Io Galileo SSI / Voyager Color Merged Global Mosaic 1km

To present more information-rich views of Io, the global color derived from the Galileo color images was superimposed on the more detailed, higher resolution monochrome mosaics. The procedure adopted was to calculate color ratio images from the Galileo data and apply them to the monochrome mosaics, requiring that the color ratios of the composite images match the color ratios of the Galileo data. The Galileo Solid-State Imaging (SSI) camera’s silicon charge-coupled device (CCD) was sensitive to longer wavelengths than the vidicon cameras of Voyager, so distinctions between red and yellow hues can be more easily discerned. However, this approach suffers from an obvious disadvantage in areas where the surface appearance changed dramatically during the 20+ year interval between the Voyager and Galileo eras, for example near Kanehekili.

References: * Belton, M.J.S., Klaasen, K.P., Clary, M.C., Anderson, J.L., Anger, C.D., Carr, M.H., Chapman, C.R., Davies, M.E., Greeley, R., and Anderson, D. 1992. The Galileo Solid-State Imaging experiment. Space Science Reviews 60. doi:10.1007/BF00216864

* Williams, D.A., Keszthelyi, L.P., Crown, D.A., Yff, J.A., Jaeger, W.L., Schenk, P.M., Geissler, P.E., and Becker, T.L. 2011. Volcanism on Io: New insights from global geologic mapping. Icarus 214. doi:10.1016/j.icarus.2011.05.007

* Becker, T.L. and Geissler, P.E. 2005. Galileo Global Color Mosaics of Io. Lunar and Planetary Institute Science Conference Abstracts 36. URL: http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1862.pdf

* P.E. Geissler, A.S. McEwen, L. Keszthelyi, R. Lopes-Gautier, J. Granahan, D.P. Simonelli, 1999, Global color variations on Io, Icarus, 140 (1999), pp. 265–282. URL: http://www.sciencedirect.com/science/article/pii/S0019103511001710

* Veeder, G.J., Davies, A.G., Matson, D.L., and Johnson, T.V. 2009. Io: Heat flow from dark volcanic fields. Icarus 204. doi:10.1016/j.icarus.2009.06.027

* Barth, B., Radebaugh, J., and Christiansen, E.H., 2009, Classification of Io's Paterae: Active vs Inactive. Lunar and Planetary Institute Science Conference 40.

Publisher: USGS Astrogeology Science Center
Author: USGS Astrogeology Science Center
Originator
Group: Astrogeology
Added to Astropedia: 14 March 2012
Modified: 17 June 2019

General

Purpose: This product updates Voyager mission global maps with Galileo SSI data of superior resolution and geometric fidelity. The color mosaic improves the previous product of Geissler (1999) by using later, higher resolution images with better geometric control and a more consistent range of phase angles. This mosaic has been used as a base to map global geologic units [Williams], paterae [Barth], and volcanic fields [Veeder] and as a base map for formal planetary nomenclature. An animated globe produced from the merged mosaic is available from NASA’s Planetary Photojournal: http://photojournal.jpl.nasa.gov/catalog/PIA09257.
Geospatial Data Presentation Form: Global Mosaic, Remote-sensing Data
Online Linkage: https://planetarymaps.usgs.gov/mosaic/Io_GalileoSSI-Voyager_Global_Mosaic_ClrMerge_1km.tif
Native Data Set Environment: ISIS v3
Supplemental Information: http://photojournal.jpl.nasa.gov/catalog/PIA09257

Keywords

System: Jupiter
Target: Io
Theme: Geographic Information System (GIS), Image Processing, Remote Sensing, Satellites
Mission: Galileo, Voyager
Instrument: SSI, ISS

Contact and Distribution

Access Constraints: public domain
Use Constraints: None

Data Status and Quality

Currentness Reference

Publication date

Progress

Complete

Update Frequency

None planned

Logical Consistency Report

All data were projected to a triaxial ellipsoid shape model using the best available Galileo control network (Archinal, B.A., Davies, M.E., Colvin, T.R., Becker, T.L., Kirk, R.L., Gitlin, A.R., 2001. An improved RAND-USGS control network and size determination for Io. Lunar Planet. Sci. XXXII. Abstract #1746). This network suffers from a lack of control points in the region of 320° to 20° (east) longitude. The Voyager 1 images of regions west of 0° longitude appeared displaced from the positions predicted from the control net derived from the solution of the combined Galileo and Voyager data set. We suspect that the discrepancy arises from regional topography west of the sub-Jupiter point, and have adjusted the positions of the Voyager 1 images (all acquired near the limb of Io) to match the best-fit geometry. Horizontal accuracy is nominally 1 pixel, translating to 1 kilometer in low latitude regions with good coverage.

Completeness Report

The color mosaic has no coverage within ~5° of the north and south poles. Smaller data gaps occur at both poles in both of the monochrome mosaics. The poles are filled in by interpolation in the merged mosaic.

Each of the mosaics is made up of images with mixed resolution, with the poorest coverage on the Jupiter-facing hemisphere. Resolution of the color mosaic ranges from 1.3 to 21 km/pixel at the equator, while the monochrome and merged mosaics range from 1 to 10 km/pixel.

Process Description

PDS images were ingested into Integrated Software for Imagers and Spectrometers (ISIS, version 2) and were calibrated using the best end-of-mission calibration information, co-registered to subpixel precision, and map projected using the camera-pointing corrections of Archinal et al. (2001). A Lunar–Lambert limb-darkening correction was next performed, after having first determined that a coefficient of 0.7 was adequate for all three colors. Finally, the images were mosaicked together using a numerical procedure that reduces the mismatch at the seams (Soderblom, L.A., Edwards, K., Eliason, E.M., Sanchez, E.M., and Charette, M.P. 1978. Global color variations on the Martian surface. Icarus 34. doi:10.1016/0019-1035(78)90037-4). The merged mosaic was created by superimposing the color mosaic on the more detailed combined monochrome mosaic. The procedure adopted was to calculate color ratio images from the Galileo data and apply them to the monochrome mosaic, requiring that the color ratios of the composite images match the color ratios of the Galileo data. That is, the red brightness was computed as the product of the monochrome mosaic multiplied by the ratio of the Galileo 756 nm/GRN, and the blue brightness as the monochrome mosaic times the Galileo VIO/GRN ratio.

Horizontal Positional Accuracy Value

1000

Horizontal Positional Accuracy Report

Accurate to Control Net