HDAC Instrument – Cassini/Huygens Mission
UVIS Team – Meeting
LA - JPL, 8. January 2007
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Current development in HDAC staff
ƒ Meeting Berlin, Sept. 2006
ƒ Yuichi Ito is back home and has a position
ƒ JAMSS (Japan Manned Space Systems Corporation)
ƒ JAMSS handles the work of ISS (International Space
Station)
ƒ Pascal Hedelt (PhD-Student - Prof. Dr. Heike Rauer)
ƒ Andreas Luber (Student in the Computer Science
Department)
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC, 2007
ƒ Ito presentation
ƒ Hedelt approach
ƒ Reulke: Current results
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Current Status of HDAC study
(@20061226)
Yuichi ITO1*, Horst Uwe Keller1, Axel Korth1 , Ralf Reulke2
1 : Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau,
37191, Germany
2 : Deutsches Zentrum für Luft- und Raumfahrt, Institut für
Verkehrsforschung, Rutherfordstraße 2, 12489 Berlin, Germany
TEL: +49-5556-979-124, FAX: +49-5556-979-240
20061226
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Major progress (after December)
(BEFORE) Use H cell-on data only (Regard Deuterium intensity as 0. )
(AFTER) Use H cell-on & H+D cell-on both data. Modified to fit to the both line
profiles. (Merit:We can retrieve D/H intensity ratio and line profiles
simultaneously.)
（Important point）
(1)
line profile decreases with the distance from the line center. (In principle, the line
profile must be a center-collective)
(2)
Expected optical depth of the Deuterium corona is ~ 0.1-1 (As H optical depth is
~ 1000). D-Ly-A is not negligible.
(3)
Expected Lyman-A intensity is ~ 150 [R] from empirical Lyman-A intensity of the
terrestrial planets(Earth,Venus, Mars)
(4)
The line profile of the D Ly-A is not same with that of the H Ly-A.
Î If both profile is same, the both modulation patterns are same what ratio of
the D/H Ly-A intensity is.
Î Therefore, T9 data can not be fit by H-Data only as shown in next figure.
D Ly-A must be different shape from that of H Ly-A profile.
Or it implies the existence of additional background.
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Fitting of the retrieved profile by H to H+D cell on modulation.
H fits
H+D
does not fit
Figure 1. Data analysis only by Hydrogen profile
Without Deuterium line profile, it can fit to T9 modulation data (H-cell ON). However, the retrieved
hydrogen Ly-A profile does not fit to the modulation pattern (H cell +D cell ON ). It suggests a
Deuterium intensity is not negligible and Deuterium Ly-A profile is different from
Hydrogen.(possibly the width of the line profile.)
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Monte Carlo approach
Direct Line profile retrieval method did not work.
(Mathematically strict) Î Negative profile
How can we produce only positive profiles?
MonteCarlo approach
Concept:
ƒ
Assume the line profile by the series of cosine functions. (use orthogonal
functions for the kernels ÎTo give the retrieved line profile flexibility.)
ƒ
Generating thousands of positive line profiles, then fit to T9 modulation pattern.
Only choose the line profile which satisfied the conditions. Statistically conclude
answer.
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Analysis
results
Assumed modulation(H,H+D)
T9 observation
X^2 < 0.001
S.D < 0.316
Comment1. Simulated line profiles agree not only with the T9 modulation
but also with the assumed modulation at outside.
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
H LyA line profile
ÎRetrieved profiles need to
fill additional light at outside
the HDAC scanned region.
(as T9 modulation is quite small)
D Ly-A line profile
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Conclusions:
(1) Line profile retrieval:
(2) D/H intensity ratio:
Use the cosine series for the kernels.(up to 4th)
H Ly-A: D Ly-A = 290[R] : 93[R]
（
+- 36[R]
)
(# integrating all the wings.)
(3) Background :
T9 modulation is quite small.(H-cell ~ 93% at the
closest app. H+D cell-on ~ 80% at the closest app.) To explain the small
modulation, Solutions require the space to fill the additional light at outside
the scanned region. Otherwise we must transact this light as additional
background.
(4) As to line profile's shape:
If the line profile's shape is 1-head centercollective, the wing must spread to far position. But the maximum Doppler
shift at T9 is 5km/sec, we can not solve the line profile shape over
5km/sec.We need sophisticated radiative transfer calculation to fix the windend position.
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Pascal Hedelt: Modelling H Lyman
Alpha on Titan
ƒ
ƒ
ƒ
ƒ
ƒ
Using MonteCarlo Method
Multiple Scattering
Resonance Scattering
Frequency redistribution
3D model
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Near Future Prospects
ƒ Use Ito’s Monte Carlo program
ƒ Improving models
ƒ Improving code
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Future Prospects
ƒ Calculating H LyA spectrum for HDAC FOV during T9
encounter
ƒ Calculating H+D LyA spectrum
ƒ Taking into account background sources
– LISM
– Jupiter LyA
– ???
ƒ Calculating spectra for different sources
ƒ Calculating D/H ratios
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Results, Meeting Berlin, Sept. 2006
T9 - Evaluation
ƒ L. Esposito, B. McClintock, U. Keller, Yuichi Ito, P. Heldelt, R. Reulke
ƒ Influence of ISM up to 80%
ƒ Need a better RT-model
ƒ ISM contribution for fly-by data as a function of pointing & photometry
ƒ Influence of the cell temperature
ƒ Additional Saturn modulation measurement, near equator, near
periapse
ƒ Titan: 250 R on day site, 110 R on night site
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Results, Meeting Berlin, Sept. 2006
ƒ Analysed the variance / mean value – relation
ƒ μ … mean of measured counts
2
σ
=1
ƒ σ2 … variance of the signal
μ
ƒ Variance ≈ mean
ƒ Valid for UVIS, but not for HDAC
ƒ Roll-over?
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC Status 2007:
- 2400 data sets in 2006
- HDAC run in photometer mode
- Sensitivity keeps constant
- One modulation measurement
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
Problems
ƒ HDAC sensitivity change
ƒ Hot-Model evaluation
ƒ Sun activity changes
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
ƒ Analysed data from IPHSURVEY sequences
ƒ Data, which are constant within the sequence (e.g. left
data set)
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
ƒ
ƒ
ƒ
ƒ
Analysed the variance / mean value – relation
n … number of incoming photons
m … measured counts
⟨ m⟩ = μ ⋅ ⟨ n⟩
µ … “Sensitivity”
2
σM
2
2
2
2
= ⟨ ( m – ⟨ m⟩ ) ⟩ = μ ⋅ ⟨ ( n – ⟨ n ⟩ ) ⟩ = μ ⋅
2
σM
2
2
σN
2
σN
μ ⋅
--------- = ----------------- = μ
⟨ m⟩
μ ⋅ ⟨ n⟩
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
ƒ HDAC-sensitivity - Comparison with calibrated FUV-Data
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
ƒ HDAC-sensitivity - Comparison with [variance / mean]
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
HDAC-sensitivity 2006: ∼30 cts/s/R
(IPH – Survey data)
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
HDAC sensitivity change
HDAC-sensitivity 2006: ∼30 cts/s/R
(all data)
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
Hot-Model “fit”
ƒ Hot-Model follows HDAC signal change as a function of
S/C - position and view direction
ƒ Problem: Unknown absolute Ly-a radiation, which also
depends from Sun periodic changes (e.g. the 11 year &
27 day cycles)
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
HDAC long-term Evaluation
ƒ Varying
solar flux
ƒ Model-factor = 0.01 (2002-2006)
Solar flux →
http://www.ngdc.noaa.gov/stp/SOLAR/FLUX/flux.html
http://www.drao-ofr.hia-iha.nrc-cnrc.gc.ca/icarus/www/sol_home.shtml
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Analysis of single time series
ƒ Problem: Stars & roll over
ƒ Calibration information as described before
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Analysis of single time series
Stars & roll over
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Analysis of single time series
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Long term evaluation of HDAC
signal
ƒ S/C spinning data
ƒ Correction of the sensitivity change of HDAC
ƒ Correction of variable Solar flux
ƒ Black – measurement
ƒ Red – model data with constant Hot-Model factor
ƒ Green - model data with adjusted Hot-Model factor
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Long term evaluation of HDAC
signal
ƒ Signal dynamics is less than expected
ƒ Measured shape is more sophisticated, than model data
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
ƒ
Long term evaluation of HDAC
signal
Constant Hot-Model factor was
determined from IPH – Survey data (red)
ƒ Adjusted Hot-Model factor is equivalent to the constant factor with a
standard deviation of or 5 %, no trend
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Long term evaluation of HDAC
signal
ƒ Constant Hot-Model factor was determined from IPH –
Survey data (red)
2005
ƒ Adjusted Hot-Model factor is equivalent to the constant
factor
ƒ mean - 10.8d-3, standard deviation - 0.5d-3
2006
ƒ mean - 11.3d-3, standard deviation - 0. 4d-3
2004
ƒ mean – 9.3d-3, standard deviation - 0.3d-3
UVIS Science Team Meeting
11 January 2007
HDAC Instrument – Cassini/Huygens Mission
Generation of Ly-a map of the
Saturnian system
ƒ [red, green, blue] = [2004, 2005, 2006]
UVIS Science Team Meeting
11 January 2007
Lat-Lon
Complete coverage takes 30 / 4
years
HDAC Instrument – Cassini/Huygens Mission
UVIS Science Team Meeting
11 January 2007