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Guest Duchnik

Location and orientation of Galileo images

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Guest Duchnik

Hello,

 

I'm using MATLAB to load and plot the Galileo SSI .img image files. I'm using the fread function to load the image-files and I then remove the surrounding excess data. 

 

My problem arrives when I try plotting the images on the surface. They don't seem to match up and appear to be shifted ~1deg west. In addition, the images seem to fit together better if I flip the images left/right, but I don't know why. In Nasa view, they have a totally different direction.

 

Anybody who can help me?

 

 

Thanks

 

 

- Sandy

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I'm not familiar with Galileo data but I'll try to find someone at the PDS Imaging Node to help you. Meanwhile, here are some suggestions. There are several Galileo SSI image data sets at the PDS Imaging Node. I don't know which one you are using, but if you can find your way back to the place where you downloaded it, look in the top-level directory of that data set and read the files AAREADME.TXT and ERRATA.TXT to see if they give any clues about the correct way to view the images. I assume you have already looked in the label file (.LBL) that accompanies each image. The main documentation is the file REDRSIS.PDF in the DOCUMENT directory.

 

Susie Slavney

PDS Geosciences Node

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Sandy,

Here is the response from Paul Geissler at the PDS Imaging Node.

 

"The Galileo images have to be corrected for camera pointing uncertainty.

There is exact knowledge of where the target was and where the spacecraft was, but just an estimate of where the camera was pointed. There are tools to do this in ISIS2 (limbfit in qview allows the user to pick points along the limb and fit a circle to them, and writes updated camera angles to the image label; see also the ISIS2 program deltck). These software systems are also useful for radiometric calibration (ssical in ISIS2, for example).

 

Documentation describing ISIS2 processing of Galileo images:

http://isis.astrogeology.usgs.gov/Isis2/isis-bin/voyager_mosaic.cgi

 

 

Download ISIS2 software:  http://isis.astrogeology.usgs.gov/."

 

I hope this information helps you.

 

Susie Slavney

PDS Geosciences Node

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