Calorimetric Electron Telescope
Space telescope searching for dark matter and cosmic ray sources.
The CALorimetric Electron Telescope (CALET) is a space telescope that precisely tracks electrons, protons, nuclei, and gamma rays, measuring their direction, charge, and energy. Its primary goal is to shed light on the nature of dark matter and identify nearby sources that accelerate particles to extremely high energies. The mission is led by the Japan Aerospace Exploration Agency (JAXA), with collaborating teams from Japan, Italy, and the United States. CALET launched on 19 August 2015 aboard JAXA's H-II Transfer Vehicle Kounotori 5 (HTV-5) and was installed on the International Space Station's Japanese Kibo module. Unlike optical telescopes, it operates in a scanning mode, recording each cosmic ray event that triggers its detectors in the teraelectronvolt (TeV) energy range. Data is sent to a ground station at Waseda University for analysis. The telescope also carries a sub-payload, the Compact Infrared Camera (CIRC), which observes Earth's surface to detect forest fires. CALET's objectives include understanding the origin and acceleration mechanisms of high-energy cosmic rays and gamma rays, how cosmic rays propagate through the Galaxy, and identifying dark matter. It may work in synergy with the Alpha Magnetic Spectrometer (AMS) on the ISS to find evidence of rare dark matter interactions. In 2017, CALET published its first results from half a million electron and positron events, reporting a spectral index of −3.152 ± 0.016 above 30 GeV.
- Field
- Astrophysics
- Nationality
- Japan (with Italy and United States)
- Known for
- High precision observations of cosmic rays and dark matter search
- Launch date
- 19 August 2015
- Principal investigator
- Shoji Torii (Waseda University, Japan)
Lore & Background
CALET contains a sub-payload CIRC (Compact Infrared Camera) to observe the Earth's surface in order to detect forest fires. The mission first published data on half a million electron and positron cosmic ray events in 2017, finding a spectral index of −3.152 ± 0.016 above 30 GeV.
Reader's Guide
CALET represents a significant step in high-energy astrophysics, providing direct measurements of cosmic ray electrons at teraelectronvolt energies, which are crucial for understanding particle acceleration mechanisms in our galaxy. Its search for dark matter signatures, in synergy with the Alpha Magnetic Spectrometer, addresses one of the most profound questions in modern physics. By recording individual cosmic ray events and measuring their direction, charge, and energy, CALET helps identify nearby sources of high-energy particle acceleration, such as supernova remnants or pulsars, that can accelerate particles to energies far beyond human-made accelerators. The mission's long-duration observations (more than 5 years) allow for statistically robust data, as demonstrated by its 2017 publication of half a million electron and positron events. Additionally, its sub-payload CIRC contributes to Earth observation by detecting forest fires. CALET's international collaboration—involving Japan, Italy, and the United States—and its placement on the International Space Station's Kibo module exemplify cooperative space science. The data it provides on cosmic ray composition and energy spectra are essential for refining models of cosmic ray propagation and for testing theories of dark matter, making it a key instrument in both astrophysics and particle physics.
Did You Know?
- CALET was launched aboard JAXA's H-II Transfer Vehicle Kounotori 5 (HTV-5) on 19 August 2015.
- It contains a sub-payload CIRC (Compact Infrared Camera) to detect forest fires on Earth.
- The mission works in synergy with the Alpha Magnetic Spectrometer (AMS) aboard the ISS to search for dark matter.
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