1. Auroral Update UVIS Meeting Jan 2006

2. UVIS auroral tasks completed
Jupiter auroral papers (Ajello, Pryor et al.) out in Icarus
Saturn Auroral image, spectra in Esposito’s Science publication
Newer Saturn image in JPL press release (and CU alumni magazine)
Time-series campaign (GO WEST) manuscript is in rough draft form
Hubble/VIMS/UVIS campaign completed
VIMS reports first auroral images/spectra
Auroral talks at MOP and fall AGU by Pryor et al.
EUV/FUV auroral modeling presented at DPS by Jacques Gustin et al.
Latest image Dec looks ok

3. Upcoming tasks Future HST campaigns? - Cycle 15 due Jan 27
Cycle 15 runs July 2006 to June 2007
J. Clarke is proposing 50 HST orbit Saturn campaign near Feb 2007 (before opposition) (Overlaps with Saturn EUVFUV?)
Extended mission planning- add to WIKI
Can we coordinate better with VIMS? (are we riding along on their stuff, and vice versa?)
GO WEST paper to co-authors, then GRL
Jacques Gustin to visit Arizona in Feb. to learn more about UVIS spectra
Spring AGU poster- Lyman-alpha trends
My summer plans: auroral and heliosphere work at LASP with Ajello, Stewart, Esposito, Jouchoux, McClintock, etc.

4. Saturn’s Auroras from the Cassini Ultraviolet Imaging Spectrograph (UVIS) and Visual Infrared Mapping Spectrometer (VIMS)
Wayne Pryor
Kevin Baines
Pierre Drossart
Robert West
Joseph Ajello
Candice Hansen
Ian Stewart
Larry Esposito
Joshua Colwell
William McClintock
Alain Jouchoux
Don Shemansky
Janet Tew Hallett
Frank Crary
John Steinberg
William Kurth
John Clarke
Jacques Gustin
Denis Grodent
Jean-Claude Gerard
Emma Bunce
Presented at Fall AGU, 2005 ref # 1888 pin 3329

5. Saturn auroral emissions
UV aurora (N and S) observed by
Pioneer 11 (Judge et al. 1980)
Voyager UV spectrometer (Broadfoot et al, 1981)
IUE (Clarke et al. 1981)
HST/FOC (Gérard et al, 1995, Trauger et al, 1998)
HST/STIS (Cowley et al. 2004; Prangé et al, 2004)
Cassini/UVIS (Colwell et al., DPS 2005)
=> Auroral oval observed ~ 70-80dg latitude / variations morning-afternoon / correlation with Solar activity
Saturn Kilometric Radio emission
Voyager (Desch, 1982)
Infrared aurora
H3+ spectroscopic observations : (Geballe et al 1993, Stallard et al 1999) ~ 100 times lower than Jupiter

6. UVIS and VIMS are on the Cassini Orbiter

7. VIMS Instrument VIMS Visible channel: 0.35-1.03 mm 96 pixels
Infrared channel : mm
256 pixels –
16nm spectral width
3.5 mm)
Spatial resolution :
0.5mrad

8. CH4 and H3+ emissions from Cassini/VIMS Jupiter observations
Spectral image of 19 November 2000
Spectrum of South auroral zone
compared to synthetic pure H3+ spectrum
(Trot = 1000 K)

9. VIMS Saturn spectra: auroral vs
VIMS Saturn spectra: auroral vs. non-auroral (April 23, 2005, phase angle 40 deg., 1500 km/pixel)
H3+ (thermal)
Auroral
Non auroral
CH4
(fluorescence)
Wavelength (mm)
Wavelength (mm)

10. Processed H3+ Saturn images April 23, 2005 (phase angle 40 deg
Processed H3+ Saturn images April 23, 2005 (phase angle 40 deg., 1500 km/pixel)
Images at 3 wavelengths : 3.33, 3.53, 3.7 mm
H3+
emission
Composite
Solar reflected comp.
CH4 fluorescence

11. VIMS Conclusions Oval-like emission of H3+ observed April 23, 2005
Latitude ~78 degrees South (+/- 4 degrees):
comparable to previous UV emission (between degrees )
Absolute intensity : faint ! (< 0.1 Jupiter)
Intensity variations in H3+ along the oval
(No UVIS observations that day)

12. UVIS long-slit spectroscopy
EUV channel nm
FUV channel nm
64 spatial x 1024 spectral pixels
Spectral imaging is done
by spacecraft slews
Saturn’s emissions:
H Lyman-a and H2 bands
from auroras and dayglow.
Reflected sunlight spectrum:
Rayleigh scattering in H2
and acetylene absorption bands

13. UV Saturn image July 13, 2004
H Lyman-a
H2 bands

14. Saturn Auroral Spectrum

15. June 21 (Day 172), 2005 N-S-N UVIS scan Slit E-W
Auroral oval imaged twice
Images deconvolved
Blue H2, H emission
Orange reflected sunlight
Aurora changes over ~1 hour
Oval 70-75S

16. Polar Dark Spot (2005 day 172)
ratio 1st/2nd
wavelengths (A)
Spot in 1st image is gone at longer wavelengths (2nd image)
Localized small hydrocarbons? (spectrum is noisy)
Polar convergence & downwelling?

17. 50 day time-series moving away from Saturn near phase angle 90...

18. ^ shock ^ shock

19. Color Ratio Trend (1.16= no overlying hydrocarbons)

20. Hubble Auroral Campaign Feb 17, 2005
J. Clarke, J.-C. Gerard PI’s:
Day-side S auroras by HST ACS in UV (5 orbits)
Night-side N auroras by Cassini VIMS and UVIS
Cassini VIMS_003SA_THRCYLMAP001_UVIS_FOV
Started T23:08:00 GMT, ran 8 h 22 m
Cassini at ~800,000 km range
Aurora was weak that day

21. HST Campaign ACS Images: Feb 17, 2005
16:20-16:58
17:53-18:33
19:29-20:09
21:04-21:45
22:40-23:21

22. HST Campaign UVIS Geometry VIMS_003SA_THRCYLMAP001

23. UVIS dark-side spectrum color ratio 1.9

24. EUV aurora data (black) Model w/o self-absorption (dashed brown) Model fit (solid brown) for H2 = 5x1020 cm-2 & T=500K
Relative
Intensity
Wavelength (Ångstroms)

25. UVIS Saturn Conclusions
Saturn has extended H, O clouds Small polar dark spot (hydrocarbons?) near 1750 ± 75 Å Linked to IR polar warm spot? Polar auroras vary over ~1 hour time scale Auroral brightness varies by ~3 Daily-averaged auroral counts vary with SKR (RPWS) Auroras brighten after solar wind shocks ( MAG & CAPS) Auroras brightest during (and after) shock 2004 d :30 Auroral spectrum like Jupiter’s, with CH4 absorption Auroral color ratio ( Å/ Å) steady, near ~2.5±0.2 (1.9 in HST campaign) : ~15 keV primary electrons

27. Saturn’s 3.53 mm H3+ auroral emission Oval Latitude ~ 78 degrees
composite

28. References
Esposito, L. W., et al., The Cassini Ultraviolet Imaging Spectrograph Investigation. Space Sci. Reviews, 115, , 2004.
Esposito, L. W., et al., UVIS shows an active Saturnian system, Science, 307, , 2005.
Ajello, J. M., et al., The Cassini Campaign Observations of the Jupiter Aurora by the Ultraviolet Imaging Spectrograph and the Space Telescope Imaging Spectrograph, Icarus 178, , 2005.
Pryor, W. R., et al., Cassini UVIS Observations of Jupiter’s Auroral Variability, Icarus 178, , 2005.

29. Future Work Auroral time-dependence, longitude-dependence
Auroral studies from higher inclinations
High-latitude absorber studies (acetylene, haze, ?)
H cloud variability (source(s): rings + moons (Enceladus) + hot H from sunlit Saturn due to photoelectron impact on H2)
Comparison with Saturn atmosphere models

30. Upcoming UVIS Auroras 2004-196T06:26:00..UVIS_000SA_AURORAB001_PRIME
T02:21:00..UVIS_000SA_AURORAA002_PRIME
T16:16:00...UVIS_000SA_AURORAA003_PRIME
T07:41:00...UVIS_000SA_AURORAB002_PRIME
T00:33:00..UVIS_042SA_NAURMOV001_PRIME
T09:10:00..UVIS_045SA_NAURMOV001_PRIME
T23:31:00..UVIS_054SA_EUVFUV001_PRIME
T15:18:00..UVIS_055SA_NAURMOV001_PRIME
T05:36:00..UVIS_058SA_NAURMOV001_PRIME
T08:18:00..UVIS_065SA_NAURMOV001_PRIME
T06:30:00..UVIS_067SA_NAURMOV001_PRIME

31. Saturn EUVFUV’S 2005-087T07:46:00..UVIS_005SA_EUVFUV001_PRIME
T03:30:00..UVIS_010SA_EUVFUV003_PRIME (the oval pictures)
T01:00:00..UVIS_010SA_EUVFUV002_PRIME
T21:15:00..UVIS_011SA_EUVFUV002_PRIME
T05:50:00..UVIS_012SA_EUVFUV001_PRIME
T20:27:00..UVIS_016SA_EUVFUV001_PRIME
T17:48:00..UVIS_016SA_EUVFUV003_PRIME
T16:57:00..UVIS_019SA_EUVFUV004_PRIME
T13:13:00..UVIS_020SA_EUVFUV003_PRIME
T15:28:00..UVIS_020SA_EUVFUV004_PRIME
T10:36:00..UVIS_021SA_EUVFUV005_PRIME
T16:05:00..UVIS_022SA_EUVFUV003_PRIME
T07:49:00..UVIS_022SA_EUVFUV005_PRIME
T06:11:00..UVIS_024SA_EUVFUV005_PRIME
T20:41:00..UVIS_024SA_EUVFUV002_PRIME
T02:37:00..UVIS_025SA_EUVFUV002_PRIME
T01:06:00..UVIS_025SA_EUVFUV005_PRIME
T00:21:00..UVIS_026SA_EUVFUV007_PRIME
T23:56:00..UVIS_026SA_EUVFUV006_PRIME
T01:51:00..UVIS_027SA_EUVFUV003_PRIME
T01:36:00..UVIS_027SA_EUVFUV002_PRIME
T00:16:00..UVIS_027SA_EUVFUV006_PRIME
T18:27:00..UVIS_031SA_EUVFUV003_PRIME
T21:03:00..UVIS_032SA_EUVFUV003_PRIME

32. Saturn EUVFUV’s (2) 2007-034T12:10:00..UVIS_038SA_EUVFUV001_PRIME

33. Saturn Day 172, 2005
Limb-fitting puts auroral oval in S range

34. ISS south pole methane, uv3 images

35. HST campaign UVIS map projection
Red=aurora
Green=no aurora
Auroras ~75 N
Mostly UVIS slit was too far south, but…

36. UVIS auroral time-series as Cassini recedes from Saturn…

39. EUV, SKR, CAPS solar wind

40. Abstract
Cassini's Ultraviolet Imaging Spectrograph (UVIS) has completed a year of study of Saturn's atmosphere and auroras. Two long slit spectral channels are used to obtain EUV data from nm and FUV data from nm. 64 spatial pixels along each slit are combined with slit motion to build up spectral images of Saturn, with sufficient spatial resolution to reveal Saturn's auroral oval. Saturn images include evidence for rapid auroral variations and polar UV-dark regions mostly inside the auroral ovals. Absorption bands of acetylene are clearly seen in the reflected sunlight spectrum. The auroral emission spectrum is similar to that of Jupiter, showing H2 band emission and H Lyman-alpha emission. Saturn's auroral, dayglow, and nightglow spectra show significant differences. Saturn's aurora is observed to vary in brightness by at least a factor of four. The brightest auroral emissions seen so far occurred after 2004 day :30 when Cassini CAPS and MAG recorded passage of a solar wind shock. The enhanced auroral brightness persisted for days, and is seen at both poles of Saturn. Cassini RPWS observed enhanced auroral kilometric emissions during several auroral brightening events seen by UVIS. A campaign of Hubble Space Telescope UV imaging with ACS (Advanced Camera for Surveys) of Saturn's dayside southern auroral zone took place on 2005 February 17. Cassini UVIS and VIMS observed Saturn's nightside northern aurora during this period. The UVIS long slit was aligned with lines of latitude on Saturn, providing information about intensity and spectral variations along the auroral oval. Cassini VIMS has now obtained an initial H3+ image of Saturn’s auroral oval.

41. UVIS, RPWS and MAG trends

42. EUV, SKR, CAPS solar wind

43. Future VIMS observations
Wanted ! long integration time for VIMS (1sec or more) => implies saturation for some wavelengths
North Pole observations (night side)
Diurnal rotation sequence
Time sequence : search for temporal variations
Combination ground-based/Cassini observations required for temperature/column density/spatial distribution

44. VIMS at Saturn Saturn observations with VIMS at T0 CM_1465912440_1
Sequence of Saturn VIMS images from 1 to 5 mm

45. Images at 3.56 micron
Images of VIMS from the four different cubes 3 4
S/N < 10
some artifacts
due to imperfect dark
subtraction
Strongest contrast
in polar features
observed in #2 1 2

46. Mapping Saturn’s Aurora in the Near-Infrared with VIMS
First Maps of H3+ Achieved at 3.53 mm at South Pole
Requires Long VIMS exposures (1 second)
Require Sub-S/C Latitude Away from Equator

47. Sample Saturn Spectral Images EUV FUV

48. Saturn H Lyman-a

49. Saturn Oxygen image 130 nm (peaks ~2 Rayleighs, cloud has 1012 grams of O)

50. HST Campaign UVIS spatial images
-22:44
Time increases upwards
VIMS mosaic: repeated UVIS passes near oval
UV brightest at Feb 17, 18:45
VIMS:
Non-detection (they’ve seen auroras more recently!)
-18:45
-14:59
<-East-West->
EUV FUV

51. VIMS observations Sequence of observation S10 – 23 April 2005
(CIRS ride along observations)
List of observations and characteristics
Phase angle : ~40 degrees
Spatial resolution : ~1500 km/pixel
Number
Observation ID
Date/Time
CML/SSP 1
CM _3
2005/113_07:23:56
38.90 2
CM _1
2005/113_13:04:06
230.40 3
CM _8
2005/114_04:59:56
48.51 4
CM _8
2005/114_10:40:06
240.01

52. VIMS observations April 23, 2005 (phase angle 40 deg., 1500 km/pixel)
Image at 3.53 mm : strongest contrast in polar features Spectra limb/center
H3+