adsabs/AstroCLIMB huggingface dataset:
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Truth shape models used to simulate images.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Stages of the shape modeling process used in the DART mission.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Mean tilt directions across the impact site DTMs, isolating just the max envelope of the DART spacecraft core, with respect to the spacecraft impact vector, with a tilt radius of 0.9 m. The left column (red) plots the distributions for the truth model. The blue column (right) plots the distributions for the reconstructed impact site DTMs. The difference in the mean and median tilt directions between the truth and reconstructed cases is between 1° and 33°, depending on the case.
Paper: Pre-encounter Predictions of DART Impact Ejecta Behavior and Observability
Authors: Eugene G. Fahnestock, Andrew F. Cheng, Stavro Ivanovski, Patrick Michel, Sabina D. Raducan, Alessandro Rossi, Paul A. Abell, Steven Chesley, Elisabetta Dotto, Fabio Ferrari, Ludmilla Kolokolova, Emily Kramer, Jian-Yang Li, Stephen R. Schwartz, Stefania Soldini, Gonzalo Tancredi, Adriano Campo Bagatin, Yun Zhang
Figure caption: Schematic representation of the handoff procedure and ejecta initialization in N-body codes for mid- and long-term evolution of the DART impact ejecta. (a) Properties of the ejecta plume from small-scale impacts can be recorded from laboratory impact experiments (J. Ormö et al. 2022, personal communication). (b) Shock physics codes (e.g., SPH codes) validated against laboratory impact experiments can be used to model asteroid-scale impacts. (c) Ejecta scaling relationships (i.e., Housen & Holsapple 2011) can be used to approximate the behavior of the ejecta away from the impact point and crater rim using laboratory- or numerical simulation–derived scaling constants (Housen & Holsapple 2011; Raducan et al. 2019). (d) The input conditions in N-body codes that track the mid- and long-term evolution of the DART impact ejecta particles can be initialized by direct handoff from SPH codes or by applying ejecta scaling relationships.
Paper: Pre-encounter Predictions of DART Impact Ejecta Behavior and Observability
Authors: Eugene G. Fahnestock, Andrew F. Cheng, Stavro Ivanovski, Patrick Michel, Sabina D. Raducan, Alessandro Rossi, Paul A. Abell, Steven Chesley, Elisabetta Dotto, Fabio Ferrari, Ludmilla Kolokolova, Emily Kramer, Jian-Yang Li, Stephen R. Schwartz, Stefania Soldini, Gonzalo Tancredi, Adriano Campo Bagatin, Yun Zhang
Figure caption: (a) Velocity distribution and rotational frequencies of the oblate (k = 0.2) and prolate (k = 5.0) equivalent-mass particles derived from 100 spherical IC particles. (b) Temperature and collisional dependence of the velocity achieved by oblate (k = 0.2) equivalent-mass particles derived from 10 spherical IC particles as a function of their mass.
Paper: Pre-encounter Predictions of DART Impact Ejecta Behavior and Observability
Authors: Eugene G. Fahnestock, Andrew F. Cheng, Stavro Ivanovski, Patrick Michel, Sabina D. Raducan, Alessandro Rossi, Paul A. Abell, Steven Chesley, Elisabetta Dotto, Fabio Ferrari, Ludmilla Kolokolova, Emily Kramer, Jian-Yang Li, Stephen R. Schwartz, Stefania Soldini, Gonzalo Tancredi, Adriano Campo Bagatin, Yun Zhang
Figure caption: Distribution of the ejecta velocities after 300 s as propagated with three different SRP models (see text for details). The Y-axis shows the number of objects in each bin relative to the total of 10,000 test particles. Note that, as explained in the text, the distributions match up for most of the plot; hence, only the black line is usually visible.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Mean tilt directions across the impact site DTMs with respect to the spacecraft impact vector, with a tilt radius of 0.9 m. The left column (red) plots the distributions for the truth model. The blue column (right) plots the distributions for the reconstructed impact site DTMs. The difference in the mean and median tilt directions between the truth and reconstructed cases is between 1° and 31°, depending on the case.
Paper: Pre-encounter Predictions of DART Impact Ejecta Behavior and Observability
Authors: Eugene G. Fahnestock, Andrew F. Cheng, Stavro Ivanovski, Patrick Michel, Sabina D. Raducan, Alessandro Rossi, Paul A. Abell, Steven Chesley, Elisabetta Dotto, Fabio Ferrari, Ludmilla Kolokolova, Emily Kramer, Jian-Yang Li, Stephen R. Schwartz, Stefania Soldini, Gonzalo Tancredi, Adriano Campo Bagatin, Yun Zhang
Figure caption: (a) The ICs from scaling laws (Section 2.3.1) are shown in blue; the patch used to characterize collisions is shown in red. (b) Number of collisions in time during the early transient collisional phase for different values of surface density σ.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Mean tilt directions across the impact site DTMs with respect to the spacecraft impact vector, with a tilt radius of 9 m. The left column (red) plots the distributions for the truth model. The blue column (right) plots the distributions for the reconstructed impact site DTMs. The difference in the mean and median tilt directions between the truth and reconstructed cases is between 1° and 29°, depending on the case.
Paper: Practical Stereophotoclinometry for Modeling Shape and Topography on Planetary Missions
Authors: Eric E. Palmer, Robert Gaskell, Michael G. Daly, Olivier S. Barnouin, Coralie D. Adam, Dante S. Lauretta
Figure caption: Example of a set of high-quality images for a piece of terrain. The left panel shows the position of the spacecraft as seen from the surface, looking up. The right panel shows the position of the Sun from the surface. Azimuth runs from north (0) to east (90) to south (180) to west (270). Zenith angle is marked every 30°, with zero being straight up. This figure depicts an asteroid with a near-zero obliquity and the point of view of a maplet that is north of the equator by 20°–40°. Each image station is denoted by a matching pair of numbered circles in both the spacecraft and sun geometry figures. Topographic images are numbers 1–4, with the albedo image being number 5.
Paper: Practical Stereophotoclinometry for Modeling Shape and Topography on Planetary Missions
Authors: Eric E. Palmer, Robert Gaskell, Michael G. Daly, Olivier S. Barnouin, Coralie D. Adam, Dante S. Lauretta
Figure caption: Example of a key processing output from SPC, the landmark display image. The top row shows source subimages, which are 99 × 99 pixel croppings of the original images centered at the landmark’s position. The bottom row shows the model subimages, that is, the DTM and albedo rendered with the same observing geometry as the associated real image. The agreement between each pair of source and model subimages indicates how well the DTM represents the actual topography and albedo.
Paper: Practical Stereophotoclinometry for Modeling Shape and Topography on Planetary Missions
Authors: Eric E. Palmer, Robert Gaskell, Michael G. Daly, Olivier S. Barnouin, Coralie D. Adam, Dante S. Lauretta
Figure caption: The process of increasing the resolution via tiling is as follows. (a) The current set of maplets covers a region at a specific GSD, in this case, 75 cm. (b) We create a bigmap (blue box) that resamples the current set of maplets at a GSD 30% larger than the desired GSD; desired is 35 cm, so the bigmap has a GSD of 45 cm. (c) A new set of maplets with the desired GSD is created and loaded with topography from the bigmap as a starting point, then new higher-resolution images are associated with these new maplets. The AES process is started with these new maplets in order to improve their topography. For visual clarity, this figure depicts a general example, specifically that panels (a) and (c) show the maplets touching one another. In practice, there is a 30% overlap between maplets.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: Example NFT rendering and correlation surface (x- and y-axes in pixels). Panel (a) includes a patch of an image captured by the onboard navigation camera. The resolution of this image is 7.98 cm pixel−1, and the FOV is ∼6.6 m. Panel (b) shows the corresponding rendering on board by NFT using the uploaded DTMs. Panel (c) shows the resulting correlation surface when correlating the rendering against the image patch. The peak of this surface is a correlation score of 0.84.
Paper: Practical Stereophotoclinometry for Modeling Shape and Topography on Planetary Missions
Authors: Eric E. Palmer, Robert Gaskell, Michael G. Daly, Olivier S. Barnouin, Coralie D. Adam, Dante S. Lauretta
Figure caption: Comparison between a rendered image and an actual image of the OSIRIS-REx target, asteroid (101955) Bennu. Left is the SPC 35 cm (v42) DTM rendered with matching spacecraft position and pointing. Right is a MapCam image from the Preliminary Survey mission phase, image 20181213T022027S610. The orientation is based upon how the spacecraft imaged Bennu, and in this case, the north pole was facing to the right. The polar radius of Bennu (in this image, left to right) is 508 m.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: Feature model resolutions (GSDs) used by NFT during the TAG trajectory. Image 1 is the first, highest-altitude image acquired during the descent to the surface, and image 30 is the last, lowest-altitude image.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: NavCam 2 image processed by NFT during the approach to the OSIRIS-REx TAG site (called Nightingale) with five matched features. Feature search regions are depicted by yellow dashed boxes. The predicted location of the feature is denoted with red crosses. Matched locations are depicted by green plus signs. This image captures a 22 m × 16 m area near the TAG site.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: View to the north from Bennu’s southern hemisphere. The FOV in this OCAMS (PolyCam) image is 52 m wide. For scale, the largest boulder in the upper left corner of the image is 14.5 m wide, which is about the length of a semitruck trailer.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: Examples of high- and low-scoring features (x- and y-axes in pixels). In this figure, panels (a) and (d) show the NavCam 2 image subsection, panels (b) and (e) show the NFT feature rendering, and panels (c) and (f) show the resulting NFT correlation surface. The top row represents a high-scoring feature, where the feature model captured all important aspects of terrain needed for correlation and resulted in a sharp correlation peak of 0.86. The image in panel (a) has a resolution of 9.0 cm pixel−1 and is ∼8 m across. The bottom row represents a lower-scoring feature, where the feature model did not capture all terrain variation or the very bright albedo region and resulted in a broader correlation peak of 0.57. The image in panel (d) has a resolution of 1.3 cm pixel−1 and is ∼0.7 m across.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: NFT 3σ predicted deliverability ellipse (blue) and hazardous sampling locations (green) overlaid onto a NavCam 2 image mosaic of the Nightingale site. The deliverability ellipse shows the area within which 99.73% of predicted TAG attempts will fall. Everything outside of the green boundary is hazardous to the spacecraft. Green outlines within the green boundary represent hazards within site Nightingale. The TAG target represented by a green plus sign is the targeted location within Nightingale. The blue plus sign is the mean of the predicted TAG locations, and the magenta plus sign is the final TAG location estimate made by NFT during TAG.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: OSIRIS-REx TAG trajectory propagated from the Checkpoint maneuver. The nominal trajectory represents the planned trajectory to the target within the TAG site. The propagated trajectory without guidance updates shows the trajectory the spacecraft would have taken if the pre-planned Checkpoint and Matchpoint maneuvers were not updated based on NFT state knowledge. The reconstructed flight trajectory shows the trajectory the spacecraft flew during TAG using the onboard NFT knowledge.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: TAG deliverability when using NFT (left) and without using NFT (right). The black plus sign in each diagram represents the targeted location within the TAG site, and the black ellipse in each diagram represents the 98.3% TAG deliverability error considering all total spacecraft error sources. The blue dot in each diagram is the predicted TAG location when using NFT (left) and when not using NFT (right). The blue ellipse represents the 98.3% TAG location knowledge error from the NFT covariance.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: As-flown incidence and emission angles of features used during the TAG trajectory vs. NFT image number. Blue crosses represent the incidence angles of the features used by NFT during TAG, and green open circles represent the emission angles of the features used by NFT during TAG.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: OSIRIS-REx TAGSAM head at initial contact with the surface of Bennu. The TAG location predicted by NFT (red) is overlaid on this OCAMS (SamCam) image side by side with the actual TAG location (cyan) reconstructed from image data.
Paper: The Use of Digital Terrain Models for Natural Feature Tracking at Asteroid Bennu
Authors: R. D. Olds, C. J. Miller, C. D. Norman, C. E. Mario, K. Berry, E. Palmer, O. S. Barnouin, M. G. Daly, J. R. Weirich, J. A. Seabrook, C. A. Bennett, D. Lorenz, B. Rizk, B. J. Bos, D. S. Lauretta
Figure caption: Location of NFT features on the surface of Bennu. Red crosses denote the center of each feature. The target TAG site is also denoted in teal.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Mean tilt of facets in the impact site DTM. Tilts are computed with respect to the spacecraft impact vector, thereby providing information about the relative impact angle between DART and the asteroid. The figure shows tilts at two different radii: (a) the 0.9 m tilt radius provides information on tilts at the length scale of the core of the DART spacecraft; (b) the 9 m tilt radius provides information about tilts at the length scale of the DART spacecraft with solar arrays extended. All maps use a common color scale to facilitate comparisons between the 0.9 and 9 m tilt maps. The yellow circle is 2.5 m in diameter, the size of the maximum envelope of the DART spacecraft core. The impact site DTMs are 18.9 m on a side; the extended solar arrays would span almost the entire width of the impact site DTM.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Locations of the truth and reconstructed impact sites in the final simulated DRACO image for each test. Yellow (truth) and cyan (reconstructed) circles are 2.5 m in diameter, which is the maximum envelope of the DART spacecraft core. In all cases, the circles almost entirely overlap, which demonstrates that we will be able to both precisely and accurately identify the impact site, regardless of asteroid shape, whether LEIA images are available, and errors in spacecraft position and camera pointing. The insets are a zoom-in view of the impact site; the geologic context is clear. Although the insets do not have separate scale bars (for clarity of the image), the 2.5 m diameters of the circles provide a sense for scale.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Mean tilt directions of facets in the impact site DTMs. Tilt directions are computed with respect to the spacecraft impact vector, thereby providing information about the relative impact angle between DART and the asteroid. The figure shows tilts at two different radii. The 0.9 m tilt radius provides information on tilts at the length scale of the core of the DART spacecraft. The tilt direction is the direction projected on a clock, with a 0° tilt direction pointing to the north pole of the asteroid.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Mean tilts across the impact site DTMs, focusing only on the region of the DTM within the spacecraft core maximum envelope (2.5 m), with respect to the spacecraft impact vector, with a tilt radius of 9 m. The left column (red) plots the distributions for the truth model. The blue column (right) plots the distributions for the reconstructed. The difference in the mean and median tilts between the truth and reconstructed cases is between 1° and 7°, depending on the case.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Location of the truth and reconstructed impact sites for each of the tests reported in this paper. The absolute location of the impact in 3D space is up to a few meters off from where it should be in the truth model, but that offset is small enough to not meaningfully affect the outcome of the DART experiment. The axes scales are different for each panel. Each blue dot corresponds to the solution for a given image in the reconstructed shape model. The reconstructed impact site is the average of the locations in the last five images.
Paper: Shape Modeling of Dimorphos for the Double Asteroid Redirection Test (DART)
Authors: R. Terik Daly, Carolyn M. Ernst, Olivier S. Barnouin, Robert W. Gaskell, Eric E. Palmer, Hari Nair, Ray C. Espiritu, Sarah Hasnain, Dany Waller, Angela M. Stickle, Michael C. Nolan, Josep M. Trigo-Rodríguez, Elisabetta Dotto, Alice Lucchetti, Maurizio Pajola, Simone Ieva, Patrick Michel
Figure caption: Comparison between the truth (ivory), reconstructed (blue), and starter ellipsoids (dashed white line) as viewed in the −Z direction for a portion of the shape imaged by DRACO. The reconstructed shape hews closely to the starter shape.