Re: [time-nuts] Pulsar Source?
Hi Pulsars are an interesting clock. That by no means equates to them being a better clock than an ion standard or possibly a neutron standard. If you look at ADEV numbers, there's pretty much no way a pulsar will be anywhere near the level a good atomic clock can deliver over useful time spans. For long time spans you get into a what indeed is time? issue. Atomic clocks have been more stable than the earth's rotation for quite a while. We correct things to allow for the earth as a result. If you are going to do that for atomic clocks - the same issues get into a pulsar source as delivered on earth's surface. Weather you pick it up in space and relay it or not, you still have the math issues of getting it to the surface. Bob On Mar 28, 2012, at 2:29 PM, Tom Knox wrote: If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
The same issue we have for rotating clocks on board of GPSes and differently rotating clocks on the Earth's surface? On Fri, Mar 30, 2012 at 12:02 AM, Bob Camp li...@rtty.us wrote: Hi Pulsars are an interesting clock. That by no means equates to them being a better clock than an ion standard or possibly a neutron standard. If you look at ADEV numbers, there's pretty much no way a pulsar will be anywhere near the level a good atomic clock can deliver over useful time spans. For long time spans you get into a what indeed is time? issue. Atomic clocks have been more stable than the earth's rotation for quite a while. We correct things to allow for the earth as a result. If you are going to do that for atomic clocks - the same issues get into a pulsar source as delivered on earth's surface. Weather you pick it up in space and relay it or not, you still have the math issues of getting it to the surface. Bob On Mar 28, 2012, at 2:29 PM, Tom Knox wrote: If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
El 30/03/2012 05:02, Jim Lux escribió: and orientation. Sort of like a super star tracker all in one! (You can see why NASA is interested..) And ESA. Last year they published an invitation to tender called Deep Space Navigation with Pulsars, with the following description excerpt: The activity will focus on the study of the use of Pulsars for Deep Space Navigation. Localization of spacecrafts in deep space is today very challenging and, in same cases, not enough precise and/nor reliable. Highly rotating neutron starts (also called Pulsars)generate pulses with high stable periodicity that can be used to locate an object in space. It had quite a low budget assigned... but seems that it had some interest. I think I can get the statement of work if somebody is interested. Best regards, Javier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
act...@hotmail.com said: Forth: The problems I foresee are can an practical algorithm accounting for the complex motion of all these bodies be built ... Radio astronomers are pretty good at that sort of calculation. Google for VLBI. The key step for VLBI is modeling the exact location of each antenna over time. They even include tides in solid rock. (about a foot) I think there is a chicken-egg step in there. You can use a bright object and the known location of several antennas to figure out the location of a new antenna. I assume they iterate. So, if you can figure out the orbital parameters for your receivers, they can do the math. Note the comment from: Little Green Men, White Dwarfs or Pulsars? By S. Jocelyn Bell Burnell http://www.bigear.org/vol1no1/burnell.htm (It's a good read.) So were these pulsations man-made, but made by man from another civilization? If this were the case then the pulses should show Doppler shifts as the little green men on their planet orbited their sun. Tony Hewish started accurate measurements of the pulse period to investigate this; all they showed was that the earth was in orbital motion about the sun. That was back in 1967. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
On Wed, 28 Mar 2012 16:20:49 -0700 Hal Murray hmur...@megapathdsl.net wrote: All that is of course correct. But ultimately the pulsars are a better source, I see it as an application question, could it be utilized? Perhaps building an algorithm and basing corrections on multiple pulsars x-ray pulses like a GPS constellation for the next generation of conventional GPS. I think modern atomic clocks are better than Pulsars. Unfortunately, I don't have a good reference handy. I think the theorists have several ideas for why the period of Pulsars change. See [1] for a short overview and pointers to more literature Attila Kinali [1] http://www.astro.oma.be/IAU/COM31/pdf/JD6/JD06_Kopeikinx.pdf -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
On 03/29/2012 01:50 AM, Jim Palfreyman wrote: Folks, I'm currently writing my thesis on pulsars, but I need to spend time on it rather than here. :-) But since a lot of this discussion is right at the front of my brain, here's a summary. Some pulsars glitch or speed up. The Vela pulsar (PSR J0835-4510) does this (this is the pulsar I've been studying) and yes these type of pulsars are bad clocks. A jump of its pulse rate of the order of 10^-6 s/s randomly every few years is not good. It does nearly settle back to its original rate after a few months. The nature of these glitches (in Vela at least) is not well understood, but three theories have been put forward: - An orbiting planet - but this has been discarded due to their irregularity. - Star quakes caused by a separation of the crust on the surface of the neutron star from its super-fluid interior. (Not very popular any more) - The effects of tiny micro vortices in the internal super-fluid. (If you can understand this paper - good luck to you!) Now faster pulsars, in particular millisecond pulsars (~700 Hz from memory is the fastest) are quite good clocks and they do rival atomic clocks. The hunt is on to find as many of these as they can, well spread across the sky, so they can look at the effects of gravitational waves on the beams of these super accurate clocks. This is one proposed method to detect gravitational waves. The main problem I see from the original suggestion is that most pulsars are quite faint and you need a very decent telescope to see individual pulses. Vela is very bright, and the 26m telescope I used can only just see the average pulse. I'm studying bright pulses and we can see those easily. So to dedicate a massive radio telescope (or two) pointing at a millisecond pulsar just so we can re-transmit it, is probably not sensible. However, studies of these remarkable pulsars is ongoing. Hmm, wouldn't the space-located antenna have a good chance of better S/N as the antenna sees cold space and could be kept cold itself? I was also thinking antenna size would be a limitation. Then I was thinking about what WMAP has achieved in measuring the background temperature and look back at the very early years of the universe. Cheers, Magnus Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
On 3/29/12 3:17 PM, Magnus Danielson wrote: just so we can re-transmit it, is probably not sensible. However, studies of these remarkable pulsars is ongoing. Hmm, wouldn't the space-located antenna have a good chance of better S/N as the antenna sees cold space and could be kept cold itself? I was also thinking antenna size would be a limitation. Then I was thinking about what WMAP has achieved in measuring the background temperature and look back at the very early years of the universe. Yes and no.. depending on the frequency. A reasonably high gain dish antenna that is under illuminated (i.e. the feed doesn't see the earth behind the antenna) is basically looking at cold space anyway. One reason that Cassegrain and similar designs are possible.. the primary feed is looking at space with the secondary reflector in the way, so spillover is going towards the sky. (moisture in the air is the big factor here.. it's easy to tell when there are clouds overhead with a microwave radiometer) Cryogenically cooled feeds are pretty standard items and not particularly expensive (compared to the cost of even the smallest launch vehicle). Cryocoolers, not dewars of LHe, by the way. As the frequency goes up, though, the atmospheric loss rises, and eventually, it's worth it to get above the atmosphere (Mauna Kea and Atacama are pretty close, but there's still moisture above them). In the mm wave and far IR is where it's really worth while, so you have things like SIRTF and JWST. The latter is a good example of high cost, though.. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
I thought I might apologize because I didn't explain my idea very well initially, and reiterate my original thoughts on a pulsar timing idea. The basis of my idea was that if problems could be overcome certain pulsars could provide not only Time but also Position info directly to orbiting platforms. First: I assumed from the start that this was not a DIY idea, but mainly an intellectual exercise, far beyond the resources of all but a few governments. And most likely beyond the scope of our current GPS system. But since I have been a TimeNuts I have been constantly amazed by the complex problems that have been taken on and solved by this brilliant group. So I thought I would throw in something purely theoretical. I should have known there would be at least one TimeNuts writing a thesis on Pulsars. It reminds me, I have been very lucky to have worked around some brilliant people, when I am asked about their depth of knowledge I usually reply They are not that smart, I can get coffee for anyone of them and get it right three out of four times. My point is Do you want any coffee. Second: What I was envisoning was collecting data on Ultra stable pulsars including location, motion and timing needed to use them as a defacto GPS constallation for a set of earth based satalites. With this information you could ascertain the exact position of each satellite. This idea has been under investigation for long distance satellite navigation for some time. I see no advantage terrestrially receiving pulsar signals as a atlernative freq standard in place of the USNO since the cool thing about this concept is that the pulsars would provide both time and position directly to the orbiting platform. Third: Does observing these pulsars from space allow reception of signals at levels and in bands that would be blocked by the earth atmosphere. If not could some of the advances in superconductivity provide an amp of sufficient sensitivity to overcome these problems. Forth: The problems I foresee are can an practical algorithm accounting for the complex motion of all these bodies be built, and can Pulsar signals be received at a high enough signal to noise ratio for this system to produce a coherent time source. I have really enjoyed all the topics lately thanks all for the contributions. Clearly Time Nuts; Thomas Knox Date: Fri, 30 Mar 2012 00:17:33 +0200 From: mag...@rubidium.dyndns.org To: time-nuts@febo.com Subject: Re: [time-nuts] Pulsar Source? On 03/29/2012 01:50 AM, Jim Palfreyman wrote: Folks, I'm currently writing my thesis on pulsars, but I need to spend time on it rather than here. :-) But since a lot of this discussion is right at the front of my brain, here's a summary. Some pulsars glitch or speed up. The Vela pulsar (PSR J0835-4510) does this (this is the pulsar I've been studying) and yes these type of pulsars are bad clocks. A jump of its pulse rate of the order of 10^-6 s/s randomly every few years is not good. It does nearly settle back to its original rate after a few months. The nature of these glitches (in Vela at least) is not well understood, but three theories have been put forward: - An orbiting planet - but this has been discarded due to their irregularity. - Star quakes caused by a separation of the crust on the surface of the neutron star from its super-fluid interior. (Not very popular any more) - The effects of tiny micro vortices in the internal super-fluid. (If you can understand this paper - good luck to you!) Now faster pulsars, in particular millisecond pulsars (~700 Hz from memory is the fastest) are quite good clocks and they do rival atomic clocks. The hunt is on to find as many of these as they can, well spread across the sky, so they can look at the effects of gravitational waves on the beams of these super accurate clocks. This is one proposed method to detect gravitational waves. The main problem I see from the original suggestion is that most pulsars are quite faint and you need a very decent telescope to see individual pulses. Vela is very bright, and the 26m telescope I used can only just see the average pulse. I'm studying bright pulses and we can see those easily. So to dedicate a massive radio telescope (or two) pointing at a millisecond pulsar just so we can re-transmit it, is probably not sensible. However, studies of these remarkable pulsars is ongoing. Hmm, wouldn't the space-located antenna have a good chance of better S/N as the antenna sees cold space and could be kept cold itself? I was also thinking antenna size would be a limitation. Then I was thinking about what WMAP has achieved in measuring the background temperature and look back at the very early years of the universe. Cheers, Magnus Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go
Re: [time-nuts] Pulsar Source?
On 3/28/2012 4:50 PM, Jim Palfreyman wrote: Folks, I'm currently writing my thesis on pulsars, but I need to spend time on it rather than here I'd love to hear more about your thesis (offline question most likely). I thought I'd add in the detail that I found on another site about one pulsar. For example, a pulsar called PSR J1603-7202 is known to have a period of 0.0148419520154668 seconds. However the periods of all radio pulsars are increasing extremely slowly. The period of PSR J1603-7202 increases by just 0.005 seconds every million years! I don't know how close you could get to syncing with a pulsar signal, but this is one to discuss. Thanks Jim http://outreach.atnf.csiro.au/education/everyone/pulsars/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
On 3/29/12 6:19 PM, Tom Knox wrote: I thought I might apologize because I didn't explain my idea very well initially, and reiterate my original thoughts on a pulsar timing idea. The basis of my idea was that if problems could be overcome certain pulsars could provide not only Time but also Position info directly to orbiting platforms. I think that trying to figure out how to use pulsars as as timing source is certainly worthy of contemplation. And as for resources.. who'd have thunk 20 years ago that you could have atomic clocks (real ones, not WWVB receivers) in your house as a hobby using surplus. First: I assumed from the start that this was not a DIY idea, but mainly an intellectual exercise, far beyond the resources of all but a few governments. And most likely beyond the scope of our current GPS system. But since I have been a TimeNuts I have been constantly amazed by the complex problems that have been taken on and solved by this brilliant group. So I thought I would throw in something purely theoretical. I should have known there would be at least one TimeNuts writing a thesis on Pulsars. It reminds me, I have been very lucky to have worked around some brilliant people, when I am asked about their depth of knowledge I usually reply They are not that smart, I can get coffee for anyone of them and get it right three out of four times. My point is Do you want any coffee. Second: What I was envisoning was collecting data on Ultra stable pulsars including location, motion and timing needed to use them as a defacto GPS constallation for a set of earth based satalites. I think that's been done.. At least there is a good list of candidates. With this information you could ascertain the exact position of each satellite. This idea has been under investigation for long distance satellite navigation for some time. I see no advantage terrestrially receiving pulsar signals as a atlernative freq standard in place of the USNO since the cool thing about this concept is that the pulsars would provide both time and position directly to the orbiting platform. and orientation. Sort of like a super star tracker all in one! (You can see why NASA is interested..) Third: Does observing these pulsars from space allow reception of signals at levels and in bands that would be blocked by the earth atmosphere. Certainly yes for X-ray pulsars.. the atmosphere blocks them. For radio pulsars, the attenuation through the atmosphere isn't huge (at least at microwave frequencies, and if you don't pick something like 60GHz where there's an absorption band). If not could some of the advances in superconductivity provide an amp of sufficient sensitivity to overcome these problems. The limiting thing on weak signals is typically noise, and cooling helps. Forth: The problems I foresee are can an practical algorithm accounting for the complex motion of all these bodies be built, Yes. It's just geometry, and probably not more difficult than any other triangulation problem. Surveyors use a form of least squares in some cases, and that's sort of what a Kalman filter does, as well. That's probably the easy part. and can Pulsar signals be received at a high enough signal to noise ratio for this system to produce a coherent time source. That's the hard part. I have really enjoyed all the topics lately thanks all for the contributions. Clearly Time Nuts; Thomas Knox Date: Fri, 30 Mar 2012 00:17:33 +0200 From: mag...@rubidium.dyndns.org To: time-nuts@febo.com Subject: Re: [time-nuts] Pulsar Source? On 03/29/2012 01:50 AM, Jim Palfreyman wrote: Folks, I'm currently writing my thesis on pulsars, but I need to spend time on it rather than here. :-) But since a lot of this discussion is right at the front of my brain, here's a summary. Some pulsars glitch or speed up. The Vela pulsar (PSR J0835-4510) does this (this is the pulsar I've been studying) and yes these type of pulsars are bad clocks. A jump of its pulse rate of the order of 10^-6 s/s randomly every few years is not good. It does nearly settle back to its original rate after a few months. The nature of these glitches (in Vela at least) is not well understood, but three theories have been put forward: - An orbiting planet - but this has been discarded due to their irregularity. - Star quakes caused by a separation of the crust on the surface of the neutron star from its super-fluid interior. (Not very popular any more) - The effects of tiny micro vortices in the internal super-fluid. (If you can understand this paper - good luck to you!) Now faster pulsars, in particular millisecond pulsars (~700 Hz from memory is the fastest) are quite good clocks and they do rival atomic clocks. The hunt is on to find as many of these as they can, well spread across the sky, so they can look at the effects of gravitational waves on the beams of these super accurate clocks. This is one proposed method to detect gravitational waves
Re: [time-nuts] Pulsar Source?
Jim, If you look at some atomic clocks, they really do look like they were built in somebody's basement... out of WW II RADAR parts and Home Depot plumbing fittings. -John On 3/29/12 6:19 PM, Tom Knox wrote: I thought I might apologize because I didn't explain my idea very well initially, and reiterate my original thoughts on a pulsar timing idea. The basis of my idea was that if problems could be overcome certain pulsars could provide not only Time but also Position info directly to orbiting platforms. I think that trying to figure out how to use pulsars as as timing source is certainly worthy of contemplation. And as for resources.. who'd have thunk 20 years ago that you could have atomic clocks (real ones, not WWVB receivers) in your house as a hobby using surplus. [snip] ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Pulsar Source?
If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
On Wed, Mar 28, 2012 at 11:29 AM, Tom Knox act...@hotmail.com wrote: If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? The problem is in the rebroadcasting which will have the same problems as GPS. One needs to know the exact location of the satellite transmitter and there is the problem if the patch through the atmosphere effecting the signal in non-predictable ways. The solutions to these problem apply to GPS as well. There is also the problem of Doppler shift between Earth and the pulsar. For that reason you need to look at many of them and try and back all the shifts out to get a kind of average reference frame. A bet of processing is involved. You can't simply re-transmit the signal from one of them. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
What would it take (how big a dish) to receive a pulsar directly, such as the millisecond one in the Crab Nebula? DBTV, TVRO? David On 3/28/12 2:29 PM, Tom Knox wrote: If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
If I recall correctly, In one of my trips to the NRAO in Greenbank, WV they were, at one time, using a dedicated 60ft dish to track a pulsar to compare it against their local H-Maser. (It was interesting to see the Maser as it looked like a homebrew version. I saw no manufacturer's name on it.) It would come down to what value of S/N do you want or need to make your own measurment. -Brian, WA1ZMS - Original Message From: David McGaw n1...@alum.dartmouth.org To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, March 28, 2012 3:16:03 PM Subject: Re: [time-nuts] Pulsar Source? What would it take (how big a dish) to receive a pulsar directly, such as the millisecond one in the Crab Nebula? DBTV, TVRO? David On 3/28/12 2:29 PM, Tom Knox wrote: If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
On Wed, Mar 28, 2012 at 12:16 PM, David McGaw n1...@alum.dartmouth.org wrote: What would it take (how big a dish) to receive a pulsar directly, such as the millisecond one in the Crab Nebula? DBTV, TVRO? Amateurs have observed it using Yagi type antenna. You'd need at least a pair of them spaced out on an east-west line. It is within the realm of a reasonable project for a person working at home Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
Hi Chris; All that is of course correct. But ultimately the pulsars are a better source, I see it as an application question, could it be utilized? Perhaps building an algorithm and basing corrections on multiple pulsars x-ray pulses like a GPS constellation for the next generation of conventional GPS. Thomas Knox From: albertson.ch...@gmail.com Date: Wed, 28 Mar 2012 12:13:24 -0700 To: time-nuts@febo.com Subject: Re: [time-nuts] Pulsar Source? On Wed, Mar 28, 2012 at 11:29 AM, Tom Knox act...@hotmail.com wrote: If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? The problem is in the rebroadcasting which will have the same problems as GPS. One needs to know the exact location of the satellite transmitter and there is the problem if the patch through the atmosphere effecting the signal in non-predictable ways. The solutions to these problem apply to GPS as well. There is also the problem of Doppler shift between Earth and the pulsar. For that reason you need to look at many of them and try and back all the shifts out to get a kind of average reference frame. A bet of processing is involved. You can't simply re-transmit the signal from one of them. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
Pulsars use for high accuracy timing was discarded in about the 1960s-1970s. There are sudden pulsar rate changes, related to starquakes as I remember. Counselman et al did the expeeriment. Also, there are very few microwave photons per pulse. It takes a lot of correlation to get anything, even with as big a dish as Aricebo. -John If I recall correctly, In one of my trips to the NRAO in Greenbank, WV they were, at one time, using a dedicated 60ft dish to track a pulsar to compare it against their local H-Maser. (It was interesting to see the Maser as it looked like a homebrew version. I saw no manufacturer's name on it.) It would come down to what value of S/N do you want or need to make your own measurment. -Brian, WA1ZMS - Original Message From: David McGaw n1...@alum.dartmouth.org To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, March 28, 2012 3:16:03 PM Subject: Re: [time-nuts] Pulsar Source? What would it take (how big a dish) to receive a pulsar directly, such as the millisecond one in the Crab Nebula? DBTV, TVRO? David On 3/28/12 2:29 PM, Tom Knox wrote: If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
I have enough trouble with wwvb :-) Going to skip this project On Wed, Mar 28, 2012 at 4:02 PM, J. Forster j...@quikus.com wrote: Pulsars use for high accuracy timing was discarded in about the 1960s-1970s. There are sudden pulsar rate changes, related to starquakes as I remember. Counselman et al did the expeeriment. Also, there are very few microwave photons per pulse. It takes a lot of correlation to get anything, even with as big a dish as Aricebo. -John If I recall correctly, In one of my trips to the NRAO in Greenbank, WV they were, at one time, using a dedicated 60ft dish to track a pulsar to compare it against their local H-Maser. (It was interesting to see the Maser as it looked like a homebrew version. I saw no manufacturer's name on it.) It would come down to what value of S/N do you want or need to make your own measurment. -Brian, WA1ZMS - Original Message From: David McGaw n1...@alum.dartmouth.org To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, March 28, 2012 3:16:03 PM Subject: Re: [time-nuts] Pulsar Source? What would it take (how big a dish) to receive a pulsar directly, such as the millisecond one in the Crab Nebula? DBTV, TVRO? David On 3/28/12 2:29 PM, Tom Knox wrote: If pulsars are natures best clocks, I wonder how practical it would be to use satellites to receive and rebroadcast a highly accurate timing signal based on their signals? Thomas Knox ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
My thought was to rec it in space before it is degraded and perhaps rec it in the x-ray region. A few Geo Sync Sats doing a correction algorithm for earth position vs the pulsars would not be that complex. Thomas Knox From: albertson.ch...@gmail.com Date: Wed, 28 Mar 2012 12:51:20 -0700 To: n1...@alum.dartmouth.org; time-nuts@febo.com Subject: Re: [time-nuts] Pulsar Source? On Wed, Mar 28, 2012 at 12:16 PM, David McGaw n1...@alum.dartmouth.org wrote: What would it take (how big a dish) to receive a pulsar directly, such as the millisecond one in the Crab Nebula? DBTV, TVRO? Amateurs have observed it using Yagi type antenna. You'd need at least a pair of them spaced out on an east-west line. It is within the realm of a reasonable project for a person working at home Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
All that is of course correct. But ultimately the pulsars are a better source, I see it as an application question, could it be utilized? Perhaps building an algorithm and basing corrections on multiple pulsars x-ray pulses like a GPS constellation for the next generation of conventional GPS. I think modern atomic clocks are better than Pulsars. Unfortunately, I don't have a good reference handy. I think the theorists have several ideas for why the period of Pulsars change. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
Ultimately all pulsars slow down. Pulsars are rotating neutron stars. We see the pulse whenever the beam from one of the poles points in our direction. A pulsar emits a massive amount of energy and there is drag from the rotating magnetic field in its stellar environment. There is also matter falling onto the neutron star and the crust can flex and shift (star quakes). All these lead to variations in the period. Mike On 3/28/2012 6:20 PM, Hal Murray wrote: All that is of course correct. But ultimately the pulsars are a better source, I see it as an application question, could it be utilized? Perhaps building an algorithm and basing corrections on multiple pulsars x-ray pulses like a GPS constellation for the next generation of conventional GPS. I think modern atomic clocks are better than Pulsars. Unfortunately, I don't have a good reference handy. I think the theorists have several ideas for why the period of Pulsars change. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
Folks, I'm currently writing my thesis on pulsars, but I need to spend time on it rather than here. :-) But since a lot of this discussion is right at the front of my brain, here's a summary. Some pulsars glitch or speed up. The Vela pulsar (PSR J0835-4510) does this (this is the pulsar I've been studying) and yes these type of pulsars are bad clocks. A jump of its pulse rate of the order of 10^-6 s/s randomly every few years is not good. It does nearly settle back to its original rate after a few months. The nature of these glitches (in Vela at least) is not well understood, but three theories have been put forward: - An orbiting planet - but this has been discarded due to their irregularity. - Star quakes caused by a separation of the crust on the surface of the neutron star from its super-fluid interior. (Not very popular any more) - The effects of tiny micro vortices in the internal super-fluid. (If you can understand this paper - good luck to you!) Now faster pulsars, in particular millisecond pulsars (~700 Hz from memory is the fastest) are quite good clocks and they do rival atomic clocks. The hunt is on to find as many of these as they can, well spread across the sky, so they can look at the effects of gravitational waves on the beams of these super accurate clocks. This is one proposed method to detect gravitational waves. The main problem I see from the original suggestion is that most pulsars are quite faint and you need a very decent telescope to see individual pulses. Vela is very bright, and the 26m telescope I used can only just see the average pulse. I'm studying bright pulses and we can see those easily. So to dedicate a massive radio telescope (or two) pointing at a millisecond pulsar just so we can re-transmit it, is probably not sensible. However, studies of these remarkable pulsars is ongoing. Jim On 29 March 2012 10:20, Hal Murray hmur...@megapathdsl.net wrote: All that is of course correct. But ultimately the pulsars are a better source, I see it as an application question, could it be utilized? Perhaps building an algorithm and basing corrections on multiple pulsars x-ray pulses like a GPS constellation for the next generation of conventional GPS. I think modern atomic clocks are better than Pulsars. Unfortunately, I don't have a good reference handy. I think the theorists have several ideas for why the period of Pulsars change. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Pulsar Source?
On 3/28/12 1:11 PM, Tom Knox wrote: My thought was to rec it in space before it is degraded and perhaps rec it in the x-ray region. A few Geo Sync Sats doing a correction algorithm for earth position vs the pulsars would not be that complex. Thomas Knox What you're talking about is generically called the X-Nav deep space navigation system. googling NASA XNAV turns up a lot XNAV holds great potential for NASA as an enabling technology for fully autonomous interplanetary navigation and... The problem is that nobody has a small, light, X-ray detector that is good enough. Invent one and people will beat a path to your door and fling some money at you (not billions, but certainly enough to tinker on X-ray detectors for the rest of your life) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
