Cassini-Huygens is a mission to the Saturn system. It is a joint mission between NASA Jet Propulsion Laboratory (JPL), which built the Cassini Orbiter, and the European Space Agency (ESA), which built the Huygens Probe. The spacecraft was launched on 15 October 1997, Jupiter flyby was 30 December 2000 and Saturn orbit insertion was 1 July 2004. The Huygens Probe will enter Titan’s atmosphere on 14 January 2005. The Cassini orbiter is a three-axis stabilized spacecraft with 12 science instruments. Remote sensing instruments include cameras, spectrometers, radar and radio sensors. The fields and particles instruments take in-situ direct sensing measurements of the environment around the spacecraft measuring magnetic fields, neutral and charged particle composition, the composition of dust particles and the properties of plasma waves. Three radioisotope thermo-electric generators provide spacecraft power.
Cassini Orbiter science targets include Saturn and its rings, Titan (Saturn’s largest moon with a substantial atmosphere of N2, CH4, and other hydrocarbons and nitriles), the icy satellites, and the Saturnian magnetosphere. INMS measurements are possible in all of these regions.
During the 4-year tour, the Orbiter will make 75 orbits around Saturn and 45 flybys of Titan, changing from near equatorial to near-polar inclination.
INMS science
The normal INMS sensor is a quadruple mass spectrometer designed to measure in-situ low-density gas and positive ions in planetary upper atmospheres without pressure reduction.
INMS is mounted on the fields and particles platform of the Cassini Orbiter. It will make measurements in Titan’s upper atmosphere above 950 km, in the icy satellite environment and the inner magnetosphere of Saturn.
Heritage: Upper xmeasurement missions: Atmosphere Explorer, Dynamics Explorer and Pioneer Venus. Dual ion- source/gas-inlet design: Comet Rendezvous and Flyby mission and CONTOUR (Comet Nucleus Tour) missions.
Mission type: Saturn orbiter with flybys of Titan, its rings and several icy satellites.
NASA Goddard Space Flight Center
Task Manager, Hasso B. Niemann
Hasso.B.Niemann@nasa.gov
University of Michigan
Facility Team Leader
J. H. Waite, Jr.
T.
E. Cravens
University of Kansas
W.-H. Ip
National Central University
Chung-Li, Taiwan
W.
T. Kasprzak
NASA Goddard Space Flight Center
J.
G. Luhmann
University of California, Berkeley
R.
L. McNutt
Johns Hopkins University
R. V. Yelle
University of Arizona
V.
G. Anicich
NASA Jet Propulsion Labaoratory (NASA JPL)
References
Waite, Jr., J. H., W. S. Lewis, W. T. Kasprzak, V. G. Anicich, B. P. Block, T. E. Cravens, G. G. Fletcher, W.-H. Ip, J. G. Luhmann, R. L. McNutt, H. B. Niemann, R. L. Thorpe and R. V. Yelle, 2004: The Cassini Ion and Neutral Mass Spectrometer (INMS) investigation. Space Science Review, in press.
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objectives are to investigate:
1) The upper atmosphere of Titan, its ionization and its role as a source of neutral and ionized material for the Saturn magnetosphere
2) The environment of the rings
3) The interaction of the icy satellites and ring systems with the magnetosphere and possible gas injection into the magnetosphere
4) The effect of Titan’s interaction with the solar wind and magnetosphere plasma
5) The interaction of Titan’s atmosphere and exosphere with the surrounding plasma.
INMS was designed, constructed, tested and calibrated by NASA GSFC, Code 915. A Facility Science Team is performing operation and data analysis after spacecraft launch.
INMS Data Products
Titan upper atmosphere: neutral gas composition (H, H2, N, NH, N2, CH4, HCN, C2H2, C2H4 and C2H6)
- Ion composition (N2+/H2CN+, C2H5+, CH5+, CH3+, CH4+, CmHn+ (m=4,5)
- Icy satellite and ring composition (H, OH, O; H+, H2+, H3+, O+, OH+, H2O+, H3O+, O2+)
INMS Parameters
- Package Mass 10.29 kg (includes 1.4 kg tantalum radiation shield)
- Average Power: 23.3 W, neutral mode; 20.9 W ion mode; 13.1 W sleep
- Package Size: 20.3 cm (H) x 42.2 cm (L) x 36.5 cm (W)
- Data Rate: 1498 bps telemetry rate, 31.1 ms integration period, 34.0 ms total sample period
- Mass Range: 1-8, 12-99 Da
- Electron impact ion source energy: 70 eV, 25 eV
- Detectors: Two secondary electron multipliers operating in pulse-counting mode
- Closed Source: Spacecraft speed enhanced sampling of non-reactive neutral gases (e.g. N2, factor 50); neutral source density >5x104 cm3
- Open Source: Sampling of neutral gas, neutral radicals and ions with no surface interaction (e.g. N, H2CN+); neutral source density >2x105 cm3; ion flux >104 cm-2 sec-1
