New Horizons images enable first test of interstellar navigation
newscientist.com51 points by jnord 24 days ago
51 points by jnord 24 days ago
> In comparison, the parallax method was far less accurate, locating New Horizons within a sphere with a radius of 60 million kilometres, about half the distance between Earth and the sun.
NASA SEXTANT mission demonstrated pulsar navigation to about 10km of error, and should be valid through interstellar space. This parallax method seems not really in the ballpark? Still pretty cool they are able to teach an old dog new tricks given New Horizons launched in 2006!
That's a remarkable result. Looks like (if I haven't misunderstood) SEXTANT a software experiment that piggybacks on the raw datastream from the NICER x-ray telescope, and estimates the phases of the time-of-arrival of bright millisecond pulsars (in x-ray photons). From differential phases (at microsecond accuracy), they infer differential position (kilometers). I understand it's eight (8) pulsars in the catalog.
https://arxiv.org/abs/1711.08507
I wonder if it's really that easy to extend this to interstellar scales. If you move 300 km, a 1-ms source is reset to its original phase. Go out to New Horizons distances, and all your phases are millions of cycles offset from Earth, by highly jumbled fractional parts. Is it mathematically feasible to reconstruct everything then? Or: do you maintain a continuously-updated model across the entire mission—and hope that you don't lose count of your cycles?
That paper says this kind of pulsar can be as slow as several seconds, and the main discussion link says the parallax navigation could be made a lot better with a better camera. Maybe that could provide enough overlap?
An usual tangent from TFA. NewScientist looks like worth subscribing for and I haven’t heard anything about it. Any opinions about it?
New Scientist used to be a pretty respectable popular science magazine - it was founded in the 1950s. It had a more technical slant than something like Popular Science, and was a bit more accessible and news-oriented than Scientific American.
Once the internet started eating magazines, like many other magazines, New Scientist turned into a clickbaity, ad-heavy rag.
It's possible it's improved recently, but many people wrote it off a long time ago, which is probably why you don't hear much about it.