A Canadian Space Telescope

The Cosmological Advanced Survey Telescope for Optical and uv Research (CASTOR) is a proposed Canadian Space Agency (CSA) mission that would image the skies at ultraviolet (UV) and blue-optical wavelength regions. Operating close to its diffraction limit (the best possible angular resolution achievable for a mirror of a given size), the 1m CASTOR telescope would have a spatial resolution similar to the Hubble Space Telescope (HST), but would cover a field of view about one hundred times larger.

The origins of CASTOR mission concept can be traced back to 2010. That year, the Canadian astronomical community released its "Long Range Plan" for the period 2010 to 2020. That report, Unveiling the Cosmos: A Vision for Canadian Astronomy, outlined the broad goals and directions of astronomy research in Canada. Aiming to identify research priorities and focus economic resources in a way that maximizes scientific impact, the LRP report noted that "... Canadian space astronomy technology has reached the point that [Canada] could [now] lead a large space astronomy mission."


The report concluded that the highest priority in Canadian space astronomy was "...significant involvement in the next generation of dark energy missions — ESA‘s Euclid, or the NASA’s WFIRST mission, or a Canadian-led mission, the Canadian Space Telescope (CST)."

The CASTOR mission concept is the outcome of that vision. Since 2011, a team of Canadian scientists and engineers — working in industry, academia and government — has developed a mission concept that is uniquely powerful and scientifically versatile. Although Canada will not be providing a hardware contribution to either Euclid or WFIRST, CASTOR has the potential to make a transformational impact in astrophysics in the 2020s.

The 2010 Long Range Plan for Canadian Astronomy.

CASTOR in the International Landscape

During the next decade, sensitive new telescopes on the ground and in space will monitor the sky at optical and infrared wavelengths.


On the ground, the US Large Synoptic Survey Telescope (LSST), a partnership between NSF and the DoE, will repeatedly survey the southern skies at optical wavelengths. In space, ESA's Euclid mission and NASA's WFIRST mission will image the sky at red-optical and infrared wavelengths. These facilities have been designed to address some of the key outstanding questions in astronomy, including the nature of Dark Energy — a mysterious component of the universe that leads to an acceleration in the rate of cosmic expansion. But the legacy value of these telescopes is so immense that no field in astronomy will remain untouched.


A critical, but missing, capability among these next generation telescopes is high-resolution imaging at short wavelengths: i.e., in the UV and blue-optical regions. At present, the legendary Hubble Space Telescope (HST) offers such a capability, but only over very small fields. And, HST, which was launched in 1990, relies on a number of critical systems (such as batteries and gyroscopes) that have limited lifetimes.  Astronomers worldwide have come to rely on Hubble but, by the middle of the next decade when the next generation of ground- and space-based telescopes are in routine operation, high-resolution imaging at UV/blue-optical wavelengths will be a missing capability among the international portfolio of astronomical facilities. CASTOR mission would fill that void.

A New Canadian Icon in Space

As one of the world's first space-faring nations, Canada has a proud history in space.


The Alouette 1 satellite, which carried out pioneering studies the Earth's upper atmosphere, was built by Canada and launched by NASA in 1962. It was the first satellite designed and constructed by a country other than the United States or the Soviet Union, and operated successfully for ten years.

The Shuttle Remote Manipulator System (SRMS, or Canadarm), a series of robotic arms that were used on NASA's Space Shuttles to capture and deploy payloads, flew on 90 Shuttle missions between 1981 and 2011.


In 2020, NASA will launch the James Webb Space Telescope (JWST), an ambitious 6.5m space telescope that will provide unparalleled views of the Universe at infrared wavelengths. JWST, a collaboration between NASA, ESA and the CSA, includes key Canadian hardware contributions — namely its guidance system and an infrared imaging spectrograph (FGS/NIRISS).

As the world's preeminent UV/blue-optical imaging telescope, CASTOR would build on this legacy. It would offer the same high-resolution imaging capabilities of HST — a capability that has captured the imagination of the public for more than a quarter century — but over much larger fields than is possible with HST. It would be a unique tool for communicating the importance of science, technology, engineering and mathematics to the public and a worthy heir to Alouette 1 and Canadarm as icons of Canada's presence in space.

Artist's conception of the Alouette I satellite, launched in 1962.

The Shuttle Remote Manipulator System (SRMS), or Canadarm, mounted on the port side of the cargo bay during Shuttle mission STS-72.