Computational Astrophysics Laboratory

Outline

We promote the JEM-EUSO (Extreme Universe Space Observatory onboard Japanese Experiment Module) mission to explore the origin of extreme energy particles above 1020 eV. This is a project to observe from orbit giant air showers of extreme energy cosmic rays. The JEM-EUSO has a super wide-field (60-degree) telescope with a diameter of 2.5 meters planned for installation on the International Space Station, and has been selected as the candidate mission for the second utilization of JEM/EF. A two-year Phase-A/B study has begun, with JEM-EUSO planned for launch in 2016 by the Japanese H II B heavy lift rocket, and then conveyed to the ISS by HTV (H-II Transfer Vehicle).

Other active projects being conducted in parallel with this include the development of super high-speed special-purpose computers, large-scale simulations for the study of biomolecules and the formation of super-massive black holes and the relation of the latter to hypernova/gamma-ray bursts, earth materials sciences exploration via quantum simulation, the development of a G-APD camera for sub-μsec sampling and exploring its application to biomolecular science, the development of ReKOS, a user-friendly software application package to facilitate information sharing among researchers, and promoting the use of computers in education.

Recent Research Topic

Exploring the origins of extreme energy cosmic rays with the International Space Station

Fig. 1 Artist's conception of the JEM-EUSO telescope observing an air shower

Fig. 2 Trajectory of charged particles in the Milky Way Galaxy

Low-energy charged particles are bent and wound by magnetic fields, but those above 1020 eV travel along almost straight trajectories with little influence from magnetic fields, thereby retaining the original directional information.

Fig. 3 A real-size bread board model of the central part of the JEM-EUSO optics (1.5 m in diameter)

JEM-EUSO is a new type of observatory that uses the earth's atmosphere as a detector. JEM-EUSO will be in orbit on the International Space Station (ISS) to observe transient luminous phenomena taking place in the earth's atmosphere caused by particles coming from space. This remote-sensing instrument is a super wide-field telescope that will detect extreme energy cosmic-rays with energy above 1019 eV, and will orbit the earth once every 90 minutes at an altitude of approximately 400 km.

The JEM-EUSO telescope has a super-wide field-of-view (±30°) with two double-sided curved Fresnel lenses, able to record the track of an EAS (extensive air shower, caused by a cosmic ray) with a time resolution of 2.5 microseconds and a spatial resolution of about 0.75 km (corresponding to 0.1 degrees). These time-segmented images allow the determination of the energies and directions of the primary particles.

The JEM-EUSO instrument can reconstruct the incoming direction of the extreme energy particles at an accuracy of greater than several degrees. It can observe a ground area up to a radius of 250 km with a 60-degree field of view, the atmospheric volume above which will consist of one tera-ton or more. Extreme energy particles detected will be traced back to their origin by measuring arrival direction with an accuracy of several degrees.

JEM-EUSO will also observe atmospheric luminous phenomena such as lightning, nightglow, and meteors.

JEM-EUSO has been selected as the candidate mission for the second utilization of JEM/EF. A two-year-long study project has begun that plans the launch of JEM-EUSO in about 2016 by the Japanese heavy lift rocket H II B, and its conveyance to ISS by HTV (H-II Transfer Vehicle).

The JEM-EUSO telescope has a diameter of 2.5 m, the largest refractive telescope ever made, the transparent lens of which was enabled using nano-precision fabrication technology, and the Fresnel lens design was chosen to reduce mass and eliminate color aberration in the optics. The Materials Fabrication Laboratory manufactured a real-size bread board model of the central part of the JEM-EUSO optics (1.5 m in diameter) in December 2010.