75 research outputs found
Five years of Ulysses dust data: 2000-2004
No full textKrueger H, Altobelli N, Anweiler B, et al. Five years of Ulysses dust data: 2000-2004. Planetary and Space Science. 2006;54(9-10):932-956.The Ulysses spacecraft has been orbiting the Sun on a highly inclined ellipse (i = 79 degrees, perihelion distance 1.3 AU, aphelion distance 5.4 AU) since it encountered Jupiter in 1992. Between January 2000 and December 2004, the spacecraft completed almost an entire revolution about the Sun, passing through perihelion in May 2001 and aphelion in July 2004. In this five-year period the dust detector on board recorded 4415 dust impacts. We publish and analyse the complete data set of both raw and reduced data for particles with masses 10(-16) g <= M <= 10(-7) g. Together with. 1695 dust impacts recorded between launch of Ulysses and the end of 1999 published earlier (Grain, E., Baguhl, M., Divine, N., Fechtig, H., Hamilton, D.P, Harmer, M.S., Kissel, J., Lindblad, B.A., Linkert, D., Linkert, G., Mann, L, McDonnell, J.A.M., Morfill, G.E., Polanskey, C., Riemann, R., Schwehm, G.H., Siddique, N., Staubach, P., Zook, H.A., 1995a. Two years of Ulysses dust data. Planetary Space Sci. 43, 971-999, Paper III; Kruger, H., Grun, E., Landgraf, M., Baguhl, M., Dermott, S.F., Fechtig, H., Gustafson, B.A., Hamilton, D.P., Harmer, M.S., Horanyi, M., Kissel, J., Lindblad, B., Linkert, D., Linkert, G., Mann, L, McDonnell, J.A.M., Morfill, G.E., Polanskey, C., Schwehm, G.H., Srama, R., Zook, H.A., 1995. Three years of Ulysses dust data: 1993 to 1995. Planetary and Space Sci. 47, 363-383, Paper V; Kruger, H., Grun, E., Landgraf, M., Dermott, S.F., Fechtig, H., Gustafson, B.A., Hamilton, D.P., Harmer, M.S., Horanyi, M., Kissel, J., Lindblad, B., Linkert, D., Linkert, G., Mann, I., McDonnell, J.A.M., Morfill, G.E., Polanskey, C., Schwehm, G.H., Srama, R., Zook, H.A., 2001b. Four years of Ulysses dust data: 1996 to 1999. Planetary Space Sci. 49, 1303-1324, Paper VII), a data set of 6110 dust impacts detected with the Ulysses sensor between October 1990 and December 2004 is now available. The impact rate measured between 2000 and 2002 was relatively constant with about 0.3 impacts per day showing a maximum at 1.5 per day around ecliptic plane crossing in early-2001. The impact direction of the majority of impacts between 2000 and 2002 is compatible with particles of interstellar origin, the rest are most likely interplanetary particles. In 2003 and 2004 dust stream particles originating from the jovian system dominated the overall impact rate. Twenty-two individual dust streams were measured between November 2002 and December 2004. The observed impact rates are compared with models for interplanetary and interstellar dust. The dust measurements from the entire mission since Ulysses launch give good agreement with the interplanetary flux model of Staubach, P., Grun, E., Jehn, R., 1997. The meteoroid environment near Earth, Adv. Space Res. 19, 301-308. (c) 2006 Elsevier Ltd. All rights reserved
Mars Odyssey: Off-nadir Imaging
No full textScience Objectives for off-nadir imaging: a) Daily observations of high activity and high interest targets in the Polar Regions; b) Daily imaging of regions of gas jetting through vents and the formation of dark spots and fans; c) Increases likelihood of observing these processes in an active phase; d) Stereo imaging for geographical analysis and landing site characterization; and e) Fill in existing gaps and gores
Minimizing distortion introduced by Psyche's ellipsoidal shape in cartographic products
No full textAfter its successful launch in October 2023, the NASA Psyche mission is currently on its way to asteroid (16) Psyche where it will arrive in 2029. Psyche is the first metal-rich asteroid to be orbited by a spacecraft (Elkins-Tanton et al., 2016). Thus, the Psyche mission plans a detailed geologic and morphologic survey of the asteroid (Jaumann et al., 2022) supported by an extensive imaging campaign conducted by the Psyche Multispectral Imager (Bell et al., 2016; Polanskey et al., 2018). Previous space missions, in particular the Dawn mission at asteroid Vesta (Russell et al., 2013), provide a base for the science and mission operations to collect the desired data (Polanskey et al., 2018).
High quality data products including, mosaics and digital terrain models are vital to perform a geologic and geomorphologic analysis, however Psyche is an irregularly shaped body (Shepard et al., 2021) that makes the illustration and interpretation of such data challenging. Psyche can approximately be described by a bi-axial ellipsoid with axes of 129 km and 86 km (Shepard et al., 2021), resulting in a flattening of 0.33 (the flattening is defined as , where and are the semi-major and semi-minor axes, respectively). As comparison, the also ellipsoidal asteroid Vesta has a flattening of 0.20 with bi-axial axes of 285 km and 229 km.
The Dawn mission conducted an extensive mapping campaign at Vesta (Williams et al. 2014) and although the digital terrain models were referenced to the best fit ellipsoid describing Vesta’s shape, the cartographic products (e.g. maps) were usually presented in a geocentric projection (Roatsch et al. 2012, 2013). This means that images of the surface of Vesta were projected onto a sphere of 255 km radius before being map projected. Although this approach is straight forward and did not hinder the geologic interpretation, the surface images are distorted. As a consequence, measuring feature lengths, such as crater diameters, is incorrect, albeit often negligible in the case of Vesta. However, distortion effects will be significantly increased if such techniques are being applied to even flatter Psyche.
To mitigate such distortion effects on Psyche, one could use a mapping tool that enables mapping directly on the three-dimensional surface (Ernst et al.). However, to make use of the full capacity of the data, it is desirable to generate map products that can be used in standard geoinformation systems, such as QGIS. For such tools, a suited image projection needs be applied, that incorporates the ellipsoidal shape of Psyche. An improvement on distortion can be achieved when applying a geodetic projection, which projects surface images though an ellipsoid’s surface normal rather than a central point.
In this work, we will access the effects of Psyche’s ellipsoidal shape on producing and interpreting cartographic products. As a guide to the future generation of Psyche cartographic products, we will show how potential surface features and measurements on Psyche in geocentric projection will be distorted compared to geodetic projections
Science Opportunity Analyzer (SOA): Science Planning Made Simple
No full text.For the first time at JPL, the Cassini mission to Saturn is using distributed science operations for developing their experiments. Remote scientists needed the ability to: a) Identify observation opportunities; b) Create accurate, detailed designs for their observations; c) Verify that their designs meet their objectives; d) Check their observations against project flight rules and constraints; e) Communicate their observations to other scientists. Many existing tools provide one or more of these functions, but Science Opportunity Analyzer (SOA) has been built to unify these tasks into a single application. Accurate: Utilizes JPL Navigation and Ancillary Information Facility (NAIF) SPICE* software tool kit - Provides high fidelity modeling. - Facilitates rapid adaptation to other flight projects. Portable: Available in Unix, Windows and Linux. Adaptable: Designed to be a multi-mission tool so it can be readily adapted to other flight projects. Implemented in Java, Java 3D and other innovative technologies. Conclusion: SOA is easy to use. It only requires 6 simple steps. SOA's ability to show the same accurate information in multiple ways (multiple visualization formats, data plots, listings and file output) is essential to meet the needs of a diverse, distributed science operations environment
Electric charge within volcanic plumes on Earth and Io
No full textField, experimental and theoretical investigations have been carried out into the electrification of volcanic plumes. At Sakurajima volcano, Japan, ground-level perturbations of the atmospheric electric potential gradient generated by particulate plumes were recorded. Simultaneous measurements, made at up to five sites around the volcano, are shown to be capable of detecting even very small quantities of volcanic particles, and tracking a continuously produced (over a period of several hours), dilute plume as it was dispersed by the wind. Data collected during one small Vulcanian eruption suggest that charges, about 1 C in magnitude, were generated and then separated, with the positive charge centre residing above the negative charge centre. Experiments have been carried out in order to assess fracto-emission (the release of ions, neutral atoms and various frequencies of electromagnetic radiation from fracture surfaces) as a charging mechanism for the electrification of silicate particles in plumes. Silicate particles, generally less than 100 µm in diameter, were produced by colliding pumice samples together and were shown to have net specific charges of approximately 10-5 to 10-6 C kg-1 (similar to previous field measurements on ashfall). Most (but not all) of the experimental samples produced net negatively charged ash, and demonstrated a positive-above-negative charge separation. Additional charge thought to have been released in the form of ions was also detected, supporting fracto-emission as the charging mechanism for volcanic plumes. The magnitude of the net ash charge is shown to be a function of the particle size, with relative humidity having only a small effect. The polarity of the net charge appears to be a function of a property of individual pumice types, possibly their geochemistry. Experiments during which the particles were separated by their polarity indicate that the net charges reflect only a small imbalance in much larger, individual particle charges (10-3 C kg-1) of both polarities. The particle charges are shown to vary with the sample impact velocity, the number of impacts carried out within an experiment and, to a lesser degree, relative humidity. Variation within the results appears to be partly an effect of particle aggregation within the experiment. Investigation of any effects that this particle charging may have on the plumes observed on Io (one of Jupiter’s moons) suggests that luminous discharges and particle aggregation are both probable in this environment. It is shown that the distinct asymmetries observed in plumes are unlikely to be a result of electromagnetic interactions, but probably represent decompression features and asymmetric vent or crater morphologies
Solar wind interaction with small bodies: 2. What can Galileo's detection of magnetic rotations tell us about Gaspra and Ida
No full textSolar wind interaction with small bodies: 1. Whistler wing signatures near Galileo's closest approach to Gaspra and Ida
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