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The Deep Synoptic Array 2000, or DSA-2000 is a large radio telescope currently under construction by the Owens Valley Radio Observatory, but located in Nevada USA. Its main goal is a sky survey, acting as a radio camera to produce an archive of images of the entire sky visible from that site. The completed array, scattered over an area of 19 × 15 km, will contain 2000 steerable 5-meter parabolic antennas that cover the 0.7–2 GHz frequency range. It is financed by Schmidt Sciences and expected to be operational in 2028. [1] [2] The DSA-110 was an earlier effort that demonstrated many of the needed technologies, but was not as general-purpose and specialized in detecting and localizing fast radio bursts. [3] [4]
The DSA-2000 incorporates two main technical advances, both related to its architecture of a large number of small antennas. The first is that having a large number of randomly distributed antennas makes it much easier to convert the radio signals into images. This strategy had never been practical before, since antennas sensitive enough for radio astronomy historically required cooling to very low temperatures, which made each antenna too expensive to build such a large array. So the second advance was a receiver, using modern semiconductor technology, that could achieve the needed sensitivity without cooling.
Traditional radio telescope arrays have had a relatively small number of relatively large antennas (the VLA, for example, has 27 dishes of 25 meters diameter). This results in a hideous point spread function, which requires considerable post-processing to turn into useful images. In particular, additional non-linear constraints (such as positivity) must be assumed, both vastly complicating the aperture synthesis calculations and making them dependent on the particular assumptions used. In turn the need for complex processing requires huge data storage and transport requirements, as the raw data (or the visibilities, the correlations between pairs of antennas) need to be saved and delivered to the end user for later post-processing.
The DSA-2000, in comparison, will have near-complete sampling of the uv-plane. This gives a native point spread function which is sufficiently good that much-less-complex algorithms can be used create images in real time, acting as a "radio camera".
Traditional radio telescope receivers have required cooling (often to cryogenic temperatures) to get low-enough noise to be useful for astronomical observations. This typically resulted in a cost of at least $100,000 per receiver, making arrays with a large number of antennas impractical. However, recent developments in indium phosphide technology have resulted in transistors with a low-enough noise figure at room temperature [5] to remove the need for cooling. [6] In addition, very low loss feeds and matching networks are required, since any losses in these components contribute directly to system noise in proportion to their physical temperature.
Since the DSA-2000 digitizes the whole 0.7–2.0 GHz bandwidth, processing in software can simultaneously generate radio images at many different frequency resolutions for different purposes. These outputs of the radio camera are:
Although the main goal of DSA-2000 is a sky survey, it will pursue other projects as well. Operations other than radio imaging (such as pulsar timing and searches for transients) are possible as the signal processing is programmable since it is implemented in general purpose FPGAs and GPUs.
{{cite journal}}: CS1 maint: numeric names: authors list (link)
