365daysDate: June 4, 2009

Title: JPL’s Greatest Hits


Podcaster: Bruce Irving

Organization: JPL Main Web Site:
JPL Solar System Ambassadors:

Description: The Jet Propulsion Laboratory (JPL) has been involved in space exploration since 1958 when its Explorer 1 spacecraft became the United States’ first successful Earth-orbiting satellite. Operated for NASA by the California Institute of Technology in Pasadena, California, JPL’s space accomplishments would take hours to even list, but in the semi-grand tradition of top 10 lists, and while staying within the bounds of a 10 minute podcast, Bruce Irving will try to select and briefly describe what he believes to be “JPL’s Greatest Hits.” This admittedly subjective exercise will take us from the dawn of the space age to the edge of the solar system and beyond.

Bio:Bruce Irving is an optical engineer, singer/songwriter, space enthusiast, and blogger. He is not an employee of JPL or NASA, but since he enjoys talking with people about space and astronomy, he feels fortunate to have a small JPL connection as a volunteer Solar System Ambassador, doing educational outreach in Central Massachusetts.

To supplement this podcast when it goes live, and to illustrate “JPL’s Greatest Hits,” Bruce will provide links to pictures, web pages, and space flight simulation models on his blog, Music of the Spheres ( and on his Flickr Photo Site

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by the Palomar Observatory.


Hi everybody, I’m Bruce Irving, and in today’s podcast I’m going to talk about JPL’s greatest hits. For those of you who don’t even remember a band called JPL, don’t worry – it’s not a band. It’s the Jet Propulsion Laboratory, operated for NASA by the California Institute of Technology in Pasadena, California. JPL has long been known as the premier center for unmanned space exploration. I don’t work for JPL, though I do have a connection I’ll mention later. But first, I’d like to count down JPL’s top ten, some of the greatest hits of the space age, in order of their influence and importance according to… me! Cue the spacey music and the corny DJ voice…

Number 10 was JPL’s and the United States’ very first space mission, the Earth orbiting Explorer 1. Designed and built by JPL in just three months, it was launched on January 31, 1958, four months after the Soviets’ Sputnik 1. Explorer 1 sent back data on cosmic rays that led to the discovery of the Van Allen radiation belts.

At number 9, Magellan – a cool spacecraft for a hot planet, Venus. Magellan entered Venus’ orbit in 1990 and spent three years mapping the cloud-shrouded planet in great detail. But how could it see through those thick clouds? With special high resolution synthetic aperture radar. Thanks to JPL’s Magellan, we know what the volcanic surface of Venus looks like even though we can never see it.

Coming in at number 8 is a family of spacecraft called Surveyor. To prepare for the manned Apollo moon landings, NASA soft-landed five Surveyor spacecraft at different lunar sites between 1966 and 1968. They returned thousands of images and performed the first soil analysis on another world. In November 1969, Pete Conrad and Alan Bean landed Apollo 12 just 156 meters from Surveyor 3 and later returned parts of it to Earth.

Number 7 is another “surveyor,” the Mars Global Surveyor or MGS for short. Orbiting Mars from pole to pole between 1997 and 2006, MGS sent back thousands of high resolution images covering Mars’ entire surface. This vast treasure trove of imagery and other data virtually defined the Mars we know today, a place with diverse and complex geology and a watery past.

For number 6, I picked Galileo, a huge and hugely successful Jupiter orbiter. Galileo was launched from the payload bay of the shuttle Atlantis in 1989 and took a roundabout route to Jupiter, using Venus and Earth for gravitational assists, and buzzing a couple of asteroids on the way. Between 1995 and 2000, Galileo studied the Jovian system, sending back thousands of images of Jupiter and its surprisingly varied moons. Galileo’s mission ended in 2003 when it was flown into Jupiter’s atmosphere to avoid possible accidental contamination of one of Jupiter’s moons.

Before getting to the Top 5, I’d like to mention an important JPL mission that never ends – communication and public outreach. JPL has always taken seriously the need to communicate its discoveries not only to scientists, but to the world. Of course the web makes it easier and faster than ever to share images and other information, and JPL’s web site is really great. But they have other outreach programs too, including one that I especially like, the Solar System Ambassadors program. This program enlists volunteers in every U.S. state to help spread the word about the great things that NASA is doing. I’m proud to be a Solar System Ambassador in Central Massachusetts, giving presentations at schools, scout meetings, libraries, and other venues.

Now back to the countdown. Number 5 is Cassini/Huygens, which has been exploring the Saturn system since 2004. Early in the mission, Cassini dipped low over Saturn’s cloud-covered moon Titan and released the ESA-built Huygens spacecraft which parachuted to the surface. Cassini is a huge spacecraft with many scientific instruments, but it’s the pictures of Saturn, its beautiful ring system, and its always surprising collection of moons that have captured the imaginations of so many people – me included!

With number 4, I’m cheating a little, since Mariner was actually a long series of missions to Venus, Mars, and finally Mercury, from 1962 to 1975. Mariners 2, 5, and 10 were Venus fly-by missions (Mariner 10 also visited Mercury). Mariners 4, 6, and 7 were Mars fly-by’s, and Mariner 9 in 1971 was the first spacecraft to orbit Mars. The amazing Mariner series gave humankind its first up-close views of our neighboring planets.

Number 3 was the Millenium Falcon… wait, sorry, no, that was George Lucas, not JPL. Number 3 was the incredible Mars Viking program which sent two spacecraft to Mars in 1976. Viking 1 and Viking 2 both achieved Mars orbit, and both released lander spacecraft that successfully reached the surface in different areas of Mars. While the landers sent back the first pictures from the surface of Mars, the Viking orbiters continued to circle the planet and sent back thousands of images that allowed Mars to be mapped and studied in great detail.

It was tough to decide the two top spots, but I finally put the Voyager program at number 2. Voyagers 1 and 2 were launched in 1977 to take advantage of a rare alignment of the outer planets that could allow fly-by’s of both Jupiter and Saturn, and in the case of Voyager 2, Uranus and Neptune as well. Clever trajectory design allowed for close-up views of several of the moons of Jupiter and Saturn as well as the planets themselves, and gravitational assists gave the Voyagers the energy they needed to continue their voyages. Amazingly enough, both spacecraft are still operating today, 32 years after launch, sending back data from the farthest reaches of the solar system, Earth’s first interstellar voyagers. Voyager 1 is now about 17 billion kilometers from the sun, the farthest man-made object.

Finally, at number 1, we have the incredible Mars Exploration Rover program, the tireless Spirit and Opportunity and the often tired but proud teams of JPL engineers and scientists who keep them going and going and going. These plucky 6-wheeled robots have been roving Mars since January 2004 on a 90 day mission that has now lasted more than 5 years. Although both rovers have seen tough times, they succeeded in proving that liquid water once flowed on Mars, and they continue to send back valuable data almost every day. “Spirit” and “Oppy” are perhaps the most famous robots in the solar system, and justifiably so.

So there you have it, MY choices for JPL’s Top 10 Greatest Hits in space exploration. I felt bad leaving out great historical programs like Pioneer and Mars Pathfinder, and great ongoing programs like Mars Reconnaissance Orbiter and Spitzer, but that’s the nature of a top 10 list, not to mention a 10 minute podcast.

Of course you can learn more from JPL’s web site, but please also visit my blog, Music of the Spheres,, where I will have more details on the programs I discussed here, including information on how you can experience parts of these famous missions yourself with the free Orbiter space flight simulator and various free add-ons.

I’d like to close this podcast with a quote from the great Carl Sagan, a planetary scientist who spent quite a lot of time at JPL. In his 1973 book The Cosmic Connection, he wrote:

“In all the history of mankind, there will be only one generation that will be the first to explore the Solar System, one generation for which, in childhood, the planets are distant and indistinct discs moving through the night sky, and for which, in old age, the planets are places, diverse new worlds in the course of exploration.

There will be a time in our future history when the Solar System will be explored and inhabited. To them, and to all who come after us, the present moment will be a pivotal instant in the history of mankind. There are not many generations given an opportunity as historically significant as this one. The opportunity is ours, if we but grasp it. To paraphrase K.E. Tsiolkovsky, the founder of astronautics: The Earth is the cradle of mankind, but one cannot live in the cradle forever.”

I’m sure that many of you listening to this podcast are, like me, members of that fortunate generation, and it is in large part thanks to the people of JPL that we already do know many parts of the Solar System as places, and not only as faint discs in the sky.

End of podcast:

365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by the New Media Working Group of the International Year of Astronomy 2009. Audio post-production by Preston Gibson. Bandwidth donated by and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at or email us at Until tomorrow…goodbye.

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