A mosaic of Io from Galileo. Photo: NASA

A group of planetary scientists and space activists are petitioning NASA to keep the cameras on the Galileo spacecraft active long enough to take images of the volcanic moon Io during a unique flyby opportunity next year.

An online petition, organized by a Kansas high school student and backed by a number of leading planetary scientists, asks the space agency to provide the funding needed to support imaging of Io during the January 2002 flyby of the moon, the innermost of Jupiter's large Galilean satellites.

Last month NASA announced plans to extend the mission of Galileo, a spacecraft that has been orbiting Jupiter since December 1995 and whose mission had already been extended twice before. The extension, which runs though August 2003, includes a close flyby of the moon Callisto next month as well as three flybys of Io late this year and early next year.

Galileo will collect images during its Callisto flyby and the Io flybys slated for August and October. However, in a cost-saving move, NASA plans to take no images of Io during a third and final flyby of the moon on January 17, 2002, as well as its only close flyby of the small inner moon Amalthea scheduled for November 2002.

That decision not to take images during the final Io flyby, designated "I33" as it takes place during Galileo's 33rd orbit of Jupiter, has upset a number of planetary scientists. The I33 flyby, they note, is the only opportunity to study in detail the hemisphere of Io that faces Jupiter: all previous Io flybys have either viewed the opposite hemisphere or the moon's poles.

"Every time we look at Io we see something unexpected and amazing," said John Spencer of Lowell Observatory. "I33 gives Io one more chance to blow our socks off! The fact that we will be looking at a hemisphere not seen close-up since Voyager increases the chances of new and surprising discoveries."

"This is a unique opportunity to view Io's Jupiter facing hemisphere at high resolution using Galileo's remote sensing instruments," added Rosaly Lopes, a planetary scientist at JPL. "It is very hard to understand the rationale for turning off the remote sensing instruments after October. With 3 more months of funding, we could have this unique I33 fly-by!"

The petition's organizers estimate that adding imaging of Io during the I33 flyby would cost on the order of $1.5 million. That is a significant fraction of the $9 million allocated for Galileo operations through the end of the mission in 2003, but barely more than 0.01% of NASA's overall proposed budget for 2002, and a tiny fraction of the more than $1 billion spent on the mission to date. "Considering the amount of money it took us to get there, not funding I33 imaging makes absolutely no sense," said Joseph Plassmann of the Planetary Image Research Laboratory.

NASA officials are defending their decision to end imaging operations before the I33 flyby. In a statement provided to Spaceflight Now, Galileo program executive Paul Hertz said that the decision not to collect images was based on a combination of limited resources and scientific priorities. "Since NASA can not afford to do all of the excellent science which is proposed, we use members of the science community to prioritize the proposed science for us and we use that prioritization to guide our decisions," he said.

Hertz referred to a senior review of Galileo and other NASA science missions conducted last year by an outside group of scientists. That panel reviewed a set of proposed scientific programs for Galileo's extended mission and prioritized them on a "science per dollar" basis, in an effort to maximize the scientific data returned by the mission given limited financial resources. "Galileo is clearly a valuable and unique scientific resource, but one that is very expensive," the panel noted in its report. "It may not be possible to afford the entire extended mission as proposed by the Galileo project."

That panel ranked imaging of Io during the I33 flyby sixth out of nine proposed programs, noting that the high cost associated with imaging work gave the proposal a lower science per dollar ranking that other proposals, such as studies of the particle and field environment around Io and near Jupiter. Of the nine proposed programs, only the I33 imaging as well as the Amalthea imaging planned for later in 2002 -- which ranked last among the nine proposals -- were not funded by NASA for this extended mission.

The organizer of the online petition, Jason Perry, does not dispute the overall prioritization of Galileo's scientific objects, but believes that extra funding should be added so that studies of Io are on a par with the other major Jovian moons. "I am not saying that it should be funded over other higher-priority objectives," he told Spaceflight Now. "This is a petition to get additional funding so that there can be remote sensing in this flyby. The other Galilean satellites have much better overall up-close coverage than Io. This flyby would complete a map of Io at better than 2 km/pixel."

By late Wednesday the petition, on the web at http://fullspeed.to/Io, had collected 175 signatures. Perry hopes to collect at least 1,000 by August 6, the date of the next Io flyby, at which point he will turn them over to NASA Headquarters for their consideration.

Perry, a high school junior in Leavenworth, Kansas, has had a long-term fascination with Io. "I have been interested in Io for a long time. I really don't know why I became interested in it but I think it might be because I like the idea that right now, Œstuff' is happening on Io: mountains are building, massive eruptions are taking place in over 400 volcanoes, gas is being blasted 300-400 km into space." He will spend the summer studying Io as part of a summer job at the University of Arizona's Lunar and Planetary Laboratory.

Perry's petition marks the second time in recent months that a high school student has led a crusade to save an endangered planetary science mission. Last fall Pennsylvania high school student Ted Nichols established plutomission.com after NASA issued an order stopping work on the Pluto-Kuiper Express mission. Scientific and public support for a Pluto mission, evidenced in part by the thousands of signatures collected by Nichols' site, led NASA to issue a request for proposals for a revised Pluto mission late last year. However, earlier this year NASA announced it was canceling the Pluto mission outright, citing a preference to fund propulsion technologies that could be used to shorten the travel time of such missions in the future.