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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1995

Cassini radar: Instrument description and performance status

The spacecraft of the Cassini mission is planned to be launched towards Saturn in October 1997. The mission is designed to study the physical structure and chemical composition of Titan. The results of the tests performed on the Cassini radar engineering qualification model (EQM) are summarized. The approach followed in the verification and evaluation of the performance of the radio frequency subsystem EQM is presented. The results show that the instrument satisfies the most relevant mission requirements.

Johnson, W. T. K.↗
NASA NTRS1991

Outer planet studies

The focus is on observational studies of the composition, structure, and variability of planetary, satellite, and cometary atmospheres. The techniques used include spectroscopy, spectrophotometry, and photometric imaging in the spectral region from 3000 A to 5 microns. In addition to carrying out basic research into the origin, evolution, and current state of the solar system, these studies provide ground-truth support for observations of the solar system by NASA's missions, including the Voyager and Galileo Spacecraft, the Hubble Space Telescope, and the proposed Comet Rendezvous Asteroid Flyby (CRAF)-Cassini Mission.

Lutz, Barry L.↗
NASA NTRS1999

Cassini Radio Science Experiments on Saturn and Titan Preserved Because of Lewis Analysis

The Cassini mission to Saturn is an international venture with participation from NASA, the European Space Agency, and the Italian Space Agency. The Cassini spacecraft was launched from Cape Canaveral in October 1997 and is scheduled to arrive at Saturn in July 2004. After arrival, the spacecraft will orbit Saturn about 60 times over a period of 4 years. During this time, the Cassini Radio Science Subsystem will be used to investigate the atmosphere and rings of Saturn and the atmosphere of its largest moon, Titan--which is larger than Mercury and is the only moon in our solar system with a dense atmosphere. A critical component in Cassini s Radio Science Subsystem is a traveling-wave tube (TWT) that was designed at the NASA Lewis Research Center and built by Hughes Electronic Dynamics Division (ref. 1). This TWT will amplify downlink microwave signals at a frequency of 32 GHz for the Deep Space Network and will be involved in a number of experiments. These include occultation experiments in which the microwave signal will be beamed through rings and atmospheres toward Earth. Researchers will analyze the received signals to determine the sizes and distributions of the particles in the rings and the structure and composition of the atmospheres. The Radio Science Subsystem also will also be used to more accurately determine the mass and size of Saturn and its moons, to investigate the solar corona, and to search for gravity waves from outside the solar system.

Wilson, Jeffrey D.↗
NASA NTRS2012

In-Flight Position Calibration of the Cassini Articulated Reaction Wheel Assembly

NASA's long-lived Cassini-Huygens spacecraft is currently in its 14th year of flight and in the midst of its second, and final, extended mission. Cassini is a massive interplanetary spacecraft that is three axis stabilized and can maintain attitude control using either its reaction control system thrusters or using reaction wheel control. Cassini has four identical reaction wheels, of which three are mutually orthogonal and have a fixed orientation. The fourth reaction wheel has an articulation motor that allows this reaction wheel to be aligned with the momentum direction of any of the other three fixed reaction wheels. The articulation motor allows this reaction wheel to be used as a replacement for any of the other three wheels without any performance degradation. However, due to limitations in the design of this backup system, there are few telemetric indications of the orientation of this reaction wheel following an articulation. This investigation serves to outline the procedures that have been developed by the Cassini Attitude and Articulation Control Subsystem to calibrate the position of the articulated reaction wheel assembly in the event that the momentum direction of this reaction wheel must be reoriented.

Brown, Todd S.↗
NASA NTRS1996

Touring the Saturnian System

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 series of orbits incorporating flybys of the Saturnian satellites called the Satellite Tour.

Cassini↗
NASA NTRS2011

LIFE: Enceladus Sample Return Mission Concept for Searching Evidence of Life

One of the most promising targets for the search for life other than Mars in our Solar System is the tiny Saturn moon Enceladus. The Cassini mission to the Saturian system detected an active region on Enceladus where small water particles and gas containing organic materials were being flung into space from a region near the south pole known as the tiger stripes. This discovery indicated that there is very likely a liquid subsurface ocean heated through tidal interactions as Enceladus orbits Saturn. On Earth, whenever there is an energy source, liquid water and organics, there is life; this makes Enceladus one of the prime candidates for a search for life missions. In this presentation, we describe LIFE (Life Investigation For Enceladus) sample return concept from Enceladus in the search for evidence of life.

Enceladus↗
NASA NTRS2016

Enceladus Life Finder: the Search for Life in a Habitable Moon

Enceladus is one of the most intriguing bodies in the solar system. In addition to having one of the brightest and youngest surfaces, this small Saturnian moon was recently discovered to have a plume erupting from its south polar terrain and a global subsurface ocean. The Cassini Mission discovered organics and nitrogen-bearing molecules in the plume, as well as salts and silicates that strongly suggest ocean water in contact with a rocky core. However, Cassini's instruments lack sufficient resolution and mass range to determine if these organics are of biotic origin. The Enceladus Life Finder (ELF) is a Discovery-class mission that would use two state-of-the-art mass spectrometers to target the gas and grains of the plume and search for evidence of life in this alien ocean.

Saturn↗
NASA NTRS1993

Science planning and sequencing for Cassini

This paper will address the science planning and sequencing aspects of the command generation process for the scientifically diverse Cassini Mission. The mission's prime objectives are to study the Saturnian system and deliver the Huygens Probe to the moon Titan. Together, the spacecraft and probe will be the largest and most complicated craft ever launched to another planet. The presentation will begin with an overview of the Cassini spacecraft and its scientific instrumentation. This will be followed with a description of the Oct. 1997 mission. Next, the structure of the science planning and sequencing process, with special emphasis on science's role, will be outlined. Finally, this presentation will conclude with a discussion of some of the unique challenges faced by the Ground System during Cassini's four-year orbital tour.

Wessen, Randii R.↗
NASA NTRS1990

Mapping photopolarimeter spectrometer instrument feasibility study for future planetary flight missions

Evaluations are summarized directed towards defining optimal instrumentation for performing planetary polarization measurements from a spacecraft platform. An overview of the science rationale for polarimetric measurements is given to point out the importance of such measurements for future studies and exploration of the outer planets. The key instrument features required to perform the needed measurements are discussed and applied to the requirements for the Cassini mission to Saturn. The resultant conceptual design of a spectro-polarimeter photometer for Cassini is described in detail.

Source record↗
NASA NTRS2019

Sampling tool concepts for Enceladus Lander in-situ analysis

A potential future in-situ lander mission to the surface of Enceladus could be the lowest cost mission to determine if life exists beyond Earth since material from the subsurface ocean, where the presence of hydrothermal activity has been strongly suggested by the Cassini mission, is available on its surface after being ejected by plumes and then settling on the surface. In addition, the low radiation environment of Enceladus would not significantly alter the chemical makeup of samples recently deposited on the surface. A study was conducted to explore various sampling devices that could be used by an in-situ lander mission to provide 1cc to 5cc volume samples to instruments. In addition to temperature and vacuum environmental conditions, the low surface gravity of Enceladus (1% of Earth gravity) represents a new challenge for surface sampling that is not met by sampling systems developed for microgravity (e.g., comets and asteroids) or higher gravity (e.g., Europa 13%g, Moon 16%g, or Mars 38%g) environments. It is desired to acquire surface plume material that has accumulated in the top 1cm to ensure acquisition of the least processed material. Several sampling devices were developed or adapted and then tested in simulated conditions that resemble the Enceladus surface properties. These devices and test results are presented in this paper.

Genta, Giancarlo↗
NASA NTRS2005

Low-Cost Innovation in Spaceflight: The Near Earth Asteroid Rendezvous (NEAR) Shoemaker Mission

On a spring day in 1996, at their research center in the Maryland countryside, representatives from the Johns Hopkins University Applied Physics Laboratory (APL) presented Administrator Daniel S. Goldin of the National Aeronautics and Space Administration (NASA) with a check for $3.6 million. 1 Two and a half years earlier, APL officials had agreed to develop a spacecraft capable of conducting an asteroid rendezvous and to do so for slightly more than $122 million. This was a remarkably low sum for a spacecraft due to conduct a planetaryclass mission. By contrast, the Mars Observer spacecraft launched in 1992 for an orbital rendezvous with the red planet had cost $479 million to develop, while the upcoming Cassini mission to Saturn required a spacecraft whose total cost was approaching $1.4 billion. In an Agency accustomed to cost overruns on major missions, the promise to build a planetary-class spacecraft for about $100 million seemed excessively optimistic.

McCurdy, Howard E.↗
NASA NTRS1992

Fiber optic rotation sensor for long lifetime space missions

The present F-O rotation sensors (FORS) are all-solid state devices for measuring rotations and rotation rates in inertial space that may reach the 0.003 deg/hr (1-sigma) accuracies required for NASA's Saturn-orbiting Cassini mission. Attention is presently given to the mission, inertial reference unit, and FORS instrument optoelectronic component requirements envisioned for such spacecraft applications.

Dorsky, L.↗
NASA NTRS2013

Estimation of Gravitation Parameters of Saturnian Moons Using Cassini Attitude Control Flight Data

A major science objective of the Cassini mission is to study Saturnian satellites. The gravitational properties of each Saturnian moon is of interest not only to scientists but also to attitude control engineers. When the Cassini spacecraft flies close to a moon, a gravity gradient torque is exerted on the spacecraft due to the mass of the moon. The gravity gradient torque will alter the spin rates of the reaction wheels (RWA). The change of each reaction wheel's spin rate might lead to overspeed issues or operating the wheel bearings in an undesirable boundary lubrication condition. Hence, it is imperative to understand how the gravity gradient torque caused by a moon will affect the reaction wheels in order to protect the health of the hardware. The attitude control telemetry from low-altitude flybys of Saturn's moons can be used to estimate the gravitational parameter of the moon or the distance between the centers of mass of Cassini and the moon. Flight data from several low altitude flybys of three Saturnian moons, Dione, Rhea, and Enceladus, were used to estimate the gravitational parameters of these moons. Results are compared with values given in the literature.

angular momentum↗
NASA NTRS2019

ALMA Spectral Imaging of Titan Contemporaneous with Cassini's Grand Finale

The Cassini mission performed 127 targeted ybys of Titan during its 13 yr mission to Saturn, culminating in the Grand Finale between 2017 April and September. Here we demonstrate the use of the Atacama Large Millimeter/ submillimeter Array (ALMA) to continue Cassini's legacy for chemical and climatological studies of Titan's atmosphere. Whole-hemisphere, interferometric spectral maps of HCN, HNC, HC3N, CH3CN, C2H3CN, C2H5CN,and C3H8 were obtained using ALMA in 2017 May at moderate (0 2, or 1300 km) spatial resolution, revealing the effects of seasonally variable chemistry and dynamics on the distribution of each species. The ALMA submillimeter observations of HCN and HC3N are consistent with Cassini infrared data on these species, obtained in the same month. Chemical/dynamical lifetimes of a few years are inferred for C2H3CN and C2H5CN, in reasonably close agreement with the latest chemical models incorporating the sticking of C2H5CN to stratospheric aerosol particles. ALMA radial limb ux proles provide column density information as a function of altitude, revealing maximum abundances in the thermosphere (above 600 km) for HCN, HNC, HC3N, and C2H5CN. This constitutes the rst detailed measurement of the spatial distribution of HNC, which is found to be conned predominantly to altitudes above 730 ± 60 km. The HNC emission map shows an east-west hemisphericasymmetry of 13% ± 3%. These results are consistent with very rapid production (and loss) of HNC in Titan's uppermost atmosphere, making this molecule an effective probe of short-timescale (diurnal) ionospheric processes.

Cordiner, M. A.↗
NASA NTRS2021

Midsummer Atmospheric Changes in Saturn’s Northern Hemisphere from the Hubble OPAL Program

Using the Hubble Space Telescope, Saturn was observed in 2018, 2019, and 2020, just after the northern hemisphere summer solstice. Analysis of multispectral imaging data reveals three years of cloud changes associated with a 70° N storm that began in 2018. Additionally, there is an increase in equatorial brightness and perhaps haze optical depth at 0° to 7° N. There are small midsummer changes at the north pole, with a thin blue feature near the polar hexagon's outer edge disappearing between 2019 and 2020 and increasingly reddish polar haze. Zonal winds at most latitudes remain close to values obtained by the Cassini mission with a slight increase of winds in the equatorial zone. Yearly cloud changes, while noticeable, are small compared with the changes observed between the Voyager (northern spring) and Cassini (southern summer to northern spring) eras, but further observations will provide a longer baseline for comparison.

Amy A Simon↗
NASA NTRS1987

Ka-band (32 GHz) spacecraft development plan

A road map for the development of a protoflight 32 GHz spacecraft solid state transmitter is given. The major milestones include the development of device and component technology required for use in the spaceborne experimental and operational transmitter systems. Two experimental spacecraft transmitter systems are envisioned: first, a low power beacon, to determine the performance of a 32 GHz downlink communications system; and second, an array feed, to further verify the results of the first experiment and service as a test bed for technology required for an operational system. The first experiment was proposed to NASA Headquarters for flight aboard the Mars Observer spacecraft with spacecraft integration in early 1989. The second is to be available for integration aboard a spacecraft such as the Comet Rendezvous Asteroid Flyby (CRAF) mission in the 1990 time frame. These experimental systems are to lead to the development of a protoflight transmitter for subsequent spacecraft integration in 1992, the time frame of the Cassini mission to Saturn.

Riley, A. L.↗
NASA NTRS2017

The Epic Chronicle of Designing Cassini's Titan Flyby Altitudes

The selection and optimization of Titan flyby altitudes for NASA's Cassini mission at Saturn has traveled a long, fascinating, and often torturous sixteen-year path - starting in 2001, when pre-arrival trajectory design decisions had to be made, through April of 2017 when Cassini's last, and arguably most critical, low flyby takes place. The chronicle of designing and updating the Titan flyby altitudes have twists and turns enough to satisfy a full-length novel or feature film, including: critical design decision-making before arrival with multiple atmospheric models, high uncertainties, and limited data; early flybys that seemed to show trends that weren't there; use and misuse of statistical analysis; unexpected surprises with limited reaction time; navigation of a scientific, engineering, and management community with a wide array of inherent biases; and consideration of a variety of project risk postures in a high-scrutiny, high-impact, high-reward environment.

Bittner, Molly↗