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Image artifacts - Beacon data

STEREO has two separate telemetry streams coming down from each spacecraft, the space weather beacon telemetry, and the science recorder playback telemetry. The beacon telemetry contains the most recent data and images, and is transmitted 24 hours per day. A volunteer network of antenna stations around the world collect as much as possible of this real-time data stream, and send it to the STEREO Science Center for processing. However, because the beacon telemetry rate is very low, the images need to be compressed by large factors, and are thus of much lower quality than the actual science data.

The science data collected by the STEREO spacecraft are written to the on-board recorder, which is then read out and transmitted to the ground during daily telemetry tracks using the NASA Deep Space Network. These data are of much higher quality than the beacon data, but take several days to reach the STEREO Science Center website. Thus, the most recent images on the STEREO Science Center browse tool will always be beacon images. These temporary beacon images are replaced with the full-quality versions as they become available, generally about 2-3 days later.

Beacon images can always be recognized by having the character "7" near the end of the filename, e.g. "n7euA", while the full resolution images will have the character "4" in that location.

Also check out the write-up on cosmic rays to see how the high compression factors used for the beacon data affect those artifacts.

Although the initial beacon JPEG images on the browse pages are replaced by the high resolution images as they become available, the original FITS versions of the beacon files are saved, and can be read using any of a large number of software packages, most of which are free.

Back to image artifacts page.