Cassini project in Oulu
email@example.com - last update: 20 September 2006 (RR & JV)
In Finnish - suomenkielinen sivu
NASA satellite CASSINI was launched towards Saturn on
15 October 1997. Cassini arrived to Saturn in summer 2004 and it had an
orbital insertion on the 1st of July. Cassini will provide information about the Saturn's
magnetosphere, its satellites (especially
Titan) and the ring system
during the four year official mission. There are also plans for the two
year extension of the mission. Titan will be
passed several times from the very close distance during the mission
as well as the numerous icy satellites of the Saturnian system. The
Meteorological Institute (FMI) has simulated the Titan plasma
environment. These simulations will be used when CAPS Titan flyby data
is analysed. Also solar wind
plasma will be studied at the distance of Saturn while the satellites
travel in the solar wind at the far distance from Saturn. Oulu has a
co-Investigator status in the CAPS (Cassini Plasma Spectrometer) plasma
The group has simulated numerically the ion beam
spectrometer (IBS) behaviour in order to optimise its properties. The
other parts of the CAPS instruments
are IMS (ion mass spectrometer) and ELS (electron spectrometer), as
shown in the figure below (DPU=Data Processing Unit and ACT = Actuator;
click for better resolution).
The IBS instrument is a hemispherical electrostatic analyzer with three fan-shaped
entrance windows for incoming ions. The angular field of view for each
entrance window is 1.5°×150°. Thus angular resolution of the IBS
instrument is 1.5°×1.5°. Channel electron multipliers (CEM) are used as
detectors. Our simulations shows the energy resolution of the IBS to be 1.4 +- 0.2 %. The
deviation comes from minor manufacturing faults: an indentation in the inner hemisphere as
well as the misalignment of the hemispheres. The IMS consists of a
toroidal electrostatic analyser with following linear electric field
time of flight analyser. The ELS is a top hat electrostatic analyser.
The IMS and ELS consist of eight separate detectors in 20 sectors.
The IMS angular resolution for each detector is 11°×20° and the ELS
angular resolution for each detector is 5°×20°. The energy
resolution of the ELS is 17%. The energy resolution of the IMS is also
17% and the mass resolution (M/dM) is 80 for particles with energy
less than 16 keV/q and 8 for particles with energy more than 16
Cassini related papers of the Oulu group
- Vilppola, J. H., J. T.Keisala, P. J. Tanskanen and H.
Huomo, Optimization of hemispherical electrostatic
analyzer manufacturing with respect to resolution requirements, Rev.Sci.Instrum.,
64, 2190, 1993.
- Vilppola, J. H., P. J. Tanskanen, H. Huomo and B.L.
Barraclough, Simulations of the Response Function of a Plasma
Ion Beam Spectrometer for the Cassini Mission to Saturn, Rev.Sci.Instrum., 67,
- Vilppola J. H., P. J. Tanskanen and B. L.
Barraclough, Simulation of a spherical section electrostatic
analyzer, in Magnetospheric research with advanced techniques ed. by
R. L. Xu and A. T.Y. Lui of COSPAR Colloquium, April 1996, Beijing,
China. ISBN 0-08-043330-8, Elsevier Science Ltd, July 1998.
- Vilppola, J. H., P. J. Tanskanen, B.L. Barraclough
and D. J. McComas, Comparison
between simulations and calibrations of a high resolution
electrostatic analyser, Rev.Sci.Instrum., 72,
- Vilppola, J. H., PhD-thesis:
"Solar wind: detection methods and long term
- D.T. Young, J.J. Berthelier, M. Blanc, J.L. Burch, A.J. Coates, R.
Goldstein, M. Grande, T.W. Hill, R.E. Johnson, V. Kelha, D.J. McComas,
E.C. Sittler, K.R. Svenes, K. Szego, P. Tanskanen, K. Ahola, D.
Anderson, S. Bakshi, R.A. Baragiola, B.L. Barraclough, R.K. Black, S.
Bolton, T. Booker, R. Bowman, P. Casey, F.J. Cr ary, D. Delapp , G.
Dirks, N. Eaker, H. Funsten, J.D. Furman , J.T. Gosling, H. Hannu la,
C. Holmlund, H. Huomo, J.M. Illiano, P. Jensen, M.A. Johnson, D.R.
Linder, T. Lu ntama, S. Maurice, K. P. McCabe, K. Mursula, B.T.
Narheim, J.E. Nordholt, A. Preece, J. Rudzki, A. Ruitberg, K. Smith,
S. Szalai, M.F. Thomsen, K. Viherkanto, J. Vilppola, T. V ollmer, T.E.
Wahl, M. West, T. Ylikorpi, C. Zinsmeyer,
Cassini Plasma Spectrometer Investigation, Space Science Reviews,
114, pages 1-112, 2004.
- D.T. Young, J.J. Berthelier, M. Blanc, J.L. Burch, S. Bolton, A.J. Coates,
F. Crary, R.
Goldstein, M. Grande, T.W. Hill, R.E. Johnson, R.A. Baragiola, V. Kelha, D.J. McComas,
E.C. Sittler, K.R. Svenes, K. Szego, P. Tanskanen, M.F. Thomsen,
S.Bakashi, B.L. Barraclough, Z. Bebesi, D. Delapp, M.W. Dunlop, J.T.
Gosling, J.D. Furman, L.K. Gilbert, D. Glenn,
C. Holmlund, J.-M. Illinao, G.R. Lewis, D.R.
Linder, S. Maurice, H.J. McAndrews, B.T.
Narheim, E. Pallier, D. Reisenfeld, A.M. Rymer, H.T. Smith, R.L.
Tokar, J. Vilppola, C. Zinsmeyer,
Composition and Dynamics of Plasma in Saturn's Magnetosphere, Science,
Vol. 307, Page 1262, 25th February 2005.
- K. Szego, Z. Bebesi, G. Erdos, L. Foldy, F. Crary, D. J. McComas,
D. T. Young, S. Bolton, A. Coates, A. Rymer, J. J. Bethelier, R. E.
Hartle, E. C. Sittler, D. Reisenfeld, R. E. Johnson, H. T. Smith, T.
W. Hill, J. Vippola, J. Steinberg, N. Andre,
The global plasma environment of Titan as observed by Cassini Plasma
Spectrometer during the first two close encounters with Titan,
Geophys. Res. Lett., Vol. 32, No. 20, L20S05, 2005
- I. Sillanpää, E. Kallio, P. Janhunen, W. Schmidt, K. Mursula,
J. Vilppola, P. Tanskanen, Hybrid simulation study of ion escape at Titan
for different orbital positions, Advances in Space Research, Available online
since 13th of February 2006.
- R. E. Hartle, E. C. Sittler Jr., F. M. Neubauer, R. E. Johnson,
H. T. Smith, F. Crary, D. J. McComas, D. T. Young, A. J. Coates,
D. Simpson, S. Bolton, D. Reisenfeld, K. Szego, J. J. Bethelier,
A. Rymer, J. Vippola, J. T. Steinberg, N. Andre,
Preliminary interpretation of Titan plasma interaction as observed by
the Cassini Plasma Spectrometer: Comparisons with Voyager 1,
Geophys. Res. Lett., Vol. 33, No. 8, L08201, 20 April 2006
In Finnish - suomenkielinen sivu