Saturn's rings wobble , as seen from Pan

[Pierluigi Panunzi]

Hi!
I'm working with Saturn and it's famous rings...
I have created a data packet for its satellite PAN, whose orbit lies inside Enke's Division.
Collecting data from wikipedia, I organized the relevant data for Pan :

[pan]
albedo=0.5
color=1., 0.9, 0.75
coord_func=ell_orbit
halo=true
lighting=true
name=Pan
orbit_AscendingNode=263.0
orbit_Eccentricity=0.000035
orbit_Epoch=2453177.5
orbit_Inclination=0.0
orbit_LongOfPericenter=209.0
orbit_MeanLongitude=106.645
orbit_Period=0.57505
orbit_SemiMajorAxis=133584.0
orbit_visualization_period=0.57505
parent=Saturn
radius=15
rot_equator_ascending_node=213.7
rot_obliquity=0.0
rot_periode=13.8012
rot_rotation_offset=287
tex_halo=star16x16.png
tex_map=lune.png
type=moon

practically organizing data as other satellites with "ell_orbit" coord_func value: I started from Jupiter's Adrastea and modified values accordingly.
Please note the null values for "orbit_Inclination" and "rot_obliquity".
Now insert these data in ssystem.ini file and follow my instructions! You can witness a really awesome sight!

- choose Pan as Location (F6) and set coordinates to +40°00'00", +100°00'00", in order to see a magnificent view of Saturn
- with the mouse move horizontally a little in order to see rings edge-on
- choose a FOV of about 80°, just to see a smaller Saturn...
Awesome view!!!

- press 3 times the L key, in order to increase the speed of time: you can see the magnificent show of Saturn crossed by the rings' shadows, but you can see also that there's something strange and wrong with the rings, that "flash" cyclically at that rate...

If you return to the normal speed of time (K) then you can see that rings are not always edge-on as you can expect: please remember that both inclinations are put to streight 0.0

What is wrong with my Pan's setup? Or is there any kind of issue in the "ell_orbit" algorithm?

If you try the same, starting now from Enceladus (for which we have "coord_func=enceladus_special") you can see that rings remain always edge-on without any wobbling.
then if you further zoom towards Saturn (I suggest you, in full screen view!) you can see also Pan wandering along the edge-on rings, as you would expect. Mimas instead has an orbital inclination of only 1.57°, but that's enough to see it detached from the rings' line. (as in the attached screenshot)

Thanks for your attention!
Pierluigi Panunzi

My log.txt file is this.
BTW what about the series of messages "libpng warning: iCCP: known incorrect sRGB profile"? I have never seen them...

2016-03-20T10:09:37
Windows 10
Compiled using MSVC++ 12.0 (Visual Studio 2013)
Qt runtime version: 5.5.1
Qt compilation version: 5.5.1
Addressing mode: 64-bit
Total physical memory: 8174 MB
Available physical memory: 7017 MB
Physical memory in use: 14%
Processor speed: 2794 MHz
Processor name: Intel(R) Core(TM) i5-2300 CPU @ 2.80GHz
Processor speed: 2794 MHz
Processor name: Intel(R) Core(TM) i5-2300 CPU @ 2.80GHz
Processor speed: 2794 MHz
Processor name: Intel(R) Core(TM) i5-2300 CPU @ 2.80GHz
Processor speed: 2794 MHz
Processor name: Intel(R) Core(TM) i5-2300 CPU @ 2.80GHz
C:\Program Files\Stellarium\stellarium.exe
 -------------------------------------------------------
[ This is Stellarium 0.14.2 - http://www.stellarium.org ]
[ Copyright (C) 2000-2016 Fabien Chereau et al. ]
 -------------------------------------------------------
Writing log file to: "C:\\Users\\pierlu\\AppData\\Roaming\\Stellarium\\log.txt"
File search paths:
  0 . "C:\\Users\\pierlu\\AppData\\Roaming\\Stellarium"
  1 . "."
Config file is: "C:\\Users\\pierlu\\AppData\\Roaming\\Stellarium\\config.ini"
Detected: OpenGL "3.3"
Driver version string: "3.3.0"
GL vendor is "NVIDIA Corporation"
GL renderer is "GeForce 405/PCIe/SSE2"
GL Shading Language version is "3.30 NVIDIA via Cg compiler"
GLSL Version Number detected: 3.3
GLSL version is fine, we should not see a graphics problem.
Cache directory is: "C:\\Users\\pierlu\\AppData\\Local\\stellarium\\stellarium\\cache"
Sky language is "en"
Application language is "en"
Loading Solar System data ...
Loading star data ...
"Loading \".\\stars\\default\\stars_0_0v0_5.cat\": 0_0v0_2; 4963"
"Loading \".\\stars\\default\\stars_1_0v0_5.cat\": 1_0v0_2; 21598"
"Loading \".\\stars\\default\\stars_2_0v0_5.cat\": 2_0v0_2; 150090"
"Loading \".\\stars\\default\\stars_3_1v0_3.cat\": 3_1v0_3; 428466"
Finished loading star catalogue data, max_geodesic_level: 3
navigation/preset_sky_time is a double - treating as jday: "2451514.25001"
Reloading DSO data...
Loaded 10756 DSO records
Loading DSO name data ...
Loaded 221 / 297 DSO name records successfully
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
Loading star names from ".\\skycultures\\western\\star_names.fab"
Loaded 340 / 340 common star names
Loading star names from ".\\stars\\default\\name.fab"
Loaded 4506 / 4506 scientific star names
Loading variable stars from ".\\stars\\default\\gcvs_hip_part.dat"
Loaded 6916 / 6916 variable stars
Loading cross-index data from ".\\stars\\default\\cross-index.dat"
Loaded 108279 / 108279 cross-index data records
Loaded 88 / 88 constellation records successfully for culture "western"
Loaded 85 / 85 constellation art records successfully for culture "western"
Loaded 88 / 88 constellation names
Loading constellation boundary data ...
Loaded 782 constellation boundary segments
Initializing basic GL shaders...
Creating GUI ...
libpng warning: iCCP: known incorrect sRGB profile
Loaded plugin "AngleMeasure"
Loaded plugin "CompassMarks"
Loaded plugin "FOV"
Loaded plugin "MeteorShowers"
libpng warning: iCCP: known incorrect sRGB profile
MeteorShowersMgr: Loading catalog file: "C:\\Users\\pierlu\\AppData\\Roaming\\Stellarium\\modules\\MeteorShowers\\showers.json"
Loaded plugin "SolarSystemEditor"
Using the ssystem.ini file that already exists in the user directory...
Unable to find module called "TimeZoneConfiguration"
Loaded plugin "TimeZoneConfiguration"
Dubious result: Landscape "Guereins" not calibrated. Opacity test represents mathematical horizon only.
Initializing planets GL shaders...
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
libpng warning: iCCP: known incorrect sRGB profile
INFO Saving screenshot in file: "C:\\Users\\pierlu\\Desktop\\stellarium-000.png"
Unloaded plugin "TimeZoneConfiguration"
Unloaded plugin "SolarSystemEditor"
Unloaded plugin "MeteorShowers"
Unloaded plugin "FOV"
Unloaded plugin "CompassMarks"
Unloaded plugin "AngleMeasure"
Downloaded 0 files (0 kbytes) in a session of 1363.59 sec (average of 0 kB/s + 0 files from cache (0 kB)).

[Alexander Wolf (alexwolf)]

Orbit inclination of Pan is not zero. Why you do not use HORIZONS as source of data http://ssd.jpl.nasa.gov/horizons.cgi ?

[Pierluigi Panunzi (piellepi)]

yes ok!thanks
now I'll get precise values...
but if I set Pan's orbit and rotation inclination to 0.0, why do I see the rings wobble?
I'd expect to see Pan always inside and aligned to the rings... :o
Pierluigi

    On Sunday, March 20, 2016 12:31 PM, Alexander Wolf <email address hidden> wrote:

 Orbit inclination of Pan is not zero. Why you do not use HORIZONS as
source of data http://ssd.jpl.nasa.gov/horizons.cgi ?

--
You received this bug notification because you are subscribed to the bug
report.
https://bugs.launchpad.net/bugs/1559657

Title:
  Saturn's rings wobble , as seen from Pan

Status in Stellarium:
  New

Bug description:
  Hi!
  I'm working with Saturn and it's famous rings...
  I have created a data packet for its satellite PAN, whose orbit lies inside Enke's Division.
  Collecting data from wikipedia, I organized the relevant data for Pan :

  [pan]
  albedo=0.5
  color=1., 0.9, 0.75
  coord_func=ell_orbit
  halo=true
  lighting=true
  name=Pan
  orbit_AscendingNode=263.0
  orbit_Eccentricity=0.000035
  orbit_Epoch=2453177.5
  orbit_Inclination=0.0
  orbit_LongOfPericenter=209.0
  orbit_MeanLongitude=106.645
  orbit_Period=0.57505
  orbit_SemiMajorAxis=133584.0
  orbit_visualization_period=0.57505
  parent=Saturn
  radius=15
  rot_equator_ascending_node=213.7
  rot_obliquity=0.0
  rot_periode=13.8012
  rot_rotation_offset=287
  tex_halo=star16x16.png
  tex_map=lune.png
  type=moon

  practically organizing data as other satellites with "ell_orbit" coord_func value: I started from Jupiter's Adrastea and modified values accordingly.
  Please note the null values for "orbit_Inclination" and "rot_obliquity".
  Now insert these data in ssystem.ini file and follow my instructions! You can witness a really awesome sight!

  - choose Pan as Location (F6) and set coordinates to +40°00'00", +100°00'00", in order to see a magnificent view of Saturn
  - with the mouse move horizontally a little in order to see rings edge-on
  - choose a FOV of about 80°, just to see a smaller Saturn...
  Awesome view!!!

  - press 3 times the L key, in order to increase the speed of time: you
  can see the magnificent show of Saturn crossed by the rings' shadows,
  but you can see also that there's something strange and wrong with the
  rings, that "flash" cyclically at that rate...

  If you return to the normal speed of time (K) then you can see that
  rings are not always edge-on as you can expect: please remember that
  both inclinations are put to streight 0.0

  What is wrong with my Pan's setup? Or is there any kind of issue in
  the "ell_orbit" algorithm?

  If you try the same, starting now from Enceladus (for which we have "coord_func=enceladus_special") you can see that rings remain always edge-on without any wobbling.
  then if you further zoom towards Saturn (I suggest you, in full screen view!) you can see also Pan wandering along the edge-on rings, as you would expect. Mimas instead has an orbital inclination of only 1.57°, but that's enough to see it detached from the rings' line. (as in the attached screenshot)

  Thanks for your attention!
  Pierluigi Panunzi

  My log.txt file is this.
  BTW what about the series of messages...

[Pierluigi Panunzi (piellepi)]

I sent another mail, but it doesn't appear here...
this is the contents of it

my intent is to explain to my site readers the motion of Saturn as seen from Pan
at this stage (before publishing anything) I'm only verifying that Stellarium algorithms and computations are correct, with null values for the inclination, with less care for real values.
but I can't explain wobbling...

I have done other tests involving Pan's orbital elements...
- increasing the distance of Pan, beyond the "ring_outer_size=140390", the wobbling effect disappears and rings are always edge-on
- decreasing it, the wobbling is always present and not so easy to understand, if not for a "strange" graphical modeling of the rings in Stellarium, that perhaps involves an inclination of the rings...

nowhere I found that rings of Saturn have an inclination: what about stellarium model "saturn_special" or else?
a small inclination of the ring plane to Saturn equatorial plane could explain the effect I found...
that sounds interesting!

BTW if you give a look at Celestia, there is no such effect...

[Pierluigi Panunzi (piellepi)]

why "incomplete" ??? :)

I posted the complete sequence that returns the issue!
The problem is always present.

if you need other info please ask me! ;)
Pierluigi

[Alexander Wolf (alexwolf)]

Sorry for late answer, I didn't receive any notifications for new answers.

The report has been marked as "Incomplete" because I don't see updated version of orbit elements for Pan.

[Alexander Wolf (alexwolf)]

I checked Pan on Celestia - it has wobbling too, plus in some cases it has artifacts in rendering of rings. Of course Stellarium has an artifacts when rings are rendering.

[Alexander Wolf (alexwolf)]

Dear Pierluigi, do you have any progress for this issue?

[Pierluigi Panunzi (piellepi)]

Hi Alexander!no, I did no further investigation about this issue...the strange fact is that the data I set for Pan contain a 0 degrees inclination for the orbit (orbit_Inclination=0.0), so I can't explain why the satellite doesn't orbit Saturn in a steady, fixed orbit along the equatorial plane.what you can see is that the orbit oscillates up and down in time as if it were inclined by a small amount of degrees.
It sounds as the rings themselves oscillate as if they were inclined to the equatorial plane: this fact is really new to me, as I never heard about it. Rings should have an ascending node and an inclination to the equatorial plane.
I can't explain such a strange behavior, without thinking about a small bug in the orbit algorithm...
I wonder what should happen creating a completely new and fictitius object in the solar system with at least one satellite, with easy and convenient orbital parameters: once angain a 0 degrees inclination and other simple values. And also a synchronous orbit and rotation
then after landing on the satellite it'd be interesting to see the movements of the planet and verify its steadiness in time...This is a common practice for programs as Celestia, but unfortunately this is not updated since a lot of time...
what do you think about this "experiment" ?
 Pierluigi

    On Sunday, May 22, 2016 12:07 PM, Alexander Wolf <email address hidden> wrote:

 Dear Pierluigi, do you have any progress for this issue?

--
You received this bug notification because you are subscribed to the bug
report.
https://bugs.launchpad.net/bugs/1559657

Title:
  Saturn's rings wobble , as seen from Pan

Status in Stellarium:
  Incomplete

Bug description:
  Hi!
  I'm working with Saturn and it's famous rings...
  I have created a data packet for its satellite PAN, whose orbit lies inside Enke's Division.
  Collecting data from wikipedia, I organized the relevant data for Pan :

  [pan]
  albedo=0.5
  color=1., 0.9, 0.75
  coord_func=ell_orbit
  halo=true
  lighting=true
  name=Pan
  orbit_AscendingNode=263.0
  orbit_Eccentricity=0.000035
  orbit_Epoch=2453177.5
  orbit_Inclination=0.0
  orbit_LongOfPericenter=209.0
  orbit_MeanLongitude=106.645
  orbit_Period=0.57505
  orbit_SemiMajorAxis=133584.0
  orbit_visualization_period=0.57505
  parent=Saturn
  radius=15
  rot_equator_ascending_node=213.7
  rot_obliquity=0.0
  rot_periode=13.8012
  rot_rotation_offset=287
  tex_halo=star16x16.png
  tex_map=lune.png
  type=moon

  practically organizing data as other satellites with "ell_orbit" coord_func value: I started from Jupiter's Adrastea and modified values accordingly.
  Please note the null values for "orbit_Inclination" and "rot_obliquity".
  Now insert these data in ssystem.ini file and follow my instructions! You can witness a really awesome sight!

  - choose Pan as Location (F6) and set coordinates to +40°00'00", +100°00'00", in order to see a magnificent view of Saturn
  - with the mouse move horizontally a little in order to see rings edge-on
  - choose a FOV of about 80°, just to see a smaller Saturn...
  Awesome view!!!

  - press 3 times the L key, in order to increase the speed of time: you
  can see the magnificent sh...

[Launchpad Janitor (janitor)]

[Expired for Stellarium because there has been no activity for 60 days.]

[Alexander Wolf (alexwolf)]

Pan has been added into version 0.90.0.9620 in default list of major bodies.

[Alexander Wolf (alexwolf)]

Pierluigi, please check the last beta (the issue is exists still, but it's better now IMHO)

[Alexander Wolf (alexwolf)]

The bug report was moved to https://github.com/Stellarium/stellarium/issues/435