arecibo radio telescope

 arecibo

 

    Single radio elements have limited spatial resolution (the diffraction limit of the telescope).  This diffraction limited resolution is proportional to wavelength (as it is also for optical telescopes, but it seems more extreme for radio telescopes due to the huge range of wavelengths over which they are typically used).  The diffraction limit for a circular aperture of diameter D is q ~ 1.22 l/D, where q is the angular diameter of the Airy Disk at the half-power point (the full-width-half-maximum, or FWHM) in radians.  At a frequency of 5 GHz, even the Arecibo dish has an angular resolution of only about 50 arcseconds.  The fully-steerable GBT has a resolution at this frequency of only 150 arcseconds.

    Because of the limited spatial resolution of single element telescopes, sophisticated techniques have been developed to combine single elements into multiple-element arrays, which work together to form a single telescope.  In such arrays, the spatial resolution is determined not by the size of the individual elements, but rather by the maximum separation between elements, which is referred to as the baseline length, B.  With an interferometer, the diffraction limit is q ~ l/B, where B can extend to many (even thousands of) km. 

19 Nov, 2020 NSF announcement:

Following a review of engineering assessments that found damage to the Arecibo Observatory cannot be stabilized without risk to construction workers and staff at the facility, the U.S. National Science Foundation will begin plans to decommission the 305-meter telescope, which for 57 years has served as a world-class resource for radio astronomy, planetary, solar system and geospace research.

 

The (decommissioning) decision comes after NSF evaluated multiple assessments by independent engineering companies that found the telescope structure is in danger of a catastrophic failure and its cables may no longer be capable of carrying the loads they were designed to support.

 Arecibo is one of a number of telescopes around the world that is threatened by the need to allocate funding to the science being done at more modern facilities like the Atacama Large Millimeter Array (ALMA) in northern Chile. The Green Bank Telescope in West Virginia, the Very Long Baseline Array (ten radio telescopes spread across the U.S.), and the Parkes radio telescope in Australia are also struggling with funding reallocation.

1 Dec 2020

the 900 ton platform collapsed on its own

 

funding uncertainty in 2017

njit

nature magazine

eso