CALET (CALorimetric Electron Telescope) is an observation instrument equipped with cutting-edge detectors and electronic technology to perform very high precision observations of extremely high-energy electrons, gamma-rays, protons and atomic nucleus, which have been difficult to perform to date, and also measure gamma-ray burst phenomena. Through the CALET observations, we are aiming at elucidating cosmic / universal mysteries including 1) origin and acceleration mechanism of high-energy cosmic rays, 2) diffusion mechanism of cosmic rays within the Galaxy, and 3) dark matter signature. CALET was transported to Kibo by the KOUNOTORI5 launched from the Tanegashima Space Center in August 2015 to be installed on the Kibo's Exposed Facility. After completing the initial verification of observation instruments, CALET is now under calibration and verification of detected data. In the early stage of the verification process, the TeV electrons (candidates) have already been observed as shown in the previous page. CALET will move to regular observation mode after data calibration and verification to perform high-precision observations for over two years. We will achieve our observation goals through statistical processing with fewer errors. The mission instrument will observe high-energy cosmic rays in space. CALET is installed on the Exposed Facility of the Japanese Experiment Module "Kibo" at the International Space Station (ISS). It is a joint research project of JAXA and Waseda University led by Professor Shoji Torii (Faculty of Science and Engineering, Waseda University). Among the Japanese team, 22 research institutes such as Kanagawa University, Aoyama Gakuin University, and the Institute for Comic Ray Research, University of Tokyo, are also participating in this project. In addition, NASA and the Italian Space Agency (Agenzia Spaziale Italiana, ASI) cooperated to develop CALET. NASA and American researchers provided us with technical support for the cosmic rays observation sensor technology, while ASI and Italian researchers assisted us with high-voltage power and cosmic rays observation sensor technology. Both of them will mutually cooperate in analyzing CALET observation data. The calorimeter that can detect positions of shower particles is installed on CALET. The calorimeter was developed under the cooperation of Japan, NASA and ASI by carrying out beam tests of a CALET proto-type model at the European Organization for Nuclear Research (CERN). By imaging the "shower particles" that are generated by cosmic rays within the calorimeter, high energy cosmic rays can be observed precisely. The calorimeter is an instrument to measure the energy of high-energy particles. When an electron or gamma-ray passes through a matter, electromagnetic interactions, such as bremsstrahlung and electron-positron pair creation, occurs successively and increases particles (cascade shower). The calorimeter is an instrument to determine energy of incoming particles by measuring energy loss of the shower particles. CALET is a three layer structure. The TASC, which lies at the bottom, adopts "lead tungstate (PbWO4) crystals" for a scintillator. It is the thickest scintillator as a cosmic ray observation instrument, and has the incomparable capability of precisely determining energy and identifying particle at high energies over 1 TeV. The cross section of the scintillating fibers used in the IMC in the middle layer is 1 square mm so that we can obtain sufficient information by read-out of each fiber data, which is necessary for determining the arrival direction and types of incoming cosmic rays. Therefore, CALET can explore the high-energy region as a whole calorimeter, which had been difficult to observe by a conventional method. Conventional research says that dark matter is highly likely the "weakly interacting massive particles (WIMP)" which was generated at the early universe. In theory, the WIMP creates already-known elementary particles (such as electron/positron pairs) through pair annihilation and decay, and the maximum energy of the created particles is limited to the mass energy of the WIMP. The WIMP's mass is expected to be more than several 100 GeV based on the past observation of electron/positron. Therefore, observation of electrons/positrons in the TeV region by CALET calorimeter is crucial for searching dark matter. CALET is the first instrument that can achieve the electron observations in such a high-energy region.
News Article | December 20, 2015
The NASA-operated Cassini spacecraft is about to wrap up its exploration of Enceladus as it carries out the final flyby of Saturn's moon this weekend. According to the American space agency, the space probe will move past the icy moon at a distance of about 3,106 miles (4,999 kilometers) on Saturday. This will provide scientists with additional information on Enceladus' surface. While Saturday's flyby will be the final one for the Saturn mission, Cassini will still continue its observation of Enceladus at a greater distance. The space probe's mission to the planet system will carry on through September 2017. Cassini will focus on monitoring heat levels passing through Enceladus' icy surface from its interior. Researchers believe that studying this phenomenon is crucial in finding out the source of the icy particles and gas plume emanating from the moon's subterranean ocean. "Understanding how much warmth Enceladus has in its heart provides insight into its remarkable geologic activity, and that makes this last close flyby a fantastic scientific opportunity," NASA project scientist Linda Spilker said. During its scheduled pass, Cassini will keep its distance from Enceladus to allow its Composite Infrared Spectrometer (CIRS) to measure the flow of heat across the moon's south polar region. Mike Flasar, leader of NASA's CIRS team, said that Cassini's distance from the moon during the flyby is ideal to let them map the levels of heat coming from its interior at a good resolution. NASA scientists, however, do not expect to collect as many stunning photographs of Enceladus as in previous flybys because the moon's south polar area is currently covered in darkness caused by Saturn's years-long winter. Cassini is able to easily monitor the warmth coming from Saturn's moon because of the absence of heat from the sun. In October, Cassini completed its dive through Enceladus' erupting gas plume, taking the spacecraft around 30 miles above the moon's surface. Researchers are currently studying data on the plume collected during the flyby in order to understand the nature of the phenomenon and find out whether it involves the presence of hydrogen gas. The Cassini space probe has been exploring the Saturn system since 2004. Operation of the mission is conducted by NASA in cooperation with the European Space Agency (ESA) and the Italian Space Agency (ASI).
News Article | December 1, 2015
Scientists have found the first direct evidence for explosive releases of energy in Saturn's magnetic bubble using data from the Cassini spacecraft, a joint mission between NASA, the European Space Agency, and the Italian Space Agency. The research is reported in the journal Nature Physics.
News Article | September 7, 2016
“Frigid alien landscapes” are coming to light in new radar images of Saturn's largest moon, Titan, captured from NASA's Cassini spacecraft. NASA's Cassini spacecraft has radar vision that allows it to peer through the haze that surrounds Saturn's largest moon, Titan. The video below focuses on 'Shangri-la,' a large, dark area on Titan filled with dunes. The long, linear dunes are thought to be comprised of grains derived from hydrocarbons that have settled out of Titan's atmosphere. From the Cassini press team at NASA: Cassini obtained the views during a close flyby of Titan on July 25, when the spacecraft came as close as 607 miles (976 kilometers) from the giant moon. The spacecraft's radar instrument is able to penetrate the dense, global haze that surrounds Titan, to reveal fine details on the surface. One of the new views (along with a short video) shows long, linear dunes, thought to be comprised of grains derived from hydrocarbons that have settled out of Titan's atmosphere. Cassini has shown that dunes of this sort encircle most of Titan's equator. Scientists can use the dunes to learn about winds, the sands they're composed of, and highs and lows in the landscape. "Dunes are dynamic features. They're deflected by obstacles along the downwind path, often making beautiful, undulating patterns," said Jani Radebaugh, a Cassini radar team associate at Brigham Young University in Provo, Utah. Another new image shows an area nicknamed the "Xanadu annex" earlier in the mission by members of the Cassini radar team. Cassini's radar had not previously obtained images of this area, but earlier measurements by the spacecraft suggested the terrain might be quite similar to the large region on Titan named Xanadu. First imaged in 1994 by NASA's Hubble Space Telescope, Xanadu was the first surface feature to be recognized on Titan. While Hubble was able to see Xanadu's outline, the annex area went unnoticed. The new Cassini image reveals that the Xanadu annex is, indeed, made up of the same type of mountainous terrains observed in Xanadu and scattered across other parts of Titan. "This 'annex' looks quite similar to Xanadu using our radar, but there seems to be something different about the surface there that masks this similarity when observing at other wavelengths, as with Hubble," said Mike Janssen, also a JPL member of the radar team. "It's an interesting puzzle." Xanadu -- and now its annex -- remains something of a mystery. Elsewhere on Titan, mountainous terrain appears in small, isolated patches, but Xanadu covers a large area, and scientists have proposed a variety of theories about its formation. "These mountainous areas appear to be the oldest terrains on Titan, probably remnants of the icy crust before it was covered by organic sediments from the atmosphere," said Rosaly Lopes, a Cassini radar team member at JPL. "Hiking in these rugged landscapes would likely be similar to hiking in the Badlands of South Dakota." The July 25 flyby was Cassini's 122nd encounter with Titan since the spacecraft's arrival in the Saturn system in mid-2004. It was also the last time Cassini's radar will image terrain in the far southern latitudes of Titan. "If Cassini were orbiting Earth instead of Saturn, this would be like getting our last close view of Australia," said Stephen Wall, deputy lead of the Cassini radar team at NASA's Jet Propulsion Laboratory in Pasadena, California. Cassini's four remaining Titan flybys will focus primarily on the liquid-filled lakes and seas in Titan's far north. The mission will begin its finale in April 2017, with a series of 22 orbits that plunge between the planet and its icy rings. The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. JPL, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the U.S. and several European countries.
News Article | December 15, 2015
NASA's Cassini spacecraft spent more than a decade collecting data on the Saturn system. It has captured stunning images of the ringed planet as well as its collection of moons that provide researchers with a glimpse of Saturn's alien world. The latest data sent by Cassini come in the form of a high quality image showing Enceladus and Tethys, Saturn's well-known moons, in near-perfect alignment. Enceladus, the smaller of the two natural satellites, can be seen acting as the bull's eye in their positions. The similar distances between the two moons and the Cassini spacecraft allow observers to compare the sizes of Enceladus and Tethys. Enceladus measures at around 313 miles (504 kilometers) wide, while the larger Tethys comes in at around 660 miles (1,062 kilometers) across. At the time of the transit of the moons on Sept. 24, the Cassini spacecraft was situated around 1.3 million miles (2.1 million kilometers) from Saturn's Enceladus and around 1.6 million miles (2.6 million kilometers) from Tethys. This means that the two natural satellites were only around 300,000 miles (500,000 kilometers) from each other. The Cassini space mission is a joint project between the Italian Space Agency (ASI), the European Space Agency (ESA) and NASA. It is managed by the Jet Propulsion Laboratory (JPL), one of the divisions of the California Institute of Technology (Caltech) located in Pasadena, California. The JPL was responsible in creating the mission's Cassini orbiter as well as the two cameras onboard the spacecraft. Photographs sent back to Earth by Cassini are processed in the Space Science Institute's imaging operations center. Scientists are paying close attention to Saturn's Enceladus after discovering that the moon could possibly contain a subterranean ocean buried beneath its icy crust. It is believed that this body of water is made up of elements that could sustain alien life. The Cassini spacecraft is currently preparing to carry out its final flyby of Enceladus that is set to occur on Dec. 19. The mission, which is known as E-22 to represent Cassini's 22nd flyby, will have the orbital probe come within 3,106 miles (4,999 kilometers) of Enceladus' surface.