|WikiProject Astronomy||(Rated Start-class, Mid-importance)|
|WikiProject Physics||(Rated C-class, Mid-importance)|
The first section could use a rewrite, since it is hard to read for those outside the astronomy field. "Very Long Baseline Interferometry (VLBI) is a type of interferometry in which the data received at each antenna in the array is paired with timing information, usually from a local atomic clock, and then stored for later analysis on magnetic tape or hard disk.". A casual reader may wonder: which antenna, which array? Why is timing so crucial that it is mentioned in the very first sentence?
I'm not an expert in this field, so I hope someone else can do this. I suggest to first tell this has (1) something to do with radioastronomy and (2) involves multiple, geographically seperated, telescopes.
Macfreek 12:25, 6 January 2006 (UTC)
The pictures are inappropriate. Neither ALMA nor the SMA is a very long baseline array. The SMA has been used as one station of the event horizon telescope, in combination with CARMA in California and the Hertz telescope in Arizona, but the vast majority of the time it functions as a traditional interferometer. Someone should find a press photo montage of the VLBA instead. — Preceding unsigned comment added by 184.108.40.206 (talk) 21:52, 2 April 2013 (UTC)
I suspect that the most important difference of interferometry and VLBI is not explained here. AFAIU, interference patterns happen when “collapse of quantum probability” (same as “measuring”) happens after mixing two signals. And storing signals on tape/disk requires that the measuring happens before the storage. Essentially, if correct, this would mean that classical sources would not lead to any interference patterns in VLBI. One would need a measurable fraction of pairs of photons in the same quantum state (“lasing”/“masing” effect) so that one photon may be captured (“measured”) at one antenna, and its identical twin is then captured at the other antenna. IIRC, this explains most illustrations of VLBI involving the “maser” word. 220.127.116.11 (talk) 01:08, 7 June 2013 (UTC)iz
Local storage, really?
I'm not involved in the VLA but I have to wonder, in this day of computer networks, if the initial explanation of saving data and atomic clock timing to a tape is perhaps outdated. They must have power supplies and command signals running out to these things, why wouldn't they send timestamped signals back over the network. Also, why would they need an atomic clock at each antenna? Doesn't seem right.
- Seems fairly like the RX12874 - Passive Detection Linesman/Mediator radar system http://www.radarpages.co.uk/mob/linesman/pd.htm . Just replace jamming aircraft with radio stars, and you've got a real time system that did much of the same stuff back in 1956.Think the storing of the "un-correlated" data allows off line processing (when computing capacity is available/cheaper) Also expect radio telescopes might go down from time to time (or be used for other things), so it probably very important that the processing can cope with a reconfigurable array-without losing data for sources that are still part of the array. Could also allow for something like a phased array - where the array could be "virtually" pointed in any direction, even if it wasn't originally pointing in that direction.
- 18.104.22.168 (talk) 01:43, 9 September 2011 (UTC)
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