Supplementary Online Material
Ingersoll, A. P., Ewald, S. P., 2016. Decadal Timescale Variability of the
Enceladus Plumes Inferred from Cassini Images
1. Supplementary Figures
Fig. S1. As in Fig. 4 but the wings of the plume are modeled as 1/|x|1.5 functions
symmetric about the plume center. Compared with Fig. 4, which uses 1/x2 functions,
the curves here turn up on the left, indicating that the 1/x2 model is better than the
model displayed in this figure.
Fig. S2. As in Fig. 4 but the wings of the plume are modeled as 1/|x|2.5 functions
symmetric about the plume center. Compared with Fig. 4, which uses 1/x2 functions,
the curves here turn down on the left, indicating that the 1/x2 model is better than
the model displayed in this figure.
Fig. S3. As in Fig. 11, but the points are color-coded by scattering angle. Here and in
Fig. 11 the conversion from EW to slab density uses the small aggregate model of
Gao et al. (2016). Used together, Figs. 7, S3, and S4 help to explain why some points
move up and down relative to each other as the conversion factors change from the
solid sphere model to the small aggregate model, i.e., from Fig. 8 to Fig. 11. See the
main paper for details.
Fig. S4. As in Fig. 11, but the points are color-coded by filter (wavelength), which
includes BL1(451 nm), CLR(611 nm), RED(650 nm), IR1(752 nm), and IR2(862 nm),
as given in Porco et al. (2004). Here and in Fig. 11 the conversion from EW to slab
density uses the small aggregate model of Gao et al. (2016). Used together, Figs. 7,
S3, and S4 help to explain why some points move up and down relative to each
other as the conversion factors change from the solid sphere model to the small
aggregate model, i.e., from Fig. 8 to Fig. 11. See the main paper for details.
Fig. S5. As in Fig. 18 but for Δr(0) = 2100 km. This larger value of Δr(0) gives a
larger boost to the points in Fig. 17 with small eccentricity compared to the points
with large eccentricity. It boosts the ω points closer to the blue points at the same
MA, but is also boosts the 3 and θ points farther from the blue points. Δr(0) = 2050
does the best job, but there is no single value of Δr(0) that completely collapses all
the data down to a single function of MA.
2. Supplementary Description of Image Preparation
To find images suitable for processing, we searched the Planetary Data
System (https://pds.nasa.gov/) for observations that specified target = Enceladus.
Using the NAIF/SPICE subroutine library (version ICY 1.6.0, 03-May-2010) and
kernel files from the FTP site at the Jet Propulsion Laboratory, we rejected
observations where the scattering angle was larger than 30° or the
spacecraft/Enceladus distance was larger than 16.5 times the radius of Saturn
(projected image width > 6000 km). The former step was taken because the plume
is much fainter at large scattering angles, and the latter step was taken because the
spatial resolution was poorer at large distances. The NAIF kernels that we used are
given in Supplementary Table S1.
We used CISSCAL (version 3.4 with IDL version 6.2; Porco et al., 2004; West
et al., 2010) to convert the pixel values in the images to I/F, where I is the measured
intensity in one of the ISS filters and πF is the incident solar flux at Enceladus in the
same filter bandpass. CISSCAL also does flat-fielding and masking of saturated
pixels. We manually examined all images and rejected those (1) with Saturn or other
objects in the background, (2) with stray light clouding parts of the image, (3) with
excessive electronic noise, and (4) those with large numbers of cosmic ray hits.
Supplementary Table S2 gives the image ID number, event time, mean anomaly,
spatial resolution, and the alphanumeric character (A–Z, 1–9, α-ω) for each of the
701 images that were used in our study. Supplementary Table S3 gives the image ID
number and event times for each of the 394 potentially useful images that were not
used in our study.
Precise knowledge of the altitude requires precise knowledge of camera
pointing. Uncertainties arise because the observation geometry changes rapidly as
Cassini flies past Enceladus. In some cases, the bright limb of Enceladus provides a
suitable reference point. In other cases the limb and the plume are overexposed, so
the limb is invisible. In many of these cases we were able to use the dark limb, which
stands out against the relatively bright E ring background. In some cases the camera
missed Enceladus altogether and no limb was visible. These images were rejected,
although they might become useful if enough stars could be identified in the
background. Most of the images had the planet’s spin axis perpendicular to lines of
pixels, and the others were rotated into this geometry to make the processing more
uniform.
3. Supplementary Tables
Table S1. List of NAIF/SPICE kernels used in this analysis.
cas_v40.tf
cas_iss_v10.ti
naif0011.tls
pcpck03Aug2015.tpc
pcpck18Nov2009.tpc
ppck00010.tpc
cas00162.tsc
C-kernels
05042_05047ra.bc
05047_05052ra.bc
05052_05057ra.bc
05067_05072ra.bc
05072_05077ra.bc
05192_05197ra.bc
05197_05202ra.bc
05331_05331ra.bc
06017_06022ra.bc
06122_06127ra.bc
06257_06262ra.bc
07112_07117ra.bc
07272_07277ra.bc
08357_08362ra.bc
09076_09081ra.bc
09286_09291ra.bc
09301_09306ra.bc
09305_09307ra.bc
09321_09326ra.bc
09341_09346ra.bc
09356_09361ra.bc
09356_09361ra.bc.lbl
10024_10029ra.bc
10059_10064ra.bc
SP-kernels
050214R_SCPSE_04336_05015.bsp
050411R_SCPSE_05015_05034.bsp
050414R_SCPSE_05034_05060.bsp
050504R_SCPSE_05060_05081.bsp
050513R_SCPSE_05097_05114.bsp
050606R_SCPSE_05114_05132.bsp
050720AP_SCPSE_05119_08222.bsp
050825R_SCPSE_05186_05205.bsp
060321R_SCPSE_06005_06036.bsp
061013R_SCPSE_06240_06260.bsp
070605R_SCPSE_07106_07125.bsp
081031R_SCPSE_08220_08272.bsp
081126R_SCPSE_08272_08294.bsp
081217R_SCPSE_08294_08319.bsp
090120R_SCPSE_08319_08334.bsp
090202R_SCPSE_08334_08350.bsp
090423R_SCPSE_09028_09075.bsp
090507R_SCPSE_09075_09089.bsp
090520R_SCPSE_09089_09104.bsp
090609R_SCPSE_09104_09120.bsp
090624R_SCPSE_09120_09136.bsp
090701R_SCPSE_09136_09153.bsp
090708R_SCPSE_09153_09168.bsp
090806R_SCPSE_09168_09184.bsp
090817R_SCPSE_09184_09200.bsp
090921R_SCPSE_09200_09215.bsp
090924R_SCPSE_09215_09231.bsp
091005AP_SCPSE_09248_17265.bsp
091116R_SCPSE_09231_09275.bsp
091208R_SCPSE_09275_09296.bsp
110916R_SCPSE_05081_05097.bsp
111123R_SCPSE_11267_11303.bsp
10114_10119ra.bc
10134_10139ra.bc
10224_10229ra.bc
10289_10294ra.bc
10334_10339ra.bc
10354_10359ra.bc
11029_11034ra.bc
11274_11279ra.bc
11289_11294ra.bc
11294_11299ra.bc
11309_11314ra.bc
12004_12009ra.bc
12049_12054ra.bc
12084_12089ra.bc
12104_12109ra.bc
12119_12124ra.bc
12244_12249ra.bc
12264_12269ra.bc
12289_12294ra.bc
12344_12349ra.bc
12354_12359ra.bc
13018_13023ra.bc
13043_13048ra.bc
13056_13057ra.bc
13088_13093ra.bc
13163_13168ra.bc
13173_13178ra.bc
15128_15133ra.bc
15148_15153ra.bc
15188_15193ra.bc
15208_15213ra.bc
120227R_SCPSE_11357_12016.bsp
121130R_SCPSE_12199_12257.bsp
121204R_SCPSE_12257_12304.bsp
130319R_SCPSE_12328_13038.bsp
130321R_SCPSE_13038_13063.bsp
130710R_SCPSE_13087_13137.bsp
130805R_SCPSE_13137_13182.bsp
150330AP_SCPSE_15088_15133.bsp
060111R_SCPSE_05320_05348.bsp
060614R_SCPSE_06099_06130.bsp
080117R_SCPSE_07262_07309.bsp
090225R_SCPSE_08350_09028.bsp
100107R_SCPSE_09296_09317.bsp
100113R_SCPSE_09317_09339.bsp
100114R_SCPSE_09339_09355.bsp
100127R_SCPSE_09355_10003.bsp
100325R_SCPSE_10021_10055.bsp
100420R_SCPSE_10055_10085.bsp
100616R_SCPSE_10110_10132.bsp
100625R_SCPSE_10132_10146.bsp
101013R_SCPSE_10216_10256.bsp
101210R_SCPSE_10256_10302.bsp
110204R_SCPSE_10344_11003.bsp
110224R_SCPSE_10326_10344.bsp
110308R_SCPSE_11003_11041.bsp
120117R_SCPSE_11303_11337.bsp
120416R_SCPSE_12042_12077.bsp
120426R_SCPSE_12077_12098.bsp
120523R_SCPSE_12098_12116.bsp
120628R_SCPSE_12116_12136.bsp
150803R_SCPSE_15033_15066.bsp
Table S2. Catalog of all images used in the analysis. This is a separate Excel
spreadsheet. There are 701 images. The entries for each image are: filename, event
time, alphanumeric group, filter, mean anomaly, pixel scale, scattering angle,
equivalent width and slab density at 100 km.
Table S3. Catalog of 394 Enceladus images with scattering angles less than 40° that
were not used in the analysis. This is a separate Excel spreadsheet. Reasons for
rejection include: other objects in the background, no visible limb for estimating
altitude, saturated pixels, electronic noise, internal reflections, camera motion,
insufficient background due to 45° rotation around camera axis. This table does not
include images in the UV1 and IR3 filters, all of which were rejected either because
they had low signal to noise or were outside the 0.8 – 11 km range of pixel scales.
Table S4. ISS images analyzed both by Nimmo et al. (N14) and by the present
authors (IE16). Different methods of background subtraction lead to different
estimates of equivalent width (EW). The two analyzed data sets are plotted in Fig. 6.
Observation
Group
N1516298600_1 C
N1516320030_1 C
N1616348791_1 H
N1634159832_1 I
N1634163141_1 I
N1640477223_1 N
N1640478423_1 N
N1643187583_1 O
N1643192383_1 O
N1646170883_1 P
N1646174483_1 P
N1646179299_1 P
N1646182899_1 Q
N1651010460_1 r
N1652824635_1 R
N1665895088_1 S
N1665899841_1 S
N1714610318_1 5
N1725326188_1 7
Event Time
2006 JAN 18 17:33
2006 JAN 18 23:30
2009 MAR 21 17:05
2009 OCT 13 20:34
2009 OCT 13 21:29
2009 DEC 25 23:23
2009 DEC 25 23:43
2010 JAN 26 08:15
2010 JAN 26 09:35
2010 MAR 01 20:57
2010 MAR 01 21:57
2010 MAR 01 23:17
2010 MAR 02 00:17
2010 APR 26 21:16
2010 MAY 17 21:12
2010 OCT 16 03:51
2010 OCT 16 05:10
2012 MAY 01 23:46
2012 SEP 03 00:23
Our I/F
N14 I/F
0.103
0.082
0.235
0.148
0.324
0.292
0.368
0.294
0.515
0.394
0.101
0.108
0.081
0.094
0.151
0.187
0.156
0.214
0.051
0.035
0.048
0.04
0.04
0.046
0.048
0.048
0.222
0.252
0.052
0.041
0.141
0.117
0.215
0.191
0.062
0.039
0.235
0.198
Table S5. VIMS/ISS pairs taken within 1 hour of each other and analyzed by
Hedman et al. (H13) and by the present authors (IE16), respectively. The second
column gives the group symbol as used in Fig. 8 and Tables 1 and S2. The fifth
column gives the event time of the ISS image minus the event time of the VIMS
image. Different methods of background subtraction lead to different estimates of
equivalent width (EW). The two analyzed data sets are plotted in Fig. 6.
ISS Name
Gr
Event Time
VIMS Name
dt
ISS EW VIMS EW
N1635804944_1 J
2009 NOV 01 21:32 V1635804941
-1.31 0.316
0.208
N1635804944_1 J
2009 NOV 01 21:32 V1635805116
-4.23 0.316
0.2017
N1635805837_1 J
2009 NOV 01 21:47 V1635806259
-8.4 0.319
0.1591
N1635805837_1 J
2009 NOV 01 21:47 V1635806434
-11.31 0.319
0.1605
N1635813923_1
N1635815815_1
N1635816494_1
N1635816588_1
N1635817014_1
N1635817014_1
N1635817014_1
N1652824635_1
N1652824635_1
N1652824635_1
N1652824635_1
N1652824635_1
N1675108551_1
N1675110296_1
N1675110586_1
N1675110586_1
N1675110586_1
N1696149778_1
N1696149778_1
N1696149778_1
N1696149778_1
N1696149778_1
N1696149778_1
N1696150608_1
N1696150608_1
N1696150608_1
N1696153348_1
N1696154178_1
N1696154178_1
N1697687812_1
N1697687984_1
N1699226814_1
N1711536357_1
N1711536547_1
N1711538072_1
N1711538262_1
N1711538452_1
N1711539977_1
N1711540357_1
N1711541882_1
N1711544167_1
N1711544167_1
N1711544167_1
K
K
K
K
K
K
K
R
R
R
R
R
V
V
V
V
V
X
X
X
X
X
X
X
X
X
X
X
X
Y
Y
Z
3
3
3
3
3
3
3
3
3
3
3
2009 NOV 02 00:02
2009 NOV 02 00:33
2009 NOV 02 00:44
2009 NOV 02 00:46
2009 NOV 02 00:53
2009 NOV 02 00:53
2009 NOV 02 00:53
2010 MAY 17 21:12
2010 MAY 17 21:12
2010 MAY 17 21:12
2010 MAY 17 21:12
2010 MAY 17 21:12
2011 JAN 30 19:08
2011 JAN 30 19:37
2011 JAN 30 19:41
2011 JAN 30 19:41
2011 JAN 30 19:41
2011 OCT 01 07:53
2011 OCT 01 07:53
2011 OCT 01 07:53
2011 OCT 01 07:53
2011 OCT 01 07:53
2011 OCT 01 07:53
2011 OCT 01 08:06
2011 OCT 01 08:06
2011 OCT 01 08:06
2011 OCT 01 08:52
2011 OCT 01 09:06
2011 OCT 01 09:06
2011 OCT 19 03:06
2011 OCT 19 03:09
2011 NOV 05 22:36
2012 MAR 27 09:54
2012 MAR 27 09:57
2012 MAR 27 10:23
2012 MAR 27 10:26
2012 MAR 27 10:29
2012 MAR 27 10:54
2012 MAR 27 11:00
2012 MAR 27 11:26
2012 MAR 27 12:04
2012 MAR 27 12:04
2012 MAR 27 12:04
V1635813829
V1635815737
V1635816274
V1635816518
V1635817006
V1635817494
V1635817738
V1652821148
V1652821392
V1652821636
V1652822130
V1652822374
V1675109176
V1675109629
V1675110461
V1675111681
V1675111889
V1696147993
V1696148409
V1696148616
V1696148824
V1696149239
V1696149723
V1696150058
V1696150393
V1696150728
V1696153294
V1696153619
V1696153945
V1697686101
V1697688040
V1699226646
V1711536135
V1711536777
V1711537413
V1711538046
V1711538972
V1711539605
V1711540588
V1711541224
V1711544050
V1711544399
V1711544687
-0.27
-0.56
0.7
-0.76
-1.76
-9.9
-13.96
56.38
52.32
48.25
40.02
35.95
-12.15
9.38
0.15
-20.19
-23.65
27.96
21.04
17.58
14.13
7.19
-1.92
6.21
0.63
-4.96
-1.87
6.43
1.01
26.73
-2.72
0.35
1.22
-6.68
8.57
1.12
-11.51
3.79
-6.7
8.56
-0.9
-6.71
-11.51
0.418
0.527
0.518
0.551
0.58
0.58
0.58
0.052
0.052
0.052
0.052
0.052
0.037
0.038
0.037
0.037
0.037
0.124
0.124
0.124
0.124
0.124
0.124
0.128
0.128
0.128
0.147
0.147
0.147
0.111
0.111
0.098
0.087
0.089
0.092
0.098
0.095
0.104
0.102
0.119
0.141
0.141
0.141
0.3257
0.3913
0.3756
0.4105
0.4209
0.4284
0.4482
0.0936
0.0679
0.0518
0.0702
0.0564
0.0259
0.0247
0.0288
0.0315
0.039
0.0993
0.1071
0.0881
0.0965
0.099
0.1094
0.1043
0.0974
0.0957
0.0956
0.1066
0.1188
0.0779
0.065
0.0643
0.0554
0.0408
0.0534
0.0384
0.0494
0.0766
0.0734
0.0771
0.1184
0.1064
0.1143
N1711545692_1
N1711545692_1
N1711545882_1
N1711546072_1
N1711546072_1
N1711546962_1
N1711547152_1
N1711547342_4
N1711547342_4
N1711548232_1
N1711548422_1
N1711548612_1
N1711548612_1
N1711549502_1
N1711549692_1
N1711550962_1
N1711551152_1
N1711551152_1
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
2012 MAR 27 12:30
2012 MAR 27 12:30
2012 MAR 27 12:33
2012 MAR 27 12:36
2012 MAR 27 12:36
2012 MAR 27 12:51
2012 MAR 27 12:54
2012 MAR 27 12:57
2012 MAR 27 12:57
2012 MAR 27 13:12
2012 MAR 27 13:15
2012 MAR 27 13:18
2012 MAR 27 13:18
2012 MAR 27 13:33
2012 MAR 27 13:36
2012 MAR 27 13:57
2012 MAR 27 14:00
2012 MAR 27 14:00
V1711545033
V1711545321
V1711545666
V1711545954
V1711546301
V1711546589
V1711546939
V1711547227
V1711547571
V1711547859
V1711548206
V1711548494
V1711548846
V1711549134
V1711549477
V1711550750
V1711551038
V1711551375
8.57
3.77
1.12
-0.88
-6.66
3.8
1.07
-0.93
-6.66
3.8
1.12
-0.88
-6.75
3.72
1.1
1.05
-0.93
-6.56
0.17
0.17
0.174
0.171
0.171
0.186
0.192
0.186
0.186
0.206
0.211
0.204
0.204
0.223
0.224
0.242
0.234
0.234
Table S6. Brightness I/F per unit column density kg km-2. This is the quantity K0
defined by IE 11. It has units of km2 kg-1 and is equivalent to scattering cross section
per unit mass. The numbers in the top row are the wavelengths in μm, which were
chosen to match filters on the Cassini NAC. The first column contains the scattering
angle in degrees. The other columns contain K0 in km2 kg-1. This table is based on
the solid sphere model that IE11 derived to fit the ISS data that were taken as part of
the 2006 eclipse mosaic (PIA08329). The solid sphere model was used to convert
equivalent width to slab density in Fig. 8 and in related figures of this paper.
0.338
0.451
0.568
0.65
0.938
1
0.145378
0.109769
0.0836449
0.0703203
0.0422349
1.5
0.0855181
0.0739019
0.0614441
0.0539184
0.0354841
2
0.0515244
0.0498811
0.044984
0.0411518
0.0296652
2.5
0.0324801
0.0341722
0.0330587
0.0314262
0.0247386
3
0.0216495
0.0239978
0.0245451
0.0241275
0.020621
3.5
0.0152527
0.017387
0.0185116
0.0187024
0.0172134
4
0.0112884
0.0130341
0.0142408
0.0146907
0.014415
4.5 0.00871832
0.0101094
0.0112047
0.0117268
0.0121304
5 0.00698425 0.00809234 0.00902358 0.00952836
0.010272
6 0.00485047 0.00558772 0.00623636 0.00663108
0.0075334
7 0.00361904 0.00414973 0.00462159 0.00491643 0.00571539
8 0.00287347 0.00327134 0.00362588 0.00384807 0.00449346
9 0.00240775 0.00270707 0.00297494 0.00314425 0.00365186
10 0.00205829 0.00229569 0.00250811 0.00264267 0.00304876
0.1178
0.1108
0.119
0.1143
0.1306
0.1317
0.1263
0.1268
0.1326
0.1243
0.1339
0.1329
0.1486
0.1421
0.1372
0.1684
0.18
0.1886
11
12
13
14
15
16
17
18
19
20
22
24
26
28
30
35
40
45
50
0.001785
0.00158792
0.00144165
0.00130228
0.00118283
0.00109601
0.00101736
0.000932729
0.000858282
0.000800689
0.000690694
0.000598514
0.000518095
0.000447168
0.000392106
0.000275787
0.000195195
0.000139098
9.83E-05
0.00198051
0.00174887
0.00157213
0.00141399
0.00128043
0.00117931
0.0010889
0.000995845
0.000913962
0.000849648
0.000729714
0.000630376
0.000544247
0.000468785
0.000410781
0.000288412
0.000204354
0.000146035
0.000103937
0.00215655
0.00189333
0.00168896
0.00151432
0.00136869
0.00125333
0.00115104
0.00105153
0.000964009
0.000892626
0.000763621
0.000657841
0.000566354
0.000487502
0.000426109
0.000298776
0.000211846
0.000151668
0.000108499
0.00226763
0.0019847
0.00176375
0.00157851
0.00142465
0.00130015
0.0011904
0.0010868
0.000995701
0.000919727
0.000784966
0.000674894
0.000580034
0.000499209
0.000435268
0.00030493
0.000216279
0.000154994
0.000111177
0.00260096
0.00226008
0.00199241
0.00177382
0.00159289
0.00144201
0.0013111
0.00119402
0.00109125
0.0010023
0.000849942
0.000726204
0.000621803
0.000534447
0.000462588
0.000322778
0.000228664
0.000164006
0.000118335
Table S7. Brightness I/F per unit column density kg km-2. This is the same as Table
S6 except it is based on the small aggregate model of Gao et al. (2016). As in Table
S6, this table is a fit to ISS data from the 2006 eclipse mosaic (PIA08329).
0.338
0.451
0.568
0.65
0.938
1
0.907158
0.830796
0.694427
0.580758
0.262732
1.5
0.548577
0.575741
0.532152
0.467963
0.233973
2
0.293497
0.357947
0.374385
0.350942
0.19992
2.5
0.189884
0.240601
0.2673
0.261613
0.167028
3
0.132681
0.162964
0.186569
0.189316
0.135706
3.5
0.098767
0.119908
0.137973
0.14209
0.109943
4
0.0786551
0.0933133
0.104917
0.107859
0.0879944
4.5
0.0631043
0.0747433
0.0831148
0.0851461
0.0712859
5
0.0520326
0.062175
0.0682676
0.0691942
0.0579091
6
0.0359005
0.0446991
0.0489453
0.049048
0.0401174
7
0.025253
0.0333462
0.0371061
0.037093
0.0294995
8
0.0181113
0.0253301
0.029024
0.0291867
0.0228269
9
0.0134226
0.0194453
0.0231144
0.0235178
0.0183548
10
0.0104524
0.0150738
0.0185935
0.019232
0.0151674
11 0.00861325
0.0118497
0.0150586
0.0158647
0.0127792
12 0.00743816 0.00951103
0.0122668
0.0131656
0.0109157
13 0.00658729 0.00784873
0.0100629
0.0109734 0.00941273
14
15
16
17
18
19
20
22
24
26
28
30
35
40
45
50
0.00584988
0.0066893 0.00833942 0.00919038 0.00817397
0.0051274 0.00587876 0.00700597 0.00774105 0.00713239
0.00440159 0.00529136 0.00598729 0.00657288 0.00624474
0.00369925 0.00483233 0.00522027 0.00563852 0.00548291
0.00306033 0.00443406 0.00464243 0.00489957 0.00482458
0.00251589 0.00405717 0.00420751 0.00431969 0.00425369
0.00207952 0.00367991 0.00386901 0.00386863 0.00375949
0.0015014
0.0029238 0.00335559 0.00323897 0.00296122
0.00117702 0.00223003 0.00292068 0.00282719 0.00236976
0.000948337 0.00167653 0.00249089 0.00250941 0.00193961
0.000743132 0.00129002 0.00206459
0.0022167 0.00163105
0.000560747 0.00104071
0.0016698 0.00192404 0.00141118
0.000329917 0.00069237 0.000971756 0.00123832 0.00108432
0.000339778 0.000415843 0.00065603 0.000774277 0.000874243
0.000309558 0.00021979 0.000482308 0.000541559 0.000679651
0.000216451 0.000149366 0.000326394 0.000412524 0.000501182