An interstellar ‘GPS’ for future probes?
Pulsars have huge advantages. A deep space satellite network to fix position is a costly option — it doesn’t scale well as we expand deeper into the Solar System and beyond it. Autonomous navigation is clearly preferable, tying the navigation system to a natural reference frame like pulsars. The down side: Pulsar signals are quite weak and thus put demands upon spacecraft constrained by mass and power consumption concerns. So there’s no easy solution to this.
But several readers (thanks especially to Frank Smith and Adam Crowl) have pointed out a recent paper by Bartolome Coll (Observatoire de Paris) and Albert Tarantola (Institut de Physique du Globe de Paris) that speculates on a system based on four millisecond pulsars: 0751+1807 (3.5 ms), 2322+2057 (4.8 ms), 0711-6830 (5.5 ms) and 1518+0205B (7.9 ms). The origin of the space-time coordinates the authors use is defined as January 1, 2001 at the focal point of the Cambridge radiotelescope where pulsars were discovered in 1967. Thus, the paper continues:
…any other space-time event, on Earth, on the Moon, anywhere in the Solar system or in the solar systems in this part of the Galaxy, has its own coordinates attributed. With present-day technology, this locates any event with an accuracy of the order of 4 ns, i.e., of the order of one meter. This is not an extremely precise coordinate system, but it is extremely stable and has a great domain of validity.
If these numbers are correct, they represent quite a jump over the ESA study cited above, which worked out the minimal hardware requirements for a pulsar navigation system and arrived at a positioning accuracy of no better than 1000 kilometers. ESA is working within near-term hardware constraints and discusses ways of enhancing accuracy, but the report does point out the huge and perhaps prohibitive weight demands these solutions will make upon designers.
Weight demands might not be as much a concern as Paul and others speculate, if probe builders use the proposed nanotechnology previously written about on his site. And using Nature in all her glory isn’t so far-fetched as it seems!
Are UFOs and associated phenomena really supernatural angels and demons fighting over the immortal souls of human beings?
I don’t think Marzulli convinced them, but tune in and find out for yourselves!
Sir, can you spare $770 billion?
Mr Geithner is on his first official visit to China, the biggest foreign investor in US treasury bonds.
Ahead of meetings with President Hu Jintao and Premier Wen Jiabao, he said the US and China must work together to fix the global economic system.
Mr Geithner said the US would move swiftly to get its debt under control.
In a speech at Beijing University at the start of his two-day visit, Mr Geithner reassured his Chinese hosts that they need not worry about the estimated $770bn (£475bn) they have invested in US treasuries, a class of US government debt.
“Chinese financial assets are very safe,” he said, drawing laughter from the audience.
Ha-hahaha, hehehehehe, hohohoho, it is to laugh!
Ask these folks how funny things are:
Thanks to Piglipstick !