Io Galileo SSI Grayscale Global Mosaic 1km v1
Product Information:
The best quality global monitoring images taken by the Galileo spacecraft's Solid-State Imaging (SSI) camera at spatial resolutions up to 1 kilometer per pixel (km) have been assembled here to depict the global and regional morphology of Io. This mosaic is made up of 32 monochrome images taken at various phase angles and local times of day, so care must be taken to note the solar illumination direction when deciding whether topographic features display positive or negative relief. In general, the illumination is from the west over longitudes 0 to 270 W, and from the east over longitudes 270 W to 360 W. The images were empirically adjusted in brightness and contrast to match one another in areas of overlap. Most of the images were taken in the clear filter, but green and 756 nm filter images were substituted when they were more detailed than other available images. Image resolutions range from 1.3 to 10 km along the equator, with the poorest coverage on the Jupiter-facing side of Io (Belton et al., 1992).
Mission and Instrument Information:
Galileo launched on October 18, 1989 from the Kennedy Space Center in Florida aboard the space shuttle Atlantis with the aim to study Jupiter and its moons. It arrived at Jupiter on December 7th, 1995 and ended when the spacecraft entered Jupiter’s atmosphere on September 21, 2003. Galileo made seven flybys of Io during its fourteen-year mission in the Jovian system.
The Solid-State Imaging (SSI) experiment was designed to study Jupiter and it’s satellites using multi-spectral, high-resolution, charge-coupled device (CCD) camera. The camera was operated in eight filtered band passes from 350-1100nm, the eight -position filter wheel consisted of three broad-band filters: violet(404nm), green(559nm), and red(671nm). The borad-band filters allowed for the reconstruction of visible color photographs. The use of a CCD permitted the SSI to have an image geometry which was independent of brightness gradients, greater sensitivity to incident photons, and a wider spectral range than any camera previously flown on a planetary mission.
References:
Barth, B., Radebaugh, J., & Christiansen, E. H. (2009). Classification of Io's Paterae: Active vs Inactive. Paper presented at the 40th Lunar and Planetary Institute Science Conference, Lunar and Planetary Institute, Houston, TX. https://www.lpi.usra.edu/meetings/lpsc2009/pdf/2397.pdf
Becker, T. L., & Geissler, P. E. (2005). Galileo Global Color Mosaics of Io. Paper presented at the 36th Lunar and Planetary Science Conference, Lunar and Planetary Institute, Houston, TX. http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1862.pdf
Belton, M. J. S., Klassen, K. P., Clary, M. C., Anderson, J. L., Anger, C. D., Carr, M. H., Chapman, C. R., et al. (1992). The Galileo Solid-State Imaging experiment. Space Science Reviews 60(1-4), 413-455. https://doi.org/10.1007/BF00216864
Geissler, P. E., McEwan, A. S., Keszthelyi, L., Lopes-Gautier, R., Granahan, J., & Simonelli, D. P. (1999). Global color variations on Io. Icarus, 140(2), 265–282. https://doi.org/10.1006/icar.1999.6128
Veeder, G. J., Davies, A. G., Matson, D. L., & Johnson, T. V. (2009). Io: Heat flow from dark volcanic fields. Icarus, 204(1), 239-253. https://doi.org/10.1016/j.icarus.2009.06.027
Williams, D. A., Keszthelyi, L. P., Crown, D. A., Yff, J. A., Jaeger, W. L., Schenk, P. M., Geissler, P. E., & Becker, T. L. (2011). Volcanism on Io: New insights from global geologic mapping. Icarus, 214(1), 91-112. https://doi.org/10.1016/j.icarus.2011.05.007
- Publisher
- USGS
- Originator
- USGS Astrogeology Science Center
- Group
- PDS
- Added to Astropedia
- 14 March 2012
- Modified
- 3 February 2020
General
- Purpose
The Io products update Voyager mission global maps with Galileo SSI data of superior resolution and geometric fidelity. The color mosaic improves on the previous product of Geissler (1999)[2] using later, higher resolution images with better geometric control and a more consistent range of phase angles. These products have been used as a basis to map global geologic units [3], paterae [4], volcanic fields [5] 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_Galileo_SSI_Global_Mosaic_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
- Mission
- Galileo, Voyager
- Instrument
- SSI
Contact and Distribution
- Access Constraints
- Public domain
- Use Constraints
- None
Data Status and Quality
- Time Period of Content Begin
- 1 January 2009
- Time Period of Content End
- 15 March 2011
- 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
This 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 Date
- 15 March 2009
- Process Description
PDS images were ingested into ISIS 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 (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) that reduces the mismatch at the seams. 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
- Entity and Attribute Detailed Description
- Of these four, the color mosaic is the only product intended for photometric interpretations (such as deciding whether any given feature is brighter or darker than another). The global color mosaic was constructed in two steps. First, the consistent (3.5–4.5°) phase angle 756 nm (nm), green (GRN), and violet (VIO) images from orbits G2 (September 1996), C9 (June 1997), C21 (June 1999), and I31 (August 2001) 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 (referenced below). 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 to form a baseline estimate of Io’s global color, relatively free of photometric effects caused by variations in phase angle, but subject to spatial resolution limitations and geometric distortions, especially in areas imaged near the limb.The second step improved on the global color mosaic by including higher resolution images from orbit E6 (14° phase, February 1997), adjusted to match the color and contrast of the 4° phase angle data. The selected color images were processed as above, hand-edited to remove topographic shadows and pixels too near the limb, and mosaicked using a numerical procedure (Soderblom et al., 1978) that reduces the mismatch at the seams. Users should keep in mind several limitations, including: surface changes between imaging periods, the use of false color (756 nm-GRN-VIO); variations in incidence and emission angles; uncertainties in the limb-darkening correction, especially at the poles; and mixed resolutions ranging from 1.3 to 21 km/pixel at the equator, with the poorest resolution on the subjovian hemisphere of Io. The Galileo monochrome mosaic is made up of 32 monochrome images taken at various phase angles and local times of day, so care must be taken to note the solar illumination direction when deciding whether topographic features display positive or negative relief. In general, the illumination is from the west over longitudes 0–270°W, and from the east over longitudes 270–360°W. The images were empirically adjusted in brightness and contrast to match one another in areas of overlap. Most of the images were taken in the clear filter, but green and 756 nm filter images were substituted when they were more detailed than other available images. The combined monochrome mosaic includes 50 Voyager 1 images with spatial resolutions sometimes exceeding the 1 km/pixel scale of the final mosaic. These Voyager images were calibrated with an additional correction for dark current build-up during passage through the plasma torus, as described by McEwen (1988). They include both Clear and Blue filter images, empirically adjusted to match the brightness and contrast of the Galileo monochrome mosaic.
Lineage
- PDS Status
- PDS 3 Like
- Source Originator
- Planetary Data System
- Source Title
- Galileo and Voyager PDS Archives
- Source Online Linkage
- https://pds-imaging.jpl.nasa.gov/volumes/galileo.html#gllSSIREDR, https://pds-imaging.jpl.nasa.gov/volumes/voyager.html#vgrISSEDR-J, http://pds-imaging.jpl.nasa.gov/portal/galileo_mission.html, https://pds-imaging.jpl.nasa.gov/portal/voyager_mission.html
- Type of Source Media
- Online
- Attribute Accuracy Report
- Accurate to Control Net
Geospatial Information
- Minimum Latitude
- -90
- Maximum Latitude
- 90
- Minimum Longitude
- -180
- Maximum Longitude
- 180
- Direct Spatial Reference Method
- Raster
- Object Type
- Pixel
- Lines (pixels)
- 5723
- Samples (pixels)
- 11445
- Bit Type
- 8
- Quad Name
- Radius A
- 1821460
- Radius C
- 1821460
- Bands
- 1
- Pixel Resolution (meters/pixel)
- 1000
- Scale (pixels/degree)
- 31.79
- Horizontal Coordinate System Units
- Meters
- Map Projection Name
- Simple Cylindrical
- Latitude Type
- Planetocentric
- Longitude Direction
- Positive West
- Longitude Domain
- -180 to 180