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Profile David Anderson
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Message 1932459 - Posted: 28 Apr 2018, 6:56:58 UTC

Things have gone slower than I'd like, mostly because Eric Korpela and I are seldom in the same place. But work continues.

Mostly it's involved birdies - artificial ET signals, of random power, location, and frequency, barycentric and not. Seeing how well Nebula detects them is central to our scientific conclusions, so we need to generate the birdie signals as realistically as possible.

To generate these signals we look at the trajectory of pointings, for each of Arecibo's seven beams, and generate signals when the beam gets close to the birdie. The power of these signals is based on several factors, including the distance between the beam and the birdie position. We had been doing this based on the sky position of the pointing, which may be separated by as much as 5 seconds. The problem is that the beam may get much closer to the birdie - maybe pass right over it - midway between two pointings. So we changed things to look along the (linearly interpolated) path between consecutive pointings. As we expected, this produced significantly more birdie signals. And Eric fixed an error in the math, also leading to more signals. And we fixed a slew of lesser bugs.

At the end of the day, our goal is to generate birdies super-realistically, and then see how powerful they need to be for us to detect them (e.g. in the top 1000 or so multiplets). Or even better, to make a graph of detection probability as a function of birdie power.

The data shown on the web site is recent, but doesn't reflect these birdie fixes. I'll have new data up in a week or so.

-- David
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Message boards : Nebula : Status report

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