Final results of HDAC analysis P. Hedelt(1), Y. Ito(2,3), H. U. Keller(2), R. Reulke(3), P. Wurz(4), H. Lammer(5), H. Rauer(1,6), L. Esposito(7) Institut für Planetenforschung, Deutsches Zentrum für Luft- und Raumfahrt (DLR) Max Planck Institut für Sonnensystemforschung (MPS) Japan Manned Space Systems Corporation, Tsukuba, Japan Institut für Verkehrsforschung, Deutsches Zentrum für Luft- und Raumfahrt (DLR) Abteilung für Weltraumforschung und Planetologie, Universität Bern Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften Zentrum für Astronomie und Astrophysik, Technische Universität Berlin (TUB) Laboratory for Atmospheric and Space Physics, University of Colorado

HDAC T9 measurement UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 2 2 2 2 2 2 2

Difference signal UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 3 3 3 3 3 3 3 3

Radiative transfer modeling Parameter variation: Exosphere atomic hydrogen distribution: Chamberlain model (Chamberlain, 1963) Particle Monte Carlo model (Wurz & Lammer, 2003) Exobase hydrogen density Exospheric temperature  Fit to data UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 4 4 4 4 4 4 4 4 4

Exospheric densities Particle model H Chamberlain model CH4 UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 5 5 5 5 5 5 5 5 5

Density Variation Exobase densities in the literature nH = 4.2x103 cm-3 (Yung, 1984 - model) nH = 8.0x103 cm-3 (Toublanc, 1995 - model) nH = 1.0x104 cm-3 (Broadfoot, et al. 1981 - data) nH = 4.6x104 cm-3 (Garnier, et al. 2007 - model) nH = 7.0x104 cm-3 (Krasnopolsky, et al. 2009 - model) nH = 8.0x104 cm-3 (De la Haye, et al., 2007 - model) UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 6 6 6 6 6 6 6 6 6 6 6

Density Variation Chamberlain Model UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 7 7 7 7 7 7 7 7 7 7 7

Density Variation Particle Model UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 8 8 8 8 8 8 8 8 8 8 8

Difference signal during c/a Particle model Chamberlain model UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 9 9 9 9 9 9 9 9 9 9

Difference signal during ingress Chamberlain model Particle model UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 10 10 10 10 10 10 10 10 10 10

Temperature Variation Exosphere temperatures in the literature: De la Haye et al. (2008): 152.8 ± 4.6 K (TA) 149.0 ± 9.2 K (TB) 157.4 ± 4.8 (T5) UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting 2009 Pascal Hedelt 11 11 11 11 11 11 11 11 11 11 11 11

Temperature Variation Exobase H density: 8x104 cm-3, Particle model profile UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 12 12 12 12 12 12 12 12 12 12 12 12

Fit to data Best fitting density distribution using least squares fit: Particle model: Exobase H density nH=9x104 cm-3 Chamberlain model: Exobase density nH=2x104 cm-3 UVIS Team Meeting 2009 Pascal Hedelt 13 13 13 13 13 13 13 13 13 13 13 13 13

Fit to data: Chamberlain model UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting 2009 Pascal Hedelt 14 14 14 14 14 14

Fit to data: Particle model UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting 2009 Pascal Hedelt 15 15 15 15 15 15

Best fitting H profile Particle model Chamberlain model UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 16 16 16 16 16 16

Comparison with measurement UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 17 17 17 17 17 17

Comparison with measurement: Removing the background UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 18 18 18 18 18 18

Summary & Conclusion Using HDAC data we are able to determine atomic Good agreement between model and data Exospheric temperature has no influence  Best fit using Chamberlain model: nH,Exobase= 2.0x104 cm-3 validated for Earth only, static model  Best fit using Particle MC model: nH,Exobase= 9.0x104 cm-3 validated for Mercury & Mars, dynamic model From latest calculations (De la Haye, et al. 2007): nH,Exobase= 8.0x104 cm-3  Good agreement with Particle model distribution Background signal in HDAC data: about 12,000 cts (430 R) Titan Lyman α dayside brightness: 179±10 R (Ajello, et al. 2008: 208 R) nightside brightness: 50±4 R (Ajello, et al. 2008: 80 R) Using HDAC data we are able to determine atomic hydrogen distribution in Titan’s exosphere!!! UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting 2009 Pascal Hedelt 19

Outlook: T66 & T67 UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 20 20

Outlook: T66 & T67 UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 21 21

Thanks for your attention! UVIS Team Meeting 2009 Pascal Hedelt

Aims & Scope Using HDAC data gathered during T9, the distribution of atomic hydrogen in Titans exosphere is investigated: Calculate exospheric emission of resonantly scattered Hydrogen Ly-Alpha from Titan Simulate HDAC measurement during the Cassini/Titan T9 encounter Little is known about Titan‘s hydrogen exosphere Vary input parameters Determine exospheric parameters UVIS Team Meeting 2009 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt 24 24 24 24 24 24 24

Radiative transfer model (1) Apply Monte Carlo to solve RTE: 40,000,000 photons started at sunlit side of upper exosphere layer Scattered by H (isotropically) Absorbed by CH4 Trace until: Absorbed by methane Reach model boundaries Store scattering positions + WL + Directions

Radiative transfer model (2) Simulate T9 flyby: Apply „splitting“ technique: Photons are emitted in direction of detector Calculate transmission to detector Apply HDAC absorption pattern

Density model description Chamberlain model Maxwellian velocity distribution at exobase Use Liouville theorem to derive exospheric densities Static contribution of ballistic/escaping orbits Particle MC model Dynamic MC approach, single particles started at exobase with random energy & ejection angle UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting, Boulder, Colorado 2008/06/22-24 Pascal Hedelt UVIS Team Meeting 2009 Pascal Hedelt 27 27 27 27 27 27 27 27 27 27