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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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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

The ionosphere of Europa from Galileo radio occultations

The Galileo spacecraft performed six radio occultation observations of Jupiter's Galilean satellite Europa during its tour of the jovian system. In five of the six instances, these occultations revealed the presence of a tenuous ionosphere on Europa, with an average maximum electron density of nearly 10(4) per cubic centimeter near the surface and a plasma scale height of about 240 +/- 40 kilometers from the surface to 300 kilometers and of 440 +/- 60 kilometers above 300 kilometers. Such an ionosphere could be produced by solar photoionization and jovian magnetospheric particle impact in an atmosphere having a surface density of about 10(8) electrons per cubic centimeter. If this atmosphere is composed primarily of O2, then the principal ion is O2+ and the neutral atmosphere temperature implied by the 240-kilometer scale height is about 600 kelvin. If it is composed of H2O, the principal ion is H3O+ and the neutral temperature is about 340 kelvin. In either case, these temperatures are much higher than those observed on Europa's surface, and an external heating source from the jovian magnetosphere is required.

Galileo Project↗
NASA NTRS1997

Europa's differentiated internal structure: inferences from two Galileo encounters

Doppler data generated with the Galileo spacecraft's radio carrier wave during two Europa encounters on 19 December 1996 (E4) and 20 February 1997 (E6) were used to measure Europa's external gravitational field. The measurements indicate that Europa has a predominantly water ice-liquid outer shell about 100 to 200 kilometers thick and a deep interior with a density in excess of about 4000 kilograms per cubic meter. The deep interior could be a mixture of metal and rock or it could consist of a metal core with a radius about 40 percent of Europa's radius surrounded by a rock mantle with a density of 3000 to 3500 kilograms per cubic meter. The metallic core is favored if Europa has a magnetic field.

Flight Experiment↗
NASA NTRS1998

Multiple Deep Jovian Atmospheric Entry Probes: Building on the Galileo Probe

Following on the very successful Galileo Entry Probe mission, studies underway at the Jet Propulsion Laboratory (JPL) address the feasibility and cost of the Jupiter Deep Multi-probes (JDMP) mission to deliver and support multiple deep (100 bar level or deeper) atmospheric entry probes to Jupiter.

JPL Galileo Entry Probe Mission Jupiter Deep Multi↗
NASA NTRS1997

Analysis of Galileo Doppler Measurements During the Solar Occulations in 1994 and 1995

Measurements of S-band downlink frequency (Doppler) shift were collected for intervals of about 30 days during the 1994 and 1995 solar conjunctions of the Galileo spacecraft. The occulation geometries enabled coronal radio sounding of the heliographic equatoral region over a heliocentric range from about 5 to 20 R(sub s) (solar radii) for the 1994 conjuctions and from about 4 to R(sub s) for the 1995 conjunction.

Galileo Doppler Solar Occulations↗
NASA NTRS1997

Galileo Orbit Determination for the Ida Encounter

This paper summarizes Galileo's orbit determination activities leading up to its encounter with asteroid 243-Ida on August 28, 1993. In addition to the nominal 2-way S-band range and Doppler radio metric data obtained from the Deep Space Network (DSN), several navigational aids were brought together to make this encounter successful.

Galileo Ida Encounter↗
NASA NTRS1996

Dynamic Modeling and Simulation Study for the Galileo Spacecraft Pulsed-Mode Spinup/400 N Main Engine Burn/Spindown Maneuvers

Two Galileo dynamic models were developed to simulate the spinup/400-N main engine burn/spindown maneuvers for the critical events of Jupiter Orbit Insertion (JOI) and Perijove Raise Maneuver (PRM). The dynamic interaction among the spin thruster pulsing frequency science/magnetometer (SCI/MAG) boom flexible modes, and the propellant slosh modes were studied.

Galileo orbit insertion planetary spacecraft↗
NASA NTRS1997

(abstract) Modeling Ground-Based and Galileo Observations of Volcanism on Io

Io is the most volcanically active body in the solar system. Presently the Galileo spacecraft is orbiting Jupiter and carrying out an Io volcano watch. The NIMS (Near Infrared Mapping Spectrometer) instrument on board will yield both compositional and thermal data of volcanic units on Io, and will hopefully answer some long-standing questions as to the nature of volcanism on Io.

Io↗
NASA NTRS1995

The New Galileo Communication System

ave been developed to get as much data as possible from the Galileo spacecraft even without the high gain antenna. These methods include extensive data compression, a new packetized telemetry format, new error-correcting codes, new modulation, new ground receivers, and antenna arraying. (abstract only).

Galileo data compression spacecraft mission operat↗
NASA NTRS1995

JPL's Galileo Spacecraft Will Shoot an Interplanetary 'Bulls's Eye'

JPL's Galileo spacecraft, with a December 1995 rendezvous with Jupiter, shot an interplanetary 'bull's eye' when it released its probe to conduct history's first sampling of Jupiter's atmosphere. The probe will slam into Jupiter's hydrogen-helium atmosphere at 100,000 mph as the spacecraft flies overhead and receives and records the probe's data on the structure and composition of the atmosphere.

Galileo Jupiter Interplanetary Spacecraft↗
NASA NTRS1996

Galileo Orbital Operations Using the Low-Gain Antenna

A brief overview of the Galileo mission is given. The bulk of this report will focus on the orbital operations design and implementation, beginning with an updated description of the changes being made to both the flight software and ground system. Results of system functional tests of various parts of the design, and descriptions of some of the special test tools developed will also be provided.

Galileo mission overview orbital operations design↗