Io Voyager - Galileo SSI False Color Global Mosaic 1km v1
This new basemap of Jupiter’s moon Io was produced by combining the best images from both the Voyager 1 and Galileo Missions. Although the subjovian hemisphere of Io was poorly seen by Galileo, superbly detailed Voyager 1 images cover longitudes from 240˚W to 40˚W and the nearby southern latitudes. A monochrome mosaic of the highest resolution images from both Galileo and Voyager 1 was assembled that includes 29 Voyager 1 images with spatial resolutions sometimes exceeding the 1 kilometer per pixel (km) scale of the final mosaic. Because this mosaic is made up of images taken at various local times of day, 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 40 to 270 W, and from the east over longitudes 270 W to 40 W. Color information was later superimposed from Galileo low phase angle violet, green, and near-infrared (756 nanometer wavelength) images.
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 that distinctions between red and yellow hues can be more easily discerned. The “true” colors that would be visible to the eye are similar but much more muted than shown here. Image resolutions range from 1 to 10 km along the equator, with the poorest coverage centered on longitude 50 W (Becker & Geissler, 2005; Belton et al., 1992).
Mission and Instrument Information:
The Voyager I spacecraft launched September 5, 1977 and reached Jupiter on March 5th, 1979; Voyager 2 launched August 20, 1977 and made a similar encounter with Jupiter on July 9th, 1979.
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.
Galileo's 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 broad-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.
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
- USGS Astrogeology Science Center
- USGS Astrogeology Science Center
- Added to Astropedia
- 14 March 2012
- 3 February 2020
This product updates 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)  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 , paterae , and volcanic fields  and as a base map for planetary nomenclature. An animated globe produced from the merged mosaic is available from NASA Planetary Photojournal (supplemental information link below).
- Geospatial Data Presentation Form
- Global Mosaic, Remote-sensing Data
- Online Linkage
- Native Data Set Environment
- ISIS v3
- Supplemental Information
- Geographic Information System (GIS), Image Processing, Satellites, Remote Sensing
- Voyager, Galileo
- SSI, ISS
Contact and Distribution
- Access Constraints
- Public domain
- Use Constraints
Data Status and Quality
- Currentness Reference
- Publication date
- 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 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 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).
- Horizontal Positional Accuracy Value
- Horizontal Positional Accuracy Report
- Accurate to Control Net
- 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
- Attribute Accuracy Report
- Accurate to Control Net
- Minimum Latitude
- Maximum Latitude
- Minimum Longitude
- Maximum Longitude
- Direct Spatial Reference Method
- Object Type
- Lines (pixels)
- Samples (pixels)
- Bit Type
- Quad Name
- Radius A
- Radius C
- Pixel Resolution (meters/pixel)
- Scale (pixels/degree)
- Horizontal Coordinate System Units
- Map Projection Name
- Simple Cylindrical
- Latitude Type
- Longitude Direction
- Positive West
- Longitude Domain
- -180 to 180