Moon.cfg in orbiter beta

Continuing my tour of the Saturnian system:

Dione:
Difference in SidRotOffset of 0.49 rad.
Code: 
Dione
-----
PrecessionLAN = 6.099400119
PrecessionObliquity = 0.4894221523
PrecessionPeriod = -1715867.804
LAN = 0.663789478
LAN_MJD = 51544.5
Obliquity = 0.0006272896786
SidRotOffset = 1.730032333
SidRotPeriod = 236469.5055
;SidRotPeriod (days): 2.736915573
;SidRotPeriod (days - node to node): 2.736911207
;Precession Period (years): -4697.790017
;Obliquity (deg): 0.03594105111
;Ecliptic LAN (rad): 6.100221446
;Ecliptic Obliquity (rad): 0.4899163853
;Ecliptic SidRotOffset (rad): 1.922800588
;Axis RMS Error (deg): 0.03442147822
;Lat/Lon RMS Error (deg): 0.0006284636585

Rhea:
Difference in SidRotOffset of 0.88 rad.
Code: 
Rhea
-----
PrecessionLAN = 6.094968867
PrecessionObliquity = 0.4919939866
PrecessionPeriod = -12945.41576
LAN = 5.32513397
LAN_MJD = 51544.5
Obliquity = 0.006183031585
SidRotOffset = 1.22441763
SidRotPeriod = 390312.2289
;SidRotPeriod (days): 4.517502649
;SidRotPeriod (days - node to node): 4.515926777
;Precession Period (years): -35.44261672
;Obliquity (deg): 0.3542616144
;Ecliptic LAN (rad): 6.084331971
;Ecliptic Obliquity (rad): 0.4955736381
;Ecliptic SidRotOffset (rad): 1.095532053
;Axis RMS Error (deg): 1.153824146
;Lat/Lon RMS Error (deg): 0.00772789982

Iapetus:
Code: 
Iapetus
-------
PrecessionLAN = 0.390942395
PrecessionObliquity = 0.2231254157
PrecessionPeriod = -2357905.863
LAN = 4.422070305
LAN_MJD = 51544.5
Obliquity = 0.2792493401
SidRotOffset = 2.129843522
SidRotPeriod = 6854343.081
;SidRotPeriod (days): 79.33267455
;SidRotPeriod (days - node to node): 79.33010885
;Precession Period (years): -6455.594424
;Obliquity (deg): 15.99980862
;Ecliptic LAN (rad): 5.578155882
;Ecliptic Obliquity (rad): 0.3014973361
;Ecliptic SidRotOffset (rad): 1.501271458
;Axis RMS Error (deg): 0.004683714009
;Lat/Lon RMS Error (deg): 0.001598098019
 
Venus essentially doesn't precess anyway, so the modified data should be as follows (note difference in Ecliptic SidRotOffset of 0.473 rad from current cfg):
Code: 
Venus
-----
LAN = 5.23924688
Obliquity = 0.02162478054
SidRotOffset = 4.696459183
SidRotPeriod = -20996797.02
;SidRotPeriod (days): -243.018484
Moving onto Uranus:

Uranus:
Also basically doesn't precess:
Code: 
Uranus
------
LAN = 2.925986535
Obliquity = 1.436025521
SidRotOffset = 0.5200623232
SidRotPeriod = -62064
;SidRotPeriod (days): -0.7183333333
Miranda:
Code: 
Miranda
-------
PrecessionLAN = 2.927884137
PrecessionObliquity = 1.434522409
PrecessionPeriod = 6495.828751
LAN = 1.444762288
LAN_MJD = 51544.5
Obliquity = 0.07423572721
SidRotOffset = 2.320240846
SidRotPeriod = -122124.5308
;SidRotPeriod (days): -1.413478366
;SidRotPeriod (days - node to node): -1.41317171
;Precession Period (years): 17.78460986
;Obliquity (deg): 4.253393858
;Ecliptic LAN (rad): 3.002125017
;Ecliptic Obliquity (rad): 1.444216694
;Ecliptic SidRotOffset (rad): 3.766537381
;Axis RMS Error (deg): 0.03699836259
Ariel:
Code: 
Ariel
-----
PrecessionLAN = 2.927971096
PrecessionObliquity = 1.434574403
PrecessionPeriod = 257654.6889
LAN = 4.210000234
LAN_MJD = 51544.5
Obliquity = 0.004973358248
SidRotOffset = 1.745551793
SidRotPeriod = -217760.7347
;SidRotPeriod (days): -2.520378873
;SidRotPeriod (days - node to node): -2.520354219
;Precession Period (years): 705.4200929
;Obliquity (deg): 0.2849524376
;Ecliptic LAN (rad): 2.923570062
;Ecliptic Obliquity (rad): 1.432180939
;Ecliptic SidRotOffset (rad): 5.928964569
;Axis RMS Error (deg): 0.003100267543
Umbriel:
Code: 
Umbriel
-------
PrecessionLAN = 2.927843972
PrecessionObliquity = 1.434576005
PrecessionPeriod = 140917.7226
LAN = 4.116612467
LAN_MJD = 51544.5
Obliquity = 0.00349985134
SidRotOffset = 0.9982461153
SidRotPeriod = -358056.8261
;SidRotPeriod (days): -4.144176228
;SidRotPeriod (days - node to node): -4.144054359
;Precession Period (years): 385.8116977
;Obliquity (deg): 0.2005267107
;Ecliptic LAN (rad): 2.924919222
;Ecliptic Obliquity (rad): 1.432612636
;Ecliptic SidRotOffset (rad): 5.111199681
;Axis RMS Error (deg): 0.03231203637
Oberon:
Code: 
Oberon
------
PrecessionLAN = 2.927886186
PrecessionObliquity = 1.434545402
PrecessionPeriod = 26064.42255
LAN = 4.990921993
LAN_MJD = 51544.5
Obliquity = 0.002746236454
SidRotOffset = 4.639499899
SidRotPeriod = -1163223.242
;SidRotPeriod (days): -13.46323197
;SidRotPeriod (days - node to node): -13.45628133
;Precession Period (years): 71.36049978
;Obliquity (deg): 0.1573477584
;Ecliptic LAN (rad): 2.925221366
;Ecliptic Obliquity (rad): 1.435300945
;Ecliptic SidRotOffset (rad): 3.38763382
;Axis RMS Error (deg): 0.4880827534
Titania:
Code: 
Titania
-------
PrecessionLAN = 2.927884294
PrecessionObliquity = 1.434546704
PrecessionPeriod = 174445.4332
LAN = 3.563729957
LAN_MJD = 51544.5
Obliquity = 0.004887419808
SidRotOffset = 1.022146216
SidRotPeriod = -752186.7721
;SidRotPeriod (days): -8.705865418
;SidRotPeriod (days - node to node): -8.705430971
;Precession Period (years): 477.6055665
;Obliquity (deg): 0.2800285277
;Ecliptic LAN (rad): 2.925861883
;Ecliptic Obliquity (rad): 1.430088603
;Ecliptic SidRotOffset (rad): 4.587409478
;Axis RMS Error (deg): 0.002503215393
Just Neptune to go now!
 
Question: where the heck do you get such accurate information about something that is billions of miles away.
 
Hmm....well, the ephemeris data is available online, but where exactly tblaxland is getting his info is unknown to me.

As far as actually determining said data, the most probable answer is lots and lots of observations over a period of years with powerful telescopes.
 
Nemoricus said:
Hmm....well, the ephemeris data is available online, but where exactly tblaxland is getting his info is unknown to me.
Click to expand...
"Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006". The link to it is up-thread somewhere. They are due to issue a new one early next year (3 year cycle).

Nemoricus said:
As far as actually determining said data, the most probable answer is lots and lots of observations over a period of years with powerful telescopes.
Click to expand...
They are based on observations from a number of sources, ground based telescopes and interplanetary probes mostly, observing in a range of wavelengths from radio up to optical. I think the oldest data is that for Uranus and Neptune from Voyager. Some data is also calculated from orbital motion based on assumptions of Cassini States for many of the moons. You don't need to resolve a lot of detail to be able to measure a rotation rate, you just need plot its light curve (the variation in luminance over time) and measure its period.
 
tblaxland said:
Venus essentially doesn't precess anyway, so the modified data should be as follows (note difference in Ecliptic SidRotOffset of 0.473 rad from current cfg):
Code: 
Venus
-----
LAN = 5.23924688
Obliquity = 0.02162478054
SidRotOffset = 4.696459183
SidRotPeriod = -20996797.02
;SidRotPeriod (days): -243.018484
Click to expand...
Excellent. I'm just incorporating your latest data into my config files. Just to confirm: these latest Venus parameters supersede the onese you posted on July 30 - is this correct?
 
I finally got around to doing Neptune - apologies for the delay.

For those that are interested you can add these to the "Rotation Elements" section of the relevant cfg file.

It is interesting that the precession plane differs so much from the orbital plane for the bodies in this system. From what I can find, the precession of Neptune is largely due to tidal forces from Triton, rather than tidal forces from the sun. The precession plane is perpendicular to the angular momentum of Neptune + Triton, which differs by a small but significant amount from the angular momentum of Neptune itself because Triton is so highly inclined to Neptune's equator. There is some interesting reading on the subject here and here. There are also differences in the orientation of Triton in this data vs the O2010P1 config file but my data seems to fit better with other sources anyway so I am confident in it.
Code: 
Neptune
-------
PrecessionLAN = 4.000903915
PrecessionObliquity = 0.4891528611
PrecessionPeriod = 250252.1844
LAN = 5.817599258
LAN_MJD = 51544.5
Obliquity = 0.008900698828
SidRotOffset = 1.314810501
SidRotPeriod = 57996
;SidRotPeriod (days): 0.67125
;SidRotPeriod (days - node to node): 0.6712518005
;Precession Period (years): 685.1531401
;Obliquity (deg): 0.5099724775
;Ecliptic LAN (rad): 3.992524889
;Ecliptic Obliquity (rad): 0.4971209143
;Ecliptic SidRotOffset (rad): 1.253108899
;Axis RMS Error (deg): 0.001983447565
;Lat/Lon RMS Error (deg): 2.980962936e-005

Triton
------
PrecessionLAN = 4.001578381
PrecessionObliquity = 0.4890297742
PrecessionPeriod = 251197.7821
LAN = 5.816477224
LAN_MJD = 51544.5
Obliquity = 0.4046192751
SidRotOffset = 2.071973836
SidRotPeriod = -507759.2391
;SidRotPeriod (days): -5.876843045
;SidRotPeriod (days - node to node): -5.876716659
;Precession Period (years): 687.7420454
;Obliquity (deg): 23.18297677
;Ecliptic LAN (rad): 3.767303188
;Ecliptic Obliquity (rad): 0.8680049683
;Ecliptic SidRotOffset (rad): 1.738466385
;Axis RMS Error (deg): 0.003721120616
;Lat/Lon RMS Error (deg): 0.004971802

Proteus
-------
PrecessionLAN = 3.990486609
PrecessionObliquity = 0.4973010344
PrecessionPeriod = 252147.7276
LAN = 5.82580598
LAN_MJD = 51544.5
Obliquity = 0.009044585966
SidRotOffset = 4.808856698
SidRotPeriod = 96968.05768
;SidRotPeriod (days): 1.122315482
;SidRotPeriod (days - node to node): 1.122320478
;Precession Period (years): 690.3428544
;Obliquity (deg): 0.5182166033
;Ecliptic LAN (rad): 3.982237546
;Ecliptic Obliquity (rad): 0.5054304103
;Ecliptic SidRotOffset (rad): 4.543895591
;Axis RMS Error (deg): 0.00389371195
;Lat/Lon RMS Error (deg): 5.381266627e-005
 
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