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GreenMan
2010-Jan-23, 08:30 PM
Recently I've seen references to unexplained "objects" that appear near the sun in some recent images.

http://stereo-ssc.nascom.nasa.gov/browse/2010/01/21/ahead/euvi/195/1024/20100121_004530_n7euA_195.jpghttp://stereo-

ssc.nascom.nasa.gov/browse/2010/01/21/behind/euvi/195/1024/20100121_012530_n7euB_195.jpg

It seems somewhat unlikely that they're alien spacecraft but that's what this guy is actually suggesting:

http://www.youtube.com/watch?v=8POHkMQg0Dw&feature=player_embedded

They seem to take up too many pixels to be 'bad data' but what are they then?

GreenMan

Luckmeister
2010-Jan-24, 03:25 AM
Hi GreenMan, if the Youtube video author had taken one minute to Google "nascom image artifacts" this link (http://sohowww.nascom.nasa.gov/hotshots/2003_01_17/) could have saved the time and trouble of making the video.

Mike

ccart3r
2010-Jan-24, 12:36 PM
I am also curious as to what these items are? That link you posted Luckmeister looks nothing like the sphere's seen in the SOHO photos.
So any clue on what they may be? Has nasa said any words on the matter?

slang
2010-Jan-24, 11:43 PM
First link in OP broken. Fixed (http://stereo-ssc.nascom.nasa.gov/browse/2010/01/21/ahead/euvi/195/1024/20100121_004530_n7euA_195.jpg).

The caption (http://stereo-ssc.nascom.nasa.gov/browse/2010/01/21/ahead/euvi/195/1024/20100121_004530_n7euA_195.txt) for this image:


Image of the Sun, taken by the SECCHI Extreme Ultraviolet Imager (EUVI)
on the STEREO Ahead observatory on January 21, 2010 at 00:45:30 UT.
The 195 Angstrom bandpass is sensitive to the Fe XII ionization state
of iron, at a characteristic temperature of about 1.4 million degrees Kelvin.
This image was produced from the STEREO space weather beacon telemetry.
Because of the high amount of compression used for the space weather beacon,
the image quality is far lower than in the final science product.


Bold mine. If you mean the object in the lower right, it could be anything from a star to a particle coming from the spacecraft. The high JPEG compression may well be the cause for the "distortions".

As for the guy making a video by aiming a camera at a screen... Digital FAIL. His source for "interesting pictures": GLP. That's all I'll say.

Tensor
2010-Jan-25, 01:30 AM
His source for "interesting pictures": GLP. That's all I'll say.

Well then, it obviously must be true. ;)

Van Rijn
2010-Jan-27, 08:38 AM
I am also curious as to what these items are? That link you posted Luckmeister looks nothing like the sphere's seen in the SOHO photos.
So any clue on what they may be? Has nasa said any words on the matter?

Yes. This page covers that specific type of image artifact:

http://stereo.gsfc.nasa.gov/artifacts/artifacts_cosmic_rays.shtml

It's a combination of two things: Cosmic rays create blips on the image detector which are distorted by high compression on the early "beacon" images.

This page:

http://stereo.gsfc.nasa.gov/artifacts/artifacts_beacon.shtml

discusses beacon images:


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.

It also tells how to determine by file name whether you are looking at extreme compression beacon images or later higher-detail images:



Beacon images can always be recognized by having the character "7" near the end of the filename, e.g. "n7euA". When replaced by the original full-resolution version of the image from the recorder playback, the "7" is replaced with a by the character "4", with the rest of the filename being unchanged.

If you look at the file names in the video, or the names listed earlier in this thread, you can see they are the highly compressed "beacon" images.

ETA: Here's a page with links to the above pages, and other pages on Stereo spacecraft image artifacts:

http://stereo.gsfc.nasa.gov/artifacts/artifacts.shtml

Van Rijn
2010-Jan-27, 09:01 AM
By the way, when the higher resolution images are available, the old links to the extreme compression images no longer work. Naturally, in the comments on the YouTube video, they're saying that NASA is "hiding" and "retouching" the images. :doh: It never ceases to amaze me the stuff some people can imagine. If NASA was trying to hide incredibly hot (1.5 million K) planet sized objects that appeared all the time in spacecraft images, but somehow otherwise managed to stay invisible, wouldn't you think NASA might avoid making the images public rather than constantly retouching them?

NGCHunter
2010-Feb-03, 05:48 PM
I understand that STEREO, like the mars rovers, uses ICER as the compression algorithm. Does anyone know of any software out there that can save pictures using ICER compression? I'm hoping the public version of Maestro can do it, but the website for Maestro has been broken for at least the last couple of days.