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

The OSIRIS-REx Asteroid Sample Return Mission is the third mission in NASA's New Frontiers Program and is the first U.S. mission to return samples from an asteroid to Earth. The most important decision ahead of the OSIRIS-REx team is the selection of a prime sample-site on the surface of asteroid (101955) Bennu. Mission success hinges on identifying a site that is safe and has regolith that can readily be ingested by the spacecraft's sampling mechanism. To inform this mission-critical decision, the surface of Bennu is mapped using the OSIRIS-REx Camera Suite and the images are used to develop several foundational data products. Acquiring the necessary inputs to these data products requires observational strategies that are defined specifically to overcome the challenges associated with mapping a small irregular body. We present these strategies in the context of assessing candidate sample-sites at Bennu according to a framework of decisions regarding the relative safety, sampleability, and scientific value across the asteroid's surface. To create data products that aid these assessments, we describe the best practices developed by the OSIRIS-REx team for image-based mapping of irregular small bodies. We emphasize the importance of using 3D shape models and the ability to work in body-fixed rectangular coordinates when dealing with planetary surfaces that cannot be uniquely addressed by body-fixed latitude and longitude.

K. Becker2, T. Becker1, K. L. Berry1, K. L. Edmundson1, A. Goins1, I. Humphrey1, C. E. Isbell1, L. Keszthelyi1, J. Mapel1, M. P. Milazzo1, C. Neubauer1, A. Pacquette1, M. Shepherd1, S. Sides1, T. Titus1, L. Weller1, K. Williams1, and T. J. Wilson1, 1U.S. Geological Survey, 2255 N Gemini Drive, Flagstaff, Arizona 86001, USA, jwbacker@usgs.gov, 2Lunar and Planetary Laboratory, University of Arizona, 1415 N. 6th Avenue, Tucson, AZ 85705, USA.

ENVIRONMENT (IPCE) FOR PLANETARY MAPPING. Kenneth L. Edmundson, B.A. Archinal, J.C. Backer, J.M. Barrett, K.J. Becker, T.L. Becker, J.P. Bonn, D.A. Cook, M.A. Hahn, I.R. Humphrey, S. Lambright, E.M. Lee, J.A. Mapel, K.A. Oyama, A.C. Paquette, M.R. Shepherd, S.C. Sides, T.L. Sucharski, and L.A. Weller, Astrogeology Science Center, U.S. Geological Survey, Flagstaff, AZ, USA, 86001, (kedmundson@usgs.gov), USGS Retired, Tableau, Seattle, WA, USA, 98103, Naval Surface Warfare Center, Port Hueneme, CA, USA, 93043

Introduction: Light time and stellar aberration (abbreviated throughout as “light time”) corrections may be important when considering both spacecraft (observer) and planetary body (target) location during cartographic processing of data collected by planetary spacecraft. The USGS Integrated Software for Imagers and Spectrometers (ISIS) [1] utilizes rigorous camera models and the Navigation and Ancillary Information Facility (NAIF) SPICE toolkit [2-3] for these calculations. Light time correction should be applied to apparent target position relative to the observer in order to produce the most accurate cartographic products. Previous work details how ISIS utilizes the SPICE toolkit and analyzes the effect of the different light time correction options’ ability to locate well-characterized lunar control points in LROC images [4]. Here we provide a broader summary of light time correction in ISIS with an emphasis on practical considerations utilizing representative planetary data sets to describe the usage of different light time correction modes in ISIS, consider relevant anomalies and implications where light time corrections were applied to legacy data, and recognize the additional analysis and developments needed to improve the light time correction provided by ISIS. Current and Previous ISIS implementation: ISIS developers describe, and analyze the impact of, a flawed implementation of light time correction in early versions of ISIS (3.4.1 and prior) where the observer (rather than target) position was shifted while the target (rather than the observer) was held fixed [4]. Furthermore, correction calculations were originally based on distance to target center, rather than distance to the surface. The latter can “overcorrect” for light time, degrading rather than improving the cartographic precision of the ISIS products [4]. ISIS (3.4.2+) now allows for swapping (i.e., correcting) the target/observer reference frame, applying corrections based on distance to target surface, and disabling light time correction altogether. It is important to note that light time corrections are applied by default within ISIS, unless specified otherwise within the kernel parameters. Default functionality and means of invoking custom kernels are discussed further below. Correction considerations: Multiple factors are at play in determining whether light time correction should be applied. These factors primarily include the relative velocity of the spacecraft and target, distance to target surface, and instrument spatial resolution. In addition, compute time requirements for calculations at the highest precision and accuracy may be prohibitive. The following table provides, for some representative data sets, estimates of target position offsets (i.e., light time corrections) based on calculations done to the target center (default ISIS implementation) and to surface (more correct implementation).

CARTOGRAPHY. Kenneth L. Edmundson 1 , J.C. Backer 1 , J.M. Barrett 2 , K.J. Becker 1 , T.L. Becker 1 , D.A. Cook 2 , S. Lambright 3 , J.R. Laura 1 , E.M. Lee 2 , K.A. Oyama 4 , S.C. Sides 1 , T.L. Sucharski 2 , L.A. Weller 1 , 1 Astrogeology Science Center, United States Geological Survey, Flagstaff, AZ, USA, 86001, (kedmundson@usgs.gov), 2 USGS Retired, 3 Synopsys, Inc., Seattle, WA, USA, 98104, 4 Naval Surface Warfare Center, Port Hueneme, CA, USA, 93043

Background: The Integrated Software for Imagers and Spectrometers (Isis) was developed in the late1980’s, primarily to support the Galileo NIMS instrument [2]. In 1992, the cartographic capabilities of PICS were merged into Isis in order to support the Clementine mission. Since that time, software for numerous missions has been incorporated into Isis including Viking Orbiters, Voyager I/II, Galileo SSI, Pathfinder IMP, Mars Global Surveyor MOC, TES, and MOLA, Odyssey THEMIS, and Lunar Orbiter. The multi-mission capabilities in Isis make it a widely used software package among the planetary community. This version is denoted at Isis 2.1 and because of its maturity had several key issues which needed to be addressed. These include a text-based user interface, an image size limitation of approximately 2 gigabytes, and a vast FORTRAN and C Application Program Interface (API). The user interface is based on the Transportable Application Executive (TAE), a software package over 20 years old with limited software support. Although a gem in its time, a modern image processing package would be better suited to a graphical user interface. In addition, Isis 2.1 was developed to support image sizes on 32-bit architectures (2GB files). Recent instruments, such as Odyssey’s THEMIS have at times needed to exceed this limit, but have been unable. Future instruments such as Mars Reconnaissance Orbiter’s HiRISE will routinely need to exceed this limitation. Finally, the Isis API is composed of nearly 3000 FORTRAN and C source files, each with one or more internal functions or subroutines. This vast API is at times difficult to navigate, even for veteran Isis developers, and often leads to code duplication. Unfortunately, the intrinsic organizational capabilities and the added power of object oriented languages such as C++ and Java were not fully available in the initial design phase of Isis 2.1. Modernization: In December 2001, the USGS began a major effort to modernize our image processing software as Isis 3.0. This new version would incorpate a Graphical User Interface (GUI) and use C++ as the primary programming language. Other major benefits include a web-based documentation set for application programs, web-based programmer documentation, test suites for software integrity checks between releases and/or ports to new operating systems, and a greatly simplified programming environment. Examples and additional information can be found on the following url, http:/Isis.astrogeology.usgs.gov.

Geomorphic processes in and regions are particularly sensitive to climatic variability. In this context, integrated studies are being conducted to understand the response of dust emission and deposition to climatic and land-use change in the and southwestern United States. Several approaches are taken to monitor wind erosion and characterize modem dust - its sources, flux, and composition - to document the potential for desertification under future climatic conditions. Wind erosion is monitored at ecologically sensitive sites, using meteorological stations that measure sand flux within the saltation layer. Dust deposition is also monitored at these and many other sites using different types of dust collectors. In addition, new remote sensing methods detect the location, frequency, magnitude, and duration of large dust-emission events. Remotely sensed images of vegetation change, combined with those that illustrate high soil reflectivity, complement dust-detection methods to identify areas especially susceptible to wind erosion. Dust trapped in collectors and in snow is characterized for its physical, mineralogic, and chemical properties. Combined with soil and weather data, such characterization sheds light on: (1) the relation between dust storms and synoptic climatic conditions; (2) the importance of Owens (dry) Lake (California) as a dominant source of southwestern U.S. dust, for as much as 400 km downwind; (3) the impacts of human disturbances in the desert, revealed by signatures of agricultural and construction dust; and (4) the composition and flux of regional background dust composition and flux. Past dust flux is studied from late Quaternary eolian deposits, partly using a new combination of magnetic and chemical methods developed to recognize eolian dust in soils and surficial deposits over large regions. Such studies have applications to understanding current plant distribution, substrates for biologic soil crust, and paleoenvironmental histories of ecosystems.A wind-erosion model based on wind strength, atmospheric shear stress on the surface, and atmospheric stability is being developed. This model will be constrained by remote sensing and ground-based observations and will then be linked with a regional climate model and interactive vegetation package to forecast how various climatic and land-use scenarios interact with critical wind speeds required to move surface materials. We will attempt to answer the following questions: How does wind strength vary with natural climate cycles on decadal and century time scales? To what extent will winds become stronger or weaker under future climate scenarios? How have soil moisture and vegetation changes affected wind erosion in the past, and what can we expect in the future? As an example of possible future conditions, projections of doubled atmospheric CO2 (above pre-industrial levels) for the southwestern U.S. suggest a decrease in winter soil moisture, which may enhance wind erosion.