Greetings I wonder if anyone has delved into the arcania of the DSP algorithm used in the W7PAU (if I remember right) moon echo experiment? I just wonder exactly what he did with the signal processing. I know there was an integration phase, I remember 18 minutes. Is there a usenet group for this? In any case, the signal xmit power was 1.2 Watt, and the calculated strength at the receiver was -170 dB! Of course, this is not a distance record, as the Mars Rover was 1 Watt, and the distance was 140 million miles. But for a bounce, .5 million miles is to me, mind boggling. I wonder if this has any lessons for weak signal measurements in optics, etc. And to repeat, I wonder what exact signal processing approach was. Any comments welcome. JB
EME Moon Bounce Query
Started by ●February 11, 2014
Reply by ●February 11, 20142014-02-11
On 2/11/2014 10:54 AM, haiticare2011@gmail.com wrote:> Greetings > > I wonder if anyone has delved into the arcania of the DSP algorithm used in the > W7PAU (if I remember right) moon echo experiment? I just wonder exactly what he > did with the signal processing. I know there was an integration phase, I > remember 18 minutes. Is there a usenet group for this? > > In any case, the signal xmit power was 1.2 Watt, and the calculated strength at the receiver was -170 dB! > > Of course, this is not a distance record, as the Mars Rover was 1 Watt, and the > distance was 140 million miles. But for a bounce, .5 million miles is to me, > mind boggling. > > I wonder if this has any lessons for weak signal measurements in optics, etc. > > And to repeat, I wonder what exact signal processing approach was. > > Any comments welcome. > JB >Google for : Joe Taylor, K1JT Rob.
Reply by ●February 14, 20142014-02-14
On Tuesday, February 11, 2014 12:54:19 PM UTC-5, haitic...@gmail.com wrote:> Greetings > > > > I wonder if anyone has delved into the arcania of the DSP algorithm used in the > > W7PAU (if I remember right) moon echo experiment? I just wonder exactly what he > > did with the signal processing. I know there was an integration phase, I > > remember 18 minutes. Is there a usenet group for this? > > > > In any case, the signal xmit power was 1.2 Watt, and the calculated strength at the receiver was -170 dB! > > > > Of course, this is not a distance record, as the Mars Rover was 1 Watt, and the > > distance was 140 million miles. But for a bounce, .5 million miles is to me, > > mind boggling. > > > > I wonder if this has any lessons for weak signal measurements in optics, etc. > > > > And to repeat, I wonder what exact signal processing approach was. > > > > Any comments welcome. > > JBIf you want a long bounce, read about Shapiro's experiment verifying general relativity. He waited until Venus was on the farside of her orbit (from our point of view) and almost in line with the sun. Then he "radared" Venus and noted the change in time delay was consistant with the gravity well created by the sun. The round trip time was over 1700 seconds which is a little more than the 3 seconds in the case with the moon. This was a bounce off of an object more than 158 million miles away! http://en.wikipedia.org/wiki/Shapiro_delay Clay
Reply by ●February 14, 20142014-02-14
On Fri, 14 Feb 2014 08:13:51 -0800 (PST), clay@claysturner.com wrote:>On Tuesday, February 11, 2014 12:54:19 PM UTC-5, haitic...@gmail.com wrote: >> Greetings >>=20 >>=20 >>=20 >> I wonder if anyone has delved into the arcania of the DSP algorithm used = >in the >>=20 >> W7PAU (if I remember right) moon echo experiment? I just wonder exactly w= >hat he >>=20 >> did with the signal processing. I know there was an integration phase, I >>=20 >> remember 18 minutes. Is there a usenet group for this?=20 >>=20 >>=20 >>=20 >> In any case, the signal xmit power was 1.2 Watt, and the calculated stren= >gth at the receiver was -170 dB! >>=20 >>=20 >>=20 >> Of course, this is not a distance record, as the Mars Rover was 1 Watt, a= >nd the >>=20 >> distance was 140 million miles. But for a bounce, .5 million miles is to= > me, >>=20 >> mind boggling. >>=20 >>=20 >>=20 >> I wonder if this has any lessons for weak signal measurements in optics, = >etc. >>=20 >>=20 >>=20 >> And to repeat, I wonder what exact signal processing approach was. >>=20 >>=20 >>=20 >> Any comments welcome. >>=20 >> JB > >If you want a long bounce, read about Shapiro's experiment verifying genera= >l relativity. He waited until Venus was on the farside of her orbit (from o= >ur point of view) and almost in line with the sun. Then he "radared" Venus = >and noted the change in time delay was consistant with the gravity well cre= >ated by the sun. The round trip time was over 1700 seconds which is a littl= >e more than the 3 seconds in the case with the moon. This was a bounce off = >of an object more than 158 million miles away! > >http://en.wikipedia.org/wiki/Shapiro_delay > >ClayAny idea what sort of transmit power they used for that? That's an interesting engineering feat. Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●February 14, 20142014-02-14
clay@claysturner.com wrote: (snip)> If you want a long bounce, read about Shapiro's experiment > verifying general relativity. He waited until Venus was on > the farside of her orbit (from our point of view) and almost > in line with the sun. Then he "radared" Venus and noted the > change in time delay was consistant with the gravity well > created by the sun. The round trip time was over 1700 seconds > which is a little more than the 3 seconds in the case with > the moon. This was a bounce off of an object more than 158 > million miles away!> http://en.wikipedia.org/wiki/Shapiro_delayPretty neat. Reminds me that I recently heard about atomic clocks good enough that you can lift them up 1 foot (0.3m) and detect the GR change in gravity. -- glen
Reply by ●February 14, 20142014-02-14
On Friday, February 14, 2014 2:38:43 PM UTC-5, glen herrmannsfeldt wrote:> clay@claysturner.com wrote: > > > > (snip) > > > > > If you want a long bounce, read about Shapiro's experiment > > > verifying general relativity. He waited until Venus was on > > > the farside of her orbit (from our point of view) and almost > > > in line with the sun. Then he "radared" Venus and noted the > > > change in time delay was consistant with the gravity well > > > created by the sun. The round trip time was over 1700 seconds > > > which is a little more than the 3 seconds in the case with > > > the moon. This was a bounce off of an object more than 158 > > > million miles away! > > > > > http://en.wikipedia.org/wiki/Shapiro_delay > > > > Pretty neat. Reminds me that I recently heard about atomic > > clocks good enough that you can lift them up 1 foot (0.3m) > > and detect the GR change in gravity. > > > > -- glenI haven't been able to find the transmit power or the antenna gain, but I know frequencies from 500MHz up to 8.8GHz were used. In 1968 Irwin Shapiro authored a neat article entitled "Planetary Radar Astronomy" The results are quite remarkable! There are some early papers on the VLBLI (very long base line interferometer) that talks abouts recording data at over 200Mbits/sec on tape and is later processed via correlation for timing offsets.
Reply by ●February 17, 20142014-02-17
On Friday, February 14, 2014 2:53:42 PM UTC-5, cl...@claysturner.com wrote:> On Friday, February 14, 2014 2:38:43 PM UTC-5, glen herrmannsfeldt wrote: > > > clay@claysturner.com wrote: > > > > > > > > > > > > (snip) > > > > > > > > > > > > > If you want a long bounce, read about Shapiro's experiment > > > > > > > verifying general relativity. He waited until Venus was on > > > > > > > the farside of her orbit (from our point of view) and almost > > > > > > > in line with the sun. Then he "radared" Venus and noted the > > > > > > > change in time delay was consistant with the gravity well > > > > > > > created by the sun. The round trip time was over 1700 seconds > > > > > > > which is a little more than the 3 seconds in the case with > > > > > > > the moon. This was a bounce off of an object more than 158 > > > > > > > million miles away! > > > > > > > > > > > > > http://en.wikipedia.org/wiki/Shapiro_delay > > > > > > > > > > > > Pretty neat. Reminds me that I recently heard about atomic > > > > > > clocks good enough that you can lift them up 1 foot (0.3m) > > > > > > and detect the GR change in gravity. > > > > > > > > > > > > -- glen > > > > I haven't been able to find the transmit power or the antenna gain, but I know frequencies from 500MHz up to 8.8GHz were used. > > > > In 1968 Irwin Shapiro authored a neat article entitled "Planetary Radar Astronomy" The results are quite remarkable! > > > > There are some early papers on the VLBLI (very long base line interferometer) that talks abouts recording data at over 200Mbits/sec on tape and is later processed via correlation for timing offsets.I've managed to find some of the details on the Haystack radar as used for Shapiro's experiments for Venus. Frequency 7750MHz (3.8cm) 120 foot diameter dish - cassegrain inside of a radome! Antenna gain is 66.1dB Angular resolution is 0.4 arcseconds (half power points) At this resolution you can pick out parts of Venus! Transmit power is 500 kW using two parallel klystrons Transmitted signal is a coded pulse of 10 to 20 minutes duration. I'm trying to find the coding that was used. The receiver is liquid helium or nitrogen chilled and uses a maser amplifier The 3dB bandwidth is 22MHz. Not bad for 1964 - 1968 Clay
Reply by ●February 18, 20142014-02-18
On Mon, 17 Feb 2014 15:33:31 -0800 (PST), clay@claysturner.com wrote:>On Friday, February 14, 2014 2:53:42 PM UTC-5, cl...@claysturner.com wrote: >> On Friday, February 14, 2014 2:38:43 PM UTC-5, glen herrmannsfeldt wrote: >> >> > clay@claysturner.com wrote: >> >> > >> >> > >> >> > >> >> > (snip) >> >> > >> >> > >> >> > >> >> > > If you want a long bounce, read about Shapiro's experiment >> >> > >> >> > > verifying general relativity. He waited until Venus was on >> >> > >> >> > > the farside of her orbit (from our point of view) and almost >> >> > >> >> > > in line with the sun. Then he "radared" Venus and noted the >> >> > >> >> > > change in time delay was consistant with the gravity well >> >> > >> >> > > created by the sun. The round trip time was over 1700 seconds >> >> > >> >> > > which is a little more than the 3 seconds in the case with >> >> > >> >> > > the moon. This was a bounce off of an object more than 158 >> >> > >> >> > > million miles away! >> >> > >> >> > >> >> > >> >> > > http://en.wikipedia.org/wiki/Shapiro_delay >> >> > >> >> > >> >> > >> >> > Pretty neat. Reminds me that I recently heard about atomic >> >> > >> >> > clocks good enough that you can lift them up 1 foot (0.3m) >> >> > >> >> > and detect the GR change in gravity. >> >> > >> >> > >> >> > >> >> > -- glen >> >> >> >> I haven't been able to find the transmit power or the antenna gain, but I know frequencies from 500MHz up to 8.8GHz were used. >> >> >> >> In 1968 Irwin Shapiro authored a neat article entitled "Planetary Radar Astronomy" The results are quite remarkable! >> >> >> >> There are some early papers on the VLBLI (very long base line interferometer) that talks abouts recording data at over 200Mbits/sec on tape and is later processed via correlation for timing offsets. > > >I've managed to find some of the details on the Haystack radar as used for Shapiro's experiments for Venus. > >Frequency 7750MHz (3.8cm) > >120 foot diameter dish - cassegrain inside of a radome! > >Antenna gain is 66.1dB > >Angular resolution is 0.4 arcseconds (half power points) >At this resolution you can pick out parts of Venus! > >Transmit power is 500 kW using two parallel klystrons > >Transmitted signal is a coded pulse of 10 to 20 minutes duration. >I'm trying to find the coding that was used. > >The receiver is liquid helium or nitrogen chilled and uses a maser amplifier > >The 3dB bandwidth is 22MHz. > >Not bad for 1964 - 1968 > >ClayNice! I suspected it'd have to be something really gnarly like that. 500kW with 66dBi gain. 123dBW EIRP!! Woot! I can also see why the extremely long pulse was needed for both power and ambiguity resolution. Now I'm wondering how they integrated that in the receiver? Very cool stuff! Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●February 18, 20142014-02-18
Reply by ●February 18, 20142014-02-18
On Tuesday, February 18, 2014 1:43:51 PM UTC-5, mako...@yahoo.com wrote:> >The 3dB (Rx) bandwidth is 22MHz. > > > > > Really? > > > > Why use such a wide BW? > > > > MarkThat is the published spec. Not only is the planetary radar used to range the Moon and Venus, it is also used for radiometry. It is in this latter case where you use the wider bandwidth. Clay
