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Studies of Asteroids from Earth and Space

Dr. Lucy McFadden from the University of Maryland conducts a study to examine the surface of asteroid Eros using data from the Near-Infrared Spectrometer. The analysis compares the spectrum and images to the average spectrum and other XGRS data, providing insights into the surface composition.

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Studies of Asteroids from Earth and Space

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  1. Studies of Asteroids from Earth and Space Dr. Lucy McFadden Department of Astronomy University of Maryland

  2. NEAR-related Project 1. Examine the regions of Eros’ surface where the Near-Infrared spectrometer (NIS) deviated from the average spectrum. 2. Find all available data at the NEAR landing site and examine the spectrum and images • Compare it to: • The average NIS spectrum • other XGRS data • Describe the surface at the landing site.

  3. To Find NEAR data • Start at: • http://pdssbn.astro.umd.edu • On the left, go to Mission Data and Support • http://pdssbn.astro.umd.edu/missions/index.html • In the table, Completed Missions, click on NEAR http://pdssbn.astro.umd.edu/missions/near/index.html • And start reading. There is a lot of info here that is useful. Become familiar with what is there.

  4. More on finding NEAR data • There is a link to the Expert Data System • http://pdssbn.astro.umd.edu/SBNcgi/expert.cgi • Useful files include: • http://pdssbn.astro.umd.edu/NEARdb/help/mission_phases.html • http://pdssbn.astro.umd.edu/NEARdb/nis/subphases.txt • http://pdssbn.astro.umd.edu/volume/nneros_2005/data/eros/nixgg.lbl

  5. Low Phase Flybyfor Spectroscopy

  6. We want the lat and long of NEAR NIS data. • The data analyzed in McFadden et al. 2001, MAPS, 36, 1711-1726, were from the low phase flyby. Specifically, the data I analyzed were the highest signal to noise data that were taken during sub-phase GG. • I thought we could get the header data for NIS and look at the lat and long keywords. • One needs to read the fits headers. • But to do that, we need to understand the format of NIS data, which is not standard.

  7. Understanding NIS data format • I don’t understand it yet. I am working on it. • In the mean time I asked colleagues who might be familiar with the NIS fits structure to help, and Stephanie McLaughlin wrote a few lines of IDL to give us the lat and long of the footprint’s outline. I will email that to anyone who might want to use it.

  8. Map of 1-µm Band Depth See notes below and next slides for explanation of this map

  9. What areas are of interest? • Alternatively to reading the NIS headers to find lat and long, one can look at the 1-micron map and read the lat and long of the areas that deviate from the mean value. • Make a table (hand written) of lat and long that you want to look at. • Enter those lat and long into the data base, making sure that you are looking for MSI data, (reset the data base).

  10. Mineral Structure Orthopyroxene Clinopyroxene Olivine The olivine group is composed of minerals of the general formula X2SiO4 where X = Mg ,Fe2+, or Ca; Y = Al, Cr, or Fe3+; and Z = Si. The X-site is 8 coordinated, the Y -site is 6-coordinated (octahedral) and the Z-site is 4-coordianted The pyroxene group is composed of minerals of the general formula XYSi2O6, where X and Y are two divalent cations and occupy two Structurally different sites. If X and Y are the same small-radius divalent cation like Fe or Mg the resultant structure is commonly orthorhombic, giving us the orthopyroxene group.

  11. Crystal Structure: Energy Level Diagram

  12. Band parameters derived fter continuum removal

  13. Searching for MSI data • When you enter lat and long, you get multiple files of the same area. • Look at one and figure out the direction of the sun. see next slide. • Or lower. I would look in each orbit. • It may be a challenge to find a manageable number of files to work with.

  14. Finding the direction of the sun • There is a header called phase angle of average plate fov. • We thought this might be the phase angle, but taking that angle and looking at the point perpendicular to shadows confused us. • So, we decided to determine the direction of the sun from the shadows alone. • Note that there is a keyword for the direction of Celestial North. Sometimes this might be useful to get yourself oriented.

  15. Once you download data • Description of the NEAR coordinate system: • http://pdssbn.astro.umd.edu/NEARdb/neardata.html • There is a description of the file structure of the downloaded data at: • http://pdssbn.astro.umd.edu/NEARdb/help/volstruct.html

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