Calorimetric Electron Telescope
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The CALorimetric Electron Telescope (CALET) is a
space telescope A space telescope or space observatory is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launch ...
being mainly used to perform high precision observations of
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...
s and
gamma rays A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
. It tracks the trajectory of electrons, protons, nuclei, and gamma rays and measures their direction,
charge Charge or charged may refer to: Arts, entertainment, and media Films * '' Charge, Zero Emissions/Maximum Speed'', a 2011 documentary Music * ''Charge'' (David Ford album) * ''Charge'' (Machel Montano album) * ''Charge!!'', an album by The Aqu ...
and energy, which may help understand the nature of
dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not a ...
or nearby sources of high-energy
particle acceleration In a compressible sound transmission medium - mainly air - air particles get an accelerated motion: the particle acceleration or sound acceleration with the symbol a in metre/second2. In acoustics or physics, acceleration (symbol: ''a'') is def ...
. The mission was developed and sponsored by the Japan Aerospace Exploration Agency (JAXA), involving teams from Japan, Italy, and the United States. CALET was launched aboard JAXA's H-II Transfer Vehicle Kounotori 5 (HTV-5) on 19 August 2015, and was placed on the
International Space Station The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ( ...
's Japanese Kibo module.


Overview

CALET is an astrophysics mission that searches for signatures of
dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not a ...
and provides the highest energy direct measurements of the
cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
electron spectrum in order to observe discrete sources of high-energy
particle acceleration In a compressible sound transmission medium - mainly air - air particles get an accelerated motion: the particle acceleration or sound acceleration with the symbol a in metre/second2. In acoustics or physics, acceleration (symbol: ''a'') is def ...
in our local region of the galaxy. The mission was developed and sponsored by the Japan Aerospace Exploration Agency (JAXA), involving teams from Japan, Italy, and the United States. It seeks to understand the mechanisms of particle acceleration and propagation of cosmic rays in our galaxy, to identify their sources of acceleration, their elemental composition as a function of energy, and possibly to unveil the nature of dark matter. Such sources seem to be able to accelerate particles to energies far higher than scientists can achieve on Earth using the largest accelerators. Understanding how nature does this is important to space travel and has possible applications here on Earth. The CALET
Principal Investigator In many countries, the term principal investigator (PI) refers to the holder of an independent grant and the lead researcher for the grant project, usually in the sciences, such as a laboratory study or a clinical trial. The phrase is also often us ...
is Shoji Torii from the
Waseda University , mottoeng = Independence of scholarship , established = 21 October 1882 , type = Private , endowment = , president = Aiji Tanaka , city = Shinjuku , state = Tokyo , country = Japan , students = 47,959 , undergrad = 39,382 , postgrad ...
, Japan; John Wefel is the co-principal investigator for the US team; Pier S. Marrocchesi, is the co-investigator from the Italy team. Unlike
optical telescope An optical telescope is a telescope that gathers and focuses light mainly from the visible part of the electromagnetic spectrum, to create a magnified image for direct visual inspection, to make a photograph, or to collect data through elect ...
s, CALET operates in a scanning mode. It records each cosmic ray event that enters its field of view and triggers its detectors to take measurements of the cosmic ray in the extremely high energy region of teraelectronvolts (TeV, one trillion
electronvolt In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacuum ...
s). These measurements are recorded on the space station and sent to a ground station at
Waseda University , mottoeng = Independence of scholarship , established = 21 October 1882 , type = Private , endowment = , president = Aiji Tanaka , city = Shinjuku , state = Tokyo , country = Japan , students = 47,959 , undergrad = 39,382 , postgrad ...
for analyses. CALET may also yield evidence of rare interactions between
matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic part ...
and dark matter by working in synergy with the
Alpha Magnetic Spectrometer The Alpha Magnetic Spectrometer (AMS-02) is a particle physics experiment module that is mounted on the International Space Station (ISS).Kristine Rainey (April 2, 2013)Alpha Magnetic Spectrometer (AMS): How It Works NASA. Retrieved June 2, 20 ...
(AMS) – also aboard the
ISS The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA (J ...
– that is looking at positrons and
antiproton The antiproton, , (pronounced ''p-bar'') is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy. The exis ...
s to identify dark matter. Observations will be carried out more than 5 years. CALET contains a subpayload CIRC (Compact Infrared Camera) to observe Earth surface, to detect
forest fires A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identif ...
.


Objectives

The objectives are to understand the following: #origin and mechanisms of acceleration of high-energy
cosmic ray Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
s and
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...
s #propagation mechanism of cosmic rays throughout the Galaxy #identity of
dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark matter is called "dark" because it does not appear to interact with the electromagnetic field, which means it does not a ...
As a cosmic ray observatory, CALET aims to clarify high energy space phenomena and dark matter from two perspectives; one is particle creation and
annihilation In particle physics, annihilation is the process that occurs when a subatomic particle collides with its respective antiparticle to produce other particles, such as an electron colliding with a positron to produce two photons. The total energy ...
in the field of
particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
(or
nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the ...
) and the other is particle acceleration and propagation in the field of space physics.


Results

CALET first published data on half a million electron and positron cosmic ray events in 2017, finding a
spectral index In astronomy, the spectral index of a source is a measure of the dependence of radiative flux density (that is, radiative flux per unit of frequency) on frequency. Given frequency \nu and radiative flux density S_\nu, the spectral index \alpha is g ...
of −3.152 ± 0.016 above 30 GeV.


See also

*


References


External links



"Status and performance of the Calorimetric Electron Telescope (CALET) on the International Space Station". (PDF) By Roberta Sparvoli.

CALET brochure in English (PDF) at JAXA. {{DEFAULTSORT:Callorimetric Electron Telescope Astrophysics Dark matter Space telescopes Gamma-ray telescopes