Processing the Yohkoh Movies


The original data

The original data, in the form of raw (and later, processed) Yohkoh SXT CCD images, were transferred via anonymous ftp from the Institute of Space and Astronautical Science in Japan to the NASA Goddard Space Flight Center Solar Data Analysis Center (SDAC) in the U.S. Here, they were read on a Digital AlphaServer 2100 5/250 with part of an extensive package of Yohkoh processing and analysis software written in the proprietary language IDL from Research Systems in Boulder, Colorado.

A series of still images

Using IDL, we scaled each 256 x 256-pixel CCD frame and transformed it into a color PICT image. (The raw data also had to have background subtracted, including the removal of "hot" CCD pixels --- that is the primary difference between the amateurish, rush job I did early Tuesday morning and the more professional job Jim Lemen of LPARL did a few hours later.) These images were then transferred via ftp to a Power Macintosh 8100/80 running Peter Lewis's ftpd daemon. The smaller QuickTime movies wer made in the same way, after rebinning the original images to 128 x 128.

QuickTime and MPEG

On the Macintosh, which requires what amounts to strong typing of files, we used the shareware BunchTyper application to convert the generic binary files we had transferred into PICT files even the MacOS could recognize by changing the type to "PICT." We then used the freeware digital video utility Sparkle (V 2.4.5) by Maynrad Handley to convert the series of consecutively numbered PICT files into MPEG and QuickTime movies. Both types of movies were made with 12 frames per second.

The QuickTime movies were made using the video codec, one key frame every 12 frames, and medium (50%) quality to reduce file size. The processed MPEG movies were made using "exhaustive" MPEG P and B algorithms and half-pixel compression to reduce the blockiness seen in the MPEGs of the raw data.

Both sizes of QuickTime movies were converted to flattened QuickTime format (no Mac-only resource fork, so Windows and Unix systems can play the moovies as well) using Adobe Premiere 4.0's "Export flattened movie" option.

Home at last

The resulting binary files (2 QuickTime and one MPEG for each eclipse orbit) were ftp'ed back to the SDAC Web server (umbra.nascom.nasa.gov), where you download them.


A last note

The mention of various software and hardware products herein does not in any way constitute an endorsement of said products by the U.S. government, NASA, the SDAC, or yours truly: I included these details so you could determine if you had the resources to do the same sort of thing.

Web curator: Joseph B. Gurman
Responsible NASA official: Joseph B. Gurman
Facility Scientist, Solar Data Analysis Center
+1 301 286-4767

NASA Goddard Space Flight Center
Solar Physics Branch / Code 682.3
Greenbelt, MD 20771

Last revised 1996 April 12 - J.B. Gurman

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