National Aeronautics and Space Administration Logo
Follow this link to skip to the main content NASA Banner
Solar System Exploration
Science & Technology
Ralph Aims to Put Pluto in Focus

When it comes to Pluto watching, it sometimes seems like little has changed since Clyde Tombaugh discovered the planet more than 70 years ago. Pluto's small size and great distance from Earth have long conspired to make it appear as a pinpoint with the best of technologies - even the mighty Hubble Space Telescope has seen Pluto's surface as a dot in patchy shades of white and gray.

Ralph's job is visible and infrared imaging and spectroscopy.
Ralph's job is visible and infrared imaging and spectroscopy.

Atop the New Horizons scientific must-do list is gathering clear and comprehensive geological and compositional maps of the surfaces of Pluto and Charon. And the mission team will count on a digital imager named Ralph to deliver a deep-space photo op of a lifetime.

"Ralph is the New Horizons mission's main sense of sight," says Alan Stern of the Southwest Research Institute, Boulder, Colo., principal investigator for New Horizons as well as the Ralph instrument. "Among other things, Ralph will make the maps that show us what Pluto, Charon and Kuiper Belt objects look like. And Pluto is so far from the Sun that Ralph must accomplish this at light levels 1,000 times fainter than daylight at Earth, or 300 times fainter than the conditions Mars probes face."

So-named simply because it's coupled with an ultraviolet spectrometer called Alice in the New Horizons remote-sensing package - a "Honeymooners" reference classic TV fans will appreciate - Ralph is a joint project between Southwest Research Institute (SwRI), Ball Aerospace, Boulder, and NASA Goddard Space Flight Center, Greenbelt, Md. The instrument consists of three panchromatic (black-and-white) and four color imagers inside its Multispectral Visible Imaging Component (MVIC), as well as an infrared compositional mapping spectrometer called the Linear Etalon Imaging Spectral Array (LEISA).

Ralph's suite of seven detectors - all charge-coupled devices (CCDs), as you'd find in a digital camera - are fed by a single, sensitive magnifying telescope with a resolution more than 10 times better than the eye can see. The entire package weighs 11 kilograms (about 24 pounds) and draws 6 watts of power ? well under half the wattage of many Christmas tree light bulbs. "It's an absolutely incredible device," says Bob Parizek, Ralph project manager at Ball Aerospace.

A detailed view of Ralph
A detailed view of Ralph.

Pluto science encounter plans call for Ralph to take images almost daily as New Horizons approaches, flies past and then looks back at Pluto and Charon. For weeks on approach, MVIC's resolution will exceed anything obtained previously. Ultimately MVIC will map global geology and landforms with a typical resolution of about 1 kilometer per pixel, take stereo and nighttime images, and help scientists refine Pluto-Charon's radii and orbits. It will also aid the search for clouds and hazes in Pluto's atmosphere, and rings and additional satellites around Pluto and other Kuiper Belt objects.

At the same time, LEISA will map the amounts of water, methane, carbon dioxide, nitrogen ice and other materials across the sunlit surfaces of Pluto and Charon (and later Kuiper Belt objects). It will also help scientists map surface temperatures across Pluto and Charon by sensing the details of spectral features of frozen nitrogen, water and carbon monoxide.

And that's only what the mission team expects to find.

"Who knows what else we'll discover?" says Dennis Reuter, Ralph instrument scientist at Goddard Space Flight Center. "Craters, mountains, maybe even nitrogen geysers like Voyager found on [Neptune's moon] Triton - we just don't know. All we have are these vague images of Pluto and Charon. But that's going to change when New Horizons arrives."

Ralph and the other New Horizons instruments are slated for delivery and integration onto the spacecraft this summer. The mission is planning its launch for January 2006, a gravity boost and scientific swing through the Jupiter system in 2007, and arrival at Pluto-Charon in summer 2015.

Related Links

Last Updated: 2 March 2011

Science Features
Astronomy Features
Technology Assessment Reports
Sungrazing Comets


Best of NASA Science
NASA Science Highlights
Technology Features
Lectures & Discussions

Awards and Recognition   Solar System Exploration Roadmap   Contact Us   Site Map   Print This Page
NASA Official: Kristen Erickson
Advisory: Dr. James Green, Director of Planetary Science
Outreach Manager: Alice Wessen
Curator/Editor: Phil Davis
Science Writers: Courtney O'Connor and Bill Dunford
Producer: Greg Baerg
Webmaster: David Martin
> NASA Science Mission Directorate
> Budgets, Strategic Plans and Accountability Reports
> Equal Employment Opportunity Data
   Posted Pursuant to the No Fear Act
> Information-Dissemination Policies and Inventories
> Freedom of Information Act
> Privacy Policy & Important Notices
> Inspector General Hotline
> Office of the Inspector General
> NASA Communications Policy
> NASA Advisory Council
> Open Government at NASA
Last Updated: 2 Mar 2011