| 1. |
- Banaszkiewicz, M, et al.
(författare)
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Modeling of cometary evolution by kinetic theory: Method and first results
- 1996
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 72:1-3, s. 203-210
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Physical evolution of Jupiter family (JF) comets is considered as a simultaneous process of erosion and fading. Dynamical effects are Limited to discrete changes of the perihelion distance, that result in changes of the evaporation rate. Assuming that the
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| 2. |
- Biver, N, et al.
(författare)
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Long-term evolution of the outgassing of comet Hale-Bopp from radio observations
- 1997
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 78:1-3, s. 5-11
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Tidskriftsartikel (refereegranskat)abstract
- C/1995 O1 (Hale-Bopp) has been observed on a regular basis since August 1995 at millimetre and submillimetre wavelengths using IRAM, JCMT, CSO and SEST radio telescopes. The production rates of eight molecular species (CO, HCN, CH3OH, H2CO, H2S, CS, CH3CN
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| 3. |
- Bockelee-Morvan, D, et al.
(författare)
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C/1995 O1 (Hale-Bopp): Gas production curves and their interpretation
- 1997
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 79:1-3, s. 55-77
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of C/1995 O1 (Hale-Bopp) at 7 AU from the Sun provided the first opportunity to follow the activity of a bright comet over a large range of heliocentric distances r(h). Production rates of a number of parent molecules and daughter species ha
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| 4. |
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| 5. |
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| 6. |
- Kero, Johan, et al.
(författare)
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Power fluctuations in meteor head echoes observed with the EISCAT VHF radar
- 2004
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Ingår i: Earth, moon, and planets. - : Springer Science and Business Media LLC. - 0167-9295 .- 1573-0794. ; 95:1-4, s. 633-638
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Tidskriftsartikel (refereegranskat)abstract
- We present observations and preliminary results from a meteor experiment carried out with the 224 MHz EISCAT VHF radar in Tromsø, Norway, which was run for 6 h on November 26, 2003. The data set contains echoes with peculiar pulsations in received power in the frequency range 20–200 Hz, limited by instrumental parameters. The process causing the echo power pulsations has not yet been identified. Plasma effects are the most likely cause, a possible mechanism is for instance asymmetrical dust grains in rotation causing a modulation of the ionization rate.
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| 7. |
- Lagerkvist, CI, et al.
(författare)
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Physical studies of asteroids .30. The asteroid 153 Hilda
- 1995
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 71:3, s. 189-194
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Tidskriftsartikel (refereegranskat)abstract
- The asteroid 153 Kilda was studied by photometric, spectroscopic and polarimetric observations during the apparition in 1992. The rotation period was determined to 5.11 hours with a lightcurve amplitude of 0.05 magnitudes. From our spectrum we find 153 Hi
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| 8. |
- Lagerkvist, CI, et al.
(författare)
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Spin rates of asteroids
- 1996
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 72:1-3, s. 219-223
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Tidskriftsartikel (refereegranskat)abstract
- The Asteroid Photometric Catalogue was used to redetermine the rotation periods of all asteroids with data in the catalogue. The quality of the period determinations was divided into five groups. The total number of asteroids studied were 710 and 225 of t
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| 9. |
- Lagerkvist, CI, et al.
(författare)
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UESAC - The Uppsala-ESO survey of asteroids and comets
- 1996
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 72:1-3, s. 267-274
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Tidskriftsartikel (refereegranskat)abstract
- The Uppsala-ESO Survey of Asteroids and Comets was undertaken to find previously undetected comets in the vicinity of Jupiter. Over 15000 positions of moving objects have been detected on 74 plates obtained from the European Southern Observatory in Chile
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| 10. |
- Lindblad, Bertil Anders, et al.
(författare)
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IAU meteor database of photographic orbits - Version 2003
- 2003
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Ingår i: Earth, Moon and Planets. - : Springer Science and Business Media LLC. - 0167-9295 .- 1573-0794. ; 93:4, s. 249-260
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Tidskriftsartikel (refereegranskat)abstract
- The IAU Meteor Data Center in Lund has acted as a central depository for meteor orbits obtained by photographic, video and radar techniques. The database of precisely reduced photographic meteors contains data on 4581 meteor orbits obtained by 17 different stations or groups in the period 1936-1996. The orbital and geophysical data are available in two separate files as well as in an alternative file with the merged data. In various studies of meteoroid streams as well as in studies of the sporadic meteor background, it is often necessary to utilize both the orbital and the geophysical data files. Since the database is a compilation of partial, not perfectly compatible catalogues from many observing stations, the merging of parameters from one data set to another may sometimes present problems. The present contribution is a note on some problems encountered in the merging procedure. Moreover, it is evident that the database includes a small amount of erroneous data - either in the observations or in the subsequent data reductions. The latter error is not surprising in view of the lack of modern computers at several stations in the past. A final, corrected version of the IAU MDC Lund photographic meteor orbits (eq. 2000.0) can now be requested through the homepage of the Astronomical Institute, Slovak Academy of Sciences (http://www.astro. sk/(similar to)ne/IAUMDC/Ph2003/database.html).
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| 11. |
- Meisel, David D., et al.
(författare)
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Physical Characteristics of Kazan Minor Showers as Determined by Correlations with the Arecibo UHF Radar
- 2008
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Ingår i: Earth, moon, and planets. - : Springer Netherlands. - 0167-9295 .- 1573-0794. ; 102:1-4, s. 315-322
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Tidskriftsartikel (refereegranskat)abstract
- In the northern hemisphere, the month of February is characterized by a lack of major meteor shower activity yet a number of weak minor showers are present as seen by the Kazan radar. Using the Feller transformation to obtain the distribution of true meteor velocities from the distribution of radial velocities enables the angle of incidence to be obtained for the single beam AO (Arecibo Observatory) data. Thus the loci of AO radiants become beam-centered circles on the sky and one can, with simple search routines, find where these circles intersect on radiants determined by other means. Including geocentric velocity as an additional search criterion, we have examined a set of February radiants obtained at Kazan for coincidence in position and velocity. Although some may be chance associations, only those events with probabilities of association[0.5 have been kept. Roughly 90 of the Kazan showers have been verified in this way with mass, radius and density histograms derived from the AO results. By comparing these histograms with those of the ‘‘background’’ in which the minor showers are found, a qualitative scale of dynamical minor shower age can be formulated. Most of the showers are found outside the usual ‘‘apex’’ sporadic source areas where it is easiest to detect discrete showers with less confusion from the background.
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| 12. |
- Meisel, David D., et al.
(författare)
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Quantitative Comparison of a New Ab Initio Micrometeor Ablation Model with an Observationally Verifiable Standard Model
- 2008
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Ingår i: Earth, moon, and planets. - : Springer Netherlands. - 0167-9295 .- 1573-0794. ; 102:1-4, s. 411-415
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Tidskriftsartikel (refereegranskat)abstract
- The Arecibo UHF radar is able to detect the head-echos of micron-sized meteoroids up to velocities of 75 km/s over a height range of 80–140 km. Because of their small size there are many uncertainties involved in calculating their above atmosphere properties as needed for orbit determination. An ab initio model of meteor ablation has been devised that should work over the mass range 10-16 kg to 10-7 kg, but the faint end of this range cannot be observed by any other method and so direct verification is not possible. On the other hand, the EISCAT UHF radar system detects micrometeors in the high mass part of this range and its observations can be fit to a ‘‘standard’’ ablation model and calibrated to optical observations (Szasz et al. 2007). In this paper, we present a preliminary comparison of the two models, one observationally confirmable. Among the features of the ab initio model that are different from the ‘‘standard’’ model are: (1) uses the experimentally based low pressure vaporization theory of O’Hanlon (A users’s guide to vacuum technology, 2003) for ablation, (2) uses velocity dependent functions fit from experimental data on heat transfer, luminosity and ionization efficiencies measured by Friichtenicht and Becker (NASA Special Publication 319: 53, 1973) for micron sized particles, (3) assumes a density and temperature dependence of the micrometeoroids and ablation product specific heats, (4) assumes a density and size dependent value for the thermal emissivity and (5) uses a unified synthesis of experimental data for the most important meteoroid elements and their oxides through least square fits (as functions of temperature, density, and/or melting point) of the tables of thermodynamic parameters given in Weast (CRC Handbook of Physics and Chemistry, 1984), Gray (American Institute of Physics Handbook, 1972), and Cox (Allen’s Astrophysical Quantities 2000). This utilization of mostly experimentally determined data is the main reason for calling this an ab initio model and is made necessary by the fact that individual average meteoroid mass densities are now derivable from Arecibo observations.
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| 13. |
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| 14. |
- Shkolyar, S., et al.
(författare)
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Identifying Shocked Feldspar on Mars Using Perseverance Spectroscopic Instruments : Implications for Geochronology Studies on Returned Samples
- 2022
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Ingår i: Earth, Moon and Planets. - : Springer Science and Business Media LLC. - 0167-9295 .- 1573-0794. ; 126:2
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Forskningsöversikt (refereegranskat)abstract
- The Perseverance rover (Mars 2020) mission, the first step in NASA’s Mars Sample Return (MSR) program, will select samples for caching based on their potential to improve understanding Mars’ astrobiological, geological, geochemical, and climatic evolution. Geochronologic analyses will be among the key measurements planned for returned samples. Assessing a sample’s shock history will be critical because shock metamorphism could influence apparent sample age. Shock effects in one Mars-relevant mineral class, plagioclase feldspar, have been well-documented using various spectroscopy techniques (thermal infrared reflectance, emission, and transmission spectroscopy, Raman, and luminescence). A subset of these data will be obtained with the SuperCam and SHERLOC (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) instruments onboard Perseverance to inform caching decisions for MSR. Here, we review shock indicators in plagioclase feldspar as revealed in Raman, luminescence, and IR spectroscopy lab data, with an emphasis on Raman spectroscopy. We consider how this information may inform caching decisions for selecting optimal samples for geochronology measurements. We then identify challenges and make recommendations for both in situ measurements performed with SuperCam and SHERLOC and for supporting lab studies to enhance the success of geochronologic analyses after return to Earth.
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| 15. |
- Skorov, Y, et al.
(författare)
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Thermophysical modelling of Comet P/Borrelly : Effects of volume energy absorption and volume sublimation
- 2002
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Ingår i: Earth, moon, and planets. - 0167-9295 .- 1573-0794. ; 90:1, s. 293-303
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we continue revising the theoretical basis of numerical models describing the transport of matter and energy inside a porous dust-ice mixture at low temperature. A model of a light-absorbing near-surface layer of a comet nucleus is investigated. Gas transport is considered simultaneously with the solution of the general heat transfer equation. The quasi-stationary temperature distribution and the H2O mass flux and sublimation rate are computed for a nucleus model of comet 19P/Borrelly at the Deep Space 1 (DS1) encounter. The energy is deposited in a layer of about 20 particle radii: This corresponds to a solid-state greenhouse effect. The surface temperature of the layer-absorbing model as well as the gas production rate are significantly smaller than the ones in the surface-absorbing model. An active fraction of 40-50% would be required to explain the observed water production rate of P/Borrelly with our layer-absorption model at the time of the DS1 encounter.
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| 16. |
- Szasz, Csilla, et al.
(författare)
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Estimated visual magnitudes of the EISCAT UHF meteors
- 2008
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Ingår i: Earth, moon, and planets. - : Springer Science and Business Media LLC. - 0167-9295 .- 1573-0794. ; 102:1-4, s. 373-378
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the conditions for simultaneous meteor observations with the EISCAT UHF radar system and telescopic optical devices. The observed characteristics of 410 meteors detected by all three UHF receivers are compared with model simulations and their luminosity is calculated as a part of a meteoroid ablation model using a fifth order Runge–Kutta numerical integration technique. The estimated absolute visual magnitudes are in the range of +9 to +5. The meteors should therefore be observable using intensified CCD or EMCCD (Electron Multiplying CCD) cameras with telephoto lenses. A possible setup of a coordinated radar and optical campaign is suggested.
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| 17. |
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| 18. |
- Warell, J, et al.
(författare)
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Dust morphology of the inner coma of C/1995 O1 (Hale-Bopp)
- 1997
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 78:1-3, s. 197-203
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Tidskriftsartikel (refereegranskat)abstract
- Dust continuum imaging of comet C/1995 O1 (Hale-Bopp) was carried out with the Swedish Vacuum Solar Telescope (SVST) on La Palma in April, 1997. Images were reduced according to standard procedure, aligned, averaged, navigated and enhanced with azimuthal
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| 19. |
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| 20. |
- Zheng, JQ, et al.
(författare)
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Orbits of short period comets captured from the Oort cloud
- 1996
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 72:1-3, s. 45-50
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Oort cloud comets occasionally obtain orbits which take them through the planetary region. The perturbations by the planets are Likely to change the orbit of the comet. We model this process by using a Monte Carlo method and cross sections for orbital cha
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