From Johan WARELL
® .
. . . . . . .Sent: Friday, August 29, 2003 4:01 PM
Subject: Mars August
28
Dear all,
Sending you here the most recent
batch of Mars images from last night. A visual
drawing will following as it is scanned.
The preceding and southern limb hazes are substantially more
yellow in character than the northern and following. There is a white tuft of
cloud extending Nf the NPC,
rotating with the disk over almost 2 h of time.
Now it has cleared up, time again for Mars!
Best wishes,
® . . . . . . . .Sent:
Sunday, August 31, 2003 3:45 AM
Subject: Mars
August 30
Hi,
Some new Mars images with the webcam, I was too tired to
make any drawing last night. Though the SPC is thinning ever
more, no sign of localized dust or major cloud activity.
Best,
® . . . . . . . Sent: Friday, September 05, 2003 3:29 AM
Subject: Mars
September 3
Dear Dan, Richard and Masami,
I send you here two Mars images from Sep 3 obtained with the
webcam and the 25 cm SCT.
There is one interesting aspect of this data set. Note the
appearance of thin white cloud streaks longitudinally across Mare Acidalium and equatorially across N Aurorae
and Margaritifer Sinus, parallel with the edge of the
NPH. I have not found other images from these longitudes and dates to compare
with.
At first they struck me as processing artifacts due to their
linear nature and arrangement. However, they are apparent also on different
stacked-only versions of this image which have not been subjected to frequency
filtering. On such images they are naturally of subdued sharpness and contrast,
but their presence seems to verify their existence. The equatorial streak emanates
from the morning cloud which obscures all of Solis Lacus north to Niliacus Lacus.
The filtration process thus unfortunately to effectively
affect the contrast and optical depth of cloud structures in an unwanted
fashion, which is serious enough to warrant consideration. High-frequency
information is exaggerated in terms of contrast, low frequency is subdued which
means that such cloud streaks appear brighter in filtered data and regional
clouds (such as extended mo, ev
clouds) are drastically reduced in visibility.
Therefore, in terms of studies of atmospheric phenomena, it
may be of great value to publish unfiltered (but histogram intensity level
adjusted) blue channel disk images in parallel with the filtered data set.
Though softer than unfiltered images, less processing retains the natural
aspect better and is more easily comparable to visual observations. I will try
to take a further look into this problem and show you the result.
It appears that the monsoon has ended early here in
Best regards,
Johan WARELL (Lunar and Planetary
Laboratory,
