The CALET mission is designed to investigate the High Energy Universe, as a next generation experiment to build upon discoveries made by Fermi, PAMELA, AMS, Atmospheric Cherenkov Telescopes (ACT) and balloon instruments. CALET is a calorimeter-based instrument with superior energy resolution and excellent separation between hadrons and electrons and between charged particles and gamma rays. With these capabilities, it will be possible for CALET to address many of the outstanding questions in High Energy Astrophysics (HEA) including (1) signatures of dark matter in either the high energy electron or gamma ray spectrum, (2) the nature of the sources of high energy particles and photons through the high energy electron spectrum, and (3) the details of particle propagation in the galaxy by a combination of energy spectrum measurements of electrons, protons and higher-charged nuclei. Thus, CALET can be thought of as an HEA “observatory”.

CALET Infographic

CALET, an acronym for CALorimetric Electron Telescope, is a Japanese-Italian-US mission developed as part of the utilization plan for the International Space Station (ISS). CALET was launched Aug. 19, 2015 on an H2 rocket utilizing the Japanese-developed HTV (H-IIA Transfer Vehicle) and robotically attached to the Exposure Facility attached to the Japanese Experiment Module (JEM-EF) (Figure 1).

CALET is funded by JAXA in Japan, ASI in Italy, and NASA in the US. The US institutions consist of Lead Institution Louisiana State University, NASA Goddard Space Flight Center, Washington University in St. Louis, and the University of Denver.

 Selected recent publications and news articles:

“Japanese, Italian, US physicists reveal new measurements of high-energy cosmic rays”EurekAlert, June 2021.
“Measurement of the Iron Spectrum in Cosmic Rays from 10 GeV/n to 2.0 TeV/n with the Calorimetric Electron Telescope on the International Space Station”, O. Adriani et al., Phys. Rev. Lett. 126, 241101 (2021);
“Direct Measurement of the Cosmic-Ray Carbon and Oxygen Spectra from 10 GeV/n to 2.2 TeV/n with the Calorimetric Electron Telescope on the International Space Station”, O. Adriani et al., Phys. Rev. Lett. 125, 251102 (2020);
Direct measurement of the cosmic-ray proton spectrum with the CALET on the ISS“, May 2019,
Direct Measurement of the Cosmic-Ray Proton Spectrum from 50 GeV to 10 TeV with the Calorimetric Electron Telescope on the International Space Station”, O. Adriani et al., Phys. Rev. Lett. 122, 181102 (2019);
Search for GeV Gamma-ray Counterparts of Gravitational Wave Events by CALET”, O. Adriani et al., Astrophys. J. 863 (2018); .
Characteristics and Performance of the Calorimetric Electron Telescope (CALET) Calorimeter for Gamma-Ray Observations”, N. Cannady et al., Astrophys. J. Suppl. 238:5 (2018);
CALET succeeds in direct measurements of cosmic ray electron spectrum up to 4.8 TeV“, July 2018,
High Statistics Measurement of Cosmic-ray Electron and Positron Spectrum from 11 GeV to 4.8 TeV with the Calorimetric Electron Telescope on the International Space Station”, O. Adriani et al., Phys. Rev. Lett. 120, 261102 (2018);
On-orbit Operations and Offline Data Processing of CALET Onboard the ISS“, Y. Asaoka et al., Astroparticle Phys. 100, 29 (2018);
Detection of the Thermal Component in GRB 160107A“, Y. Kawakubo et al., Publ. Astronom. Soc. Japan 70, 6 (2018); pasj/psx152.
“First Cosmic-ray Results from CALET on the ISS”, CERN Courier, Dec. 2017, p.9.
NASAWaseda Univ., LSU  news releases, Nov. 2017.
“Energy Spectrum of Cosmic Ray Electron + Positron from 10 GeV to 3 TeV Observed with the Calorimetric Electron Telescope on the International Space Station”, O. Adriani et al., Phys. Rev. Lett. 119, 181101 (2017);
“Multi-Messenger Observations of a Binary Neutron Star Merger”, B.P. Abbott et al. (LIGO Scientific Collaboration, VIRGO Collaboration, and Partner Astronomy Groups), Astrophys. J. Lett. 848:L12 (2017);
“Energy Calibration of CALET Onboard the International Space Station”, Y. Asaoka et al., Astroparticle Phys. 91, 1 (2017); .
“The CALorimetric Electron Telescope (CALET) on the ISS: Preliminary Results from the On-orbit Observation since October”, S.Torii for the CALET Collaboration, Highlight talk, 35th Intl. Cosmic Ray Conf., Busan, South Korea, July 2017.
“CALET Upper Limits on X-Ray and Gamma-Ray Counterparts of GW 151226”, O. Adriani et al., Astrophys. J. Lett., 829:L20 (2016);
“Relativistic Electron Precipitation at International Space Station: Space Weather Monitoring by CALorimetric Electron Telescope”, R.Kataoka et al., Geophys. Res. Lett. 43, 4119 (2016);
“CALET sees Events in Millions”, CERN Courier, April 2016,
“Dark Matter and Particle Acceleration in Near Space”, NASA press release, Nov. 2015.
First gamma ray burst observed by CALET Gamma ray Burst Monitor, Oct. 2015

The CALorimetric Electron Telescope (CALET) aboard the International Space Station has begun taking data. An example of a TeV electron event observed during the initial commissioning period is shown in the Japanese Space Agency press release.

Gamma Ray Burst signal

The figure above is an CGBM light curve that shows two spikes peaking at T0-2s and T0+2s, and the emission ending around T0+~60s. The T90 duration measured by the CGBM data is 63 +- 5 s (30 – 1000 keV).

CALET arrives at Space Station Aug. 24, 2015

The Japanese Aerospace Exploration Agency’s (JAXA) “Kounotori” H-II Transfer Vehicle (HTV-5) arrived at the International Space Station Aug. 24 to deliver almost five tons of supplies and scientific experiments to the Expedition 44 crew. The cargo vehicle was launched atop a Japanese H-IIB rocket Aug. 19 from the Tanegashima Space Center in southern Japan.

CALET Instrument Scheduled for Launch to Space Station, Aug. 2015

The CALorimetric Electron Telescope (CALET) instrument is scheduled for launch to the International Space Station (ISS) aboard the HTV-5 vehicle on 16 August at about 10 pm JST (8 am CST) from the Tanegashima Space Center off the southern coast of Japan. An H-IIB rocket will launch the H-II Transfer Vehicle, named Kounotori-5, which will dock with the ISS on 20- 21 August. CALET will then be transferred to the Exposed Platform attached to the Japanese Experiment Module, Kibo. There it will spend the next 2-5 years measuring very high energy cosmic ray electrons, nuclei and gamma rays. The launch and ISS rendezvous can be viewed on NASA TV, at the following website ( Prof. Cherry will represent LSU at the launch.

A Japanese led international mission, CALET involves nearly 50 researchers from Japan, Italy and the USA. LSU leads the US Science Team consisting of LSU, Washington University in St. Louis, NASA Goddard Space Flight Center and The University of Denver and will host the US CALET Data Center. John P. Wefel, LSU Professor Emeritus of Physics and Astronomy and US Co-Principal Investigator for CALET said “This mission is a tribute to the importance of international scientific research.” And added, “CALET is a great instrument and we expect to make new astrophysical discoveries with the rich dataset the mission will provide. The new insights into the workings of powerful astrophysical particle accelerators can teach us how to develop better accelerating machines here on the ground. In addition, CALET may observe a signature of the elusive dark matter.”

CALET will measure the intensity of cosmic ray electrons, protons, and nuclei accelerated to near the speed of light, and also observe high energy gamma rays. The main CALET telescope consists of an array of scintillation detectors to determine the electric charge of the incoming cosmic ray particles, an imaging calorimeter of scintillating fibers to determine the particle trajectory, and a deep lead tungstate calorimeter to measure particle and gamma ray energies up to 20 Tera-electron volts, a factor of more than three times higher than the particle beams at the largest manmade accelerator on Earth, the Large Hadron Collider in Switzerland. At such high energies, CALET may be the first experiment to observe a ‘near-by’ source of high energy radiation.

LSU scientists will operate the US CALET Data Center (USCDC) linking to Japan (and Italy), to obtain and process the flight data, distribute the results to the other US institutions, and serve as a central site for the data analysis.

Additional information on the CALET science can be found on the LSU web site at CALET is funded in the US by NASA, in Italy by the Italian Space Agency (ASI), and in Japan by the Japan Aerospace Exploration Agency (JAXA).