Showing papers by "Olivier S. Barnouin published in 2017"

OSIRIS-REx: Sample Return from Asteroid (101955) Bennu

Abstract: In May of 2011, NASA selected the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission as the third mission in the New Frontiers program. The other two New Frontiers missions are New Horizons, which explored Pluto during a flyby in July 2015 and is on its way for a flyby of Kuiper Belt object 2014 MU69 on January 1, 2019, and Juno, an orbiting mission that is studying the origin, evolution, and internal structure of Jupiter. The spacecraft departed for near-Earth asteroid (101955) Bennu aboard an United Launch Alliance Atlas V 411 evolved expendable launch vehicle at 7:05 p.m. EDT on September 8, 2016, on a seven-year journey to return samples from Bennu. The spacecraft is on an outbound-cruise trajectory that will result in a rendezvous with Bennu in November 2018. The science instruments on the spacecraft will survey Bennu to measure its physical, geological, and chemical properties, and the team will use these data to select a site on the surface to collect at least 60 g of asteroid regolith. The team will also analyze the remote-sensing data to perform a detailed study of the sample site for context, assess Bennu’s resource potential, refine estimates of its impact probability with Earth, and provide ground-truth data for the extensive astronomical data set collected on this asteroid. The spacecraft will leave Bennu in 2021 and return the sample to the Utah Test and Training Range (UTTR) on September 24, 2023.

OSIRIS-REx: Sample Return from Asteroid (101955) Bennu

Abstract: In May of 2011, NASA selected the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) asteroid sample return mission as the third mission in the New Frontiers program. The other two New Frontiers missions are New Horizons, which explored Pluto during a flyby in July 2015 and is on its way for a flyby of Kuiper Belt object 2014 MU69 on Jan. 1, 2019, and Juno, an orbiting mission that is studying the origin, evolution, and internal structure of Jupiter. The spacecraft departed for near-Earth asteroid (101955) Bennu aboard an United Launch Alliance Atlas V 411 evolved expendable launch vehicle at 7:05 p.m. EDT on September 8, 2016, on a seven-year journey to return samples from Bennu. The spacecraft is on an outbound-cruise trajectory that will result in a rendezvous with Bennu in August 2018. The science instruments on the spacecraft will survey Bennu to measure its physical, geological, and chemical properties, and the team will use these data to select a site on the surface to collect at least 60 g of asteroid regolith. The team will also analyze the remote-sensing data to perform a detailed study of the sample site for context, assess Bennus resource potential, refine estimates of its impact probability with Earth, and provide ground-truth data for the extensive astronomical data set collected on this asteroid. The spacecraft will leave Bennu in 2021 and return the sample to the Utah Test and Training Range (UTTR) on September 24, 2023.

The OSIRIS-REx Laser Altimeter (OLA) Investigation and Instrument

Abstract: The Canadian Space Agency (CSA) has contributed to the Origins Spectral Interpretation Resource Identification Security-Regolith Explorer (OSIRIS-REx) spacecraft the OSIRIS-REx Laser Altimeter (OLA). The OSIRIS-REx mission will sample asteroid 101955 Bennu, the first B-type asteroid to be visited by a spacecraft. Bennu is thought to be primitive, carbonaceous, and spectrally most closely related to CI and/or CM meteorites. As a scanning laser altimeter, the OLA instrument will measure the range between the OSIRIS-REx spacecraft and the surface of Bennu to produce digital terrain maps of unprecedented spatial scales for a planetary mission. The digital terrain maps produced will measure $\sim7~\mbox{cm}$ per pixel globally, and $\sim3~\mbox{cm}$ per pixel at specific sample sites. In addition, OLA data will be used to constrain and refine the spacecraft trajectories. Global maps and highly accurate spacecraft trajectory estimates are critical to infer the internal structure of the asteroid. The global and regional maps also are key to gain new insights into the surface processes acting across Bennu, which inform the selection of the OSIRIS-REx sample site. These, in turn, are essential for understanding the provenance of the regolith sample collected by the OSIRIS-REx spacecraft. The OLA data also are important for quantifying any hazards near the selected OSIRIS-REx sample site and for evaluating the range of tilts at the sampling site for comparison against the capabilities of the sample acquisition device.

The surface roughness of Mercury from the Mercury Laser Altimeter: Investigating the effects of volcanism, tectonism, and impact cratering

Abstract: Surface roughness is a statistical measure of change in surface height over a given spatial horizontal scale after the effect of broad scale slope has been removed, and can be used to understand how geologic processes produce and modify a planet's topographic character at different scales. The statistical measure of surface roughness employed in this study of Mercury was the root-mean-square (RMS) deviation, and was calculated from 45–90°N at horizontal baselines of 0.5-250 km with detrended topographic data from individual Mercury Laser Altimeter tracks. As seen in previous studies, the surface roughness of Mercury has a bimodal spatial distribution, with the cratered terrain (dominated by the intercrater plains) possessing higher surface roughness than the smooth plains. The measured surface roughness for both geologic units is controlled by a trade off between impact craters generating higher surface roughness values and flood-mode volcanism decreasing surface roughness. The topography of the two terrain types has self-affine-like behavior at baselines from 0.5–1.5 km; the smooth plains collectively have a Hurst exponent of 0.88 +/- 0.01, whereas the cratered terrains have a Hurst exponent of 0.95 +/- 0.01. Subtle variations in the surface roughness of the smooth plains can be attributed to differences in regional differences in the spatial density of tectonic landforms. The northern rise, a 1,000-km-wide region of elevated topography centered at 65° N, 40° E, is not distinguishable in surface roughness measurements over baselines of 0.5–250 km.

Recovery of Bennu's Orientation for the OSIRIS-REx Mission

Abstract: The goal of the OSIRIS-REx mission is to return a sample of asteroid material from near-Earth asteroid (101955) Bennu. The role of the navigation and flight dynamics team is critical for the spacecraft to execute a precisely planned sampling maneuver over a specifically selected landing site. In particular, the orientation of Bennu needs to be recovered with good accuracy during orbital operations to contribute as small an error as possible to the landing error budget. Although Bennu is well characterized from Earth-based radar observations, its orientation dynamics are not sufficiently known to exclude the presence of a small wobble. To better understand this contingency and evaluate how well the orientation can be recovered in the presence of a large 1$$^{\circ }$$∘ wobble, we conduct a comprehensive simulation with the NASA GSFC GEODYN orbit determination and geodetic parameter estimation software. We describe the dynamic orientation modeling implemented in GEODYN in support of OSIRIS-REx operations and show how both altimetry and imagery data can be used as either undifferenced (landmark, direct altimetry) or differenced (image crossover, altimetry crossover) measurements. We find that these two different types of data contribute differently to the recovery of instrument pointing or planetary orientation. When upweighted, the absolute measurements help reduce the geolocation errors, despite poorer astrometric (inertial) performance. We find that with no wobble present, all the geolocation requirements are met. While the presence of a large wobble is detrimental, the recovery is still reliable thanks to the combined use of altimetry and imagery data.

The Asteroid Probe Experiment (APEX) Mission

Abstract: The Asteroid Probe Experiment (APEX) is a mission to determine the interior structure of the Near-Earth Asteroid Apophis and the response of that body to the tidal forces it experiences during a close encounter with the Earth. Apophis will make a close encounter of the Earth in 2029 (approaching within 0.000245 ± 0.000060 AU, 36700 ± 9000 km or 5.7 ± 1.4 Earth radii, 3σ uncertainties), which is just below geosynchronous orbit. While this distance is beyond the Roche limit and the asteroid is not expected to break up due to tidal forces, those tidal forces should be sufficient to deform the body, reorient its rotation and produce deformation that will create seismic energy. The baseline objectives of the mission include: (1) determine rotational dynamics, (2) establish physical dimensions, (3) determine topography, (4) determine interior structure, and (5) define surface morphology. Additional objectives could include the chemical and mineralogic composition and the surface physical properties. The mission will also provide data needed to calibrate interpretations of Earthand space-based astronomical observations and Earthbased radar observations of NEOs. We will employ a small spacecraft (Discovery or Deep Space Smallsat) that will rendezvous with Apophis and conduct a suite of observations before and after Earth encounter and deploy a seismometer on the surface. We have already examined a mission employing a spacecraft having a dry mass of about 200 kg and are now examining if it is possible to conduct the mission using a Deep Space Smallsat concept. As part of that analysis, we examine different types of propulsion (solar electric and chemical) and different spacecraft concepts to determine the minimum spacecraft requirements necessary to achieve the scientific goals of the mission.

The OSIRIS-REx laser altimeter

Abstract: The OSIRIS-REx Laser Altimeter (OLA) is a scanning laser altimeter onboard the NASA mission to the near-Earth asteroid 101955 Bennu. We will describe the operation and unique capabilities of the instrument for an asteroid mission.

The Double Asteroid Redirection Test (Dart) Element of the Asteroid Impact and Deflection Assessment (AIDA) Mission

Abstract: Introduction: The Asteroid Impact Deflection Assessment (AIDA) mission will be the first space experiment to demonstrate asteroid impact hazard mitigation by using a kinetic impactor. AIDA is a joint ESA-NASA cooperative project, consisting of the NASA Double Asteroid Redirection Test (DART) kinetic impactor mission [1] and the ESA Asteroid Impact Mission (AIM), which is the asteroid rendezvous spacecraft [2]. The original AIM concept did not receive full funding in late 2016, but a rescoping of AIM is being undertaken at ESA. The AIDA target is the near-Earth binary asteroid 65803 Didymos. During the Didymos close approach to Earth in October, 2022, the DART spacecraft will impact the Didymos secondary at 6 km/s and deflect its trajectory, changing the orbital period of the binary. This change can be measured by Earth-based optical and radar observations. The primary goals of AIDA are to (1) perform a full-scale demonstration of asteroid deflection by kinetic impact; (2) measure the resulting deflection; and (3) validate and improve models for momentum transfer in high-speed impacts on an asteroid. The combined DART and AIM missions will provide the first measurements of momentum transfer efficiency from a kinetic impact at full scale on an asteroid, where the impact conditions of the projectile are known, and physical properties and internal structures of the target asteroid are also characterized. AIDA with both DART and AIM will be the first fully documented impact experiment at asteroid scale, including characterization of the target’s properties and the outcome of the impact to test and refine our understanding and models at an actual asteroid scale. AIDA will check whether current extrapolations of material strength from laboratory scale to asteroid scale are valid. AIDA will validate the kinetic impactor technique to deflect a small body and reduce risks for future asteroid hazard mitigation. DART: The momentum transfer efficiency β of a kinetic impactor is the ratio of the momentum transferred to the target over the incident momentum. Because there is momentum carried away by impact ejecta released back towards the incident direction, this β generally exceeds unity [1,3,4]. There are many unknowns that affect β, which is critical to predicting the amount of deflection to be achieved by a kinetic impact. By performing a kinetic impact on an asteroid and observing the target both before and after the impact, AIDA will measure β and determine the magnitude and direction of deflection. It will measure physical properties of the target asteroid, especially density, and determine shape and geology of the impact site. It will further study outcomes such as changes in the target body rotation state and evolution of ejecta. Mission and Payload: The DART kinetic impactor baseline mission has changed from that given in [1]. DART will launch as a secondary payload to geosynchronous orbit and use the NASA Evolutionary Xenon Thruster (NEXT) ion propulsion system to spiral out from Earth orbit and transfer to Didymos (see Table 1). For a launch on or before 31 March 2021, the Didymos impact will now occur on Oct. 7, 2022, a few weeks later than in [1]. With a larger ~490 kg spacecraft impacting at 6 km/s, the incident momentum is significantly increased from that in [1], leading to a larger target deflection and a larger crater.