Thursday, May 12, 2005

The mystery continues...

The anomalous glow on the west flank of the crater at Mount St Helens made a re-appearance last night. I have received some advice from an engineer that works with CCD cameras and his opinion is that the bright spots on the images are unlikely to be a defective pixel. More info soon...


Anonymous Kevin said...

Just brainstorming, but could this be a reflection off the shield in front of the camera? This seems to have started around the time the JRO opened to the public. Could light within the visitor center be generated behind the VolcanoCam then reflected by the housing back into the VolcanoCam field of view?

The problem with this theory is that the anomaly is focused on 5 or so pixels. With the VolcanoCam zoom and the proximity of the source, it would seem as if locally produced light would appear over a much larger area. *shrug*

2005-05-12, 8:05 PM  
Blogger Daz said...

The anomaous glow on the west flank of the mountain appeared a week before JRO openned to the public and I doubt it is due to a reflection off the shield or housing of the camera.

My main reasoning being that the brightness and number of pixels illuminated vary continuously over the few days that it has been visible, and it seems as if it is being effected the the clouds.

It could possibly be due to a reflection off of something on the mountain (maybe a piece of monitoring equipment), but that would require a fairly bright source of illumination like an near-IR laser. But the USGS don't believe they have any equipment in the region of the glow.

So the mystery continues...

2005-05-14, 11:15 AM  
Blogger Cathy Bray said...

What fun Darryl - grest site - thanks for sending the link and for helping us unwind the mystery! Here is my attempt at discovery: Does the volcano cam have a CCD (which I have just learned through is a "Charge Coupled Device) An electronic memory that is charged by light." If so, MAYBE A COSMIC RAY STRUCK THE CCD??? and caused the strange glow? I quote:
"Cosmic rays can strike the CCD during an exposure leaving a characteristic signature: one or a few very high count pixel(s). They are normally quite unlike images of astronomical sources which distribute light over a larger area of the chip due to diffraction by the telescope optics and atmospheric turbulence. Cosmic ray removal may not be needed if you dithered while observing: when you combine the dithered images ( section 8 ) the cosmic rays may be removed by the rejection algorithm chosen in imcombine.
You can use fixpix to remove cosmic rays, but you'll need a bad pixel file for every image...Yikes!!
The task cosmicrays is found in noao/imred/ccdred. "

Cathy Bray, Friends of the Sylvia, Vancouver Canada

2005-05-15, 10:12 AM  
Blogger Daz said...

Cathy, that's a very interesting possibility.

I agree that a cosmic ray strike on the CCD would produce a bright flash. But it would be a fairly brief effect and not persist for days after the initial strike.

Also, as cosmic rays are completely random, it wouldn't be likely to re-occur in the same spot on the camera several days later - as we have seen with this mysterious little glow...

2005-05-15, 6:10 PM  

Post a Comment

<< Home

Click Here