetic energies ranging from near zero to tens of millijoules (or hundreds with uncertainties). We estimate that Bennu ejects ~10 4 g per orbit. The largest event took place on 6 January 2019 and consisted of ~200 particles. The observed mass and translational kinetic energy of the event were between 459 and 528 g and 62 and 77 mJ, respectively. Hundreds of particles not associated with the multiparticle ejections were also observed. Photometry of the best‐observed particles, measured at phase angles between ~70° and 120°, was used to derive a linear phase coefficient of 0.013 ± 0.005 magnitudes per degree of phase angle. Ground‐based data back to 1999 show no evidence of past activity for Bennu; however, the currently observed activity is orders of magnitude lower than observed at other active asteroids and too low be observed remotely. There appears to be a gentle decrease in activity with distance from the Sun, suggestive of ejection processes such as meteoroid impacts and thermal fracturing, although observational bias may be a factor.

The principal objective of the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission is to retrieve a sample of the asteroid (101955) Bennu and return it to Earth. OSIRIS-REx arrived at Bennu in December 2018. Images of the asteroid by the OSIRIS-REx Camera Suite (OCAMS) were photogrammetrically controlled to produce a global basemap and site-specific image mosaics essential to the selection of a primary and backup sample site, which were announced in December 2019. In the control process, OCAMS images were registered to shape models created from OSIRIS-REx Laser Altimeter (OLA) data and from the process of stereophotoclinometry. This paper summarizes the photogrammetric control to date of images collected at Bennu. We briefly review the mission and the OCAMS imaging sensors. We then describe the photogrammetric control process for the global mapping campaign and targeted reconnaissance surveys of candidate sample sites. Finally, we discuss ongoing and future work.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

CLUSTERING OF OSIRIS-REX IMAGES. J. L. Rizos, J. de León, J. Licandro, D. R. Golish, H. Campins, E. Tatsumi, M. Popescu, D. N. DellaGiustina, M. Pajola, J.-Y. Li, K. J. Becker, and D. S. Lauretta, 1 Instituto de Astrofísica de Canarias, Tenerife, Spain (jlrizos@iac.es), 2 Universidad de La Laguna, Tenerife, Spain, 3 Lunar and Planetary Laboratory, University of Arizona, Tucson, USA, 4 University of Central Florida, Orlando, USA, 5 University of Tokyo, Tokyo, Japan, 6 Astronomical Institute of the Romanian Academy, Bucharest, Romania, 7 INAF – Astronomical Observatory of Padova, Padova, Italy, 8 Planetary Science Institute, Tucson, USA, 9 USGS Astrogeology Science Center, Flagstaff, USA.

The OSIRIS-REx Camera Suite (OCAMS) onboard the OSIRIS-REx spacecraft is used to study the shape and surface of the mission’s target, asteroid (101955) Bennu, in support of the selection of a sampling site. We present calibration methods and results for the three OCAMS cameras—MapCam, PolyCam, and SamCam—using data from pre-flight and in-flight calibration campaigns. Pre-flight calibrations established a baseline for a variety of camera properties, including bias and dark behavior, flat fields, stray light, and radiometric calibration. In-flight activities updated these calibrations where possible, allowing us to confidently measure Bennu’s surface. Accurate calibration is critical not only for establishing a global understanding of Bennu, but also for enabling analyses of potential sampling locations and for providing scientific context for the returned sample.