A new era for Arecibo: legendary observatory begins next phase

Re:A new era for Arecibo: legendary observatory begins next ... by mandevil on Friday September 29, 2023 @12:42PM (#37706753)

For receive only, yes, aperture synthesis (like the VLA and the GVLBI) is capable of resolving more precisely than even Arecibo could. But Arecibo also did a bunch of active radar mapping of things within the solar system, which aperture synthesis cannot replace. You can't solve the coherent beam problem without actually having an antenna that really is that big.

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Re:A new era for Arecibo: legendary observatory begins next ... by markhahn on Friday September 29, 2023 @01:03PM (#37707072)

huh? wouldn't all the planes with AESA radar dispute this characterization?

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Re:A new era for Arecibo: legendary observatory begins next ... by mcpackieh on Friday September 29, 2023 @02:04PM (#37707971)

https://en.wikipedia.org/wiki/Thinned-array_curse

> The thinned-array curse (sometimes, sparse-array curse) is a theorem in electromagnetic theory of antennas. It states that a transmitting antenna which is synthesized from a coherent phased array of smaller antenna apertures that are spaced apart will have a smaller minimum beam spot size, but the amount of power that is beamed into this main lobe is reduced by an exactly proportional amount, so that the total power density in the beam is constant

So you can transmit with a sparse array, but the power you can deliver with it (for a set synthetic aperture size) decreases with the degree of sparseness. No free lunch.

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Re:A new era for Arecibo: legendary observatory begins next ... by echelon on Friday September 29, 2023 @12:45PM (#37706789)

> You can't solve the coherent beam problem without actually having an antenna that really is that big.

What's the tl;dr on the math here?

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