DN Staff

March 3, 1997

7 Min Read
More on Galileo
  • Determine the temperature and pressure of the atmosphere

  • Determine the chemical composition of atmosphere

  • Determine the physical structure of cloud layers

  • Measure the atmosphere's helium to hydrogen ratio

  • Measure the velocity and depth of Jupiter's winds

  • Measure the upward and net radioactive flux in Jupiter

  • Measure the occurrence rate and energy of lightening

  • Characterize high energy particles near Jupiter
    Some results of the mission

    • The probe entered on target but went through a hole in the cloud structure.

    • The entry deceleration load was 238 g's.

    • Wind speed in excess of 400 mph were detected.

    • The probe descended 100 miles vertically on the main chute and drifted 300 miles laterally.

    • Lightening was 10 less than on Earth and the RF frequency was much lower.

    • The abundance of helium was less than the sun.

    • A new intense radiation belt between Jupiter's ring and uppermost atmospheric layers was found.

    • Upper atmospheric temperatures were higher than predicted.

    • Atmosphere relatively dry, about a 10th of what was expected.

    • Temperature structure indicates atmosphere below cloud levels neutrally stable. Upper atmospheric temperatures greater than expected.

    • There was only one cloud layer, not multiple ones and the cloud is made up of ammonium.

    The Galileo Mission Overview

    • Probe was released on July 13, 1995 and entered the planet's atmosphere on December 7, 1995.

    • Launched during the STS 34 flight of the Atlantis orbiter, the two spacecraft were pushed out of Earth orbit by an inertial upper stage rocket

    • The trajectory that the spacecraft followed was called a VEEGA (Venus-Earth-Earth Gravity Assist) The craft headed first toward the sun for a gravity assist from Venus before encountering the Earth twice (spaced two years apart). This allowed Galileo to gain enough velocity to get out to Jupiter.

    • Galileo had a front seat view of the Comet Shoemaker-Levey 9 fragments that impacted onto the planet Jupiter.

    • Discovered a satellite of an asteroid - Dactyl, the satellite of Ida.

    The Probe Spacecraft

    Deceleration Module

    2.8 feet high with rounded top above conical base angling down to a blunted tip. At widest point, diameter is 4 feet.

  • Ablative heatshield bonded to aluminum ring-stiffened monocoque structure. The conical forward shell was carbon phenolic, the aft cover phenolic nylon.

  • Two-stage parachute system, the canopy and shroud lines of the main parachute are made of Dacron, the riser of Kevlar. The parachute was 8.2 feet in diameter.

  • Thermal control system included mylar insulation; internally mounted 1 W radioisotope heater units; partial gold tape on nose

Descent Module

Titanium fairings with 3 spin vanes

  • Thermal control with thermal blankets and passive internal airflow restrictions

  • Titanium interface ring provided load path between DCM and other structural elements

  • Main equipment shelf composed of aluminum honeycomb with aluminum facesheets bolted to the titanium ring at forward surface.

  • Scientific instruments laid out around the decent modules circular interior with sensors extending through titanium walls. Instruments weighed 66 pounds.

Probe Instruments

  • Neutral Mass Spectrometer - determined the chemical constituents of Jupiter's atmosphere and their distribution

  • Helium Abundance Detector - determined the ratio of helium to hydrogen in Jupiter's atmosphere

  • Atmosphere Structure Instrument - measured the temperature and pressure of the lower atmosphere

  • Nephelometer - determined the location of cloud layers and characteristics of cloud particles

  • Net Flux Radiometer - measured energy radiated by Jupiter and Sun

  • Lightning and Radio Emissions Detector - measured electromagnetic waves generated by lightning flashes and detected light and radio transmissions from the flashes

  • Energetic Particle Instrument - measured fluxes of protons, electrons, alpha particles and heavy ions

  • Relay Radio Hardware - determined Doppler wind determination and atmospheric absorption

Galileo Timeline

  • 1977 - Congressional approval

  • 1978 - Contract awarded to Hughes Space and Communications

  • Early 1980's - Stretch-outs and reschedulings

  • 1986 - Challenger accident

  • 1989 - Launch October 18 from Shuttle Atlantis

  • 1990 - February Venus fly-by, December Earth 1 fly-by

  • 1992 - December Earth 2 fly-by

  • 1993 - August Ida fly-by

  • 1994 - Comet impacts

  • 1995 - February ground battery tests, March probe checkout

  • 1995 - July Probe release

  • 1995 - December encounter

  • 1996 - May complete data return

  • 1996 - September, final report

Deployment sequence of the Galileo probe for entry into the atmosphere of Jupiter

  • As probe approached Jupiter, LiSO2 battery turned on by a time six hours before encounter.

  • Probe arrived at Jupiter

  • 1.8 minutes, pilot parachute deployed

  • 1.9 minutes, aft cover removed

  • 1.9 minutes, main parachute deployed

  • 2.1 minutes, heat shield dropped off

  • Begin telemetry of data through the atmosphere to the orbiter

  • 61 minutes, probe mission terminated

Jupiter facts

  • Largest planet in our solar system. Named for the Roman god.

  • Jupiter has more mass than all the planets combined. It is 300 times the mass of the earth.

  • It is composed of a thin skin of winds and clouds -- 88% hydrogen, 11% helium with small amounts of methane, ammonia and water.

  • The great red spot visible on Jupiter is 16,000 miles wide, large enough to encompass two earths. It was first discovered in 1664 by British scientist Roger Hook who was using Galileo's telescope.

  • Some scientist believe the sun and Jupiter began as unequal partners in a binary star system. For a brief period of its formation, scientists believe that Jupiter was hotter and more luminous and 10 times larger than it is now.

  • It emits twice as much heat as it receives from the sun.

  • Jupiter spins faster than any planet in the solar system; twice as fast as Earth.

Galileo Web Sites




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