Subj: soho

Date: 7/8/00 8:20:25 PM Pacific Daylight Time

Check the attached image. THe circled items have been on these images for at least the last two years. You mention on of them today on the main page. I had sent you something on them about 9 months ago.

They could be something lodged in the ccd camera, but they have always appeared to have a lighted side facing the sun and a shadow side facing the SOHO.

The arrow points to an item that may be the same thing. on the c3 mpeg Mars approaches and passes this item. It sits still, while mars and the stars move.

Subj: LASCO C3 images, stationary object(s), 2000/07/08 15:18 image
Date: 7/9/00 6:27:02 AM Pacific Daylight Time
From: dragutin.izakovic@ri.tel.hr (IZAKOVIC)
To: BARDSQUILL@aol.com (Kent Stedman)

Re: LASCO C3 images, stationary object(s), 2000/07/08 15:18 image

Dear Kent.

If you load any C3 1024x1024 resolution image in image-processing program, you shall note that every one of them contains following stationary objects (x and y coordinates in pixels - top left image corner is 0,0):
91,211;
370,496;
405,573;
435,369;
530,570;
543,282;
559,350;
663,429;
706,584;
723,487;
740,647;
739,664;
878,775 (your stationary object).

They all have surfaces with sharply divided white and black areas which makes them look as they were between SOHO and the Sun. Except in one case (first object in the list) It seems that all remaining objects have white area oriented towards the Sun.
All this makes three explanations possible:

1. Objects are visible damages of the surface of the objective lens O1, which are placed immediately behind the entrance aperture and external occulter of the C3 coronagraph optical system. They could be caused by micrometeorites. See LASCO Handbook, Chapter 3 at
2. They are satellites in nearby orbits, probably monitoring the Sun also. This does not explain why first object in the list has white area portion on the side opposite to the Sun.
3. They are faulty elements of the C3 CCD camera. This is least probable explanation because of the uniform orientation of the majority of the white/ black areas.


Anyhow, researching LASCO construction I still cannot explain the misalignment on the
C3 image. Here the Venus and original C3 occulter are in exact relative position but misaligned with CCD in inexplicable way. On-site maintenance?

Finally, did you notice that SOHO Team on 2000/07/09 08:18 1024x1024 C3 image at 211,290 marked an object with a center line?

All the best,

07-09-2000
IZAKOVIC
CROATIA