NRL's J-PEX Completes Successful Flight

1/6/2009 - 8-09r
Contact: Donna McKinney, (202) 767-2541

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The Joint Astrophysical Plasmadynamic Experiment (J-PEX) launched successfully on a NASA sounding rocket on October 20, 2008, from the White Sands Missile Range, New Mexico. Preliminary indications are that the mission was a comprehensive success. This new successful flight is a critical step along the path to a future orbital payload flown on a small satellite platform, which has the potential to harvest rich rewards in both astrophysics and atmospheric physics. A collaborative effort between the Naval Research Laboratory and Lawrence Livermore National Laboratory in the U.S., and the University of Leicester in the U.K., J-PEX is a high resolution spectrometer operating at extreme ultraviolet (EUV) wavelengths, which provides fundamental information on physical conditions within million degree plasmas. The technology of multilayer-gratings that underpins the J-PEX science opportunity is the result of basic, NRL- and NASA-funded research spanning two decades.

J-PEX first flew successfully in 2001 and made the first high-resolution extreme ultraviolet (EUV) spectrum of a non-solar object, the isolated white dwarf G191-B2B. White dwarfs are important because they are the end product of evolution for most stars in our galaxy. (For example, our sun will become a white dwarf in about 5 billion years.) White dwarfs are very dense objects, with the mass of the sun squeezed into a volume typically the size of the Earth. During the course of its evolution into a white dwarf, a star will shed some of its mass into the interstellar medium, seeding it with helium and other heavy elements. Since clouds of interstellar matter eventually collapse to form new stars and planetary systems, understanding white dwarf evolution impacts directly on our knowledge of the galaxy and ultimately the universe.

The published results of the 2001 flight included a measurement of the interstellar column of ionized helium and an indirect detection of photospheric helium. Both of these are critical to models of stellar formation and evolution, as white dwarfs are the endpoints for most stars in our galaxy, including the Sun. Advances in astrophysics at EUV wavelengths require high spectral resolution to disentangle phenomena intrinsic to sources from effects in the intervening medium, whether it be the atmosphere of the intended target or the interstellar medium. J-PEX has already achieved the world's best resolution in an EUV astrophysics instrument and now represents the path to developing the entire EUV band.

Since the 2001 flight, J-PEX has undergone extensive improvements, resulting in a three-fold increase in throughput and a 40% increase in resolution. The target for this second mission was also a white dwarf, Feige 24, but it is located in a binary system, thus introducing exciting new aspects that are complementary to those for the first mission. The raw data show the spectra from the payload's four gratings as well as an image of the target. J-PEX also observed the target as the payload ascended and descended through the atmosphere, thus extending to EUV wavelengths (altitudes>150 km) the occultation observations made at X-ray wavelengths (altitudes 75-150 km) by NRL's USA experiment flown on the STP ARGOS satellite. Such data are applicable to the NRL MSIS model atmospheric density and have implications for DoD systems.

The J-PEX project was managed in NRL's High-Energy Space Environment Branch by a team that includes: Dr. Michael P. Kowalski (Principal Investigator), Dr. Ray Cruddace, Dr. Kent Wood, the late Dr. Daryl Yentis, Dr. Fred Berendse, Dr. Michael Wolff, the late Dr. Herb Gursky, and contractors Gil Fritz, Don Woods, Greg Clifford, Janet Clifford, Dave Wagner, and Bill Hunter.

The Lawrence Livermore National Laboratory team member is Dr. Troy W. Barbee, Jr. The University of Leicester team members are Dr. Martin Barstow and Dr. Jon Lapington.

Launch of J-PEX

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