Keeping the spacecraft company is the result of a NASA campaign-- a DVD disk placed onboard the spacecraft containing the signatures of more than a half million well-wishers from 81 nations. These signatures of 616,420 people were recorded onto the disk, then strategically tucked into the side of the Cassini spacecraft. The disk is sandwiched by two pieces of aluminum and covered by a specially decorated patch of protective thermal material.
To send signatures into space is not a new concept, but it has never been done on such a widespread scale. Traditionally, spacecraft have carried thin aluminum plates containing scaled down signatures of scientists and engineers involved in creating the project. For example, Voyager 1, the farthest human-made object currently traveling on the outskirts of our solar system, carries six such plates and the Galileo spacecraft, now orbiting Jupiter, carries 11. However, such plates could only hold a maximum of about 900 signatures each -- not enough to fit the signatures of the more than 8,000 people who worked on the Cassini-Huygens mission.
The advent of the digital age gave NASA the opportunity to dramatically increase the number of signatures that could be sent to space. The invention of the CD-ROM and later of the digital videodisc or digital versatile disc -- what we now simply call "DVD" -- provided the ideal solution to increase storage space. Thus, in 1995, Richard Spehalski, then-Project Manager of the Cassini-Huygens Mission, decided to open to the public the chance to send signatures into space.
The public loved the idea. An announcement on Cassini's web site asking for a signed postcard began an enormous flood of mail.
"The response was overwhelming," recalls Charley Kohlhase, then-Science and Mission Design Manager of the Cassini-Huygens mission. "Cards began arriving from around the globe -- as many as 35,000 a week."
The success of the campaign eventually caused logistical problems, and Kohlhase, who spearheaded the signature collection, recruited volunteers from the Pasadena-based Planetary Society to help sort, count and scan all the mail.
"Signatures came from the very young, just learning how to write to the very old, whose hands were no longer steady," said Kohlhase, who also designed the cover of the DVD. "There are many reasons for the outpouring of signatures. Some of us dream of escaping Earth and venturing in the cosmos -- and sending a signature is a way of making such a journey."
Even celebrities joined the effort, such as actors Patrick Stewart and Chuck Norris. A postcard from Australia was sent by Mary Cassini, a distant descendant of Giovanni Cassini -- one of the first scientists to study Saturn and after whom the mission is named. Taken from old manuscripts, the signatures of both namesakes of the mission, Giovanni Cassini and Christiaan Huygens, are also included on the DVD.
This cooperative campaign to collect signatures lasted more than a year, and in May 1997, five months before the launch of the Cassini-Huygens spacecraft, 10 copies of the DVD were digitally mastered. One copy is on display at JPL's Space Flight Operations Facility, eight copies are in museums across the world and "the" one is billion miles from home and rapidly approaching Saturn.
Once there, the Cassini-Huygens mission will begin a four-year scientific investigation and tour of the vast Saturn system, which will extend the journey of the spacecraft, as well as that amazing number of signatures, an extra 1.6 billion kilometers (about 1 billion miles).
It's an amazing story about how international cooperation can bring so many of us together in our effort to explore the world around us and be a part of many new discoveries.