Pi Square Kilometers Array (PSKA)

The Pi Square Kilometers Array (PSKA) is a radio interferometer collaboration between the colonies of Sirona and Meredith. Each colony houses near-identical arrays of 200 m radio telescope dishes, with 100 dishes in each array. This sums to give a total collecting area over each array of about pi square kilometers.
76 of the dishes in each array sit in a central, concentrated cluster. The remaining dishes in each array extend out to baselines of around 2500 kilometers (slightly less due to the curvature of Sirona at these scales). This set-up, configured as an interferometer, would allow for extremely high resolution images while also still affording the flexibility that the smaller baseline core offers. Each array was constructed on the areas of each colony with the lowest radio interference.
The proposal for PSK was received and approved by the governing bodies of both involved colonies in 2468 with construction beginning later that year on Sirona and early the next year on Meredith. First light for both telescopes fell within the same year, early-2476 for Sirona and late-2476 for Meredith. After three additional years of testing, both telescopes were deemed fully operational in 2479.
== History ==
=== PSKA-Sirona ===
=== PSKA-Meredith ===
== Overview ==
The PSKA arrays each combine the signals received from up to 100 individual radio telescopes spread over distances from the central cluster of up to 1250 kilometers. Combining the signal from each of these via synthesis imaging, extremely high sensitivity (owing to the total surface area) and angular resolution (owing to the long baselines) can be achieved. Each telescope, though particularly the ones in the core clusters of the arrays, can also be used individually or alongside smaller arrays to provide for greater flexibility in the baseline ranges. While the large baselines allow for an excellent lower limit on the angular resolution, the upper limit—set by the smallest baseline in the array—suffers as a result. By allowing the central core (and even individual telescopes) to function independently, the PSKA arrays can also operate in modes allowing for very large fields-of-view. This makes it possible to survey very large areas of the sky at once and to pick up the larger-scale structures being observed.
This central region would contain 76 of the 100 dishes in each array. While the outer 25 dishes are fixed along a circle with a 1250 kilometer radius, 72 of the core dishes are placed along 12 radially diverging tracks, 6 dishes along each. The telescopes on these tracks can have separations ranging from 100 meters to 2.5 kilometers apart (giving arm lengths of around 1.8 to 16.2 kilometers). In the center, the remaining four dishes are fixed, evenly aligned 100 m apart and 100 meters from the ends of three of the 12 tracks.
Each telescope in the arrays shares the same design, a fully steerable hyperbolic dish 200 m across. The dishes are composed in a Ritchey-Chrétien configuration, with three support arms extending from the edge of the dish to house a secondary mirror and collection of feeds and focus signal through a hole in the center of the dish. The central design was chosen over an offset design as—while it reduces total collecting area—it avoids dependence on off-axis detections and the astigmatism those bring with them. The dishes themselves are composed of perforated aluminum panels attached to actuators that compensate for sagging as the telescopes move. Without these actuators, observations at high frequencies would lose efficiency as the wavelengths approach comparable scale to the imperfections in the surface.
Operational frequencies for the telescopes range from 100 MHz to 150 GHz (2 mm to 3 m), though the range is subdivided across the multiple feeds in the support arm, only allowing limited bands within the overall range to be observed simultaneously. The higher frequencies are also limited by atmospheric conditions, as excess water vapor and carbon dioxide in the atmospheres of Sirona or Meredith could shrink the radio window for each colony.
=== PSKA-Sirona ===
=== PSKA-Meredith ===
== Mission ==
=== Earth Survey Catalog ===
=== 2551 Radio Bounce ===
== List of Appearances ==