[X] My Assistant

[Juramike]

Here is an animated GIF of the May 5th 2009 star occultation sequence from the CL1 VIO image set:


(click to animate)

For this stack, the limb of Titan was used as the reference for alignment.
The contrast has also been balanced between the images of the sequence.

[Juramike]

Here is a graphic showing the placement of the control points for the CL1-VIO images:
(Actually, I think I used different ones originally, these show a pretty tight variation for most of the control points)



Here are the ranges for each of the points in the image sequence:

Control point 1: 81 (no changes throughout sequence)
Control point 2: 72-74
Control point 3: 116-125
Control point 4: 115-116

[Juramike]

Here is an animated GIF of the rotated and aligned image of the CL1-VIO sequence of the alpha Eridani occultation:

(click to animate)

[Juramike]

Cool! I think there is a bonus occultation by another star at slightly lower latitudes!

Look at this animated GIF. Archenar (alpha Eridani) is moving to the upper left in this rotationally coordinated image.
Dust artifacts are moving parallel to the lower left. (There is one in the haze gap going towards Archenar and another further towards the right edge of the frame.)



For three frames there is a dim star visible in the gap between the detached haze layer and the lower haze layers, indicated by a white circle. It tracks parallel to and with the same shifts as Archenar.
If I've worked Celestia right and reading from VP's Celestia screenshot, this could correspond to alpha Hydrus (magnitude 3).



Archenar is setting over the northern temperate zone at about Latitude 30N. The bonus star would be setting over the Equator.

[Juramike]

Reworked the CL1-VIO filtered image. Here is a coordinated and rotated image showing the descent of Archenar through the haze column.

(click to animate)

(The spot moving from L to R is a camera artifact. Happily, this is also moving in a straight line.)

[Juramike]

Corrected absolute altitudes of the CL1-VIO filter sequence:


These were redone based on the alignment above and using the value of 490 km for the inner edge of the detached haze layer.
The CL1-VIO filtered images probed the region betwen 427 - 336 km above Titan's surface.

[Juramike]

Stacked images of the May 5th occultation of Archenar with the CB2 CL2 filter set:


(click to animate)

[Juramike]

Here are the control points for the CB2 CL2 calibration of the images. (After leveling; before leveling the value were already very close)

[Juramike]

Here is a coordinated and rotated image showing the descent of Archenar through the haze column throught the CB2-CL2 filter set:


(click to animate)

[Juramike]

To calculate the distance from the CB2 CL2 images to the inner edge of the detached haze layer was kinda tricky.

The inner edge of the detached haze layer is not visible in the CB2 CL2 image sequence. (The outer edge is sorta visible by the steep falloff in pixel brightness).

To get the correct measurements, I took the W00056248 CL1 VIO image and coordinated to the W00056247 image in the CB2 CL2 image set.
(By my calculations, there should be less than a 1 pixel difference in the Archenar image.)
I then overlaid the two star images and made the limb sections parallel. (Titan's limb is "inflated" in CL1 VIO filtered images).
A mask was added to not interfere with the lower layer measurements so that the CL1 VIO detached haze layer is now visible in the CB2 CL image set.

The measurements were then made from the inner edge of the CL1 VIO detached haze layer.
(And they match up nicely!)

[Juramike]

Here is the graphed relative transmission data of Archenar during the May 5th 2009 occultation of Titan's haze layers:



Graphed transmission data is normalized to the initial (outermost) integrated density response for each dataset.
It is not meaningful to compare the values between the two datasets - they can only be compared inside the particular filters dataset.

-Mike

[Juramike]

Here is the same graph as above, but plotted on a log scale and with literature values.
The backround plots is a trace of Figure 1 (and references therin) from Lavvas et al. Icarus 201 (2009) 626-633. "The detached haze layer in Titan's mesosphere". doi: 10.1016/j.icarus.2009.01.004



And it all roughly fits!

(The weird bump in the CB2 CL2 data at about 365 km is not evident in integrated density measurments in the raw data. It may not be significant.)

-Mike

[Juramike]

Error analysis of my derived occultation data.

Assuming a linear detector response.

Taking worst case leveled control point variation:
For CL1 VIO filter data:
distance CL1 VIO control point 3
42671 124
42008 122
41677 122
41014 120
40683 123
40352 130
39689 137

average 125.4285714
std dev 5.996030433

2x std dev = 11.8 (95% confidence)

Error propagation of subtracting one leveled image with consensus model built from leveled image: SQRT[(11.8^2)+(11.8^2)] = 16.7
Multiplication of a constant (area = 177 x 16.7 = 2956 error in integrated density measurement) {= pixel area x pixel value error}

Value used as 100% response for normalization is 5755. (thus, 5755 +/- 2956)

Division of the integrated density value with another integrated value density value gives normalization errors ranging from (+/-)71% (uppermost measurment) down to (+/-) 54% (lowest measurement nearest limb).


For CB2 CL2 filter data:
distance CB2 CL2 control point 4 (post level)
42641 208
42310 208
41979 208
41316 209
40984 207
40322 208
39991 209
39659 207

average 208
std dev 0.755928946

2x std dev = 1.4 (95% confidence)

Error propagation of subtracting one leveled image with consensus model built from leveled image: Sqrt[(1.4^2)+(1.4^2)] = 2
Multiplication of a constant (area = 177 x 2 = 354 error in integrated density measurement) {= pixel area x pixel value error}

Value used as 100% response for normalization is 5755. (thus, 823 +/- 354)

Division of the integrated density value with another integrated value density value gives normalization errors ranging from (+/-)61% (uppermost measurement) down to (+/-) 46% (lowest measurement near limb).

Them error bars be pretty wide.

-Mike

[Juramike]

Image showing really really subtle dark details of Titan's haze layer in CL1-VIO filter image of the T55 flyby (May 21):



(The bright crescent is an artifact of the enhancement I used).