Jost, K

Aerospace Engineering. Vol. 24, no. 7, pp. 16-19. Aug. 2004

On June 30, Cassini-Huygens mission flight controllers confirmed that the engine burn needed to place the spacecraft into the correct orbit around Saturn had been successfully completed, beginning a four-year study of the planet along with its rings and 31 known moons. This is a tribute to the team at NASA and our partners at the European Space Agency (ESA), and the Italian Space Agency (Agenzia Spaziale Italiana) to accomplish this feat taking place 934 million miles away from Earth," said Ed Weiler, Associate Administrator for Space Science at NASA Headquarters in Washington.

Malik, T

Space News. Vol. 15, no. 25, pp. 18. 21 June 2004

As the Cassini-Huygens mission pushes ever closer toward Saturn, project scientists are eager to begin what they expect to be an eye-opening look at the ringed planet and its environment. During its planned four-year mission, Cassini is expected to give astronomers their closeest glimpse of the Saturn's rings, probe the gas giant's interior and magnetosphere, as well as swing by no less than seven of the 31 known moons circling the planet.

Dornheim, M A

Aviation Week & Space Technology. Vol. 160, no. 25, pp. 56-58,60,62. 21 June 2004

Next week a rocket engine should fire for 96 min. on the Cassini/Huygens spacecraft, capturing it into orbit around Saturn to start a four-year tour of the planet, its rings, moons and magnetosphere. With a nearly 3-hr. round-trip light time, officials can do little but sit back and watch the most critical maneuver of the $3.3-billion mission. The outlook is good. The spacecraft is generally in excellent health, controllers have been drilling in real-time exercises at the Jet Propulsion Laboratory (JPL) here, and a trajectory correction maneuver on May 27 was a successful mini-rehearsal of the orbit injection firing.

Deutsch, L J

2002 IEEE Aerospace Conference Proceedings - Volume 3, Big Sky, MT; 9-16 Mar. 2002. pp. 3-1295 to 3-1302. 2002

NASA's Cassini mission to Saturn carries the European Space Agency's (ESA's) Huygens probe, which it will release shortly before an encounter with Saturn's moon, Titan, a possible location for extraterrestrial life within our Solar System. As it parachutes towards Titan's surface, Huygens will acquire scientific information that will be relayed to Earth through Cassini. Comprehensive testing of this relay radio link was not performed prior to Cassini launch and cannot be done during cruise. A test using NASA's Deep Space Network (DSN) to mimic the probe's signal was performed in 2000 and uncovered an anomaly that, unchecked, would result in nearly complete loss of the Huygens mission. An international team of experts from NASA and ESA was assembled to solve this problem: the Huygens Recovery Task Force (HRTF.) This team, cochaired by the author, performed extensive testing, modeling, and simulation to understand the failure mechanism. Each Huygens science team determined mission impacts for various scenarios based on these results. This led to a suggested modification to the Cassini trajectory that will result in nearly complete data return for Huygens with minimal impact on Cassini. (Author)

Castillo, J; Rappaport, N; Mocquet, A; Sotin, C

Lunar and Planetary Science XXXIII, Houston, TX, Mar.11-15,2002, Houston, TX, Lunar and Planetary Institute, 2002

The authors examine which aspects of Titan's internal structure will be derived from gravity potential measurements by Cassini-Huygens. For that purpose, dynamic Love numbers are computed for various models of the satellite. (Author)

Lunine, J I; Soderblom, L A

Space Science Reviews. Vol. 104, no. 1-4, pp. 191-208. 2002

The Saturnian system contains 18 known satellites ranging from 10 km to 2575 km in radius. In bulk properties and surface appearance these objects show less regularity than the sparser Jupiter system. The Galilean-sized moon Titan sports a dense atmosphere of nitrogen and methane which renders surface observations difficult, but also makes this moon intriguing from the standpoints of climate change and exobiology. The Cassini-Huygens mission will make extensive observations of the satellites over a range of wavelengths, as well as using in situ sampling of satellite environments (and in the case of Titan, sampling of atmosphere and surface). The goals of these extensive investigations are to understand the bulk properties of the satellites, their surface compositions and evolution through time, as well as interactions with the magnetosphere and rings of Saturn. This knowledge in turn should provide a deeper understanding of the origin of the Saturnian system as a whole and the underlying causes for the distinctive differences from the Jovian satellite system. (Author)

Matson, D L; Spilker, L J; Lebreton, J P

Space Science Reviews. Vol. 104, no. 1-4, pp. 1-58. 2002

The international Cassini/Huygens mission consists of the Cassini Saturn Orbiter spacecraft and the Huygens Titan Probe that is targeted for entry into the atmosphere of Saturn's largest moon, Titan. From launch on October 15, 1997, to arrival at Saturn in July 2004, Cassini/Huygens will travel over three billion kilometers. Once in orbit about Saturn, Huygens is released from the orbiter and enters Titan's atmosphere. The Probe descends by parachute and measures the properties of the atmosphere. If the landing is gentle, the properties of the surface will be measured too. Then the orbiter commences a four-year tour of the Saturnian system with 45 flybys of Titan and multiple encounters with the icy moons. The rings, the magnetosphere and Saturn itself are all studied as well as the interactions among them. (Author)

Blanc, M; Bolton, S; Bradley, J; Burton, M; Cravens, T E; Dandouras, I; Dougherty, M K; Festou, M C; Feynman, J; Johnson, R E

Space Science Reviews (0038-6308), vol. 104, no. 1-4, p. 253-346

Magnetospheric and plasma science studies at Saturn offer a unique opportunity to explore in-depth two types of magnetospheres. These are an 'induced' magnetosphere generated by the interaction of Titan with the surrounding plasma flow and Saturn's 'intrinsic' magnetosphere, the magnetic cavity Saturn's planetary magnetic field creates inside the solar wind flow. These two objects will be explored using the most advanced and diverse package of instruments for the analysis of plasmas, energetic particles and fields ever flown to a planet. These instruments will make it possible to address and solve a series of key scientific questions concerning the interaction of these two magnetospheres with their environment. The flow of magnetospheric plasma around the obstacle, caused by Titan's atmosphere/ionosphere, produces an elongated cavity and wake, which we call an 'induced magnetosphere'. The Mach number characteristics of this interaction make it unique in the solar system. We first describe Titan's ionosphere, which is the obstacle to the external plasma flow. We then study Titan's induced magnetosphere, its structure, dynamics and variability, and discuss the possible existence of a small intrinsic magnetic field of Titan. Saturn's magnetosphere, which is dynamically and chemically coupled to all other components of Saturn's environment in addition to Titan, is then described. We start with a summary of the morphology of magnetospheric plasma and fields. Then we discuss what we know of the magnetospheric interactions in each region. Beginning with the innermost regions and moving outwards, we first describe the region of the main rings and their connection to the low-latitude ionosphere. Finally, we show how the unique characteristics of the CASSINI spacecraft, instruments and mission profile make it possible to address, and hopefully solve, many of these questions. (Author)

Molina-Cuberos, G J; Lopez-Moreno, J J; Rodrigo, R; Schwingenschuh, K

Advances in Space Research. Vol. 28, no. 10, pp. 1511-1516. Nov. 2001

The penetration of the Huygens probe through the atmosphere of Titan in 2004 will provide a unique opportunity to measure the electrical properties of its lower atmosphere. Many studies have been carried out to predict the density of electrons and the distribution of the major positive ions, but there is no recent analysis concerning the electrical conductivity that will be measured by Huygens. In this paper we present predictions of negative and positive conductivity by using the present models of the lower ionosphere. The predicted conductivity is delimited between a minimum and a maximum profile and compared with the capability of the PWA-HASI instrument on board Huygens to measure it. Special attention is paid to the influence of electrophilic species on the conductivity and on the decrease of the negative conductivity depending on the concentration of electrophilic species. We present an analytic expression to calculate the concentration of electrophilic species, if any, depending on the measurements of positive and negative conductivity that will measure PWA-HASI. (Author)

Raulin, F; Coll, P; Navarro-Gonzalez, R; Ramirez, S; Benilan, Y; Shindo, F; Vuitton, V; Gazeau, M C

6th Trieste Conference on Chemical Evolution, Proceedings, Trieste, Italy; 18-22 Sept. 2000. pp. 307-314. 2001

In the solar system, one can consider two classes of extraterrestrial bodies of prime interest for Exobiology. These are planetary bodies where (extinct or extent) life may be present, such as Mars and Europa, and bodies where a complex organic chemistry is taking place. Titan, Saturn's largest satellite is probably, with the comets, one of the most exobiologically interesting bodies of this second kind. Titan is the only satellite in the Solar system having a dense atmosphere and a surface not visible (due to the presence of atmospheric hazes and aerosol layers). In spite of noticeable differences (specially in size and temperature ranges), several similarities between the environments of Titan and of the primitive Earth can be pointed out. Both have a dense N2 atmosphere with the presence of greenhouse gases and anti-greenhouse species inducing analogous temperature vertical profiles, with a troposphere and a stratosphere. Titan's atmosphere also includes a noticeable fraction of methane (up to a few percent), with a low molecular hydrogen mole fraction. The atmospheric chemistry of methane, coupled to that of nitrogen allows the formation of many organics in the atmosphere, making Titan's environment very rich in organics, in both gas and condensed phases. In addition, the presence of such concentrations of methane in the atmosphere suggests the presence of a methane reservoir on the surface, which could be lakes, small seas or subsurface oceans of methane and ethane, the main product of methane photochemistry. In the present paper, we will mainly consider some new data related to Titan's organic chemistry in its atmospheric environment and briefly discuss their implications for the future exploration of Titan, through the Cassini-Huygens mission. (Author)

Taverna, M A; Smith, B A

Aviation Week & Space Technology. Vol. 155, no. 2, pp. 33-4. 9 July 2001

A European Space Agency/NASA task force has identified a new scenario for the Cassini-Huygens mission to Saturn and its big moon Titan that is expected to solve the telemetry problem on the Huygens probe and allow it and the Cassini orbiter to return close to 100%, if not all, of expected scientific data. The problem was caused by a design flaw on the Huygens receiver mounted on Cassini that limits the bandwidth needed to handle the Doppler shift as the probe enters Titan's atmosphere. Thus the receiver would be unable to compensate for the frequency shift between the signal emitted by the probe and the 1 received by the orbiter, causing a loss of a good deal of critical probe data during the descent. The solution is to reshuffle Cassini's initial orbital schedule around Saturn, adding a third orbit to provide new flyby geometry for the orbiter. Changes to the Juygens telemetry system are also envisioned. (Abstract quotes from original text)

Israel, G; Cabane, M; Coll, P; Socsia, D; Raulin, F; Niemann, H

Advances in Space Research. Vol. 23, no. 2, pp. 319-331. Jan. 1999

Some exobiological aspects of Titan that are known from observations, theoretical modeling, and simulation experiments in the laboratory are presented. The Aerosol Collector Pyrolyzer (ACP) instrument of the Huygens Probe is then described, and some examples of the expected results for the scientific experiment are discussed. (AIAA)

Raulin, F; Coll, P; Gazeau, M C; Sternberg, R; Bruston, P; Coscia, D; Israel, G; Gautier, D

Advances in Space Research. Vol. 22, no. 3, pp. 353-362. 1998

The current knowledge of Titan, the largest satellite of Saturn, is reviewed from the standpoint of exobiology using observational data, results of theoretical modeling, and simulation experiments in the laboratory. An overview is then presented of the instruments in the scientific payload of the Cassini-Huygens mission that should provide scientific data of exobiological interest. Some examples of the expected results from such experiments are presented. (AIAA)

CHILDRESS, JO

Geotimes, vol. 42, no. 12, pp. 7-8, December, 1997

At two stories high and carrying 6 tons of hardware, fuel, and scientific instruments, the Cassini mission is probably the last of NASA's huge-scale operations that have dominated the last 30 years. Seven years from now, Cassini will reach Saturn and orbit the planet some 60 times, carrying out 27 different investigations of Saturn, its moons, and its satellites. Cassini's arrival at Saturn has been timed so that the planet's rings are optimally illuminated by the sun. This satellite, named in honor of the French-Italian astronomer, Jean Dominique Cassini, will be capable of viewing Saturn's small moonlets inside its rings. It will also investigate the particles that make up the rings, their dynamics, and the effects of magnetic field interaction on them. Three hundred thousand color images are expected to be returned to Earth from Cassini. Cassini carries the Cosmic Dust Analyzer (with accompanying High-Rate Detector) (HRD), the Magnetosphere Imaging Instrument (MIMI), an ion beam spectrometer, and an ion mass spectrometer. Saturn's several moons will be studied via close flybys. Titan, the largest, will receive the mission's closest attention, with 45 flybys. Four months into the mission, Cassini will deploy the Huygens probe that will descend through the thick, brownish-orange atmosphere of Titan to learn more about the dark and light terrain seen by the Hubble Space Telescope and whether that terrain does in fact represent lakes and seas that may lie beneath solid ice or rock, as the Hubble images suggest. Cassini's mission is scheduled to end in 2008, although nothing precludes NASA from extending the satellite's study of Saturn and its neighbors. It will depend on the amount of propellant remaining on the spacecraft.

Performer: Jet Propulsion Lab., Pasadena, CA. Oct 1997. 170p. Report: NAS 1.21:533; NASASP-533

The Cassini-Huygens international mission and the Cassini spacecraft are described. Saturn, Titan, the rings and the various other parts of the Saturn system are discussed. A look at what is involved in sending a large spacecraft to the outer solar system is given.

Jaffe, L D; Herrell, L M

Journal of Spacecraft and Rockets. Vol. 34, no. 4, pp. 509-521. July-Aug. 1997

The Cassini spacecraft will take 18 scientific instruments to Saturn. After launch and a seven-year cruise, Cassini will arrive at Saturn and separate into a Saturn orbiter and an atmospheric probe, Huygens, which will descend to the surface of Titan. The orbiter will orbit the planet for four years, making close flybys of five satellites, including multiple flybys of Titan. Communication with Earth is at X-band; the maximum downlink rate from Saturn is 166 x 10 exp 3 bps. Orbiter instruments are body-mounted; the spacecraft must be turned to point some of them toward objects of interest. The orbiter's optical instruments provide imagery and spectrometry, while radar supplies imaging, altimetry, and radiometry. Radio links contribute information about intervening material and gravity fields. Other instruments measure EM fields and the properties of plasma, energetic particles, and dust particles. The probe returns data via an S-band link to the orbiter; its six instruments include sensors to determine atmospheric physical properties and composition. Radiometric and optical sensors will produce data on thermal balance and obtain images of Titan's atmosphere and surface. Doppler measurements between probe and orbiter will provide wind profiles. Surface sensors will measure impact acceleration, thermal and electrical properties, and, if the surface is liquid, density and refractive index. (Author)

Kellock, S; Austin, P; Balogh, A; Gerlach, B; Marquedant, R; Musmann, G; Smith, E; Southwood, D; Szalai, S

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 141-152. 1996

This paper describes the magnetometer instrument to be flown on the Cassini spacecraft. The instrument consists of two magnetometers and an on-board data processing unit. One magnetometer is a Vector Helium device of a type previously flown on Ulysses and several other missions which has been modified to operate in a Scalar mode providing measurements of the magnitude of the local magnetic field with very small absolute error (less than 1 nT). This is the first flight of such an instrument. The other magnetometer is a Fluxgate device of similar design to that flown on Ulysses and on many previous missions but with newly developed electronics. Both magnetometers can provide vector measurements of the three components of the magnetic field with a sensitivity of about 10 pT. The unique combination of Fluxgate /Scalar or Fluxgate/Vector Helium operation offers increased possibilities for scientific investigation of the magnetic field environment in the Saturnian system. The data processing unit contains dual redundant systems based on the 80C86 microprocessor. It features sophisticated onboard data processing, large internal data storage capability, and internal failure detection and recovery, giving the instrument the capability to operate autonomously for extended periods. (Author)

Gibbs, R

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 246-258. 1996

The Cassini spacecraft will explore the planet Saturn and its rings and moons with an orbiter and atmospheric entry probe, both of which have a sophisticated set of science instruments. The spacecraft design is responsive to mission and science objectives, and is influenced by technical and programmatic constraints, e.g., a cost cap, fixed schedule, space environment, and interfaces to other fixed systems like the launch vehicle and ground system. The spacecraft design must also consider the limited postlaunch resources allocated to do the flight operations. This paper presents an overview of the spacecraft system design with emphasis given to the orbiter and only a high level summary of the probe. (Author)

Jaffe, L D; Herrell, L M

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 84-106. 1996

The Cassini spacecraft will carry 18 scientific instruments to Saturn. After it is inserted into Saturn orbit, it will separate into a Saturn Orbiter and an atmospheric probe, called Huygens, which will descend to the surface of Titan. The Orbiter will orbit the planet for four years, making close flybys of five satellites, including multiple flybys of Titan. Orbiter instruments are body-mounted; the spacecraft must be turned to point some of them toward objects of interest. Optical instruments provide imagery and spectrometry. Radar supplies imaging, altimetry, and radiometry. Radio links contribute information about intervening material and gravity fields. Other instruments measure EM fields and the properties of plasma, energetic particles, and dust particles. The Probe is spin-stabilized. It returns data via S-band link to the Orbiter. The Probe's six instruments include sensors to determine atmospheric physical properties and composition. Radiometric and optical sensors will provide data on thermal balance and obtain images of Titan's atmosphere and surface. Doppler measurements between Probe and Orbiter will provide wind profiles. (Author)

Kahn, C L; King, W S

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 187-196. 1996

The Cassini Imaging Science Subsystem (ISS) uses two separate camera designs to satisfy the scientific objectives of the Cassini mission. The first is a Narrow Angle Camera design which obtains high resolution images of the target of interest. The second is a Wide Angle Camera (WAC) design which provides a different scale of image resolution and more complete coverage spatially. Each camera is a framing CCD imager. They differ primarily in the design of the optics: the NAC has a focal length of 2000 mm, and the WAC has a focal length of 200 mm. Both cameras have a focal plane shutter of the Voyager/Galileo type, and a two-wheel filter changing mechanism derived from the HST Wide-Field/Planetary Camera. The detector is cooled to suppress dark current, and is shielded from space radiation. The electronics for each camera are identical and contain the signal chain and CCD drivers, the Engineering Flight Computer, a command and control compressor, and a lossy compressor. The CCD detector design is a square array of 1024 x 1024 pixels. Each pixel is 12 micrometers on a side. This paper describes the ISS in detail and reviews the technologies involved and the design challenges with these cameras. (Author)

Kunde, V; Ade, P; Barney, R; Bergman, D; Bonnal, J F; Borelli, R; Boyd, D; Brasunas, J; Brown, G; Calcutt, S

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 162-177. 1996

The Composite IR Spectrometer (CIRS) is a remote sensing instrument to be flown on the Cassini orbiter. CIRS will retrieve vertical profiles of temperature and gas composition for the atmospheres of Titan and Saturn, from deep in their tropospheres to high in their stratospheres. CIRS will also retrieve information on the thermal properties and composition of Saturn's rings and Saturnian satellites. CIRS consists of a pair of Fourier Transform Spectrometers (FTS) which together cover the spectral range from 10-1400/cm with a spectral resolution up to 0.5/cm. The two interferometers share a 50-cm beryllium Cassegrain telescope. The FIR FTS is a polarizing interferometer covering the 10-600/cm range with a pair of thermopile detectors, and a 3.9-mrad FOV. The mid-IR FTS is a conventional Michelson interferometer covering 200-1400/cm in two spectral bandpasses: 600-1100/cm with a 1 x 10 photoconductive HgCdTe detector array, and 1100-1400/cm with a 1 x 10 photovoltaic HgCdTe array. Each pixel of the arrays has about a 0.3-mrad FOV. The HgCdTe arrays are cooled to about 80 K with a passive radiative cooler. (Author)

Kasprzak, W; Niemann, H; Harpold, D; Richards, J; Manning, H; Patrick, E; Mahaffy, P

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 129-140. 1996

The Cassini Orbiter Ion and Neutral Mass Spectrometer (INMS) is designed to measure the composition and density variations of (low energy) ions and neutral species in the upper atmosphere of Titan, in the vicinity of the icy satellites and in the inner magnetosphere of Saturn where densities are sufficiently high for measurement. The sensor utilizes a dual radio frequency quadrupole mass analyzer with a mass range of 1-99 amu, two electron multipliers operated in pulsemounting mode to cover the dynamic range required, and two separate ion sources. A closed ion source measures nonsurface reactive neutral species which have thermally accommodated the inlet walls such as N2 and CH4. An open ion source allows direct beaming ions or chemically active neutral species such as N and HCN to be measured without surface interaction. The instrument can alternate between these three different modes (closed neutral, open ion, and open neutral). Characterization and calibration of each of these three modes is done using a low-energy ion beam, a neutral molecular beam, and a neutral thermal gas source. (Author)

Martineau, R J; Hu, K; Manthripragada, S; Kotecki, C A; Babu, S; Peters, F A; Burgess, A S; Mott, D B; Krebs, D J; Graham, S

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 178-186. 1996

The Composite IR Spectrometer (CIRS) instrument, an important component of the Cassini Mission, consists of three focal plane arrays (FPAs) for sensing IR radiation of the Saturnian planetary system. Goddard Space Flight Center has fabricated, tested, and delivered high performance, 10-element HgCdTe photoconductive (PC) arrays for use on CIRS FP3, the focal plane responsible for detection of radiation in the 9.1- to 16.7-micron spectral band. The delivered flight array has peak responsivity 100 percent above CIRS specification, detectivity 30 percent or more above specification, and a cutoff wavelength of 17.3 microns at the operating temperature of 80 K. In order to achieve high performance at LF (25 to 46 Hz) while maintaining limited power dissipation (less than 0.5 mWatt/element), we adopted a split-geometry detector structure. This design also ensured the buttability of the PC arrays to photovoltaic arrays supplied by CE-Saclay-France for detection of radiation in the 7.1- to 9.1-micron range. The detector structure is also noteworthy for its use of 0.05-micron alumina powder-loaded epoxy to minimize reflection at the epoxy/HgCdTe interface, thus spoiling undesired optical resonance. (Author)

Garry, J R C; Zarnecki, J C

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 55-63. 1996

A system has been built at the University of Kent at Canterbury to calibrate devices that will be carried on the Huygens probe to the surface of Titan as part of the Cassini mission to the Saturnian system. This system can simulate Titan's atmosphere to an effective altitude of around 30 km, and it can condense, store, and sample quantities of liquid hydrocarbons. The tested devices form the Huygen's Surface Science Package (SSP), which measures a wide variety of parameters, making it a critical tool for exploring Titan's troposphere and surface. Preliminary results from the calibration of SSP instruments are presented, and an assessment is made of the accuracy with which a medium's composition can be determined by sensors acting alone and in concert with other SSP instruments. (Author)

Spehalski, R J

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 2-9. 1996

The Cassini mission to Saturn is a joint undertaking of NASA, ESA, Agenzia Spaziale Italiana, and numerous other European academic and industrial participants. The Cassini mission will provide a close-up investigation of the Saturn system, including Saturn's atmosphere and magnetosphere, its rings, and several of its moons. Saturn's largest moon, Titan, is of particular interest. ESA is developing the Huygens probe that will descend through Titan's atmosphere, directly sampling the atmosphere and determining its composition. To accomplish its ambitious scientific objectives, the orbiter and the probe carry 18 scientific instruments to conduct a total of 27 scientific investigations. The Cassini Spacecraft is scheduled for launch on a Titan IV/Centaur in October of 1997. Cassini will reach the Saturn system in 2004. The tour of the Saturn system is scheduled for four years and includes 63 orbits of Saturn and more than 36 flybys of Titan. During the first Saturn orbit, the Huygens probe will separate from the Cassini orbiter and descend through the atmosphere of Titan. This paper summarizes the current status of the Cassini program. (Author)

Tomasko, M G; Doose, L R; Smith, P H; Fellows, C; Rizk, B; See, S; Bushroe, M; McFarlane, E; Wegryn, E; Frans, E

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 64-74. 1996

The Huygens Probe of the atmosphere of Saturn's moon Titan includes one optical instrument sensitive to the wavelengths of solar radiation. The goals of this investigation fall into four broad areas: the measurement of the profile of solar heating to support an improved understanding of the thermal balance of Titan and the role of the greenhouse effect in maintaining Titan's temperature structure; the measurement of the size, vertical distribution, and optical properties of the aerosol and cloud particles in Titan's atmosphere to support studies of the origin, chemistry, life cycles, and role in the radiation balance of Titan played by these particles; the composition of the atmosphere, particularly the vertical profile of the mixing ratio of methane, a condensable constituent in Titan's atmosphere; and the physical state, composition, topography, and physical processes at work in determining the nature of the surface of Titan and its interaction with Titan's atmosphere. In order to accomplish these objectives, the DISR instrument makes extensive use of fiber optics to bring the light from several different sets of foreoptics to a silicon CCD detector, to a pair of InGaAs linear array detectors, and to three silicon photometers. (Author)

Mitchell, D G; Krimigis, S M; Cheng, A F; Hsieh, K C; Jaskulek, S E; Keath, E P; Mauk, B H; McEntire, R W; Roelof, E C; Schlemm, C E

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 154-161. 1996

The INCA sensor is the first Energetic Neutral Atom (ENA) imager funded for flight by NASA. It is a part of the Magnetospheric Imaging Instrument on the Cassini mission to Saturn, where it will be well suited to monitoring the global dynamics of the Saturn-Titan magnetospheric system throughout the orbital tour. INCA will perform remote sensing of the magnetospheric energetic ion plasmas by detecting and imaging charge exchange neutrals, created when magnetospheric ions capture electrons from ambient neutral gas. The escaping charge exchange neutrals were detected by the Voyager-1 spacecraft outside Saturn's magnetosphere, and can be used like photons to form images of the emitting regions, as has been done at Earth. Since Cassini is three-axis oriented, INCA is designed as a 2D imager with an FOV of 90 by 120 deg. The technique involves sensing the position of the ENA as it penetrates an entrance foil and again on the back-plane microchannel plate, thereby establishing the ENA's trajectory and time-of-flight. We discuss several of the design details unique to this instrument, as well as recent calibration results. (Author)

Lunine, J I; Lorenz, R D

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 45-54. 1996

Titan affords a remarkable opportunity to understand the evolution of an organic-rich, planet-sized world with chemical cycles powered over geologic time by sunlight. Because of the difficulties of viewing the surface remotely, a full understanding of the nature of this complex world requires a campaign of in situ and close-flyby observations. The Cassini/Huygens payload is uniquely designed to conduct such an exploration from Saturn orbit and within Titan's atmosphere. Direct sampling of the atmospheric chemistry by gas-chromatography and mass spectroscopy will be complemented by global remote spectra collected in the UV through the IR. Probe images in the optical and NIR right up to the point of impact will be complemented by Orbiter imagery in the NIR and through active radar sounding. The synergy between Orbiter and Probe observations required to do a first comprehensive exploration of Titan is a uniquely powerful capability of this mission. (Author)

Miller, E; Klein, G; Juergens, D; Mehaffey, K; Oseas, J; Garcia, R; Giandomenico, A; Irigoyen, B; Hickok, R; Rosing, D

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 206-220. 1996

The Visual and IR Mapping Spectrometer (VIMS) is a remote sensing instrument developed for the Cassini mission to Saturn by an international team representing the national space agencies of the U.S., Italy, and France. A dual imaging spectrometer, VIMS' unique design consists of two optical systems boresighted and operating in tandem, coordinated by a common electronics unit. The combined optical system generates 352 2D images (64 x 64 0.5 mrad pixels) simultaneously, each in a separate, contiguous waveband. These are combined by the electronics to produce 'image cubes' in which each image pixel represents a spectrum spanning 0.3 to 5.1 microns in 352 steps. VIMS images will be used to produce detailed spatial maps of the distribution of mineral and chemical species of Saturn's atmosphere, rings, and moons, and the atmosphere of Titan. At some wavelengths VIMS will penetrate Titan's atmosphere to map its surface and image the night side of many Saturnian objects. (Author)

Wolf, A A

Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO; 5-6 Aug. 1996. pp. 32-44. 1996

The Cassini mission to Saturn employs a Saturn orbiter and a Titan probe to conduct an intensive investigation of the Saturnian system. The Cassini orbiter flies a series of orbits, incorporating flybys of the Saturnian satellites, called the 'satellite tour'. During the tour, the gravitational fields of the satellites are used to modify and control the orbit, targeting from one satellite flyby to the next. The tour trajectory must also be designed to maximize opportunities for science observations, subject to mission-imposed constraints. Tour design studies have been conducted for Cassini to identify trades and strategies for achieving these sometimes conflicting goals. Concepts, strategies, and techniques previously developed for the Galileo mission to Jupiter have been modified, and new ones have been developed, to meet the requirements of the Cassini mission. (Author)

Haeuser, J; Xia, Y; Spel, M; Paap, H G; Eiseman, P R; Cheng, Z M

Numerical grid generation in computational field simulations; Proceedings of the 5th International Conference, Mississippi State Univ , Mississippi State; 1-5 Apr. 1996. pp. 107-116. 1996

This paper presents a novel grid generation approach in which a compiler-type grid generation has been built, on the basis of the ANSI-C syntax, which allows the user to construct and manipulate objects. The versatility and relative ease of use are demonstrated by presenting the grid generation process for the Cassini-Huygens space probe. The sequence of grids generated that lead to the final version of the Huygens grid is presented. (AIAA)

Huckins, EKIII

IAF, International Astronautical Congress, 46th, Oslo, Norway; 2-6 Oct. 1995. 1995

The Cassini/Huygens Mission to Saturn is a joint undertaking of NASA, ESA, the Italian Space Agency (ASI), and numerous other European academic and industrial participants. The mission of Cassini is to provide a close-up investigation of the Saturnian system, including Saturn's atmosphere and magnetosphere, its rings, and several of its moons. The Huygens probe, under development by ESA, will descend through the Titan atmosphere and directly sample the atmosphere and determine its composition. To accomplish its scientific objectives, the orbiter and the probe carry 18 scientific instruments to conduct a total of 27 scientific investigations. The Cassini Spacecraft is scheduled for launch on a Titan IV/Centaur in October of 1997. Cassini will reach the Saturnian system in 2004. The tour of the Saturnian system is scheduled for 4 years and includes 63 orbits of Saturn with 33 flybys of Titan. During the first Saturn orbit, the Huygens probe will separate from the Cassini orbiter and descend through the atmosphere of Titan. This paper summarizes the current status of the orbiter and its systems, the Huygens probe provided by ESA, the instruments, the ground systems, and the Titan/Centaur launch vehicle. (Author)

Ehrenfreund, P; Boon, J J; Commandeur, J; Sagan, C; Thompson, W R; Khare, B

Advances in Space Research. Vol. 15, no. 3, pp. 335-342. Mar. 1995

Comparative pyrolysis mass spectrometric data of Titan aerosol analogues, called 'tholins', are presented. The Titan tholins were produced in the laboratory at Cornell by irradiation of simulated Titan atmospheres with high energy electrons in plasma discharge. Mass-spectrometry measurements were performed of the solid phase of various tholins by Curie-point pyrolysis gas-chromatography /mass-spectrometry (GCMS) and by temperature resolved insource pyrolysis mass-spectrometry to reveal the composition and evolution temperature of the dissociation products. The results presented here are used to further define the Aerosol Collector Pyrolyzer-GCMS experiment and provide a basis for modeling of aerosol composition on Titan and for the interpretation of Titan atmosphere data from the Huygens probe in the future. (Author)

Rasmussen, R D; Singh, G; Rathbun, D B; Macala, G A

AAS, Annual Rocky Mountain Guidance and Control Conference, 18th, Keystone, CO, IN:Cassini/Huygens: A mission to the Saturnian systems; Proceedings of the Meeting, Denver, CO, Aug. 5, 6; 1-5 Feb. 1995. pp. 271-287. 1996

The pointing control functions of the Cassini spacecraft Attitude and Articulation Control Subsystem have been designed to enhance operability by establishing a behavioral model at the command interface that raises pointing operations to a more intuitive level. The control system tracks this model to closely achieve the commanded behavior. Versatility is achieved by composing the behavioral model of independently commandable, interacting modules. Each directs activities directly related to a particular pointing issue, such as observation goals, instrument characteristics, attitude constraints, and navigation. A key feature of this design is the use of propagated vectors that precisely describe the motion of targets. Our design has enabled a new, more streamlined approach to mission operations whereby the many science and engineering activities sharing this system can be given direct control over pointing activities. This is possible because the behavioral model is easy to replicate in distributed ground software, it includes enforcement of constraints, and the maintenance of its components can be performed independently. We anticipate significant gains, both in performance and in the reduction of operating cost. (Author)

Sollazzo, C; Rakiewicz, J; Wills, RD

Control Engineering Practice [CONTROL ENG PRACT], vol. 3, no. 11, pp. 1631-1640, 1995

Operations of the Cassini-Huygens missions will be carried out from two centres working in close liaison. The NASA Cassini Saturn orbiter will be operated from JPL in Pasadena, USA, while the ESA Huygens Titan probe will be operated from ESOC in Darmstadt, Germany, but with uplink and downlink through JPL and the Orbiter. Both spacecraft will be largely operated through pre-programmed time-driven command sequences, either uplinked from the ground or driven by on-board software. The Huygens probe in particular has, after separation from Cassini, no telecommand capability during its mission descent through Titan's atmosphere and the operation of its scientific instruments is then entirely automatic. To ensure the success of the mission all Probe systems are hot redundant and their performances are checked out, up to Probe release, at regular intervals throughout the 7-year cruise to Saturn. The overall Cassini Ground System is designed to meet all the requirements of operating the combined mission with a minimum reaction time of about 160 min (round-trip light-time at Cassini-Probe separation), with high reliability and within critical resource budgets over a period of more than ten years.

Bird, MK; Heyl, M

Performer: Bonn Univ. (DE). Radioastronomisches Inst. Jan 1993. 4p.

The main scientific objective of the Doppler Wind experiment is a determination of the direction and strength of the zonal winds in the atmosphere of Titan. A height profile of these winds will be derived from Doppler shift measurements of the radio signal between transmitter on the Huygens Probe and receiver on the Cassini Orbiter. The wind induced motion of the Probe will be monitored with an accuracy of +-1 m/s during the descent phase of the mission, starting at an altitude of ca. 170 km (deployment of parachute) down to impact on the surface of Titan. Further information to be extracted from the high resolution Doppler data include: (a) a more accurate Probe trajectory and the coordinates of the final landing site on Titan; (b) measurements of the spin rate and spin phase of the Probe during the descent; (c) characterisation of Titan's atmospheric turbulence. Significant progress could be achieved during the time interval covered by this report, beginning with the selection of the DWE contractor for the experiment's Ultra Stable Oscillator (USO). The USO is required by DWE for generation of the highly precise radio frequency of the Huygens telemetry signal. The more significant events of the 4 month interval are described in the report. (orig.). (Copyright (c) 1996 by FIZ. Citation no. 96:001914.)

BERTOTTI, B

Nuovo Cimento C, Serie 1. Vol. 15 C, no. 6, pp. 1129-1132. Nov.-Dec. 1992

The main aims and the general organization of the Cassini-Huygens mission, a NASA-ESA mission aimed at the exploration of the Saturnian system in the beginning of the next century, are summarized. In particular, attention is given to the planning of the interplanetary space mission, the principal equipment, organization of space telecommunications, and a general description of the radar system. (AIAA)

RAULIN, F; FRERE, C; PAILLOUS, P; DE VANSSAY, E; DO, L; KHLIFI, M

British Interplanetary Society, Journal. Vol. 45, no. 6, pp. 257-271. June 1992

The joint NASA-ESA Cassini-Huygens mission is discussed in terms of the study of extraterrestrial organic processes with the orbiter and the probe on or near Titan. The satellite of Saturn is described generally with specific references to the chemical composition of the stratospheric and atmospheric organic compounds. The compounds that are already known to exist near Titan are confirmed with results from simulations and models of N2-CH4 evolution and other processes. The organic chemistry of Titan's surface is expected to have an ocean and strong surface-atmosphere coupling, and the principal likely components of the ocean are set forth. The Cassini-Huygens mission is expected to provide data that describe the atmosphere, aerosols, and hypothesized oceans. These data are important for learning more about prebiotic chemistry generally and for gas-phase organic chemistry at low temperatures. (C.C.S.)

Boscagli, G; Comparini, M C

The CASSINI-HUYGENS mission is a deep space mission for the exploration and the study of the atmosphere of Titan. The combined Orbiter-Probe spacecraft will reach the Saturn system about 8.5 years after the launch. At that time the Probe will be separated and its mission will start transmitting scientific and housekeeping data during the descent phase to the surface of Titan via S-bank radio relay link. The Probe Data Relay Link is composed by the Probe Transmitter Terminal (PTT), on Huygens spacecraft, and the Orbiter Receiving Terminal (ORT), on Cassini spacecraft. The PTT includes two chains which transmit the phase modulated carriers at two different frequencies with opposite circular polarizations. On the orbiter the two signals are discriminated and separately amplified by the LNAs. The receivers acquire and synchronize the carrier and subcarrier and provide the data demodulation and decoding. Major requirements of the deep space receivers are fast signal acquisition and demodulation capability at very low C/No. The paper describes the Orbiter Receiver architecture underlying the advantages of a fully digital approach.

Lebreton, J P; Matson, D L

In its Environment Observation and Climate Modelling Through International Space Projects. Space Sciences with Particular Emphasis on High-Energy Astrophysics p 189-194 (SEE N93-23878 08-88); 1992

The Cassini/Huygens mission is designed to explore the Saturnian system. The Cassini spacecraft comprises a NASA provided Saturn orbiter and an ESA supplied Titan atmospheric probe named Huygens. The scientific objectives of the mission are described and the main characteristics of the payload are provided. Since emphasis is on ESA's contribution to the mission, a detailed description of the Huygens probe mission phase is given and the major features of the probe design are discussed. An overview of the probe operations center is provided. (ESA)

Scoon, G; Whitcomb, G; Eiden, M; Smith, A

SPACE TECHNOL, vol. 11, no. 4, pp. 167-177, 1991

The demanding mission and scientific requirements of the Cassini mission has stimulated European technology development in novel areas of technology, as part of a preparatory programme in support of the system design of the Huygens Probe, which has been selected as the next ESA scientific project. The mission and system requirements, in response to the scientific objectives, calls for an unguided ballistic hypersonic entry of the Probe into Titan's unique atmosphere and a descent through the layers of Titan's atmosphere for a period of 2-3 h up to and including impact on Titan's surface. Scientific measurements will be performed from an altitude of approximately 170 km to the surface. Technology studies and development are in progress in the essential areas of Aerodynamics, Aerothermodynamics, Lightweight Aerodynamic Entry Deceleration systems, Lightweight Thermal Protection Systems and Planetary Descent Systems. The continued development of these enabling and support technologies, related to the scientific exploration of planetary atmospheres and surfaces, generates the technological foundation upon which reliable and sound system designs are based. Planetary entry and descent systems are the means by which probes effect atmospheric entry and descent to the surface. An overview of the Probe's mission and a synthesis of the baseline design solutions, established as a result of the derived system requirements, are presented in this paper.