I33 Petition Letter

On March 15, 2001, the National Aeronautics and Space Administration authorized the Galileo Mission to Jupiter to proceed with a third and final mission extension, allowing the Galileo spacecraft to perform five more flybys of Jupiter's moons before plunging into the giant planet in September, 2003. The authorization allows Galileo to do remote sensing (i.e., take pictures) of the large icy moon Callisto in May 2001 and the volcanically hyperactive moon Io in August and October, 2001, while restricting the spacecraft to fields and particles experiments (i.e., no pictures) during flybys of Io in January 2002 and Amalthea in November 2002.

While the Galileo Imaging Team is happy that they will be allowed to continue their experiment for the remainder of this year, they are extremely disappointed that NASA has chosen not to allow imaging of Io in January, 2002 on orbit 33. This orbital flyby of Io, coming on the heals of the end of image playback from orbit 32, is an equitorial flyby of the subjovian (Jupiter-facing) hemisphere, which has not been observed well by Galileo. This flyby, if implemented, would include some of the highest resolution imaging of Io's enigmatic volcanic features, last observed up close by Voyager in 1979. Some of the scientific objectives of this flyby include:

  1. The I33 flyby of Io represents the first opportunity to observe the subjovian hemisphere at high resolution (meters to tens of meters per picture element) since the beginning of the Galileo Mission to Jupiter (December 1995). This hemisphere was last observed by the Voyager spacecraft in 1979, where the best resolution was hundreds of meters per pixel. This will be the last opportunity to observe Io up close for possibly decades.
  2. The I33 flyby will obtain high resolution (15-100 m/pixel) observations of several large lava flow fields, some of which are thought to be associated with ultramafic (high-temperature, magnesium-rich) silicate eruptions. These observations may provide clues to the styles of these eruptions, which last occurred on Earth millions to billions of years ago. Thus, the I33 imaging is crucial to obtain a better understanding of a style of volcanism that was important on the ancient Earth.
  3. The I33 flyby will obtain high resolution (15-100 m/pixel) observations of several large volcanoes called tholi, which are shaped like pancakes and resemble domes from some terrestrial silica-rich volcanoes. These tholi are rare on Io, and their study could provide clues into the diversity of Io's volcanism.
  4. The I33 flyby will obtain high resolution (<20 m/pixel) images of the volcano Pele at night. This observation will allows constraints to be placed on the form of the vent of this active volcano, as well as constrain the temperature of its eruptions.
  5. The I33 flyby will obtain high resolution (~100 m/pixel) observations of Hi'iaka, Gish Bar, and several other of Io's enigmatic mountains. These observations will improve our understanding of the relationship between volcanism, tectonism, and mountain formation on Io.

The cost of mission operations and data archiving for the I33 encounter is $604,000., which is a relatively small number in the scheme of funding high priority planetary encounters. For NASA to cancel scientific observations at this once-in-a-lifetime opportunity to study this part of Io up close is truly astounding.

We have prepared the following petition, in hopes that we may persuade NASA to grant the $604K required to perform the I33 imaging experiment. If you agree that the scientific objectives justify the costs involved, then please sign our petition.

We, the undersigned, believe it is a mistake for NASA to not allow the Galileo spacecraft to perform imaging of Io during orbit 33 in January of 2002, and we respectively request that NASA allocate the $604,000 required to perform the I33 imaging experiment.

Back to Pennies for Pele Page

(I want to thank David Williams for letting me use this letter. Certainly explained a lot than I would have ever been able to. Plus, the addition of the I33 SSI objectives is much appreciated and shall be much used :)