Status Report

New Horizons – The PI’s Perspective – A Road Trip, from Earth to Pluto

By SpaceRef Editor
August 3, 2005
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New Horizons – The PI’s Perspective – A Road Trip, from Earth to Pluto

Alan Stern

August 2005

As August begins, the New Horizons spacecraft continues its space-simulation testing in a large vacuum chamber at NASA’s Goddard Space Flight Center. The chamber we are using is capable of achieving a vacuum of about one-billionth of an atmosphere and running the spacecraft at any temperature it could conceivably see on its journey from Earth to Pluto. In a real sense, our spacecraft is now “at home”for the first time – in a close facsimile of the space environment that she was built to operate in.

While New Horizons is in test at Goddard’s vacuum chamber, our engineering and operations teams have been running mission simulations, thermal performance tests, and various special tests on “the bird.”Many of the tests are run at both hot and cold temperatures. In addition to testing the spacecraft subsystems, all seven of the scientific instruments aboard the spacecraft are being put through their paces. To make the testing as realistic as possible, almost every test operation is run just as it would be in flight – from the Space Science Mission Operations Center back at the Johns Hopkins University Applied Physics Lab (APL).

The testing has been going well. We have gained a great deal of experience with the spacecraft, showing it operates almost exactly as expected. The teams have worked out many of the bugs in the initial drafts of our flight procedures.

In a system as complex as a spacecraft, finding hardware and software problems during ground testing is commonplace. Last month, spacecraft testing revealed a hardware problem in one of the 64-gigabit Solid State Recorders aboard New Horizons. These flash memory devices, called SSRs, are the memory banks on which the spacecraft stores all of the scientific and engineering data it generates. For redundancy purposes, New Horizons carries two SSRs, and we require that both be operational at launch. The problem with our sick SSR is probably related to a manufacturing defect on a single circuit card, and is not expected to be hard to repair. The sick SSR will have to be removed from the spacecraft and repaired after New Horizons emerges from the vacuum chamber in September. The repaired device must be successfully tested on its own and on New Horizons before it can be certified as flight ready.

Although one would like a spacecraft that is completely free of problems from the minute it is put together, I’m very glad we found the SSR problem, since it could not be fixed after launch. Indeed, this is why we do the testing we are doing – to smoke out design, fabrication, software, and procedural problems before we get into flight.

Education and Outreach

Just as our spacecraft and mission operations teams are preparing for the journey to Pluto, so are other parts of the project. One such element of the project is what we call EPO – for Education and Public Outreach. Our EPO effort (see is coordinated by Kerri Beisser and Linda Butler of APL, and mission Co-Investigator Dr. Fran Bagenal of the University of Colorado. Very few people appreciate how much effort goes into EPO activities for NASA missions, or that this work begins years before launch.

The EPO effort for New Horizons involves many activities and several dozen people across the United States. The activities include museum exhibits, Web page development, classroom lesson plans that range from the kindergarten to university level, and radio and TV documentaries. The development of the Student Dust Counter (SDC) instrument aboard New Horizons is another example of EPO, designed to give university students an opportunity to learn to design, build and operate a scientific instrument aboard a deep space probe.

As the mission PI, my involvement in the EPO program started when the project began in 2001. As we planned the science and the mission itself, we also planned the EPO effort. Since then I’ve been involved in as many aspects as I could make time for, such as monitoring and advising SDC development; giving about 15 to 20 talks across the U.S. each year about New Horizons; providing or checking the content of literally hundreds of Web pages and dozens of printed materials; participating in radio and TV interviews; and planning and reviewing press releases.

This past month, I had the pleasure of visiting another of our EPO partner institutions, the University of Maine at Presque Isle, in far northern Maine. While there, I met with Kevin McCartney and Jeanie McGowan, who run both the New Horizons effort and the Northern Maine Museum of Science. I also had the pleasure of spending some time with a few of their staff, and giving talks to almost 100 students and a local summer camp group. For Kevin, Jeanie and their folks, New Horizons is just one of many educational and public outreach activities they are involved in, but New Horizons is clearly a labor of love for them.

The most interesting aspect of their outreach activities is the solar system scale model they have built. The model stretches along a large section of Route 1 in Maine’s Aroostook County. The center of the model, the Sun, is located on the UMPI campus in Presque Isle; the model extends outward from there, across the entire solar system to (of course!) Pluto-Charon, which is located at the Houlton, Maine, tourist information center, some 40 miles to the south, where Interstate-95 and Route 1 intersect.

Although there are other scale models of the solar system around the United States, the Maine model is by far the largest. And the scale of the Maine model solar system is truly HUGE – one mile per Astronomical Unit (or AU, the distance from the Earth to the Sun). Each of the nine classical planets is located along Route 1 at their appropriate distances, and at their appropriate size. For example, Earth is represented by a grapefruit-sized blue sphere a mile from the 50-foot diameter Sun; tiny Luna, only about an inch across, is located about 13 feet from the model Earth.

To build the model, Kevin and Jeanie had the help of literally hundreds of local people, from students and craftsmen to lawyers and educators. And the entire model was built on volunteer labor.

You can learn more about Maine’s model solar system at, but I have to tell you, it’s worth the drive to go and see. Besides being in beautiful and rural northern Maine, the model is an object lesson in the vast emptiness that so characterizes the space between the planets in our solar system.

Taking the road trip from Earth to Pluto across Aroostook County, Maine, drives home a deep appreciation for just how far New Horizons has to travel across our vast solar system to accomplish its mission. Even at highway speeds, it takes almost an hour to travel across the expanse of our planetary system. And as you drive, and drive, and drive, passing the occasional lonely orbs that represent each planet, you can’t help but viscerally feel just how far apart the planets are from one another, particularly in the outer solar system.

As we continue testing New Horizons, Kevin and Jeanie’s model reminds me that New Horizons has a very long journey ahead, before it can show scientists, students and space enthusiasts what secrets Pluto-Charon holds, some 5 billion kilometers down the road.

SpaceRef staff editor.