The advantage of many is that I get to sample the space at a lot of points, which (combined with fancy signal processing) gives me a huge amount of flexibility about where I look, and what energy I pay attention to. The advantage of one is that I get to make that one very good indeed. If I have a really big hemispherical-ish dish, like what was at Arecibo, I can turn it into a telescope by having one big receiver in the air space above it, or by having many, many receivers in the same space. Or orders of magnitude more capable for the same price. What if we could go even further, and have a much higher number of much cheaper and less complex receivers? We could, in theory, build a radar or radio telescope that’s orders of magnitude cheaper than what we’re building today. Similarly, multistatic radars change it up by having a lot of receivers. Array telescopes change this up by having an array of dishes, and one slightly less complex receiver per dish, but the complexity is still quite high. It’s the same with radars: the traditional design is for one very complex and expensive receiver. To change what frequency band you’re working in, you need to change the antenna. To focus it, you need to move the antenna. To change where the telescope looks, you need to move the antenna. It needs to be held quite still, way up in the air. What’s inside the suspended structure is an antenna, or array of antennas, equipment to keep that antenna cool, equipment to receive signal from the antenna, digitize it, denoise and compress it, and get that data back to somewhere more sensible for further processing. The dish itself is just a bunch of aluminium panels, mostly near the floor. That stuff is heavy, needs to be able to move around while being held firmly in position, creates a lot of data, and takes a lot of power. Instead, it’s the platform and gear that houses the receivers (and, in the case of radar astronomy, the transmitters). The expensive and hard part of building a telescope like Arecibo or FAST isn’t the dish itself 2, despite that being the large and iconic part.

So this is my semi-serious pitch for a sci-fi alternative: drones. The whole thing seems smart, and sensible, but a little conservative. Some of the exciting new possibilities with this instrument include searching for pulsars orbiting Sgr A*, observing molecular lines from early Universe, climate change, ISR studies both parallel and perpendicular to the geomagnetic field, space debris characterization, ac-curate velocity measurements of a larger fraction of near earth objects, space weather forecasts, dark energy and dark matter studies, gravitational wave detection through pulsar timing, etc. Just like with KAT and SKA, their proposal starts with a small array and builds up over time. Their concept is for an array of 1,112 closely-packed 9m dishes, either built in the same sinkhole as the original telescope, or elsewhere on the site. The Next Generation Arecibo Telescope white paper is one such proposal, written by a group a scientists who seem to know what they’re talking about. I’d love to see radio, and radar, astronomy gain a great new instrument. While I’ve never worked in radio astronomy, my PhD supervisor and a number of my colleagues were involved in MeerKAT 1 and HERA, so I developed a real interest in the field.

I hope eventually that they can replace the telescope with an instrument as futuristic and forward-looking as the Arecibo Telescope when first conceived. Last night I finally got around to watching Grady Hillhouse’s excellent video on the collapse of the Arecibo Telescope.

Next generation arecibo telescope