The Cosmological Advanced Survey Telescope for Optical and UV Research (CASTOR) is a proposed space telescope mission led by the

Canadian Space Agency The Canadian Space Agency (CSA; french: Agence spatiale canadienne, ASC) is the national space agency of Canada, established in 1990 by the ''Canadian Space Agency Act''. The president is Lisa Campbell, who took the position on September 3, 2020 ...

. With its 1-meter diameter primary mirror, CASTOR would provide imaging capabilities in the

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

(UV) and blue-optical regions at a spatial resolution similar to that of the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

(

FWHM In a distribution, full width at half maximum (FWHM) is the difference between the two values of the independent variable at which the dependent variable is equal to half of its maximum value. In other words, it is the width of a spectrum curve mea ...

of 0.15

arcseconds A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

), but over an instantaneous field of view about 100 times larger. CASTOR was selected as Canada's highest priority for space astronomy in the 2020s in the 2020 Long Range Plan for Canadian Astronomy.

Description

CASTOR will complement the upcoming

Nancy Grace Roman Space Telescope The Nancy Grace Roman Space Telescope (shortened as Roman or the Roman Space Telescope, and formerly the Wide-Field Infrared Survey Telescope or WFIRST) is a NASA infrared space telescope currently in development and scheduled to launch by Ma ...

Euclid Euclid (; grc-gre, Wikt:Εὐκλείδης, Εὐκλείδης; BC) was an ancient Greek mathematician active as a geometer and logician. Considered the "father of geometry", he is chiefly known for the ''Euclid's Elements, Elements'' trea ...

space telescope, and

Vera C. Rubin Observatory The Vera C. Rubin Observatory, previously referred to as the Large Synoptic Survey Telescope (LSST), is an astronomical observatory currently under construction in Chile. Its main task will be carrying out a synoptic astronomical survey, the L ...

. These three major wide-field imaging facilities will not have access to the UV portion of the

electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from ...

. CASTOR has been specifically designed to provide this missing capability, with high sensitivity and observing efficiency at UV and blue-optical wavelengths. Using dichroics, CASTOR would enable simultaneous imaging of three bandpasses (UV from 150 to 300 nm, ''u'' from 300 to 400 nm, and ''g'' from 400 to 550 nm) over an instantaneous field of view of 0.25 square degrees. In addition to its imaging capabilities, CASTOR will also be equipped with additional instruments enabling high-precision

photometry Photometry can refer to: * Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision * Photometry (astronomy), the measurement of the flux or intensity of an astronomical object's electrom ...

for the monitoring of bright targets, as well as two spectroscopic modes: low- spectral-resolution

slitless spectroscopy Slitless spectroscopy is astronomical spectroscopy done without a small slit to allow only light from a small region to be diffracted. It works best in sparsely populated fields, as it spreads each point source out into its spectrum, and crowded ...

over the entire imaging field and configurable DMD spectroscopy to provide intermediate resolution spectra in the UV in a parallel field.

Objectives

Specific science drivers of CASTOR include: * Studying

dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univer ...

and

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 ab ...

by enabling precise photometric redshift measurements * Echo mapping of active galactic nuclei * Characterization of star formation histories on sub-galactic scales * Characterization of the chemical enrichment history of nearby galaxies and star clusters * Identification and characterization of new galactic satellites and

stellar streams This is a list of stellar streams. A stellar stream is an association of stars orbiting a galaxy that was once a globular cluster or dwarf galaxy that has now been torn apart and stretched out along its orbit by tidal forces. An exception in the ...

* UV characterization of multi-messenger events * Reconstruction of the stellar formation history of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...

using

white dwarfs A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

and identification of white dwarfs polluted by rocky debris from their own planetary systems * Characterization of the

chromospheric A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the S ...

activity of M dwarfs * Characterization of

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

atmospheres * Identification of distant

Trans-Neptunian objects A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (au). Typically, ...

References

External links

CASTOR Mission Website
{{Portal bar, Astronomy, , Outer space, Solar System, Spaceflight, Stars, Technology Space program of Canada Space telescopes