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The image above shows the cryoPAF (cryogenically cooled Phased Array
Feed) viewed from above.
(
A previous ADAP showed the view from the underside.) Whereas the
ASKAP Phased Array Feed elements lie on a flat plane, the cryoPAF
elements are three-dimensional, giving the nickname of the "rocket"
PAF. The cryoPAF has 98 dual linearly-polarised elements, signals
from which can be combined to form a maximum of 72 beams.
The rockets and their LNAs
(low noise amplifiers) are all crygogenically cooled to reduce noise
and increase sensitivity. The whole cryoPAF can track in parllactic
angle, i.e., the package rotates as the altitude-azimuth telescope
tracks celestial sources, keeping the bem footprint and polarisation
orientation fixed on the sky. The cryoPAF will provide a field of
view of almost 2 square degrees, with lower sensitivity toward the
edges, and so an effective field of view of closer to one square
degree when mosiacking larger areas of sky. (Image credit: Steve
Barker)
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