Revisiting OSIRIS-REx Touch-And-Go (TAG) Performance Given the Realities of Asteroid Bennu

The Origins, Spectral Interpretation, Resource Identification, and SecurityRegolith Explorer (OSIRIS-REx) mission is a NASA New Frontiers mission that launched in 2016 and rendezvoused with the near-Earth asteroid (101955) Bennu in late 2018. Upon arrival, the surface of Bennu was found to be much rockier than expected. The original Touch-and-Go (TAG) requirement for sample collection was to deliver the spacecraft to a site with a 25-meter radius; however, the largest hazard-free sites are no larger than 8 meters in radius. To accommodate the dearth of safe sample collection sites, the project reevaluated all aspects of flight system performance pertaining to TAG in order to account for the demonstrated performance of the spacecraft and navigation prediction accuracies. More-over, the project has base lined on board natural feature tracking instead of lidar for providing the on board navigation state update during the TAG sequence. This paper summarizes the improvements in error source estimation, enhancements in on board trajectory correction, and results of recent Monte Carlo simulation to en-able sample collection with the given constraints. TAG delivery and on board navigation performance are presented for the final four candidate TAG sites

Measuring Winds From Space to Reduce the Uncertainty in the Southern Ocean Carbon Fluxes: Science Requirements and Proposed Mission

Strong winds in Southern Ocean storms drive air-sea carbon and heat fluxes. These fluxes are integral to the global climate system and the wind speeds that drive them are increasing. The current scatterometer constellation measuring vector winds remotely undersamples these storms and the higher winds within them, leading to potentially large biases in Southern Ocean wind reanalyses and the fluxes that derive from them. This observing system design study addresses these issues in two ways. First, we describe an addition to the scatterometer constellation, called Southern Ocean Storms -- Zephyr, to increase the frequency of independent observations, better constraining high winds. Second, we show that potential reanalysis wind biases over the Southern Ocean lead to uncertainty over the sign of the net winter carbon flux. More frequent independent observations per day will capture these higher winds and reduce the uncertainty in estimates of the global carbon and heat budgets

Geometry, displacement-length scaling, and extensional strain of normal faults on Mars with inferences on mechanical stratigraphy of the Martian crust

International audienceWe measure throw distributions for graben-bounding normal faults from two areas on Mars to investigate fault growth, displacement-length (D-max-L) scaling, and extensional strain using a complementary suite of techniques. Faults in the northern plains are inferred to be restricted at 2-3 km depth, as shown by a transition from linear scaling, with D-max-L ratios of similar to 1 x 10(-3), to nonlinear scaling for faults >50 km long. On the Alba Patera volcano, faults conform to linear Dmax-L scaling, with a Dmax-L ratio of similar to 6 x 10(-3), consistent with more deeply penetrating faults that are not restricted at depth. These grabens accommodate larger extensional strains (similar to 0.84%) than the faults in the northern plains (similar to 0.23%), with a temporal change from regionally distributed to localized deformation and associated increases in D-max-L ratio extensional strain, and perhaps down-dip fault height. The results suggest that both spatial and temporal variations in extensional strain and displacement-length scaling relations, along with fault restriction, are recorded by Martian fault populations. (C) 2009 Elsevier Ltd. All rights reserved

Science Operations Planning and Implementation for the OSIRIS-REx Mission, Part 1: Process

The Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft arrived at the near-Earth asteroid (101955) Bennu in December 2018 and executed a science observation campaign to comprehensively characterize the asteroid. Proximity operations at Bennu included orbital phases and flyby phases with various viewing geometries and altitudes. The complexity of the mission plan, integrated instrument operations, and the challenges of spacecraft navigation in the microgravity environment required an intricate planning and implementation process that included participation and coordination among all mission elements. The Science Planning Team (SPT) and the Implementation Team (IpT) at the University of Arizona planned and implemented all science and most optical navigation observations. Prior to the formal planning process, science requirements were mapped to mission phases and observation geometry constraints. During development of the mission phases, the navigation team produced a spacecraft trajectory, and the SPT developed the pointing and attitude profile to meet the specified constraints. In the strategic planning process, which began three months prior to execution, the SPT conducted sensitivity analysis of the observation designs against a set of perturbed trajectories delivered by the navigation team to ensure that they were robust to navigational uncertainties. Planning of the specific observations to occur within each phase was divided into units of weeks, and the plans for each week were developed and implemented on a rolling eight-week tactical planning and implementation cycle, ending with execution and data downlink. This cycle included a standardized schedule of activities and gateways to ensure that every observation plan underwent a full suite of analysis, verification, and approval in the allocated timeframe. Checklists guided the SPT and IpT through the build and verification process to confirm plan safety and fidelity. The SPT led the first four weeks of the tactical process, with participation from the IpT and other stakeholders. During the first two weeks, the SPT gathered information from stakeholders, conducted preliminary planning to confirm the science observations were feasible and obeyed spacecraft constraints, and determined how to integrate instrument commanding with the spacecraft pointing profile. The SPT started the final observation design and planning six weeks prior to execution. Once complete, plan walkthroughs were conducted with stakeholders, which culminated in a go/no-go decision to proceed with implementation at the four-week point. In the last four weeks of the tactical planning and implementation process, the IpT led the final processing of science plans with participation from stakeholders. The IpT compiled the plans, performed comprehensive safety checks against established spacecraft and instrument flight rules, and generated flight products and artifacts. After IpT delivered the flight products, the spacecraft team integrated them with the spacecraft sequencing, performed ground testing, and produced an integrated report. IpT reviewed the report, verifying instrument health and safety and confirming nominal plan execution in the ground simulation. The final flight products were uplinked to the spacecraft a few days prior to the execution week. During execution, the IpT and other stakeholders monitored instrument performance and viewed science and navigation data. Resulting science data products were used for operational decisions and science investigations.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Assessing the Sampleability of Bennu’s Surface for the OSIRIS-REx Asteroid Sample Return Mission

NASA’s first asteroid sample return mission, OSIRIS-REx, collected a sample from the surface of near-Earth asteroid Bennu in October 2020 and will deliver it to Earth in September 2023. Selecting a sample collection site on Bennu’s surface was challenging due to the surprising lack of large ponded deposits of regolith particles exclusively fine enough (≤2cm diameter) to be ingested by the spacecraft’s Touch-and-Go Sample Acquisition Mechanism (TAGSAM). Here we describe the Sampleability Map of Bennu, which was constructed to aid in the selection of candidate sampling sites and to estimate the probability of collecting sufficient sample. “Sampleability” is a numeric score that expresses the compatibility of a given area’s surface properties with the sampling mechanism. The algorithm that determines sampleability is a best fit functional form to an extensive suite of laboratory testing outcomes tracking the TAGSAM performance as a function of four observable properties of the target asteroid. The algorithm and testing were designed to measure and subsequently predict TAGSAM collection amounts as a function of the minimum particle size, maximum particle size, particle size frequency distribution, and the tilt of the TAGSAM head off the surface. The sampleability algorithm operated at two general scales, consistent with the resolution and coverage of data collected during the mission. The first scale was global and evaluated nearly the full surface. Due to Bennu’s unexpected boulder coverage and lack of ponded regolith deposits, the global sampleability efforts relied heavily on additional strategies to find and characterize regions of interest based on quantifying and avoiding areas heavily covered by material too large to be collected. The second scale was site-specific and used higher-resolution data to predict collected mass at a given contact location. The rigorous sampleability assessments gave the mission confidence to select the best possible sample collection site and directly enabled successful collection of hundreds of grams of material.National Aeronautics and Space AdministrationOpen access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

OSIRIS-APEX: An OSIRIS-REx Extended Mission to Asteroid Apophis

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

The High Resolution Imaging Science Experiment (HiRISE) during MRO’s Primary Science Phase (PSP)

The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) acquired 8 terapixels of data in 9137 images of Mars between October 2006 and December 2008, covering ~0.55% of the surface. Images are typically 5–6 km wide with 3-color coverage over the central 20% of the swath, and their scales usually range from 25 to 60 cm/pixel. Nine hundred and sixty stereo pairs were acquired and more than 50 digital terrain models (DTMs) completed; these data have led to some of the most significant science results. New methods to measure and correct distortions due to pointing jitter facilitate topographic and change-detection studies at sub-meter scales. Recent results address Noachian bedrock stratigraphy, fluvially deposited fans in craters and in or near Valles Marineris, groundwater flow in fractures and porous media, quasi-periodic layering in polar and non-polar deposits, tectonic history of west Candor Chasma, geometry of clay-rich deposits near and within Mawrth Vallis, dynamics of flood lavas in the Cerberus Palus region, evidence for pyroclastic deposits, columnar jointing in lava flows, recent collapse pits, evidence for water in well-preserved impact craters, newly discovered large rayed craters, and glacial and periglacial processes. Of particular interest are ongoing processes such as those driven by the wind, impact cratering, avalanches of dust and/or frost, relatively bright deposits on steep gullied slopes, and the dynamic seasonal processes over polar regions. HiRISE has acquired hundreds of large images of past, present and potential future landing sites and has contributed to scientific and engineering studies of those sites. Warming the focal-plane electronics prior to imaging has mitigated an instrument anomaly that produces bad data under cold operating conditions