High resolution Vesta High Altitude Mapping Orbit (HAMO) Atlas derived from Dawn framing camera images
Highlights
► The first controlled high resolution mosaic of Vesta was created using camera data from the high altitude mapping orbit. ► The first atlas of Vesta was created. ► The nomenclature for surface features was approved by the IAU.
Introduction
The Dawn mission has been mapping Vesta from three different orbital heights during Survey orbit (2700 km altitude), HAMO (High Altitude Mapping Orbit, 700 km altitude), and LAMO (Low Altitude Mapping Orbit, 210 km altitude) (Russell and Raymond, 2011). The Dawn mission is equipped with a framing camera [FC (Sierks et al., 2011)], which was the prime instrument during the HAMO phase. Dawn orbited Vesta during HAMO in 6 cycles between the end of September and early November 2011. The framing camera took about 2500 clear filter images with a resolution of about 70 m/pixel during these cycles. The images were taken with different viewing angles and different illumination conditions. Images from one cycle (cycle #3, image numbers 9899–10429) were selected for the mosaicking process to have similar viewing and illumination conditions. Cycle #3 with 518 images was selected since it was the first cycle with almost complete global coverage. Very minor gaps in the coverage were filled with three images from cycle #4 (image numbers 10559, 10632, and 10741).
Details of the image processing will be described in Section 2. Section 3 summarizes the high-level cartographic work that produced our high resolution atlas, which consists of 15 map tiles of the different regions of Vesta. Two examples of these map tiles are shown. A brief overview of future work is given in Section 4.
Section snippets
Data processing
The image data returned from the spacecraft are distributed inside the Dawn team in PDS (Planetary Data System) format [http://pds.jpl.nasa.gov ]. The first step of the image processing pipeline is the conversion to VICAR (Video Image Communication and Retrieval) format [http://rushmore.jpl.nasa.gov/vicar.html ] followed by the radiometric calibration of the images.
The next step of the processing chain deals with the ortho-rectification of the images into a cartographic map projection at a
Vesta map tiles
The Vesta atlas was produced in a scale of 1: 500,000 and consists of 15 map tiles that conform to the quadrangle scheme proposed by Greeley and Batson (1990) for medium-sized planetary bodies (Fig. 2). A map scale of 1: 500,000 guaranteed a mapping at the highest available HAMO resolution and results in an acceptable printing scale for the hardcopy map of 7 pixel/mm. The individual tiles were extracted from the global mosaic and reprojected, coordinate grids were superposed as graphic vectors
Future work
The Dawn spacecraft will continue its imaging campaign during a second HAMO phase in summer 2012; then the northern part of Versta will be illuminated providing an opportunity to obtain high resolution coverage of high northern latitudes and to fill the remaining gaps in the atlas.
Acknowledgments
The authors gratefully acknowledge helpful discussions with J. Blue (USGS) about the proposed nomenclature for Vesta features and for reviewing the Vesta HAMO atlas.
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