Datum: Fri, 28 Oct 2005 14:53:36 -0700 (PDT) Thanks for your comments below. Your round trip attenuation to Mars, compared to the moon, of 87.78 dB is correct but considers only the distances. However, Mars is larger than the moon (diameter of 6799.84 km for Mars but only 3476 km for the moon). Thus the Mars cross sectional area is 3.827 times that of the moon. This produces an echo from Mars which is 5.828 dB stronger, assumming equal incident power density and equal reflectivity coefficients -- probably a reasonable starting point until we know better. This accounts for the 5.828 dB difference between my moon-Mars echo difference of 82 dB (which I rounded up from 81.95 dB) vs your value of 87.77 for the distance effect alone. Thanks again. Its been of interest to me for a long time. 73 Derwin W5LUU --- Sergio wrote: > Derwing, > > with the distances you have mentioned the one way trip to mars > accounts > for 43.89 dB more attenuation than from earth to moon (I don't like > to > call it attenuation, but for the sake of cutting short). So the the > round trip is 87.77 dB which is a bit more than 82 dB. But you also > > mention other facts that could account for another -4dB so we are > getting close. > > Getting to Mars bounce (hey it still spells EME, hi) with a > radiotelescope class antenna it can be possible with a 'decent' tx > power, hi. > > Now assuming that, in our case, it was the probe transmitting, mars > reflecting and the big antenna on the earth receiving we'd need to > know: > probe RF power, probe ERP power (or antenna gain to determine > radiating > lobe), frequency of operation, distance from Mars to determine > 'illumination' on Mars thus the relfecting surface, and the antenna > gain > on the earth. Still remaining to be determined it will be the > reflecting coefficient of the Mars surface. And also eventual RFI on > > earth (on the detected signal they presented); this is I guess what > the > folks have worked on there. They have all the data above, of course. > > Not to forget the 3 minutes-light distance to keep antenna properly > aimed... Fascinating. > > Cheers Datum: Fri, 28 Oct 2005 09:58:20 -0400 > > What ever happened to Mars-Net, Mike? Stopped getting mails from it quite > some years back. Mars net is alive and well and living on a server in Worcester MA, USA. You are welcome to subscribe by sending a message with the word "subscribe" in the body of the message to mars-net-request@alum.wpi.edu -Joe KM1p Datum: Fri, 28 Oct 2005 13:16:02 +0100 (BST) Well if you want to bounce anything off Mars this weekend might just be the time to do it - only 69.4 million km away - take a look at http://news.bbc.co.uk/1/hi/sci/tech/4384700.stm Regards Steve, g4vbd steve.g4vbd@btinternet.com Datum: Fri, 28 Oct 2005 11:16:27 +0200 Dear Michael, dear EMEers, This article, and the discussion which has developed from it, is quite interesting. Please allow me to contribute another aspect which might motivate serious experiments in ham radio, see http://www.df5ai.net/ArticlesDL/ALBIE/ALBIE.html Your comments are very much appreciated. 73, Volker (DF5AI) ------------------------------------------------------------------------ DF5AI, JO40DF, 50-13-29 N / 8-16-53 E (dd-mm-ss), 325m asl Amateur Radio Propagation Studies: http://www.df5ai.net The BeamFinder software: http://www.beamfinder.net Datum: Thu, 27 Oct 2005 19:48:12 -0700 What ever happened to Mars-Net, Mike? Stopped getting mails from it quite some years back. AF9Y sure had all of us going on the reception schemes, was too fun. Still have an old Windows 3.11 machine with his little LAT LON window on it. That was one of the most exciting weak signal experiences I have ever had, seeing the mars beacon on FFTDSP. 73 Jeremy Datum: Thu, 27 Oct 2005 18:53:59 -0700 (PDT) Hi, One additional point that I should have mentioned in last e-mail (below). The total improvement for Earth-Mars-Earth communications compared to eme is actually "only" ((82+) - eme S/N) dB. If present eme S/N is 25 dB, for example, then only (ha) 57+ db S/N improvement is needed for E-Mars-E communications. Good Luck. Derwin, W5LUU Datum: Thu, 27 Oct 2005 15:26:06 -0700 (PDT) Randy, Further comments and info relative to Mars Bounce. My rememberances, in last e-mail, were a little too fuzzy -- in fact, about -22 dB worth. This will more clearly and accurately address the requirements for direct Earth-Mars- Earth contacts or for detection of echos. Assume an Earth- Mars distance of 55,755,006 km (a minimum which occured on 27August03) and a minimum earth-moon perigee of 356,376 km. Compared to eme, the additional path loss for comparable Earth-Mars contacts on any given band is 81.95 dB. This is true for all bands, modes, etc. In addition to the distances, this takes into account the larger diameter of Mars (6800 km) compared to the moon (3476 km). As a further consideration, the cited minimum Mars distance is the shortest in some 60,000 years. This year the minimum Mars distance (on 07Nov05) is 26% greater (this adds ~4 dB of additional loss -- to 86 dB) and will remain so, or worse, until 2018 when, for several days, it will be comparable to the 2003 example. It will be very, very difficult to make the first contact or to hear the first direct Mars reflected echo from a legal earth based ham transmitter. Means to realize the required 82+ dB S/N improvement may be available by intelligent appli- cation of the many available techniques. 73 Derwin, W5LUU Datum: Thu, 27 Oct 2005 17:47:31 -0400 I remember that the NRAO was doing radar images of planets a while ago using different dishes. I remember seeing the radar image of Mars. (Mars bounce?) Here is a page FYI: http://www.gb.nrao.edu/visitors/gbtour/radiomars.jpg http://www.gb.nrao.edu/visitors/gbtour/tourPlanet.html http://www.gb.nrao.edu/140foot/ I was first exposed to Moonbounce during EME Contest weekend many years ago at Greenbank. I was then KB4CNI and I heard my voice on 2-meter SSB bounce off the moon using the 140 foot dish! I am not sure who was running the show back there, but I was moon struck from then on! I do know it was Bud Beazell, KB4JNI that invited me back for EME weekend. Maybe W4TJ_Bill, may have had something to do with this EME project. I hear they may be getting rid of the 140 foot dish over at Greenbank. I just can't figure out how I would ever get the resources to move it and reassemble it, HI HI. ;-) I may have neighbor issues also! Nice to dream!!! I guess I will have to make the 20 footer due me for a while! 73, Cowles_K4EME **************************** My Home Page http://home.rica.net/candrus/ Datum: Thu, 27 Oct 2005 14:43:43 -0400 Andy, are you saying that the echo was a reflection of the 1 watt transmitter from Odyssey, off the Mars surface? I guess that makes sense now that I think about it more. So the path loss is cut in half compared with true EME (Earth Mars Earth). Still, it seems that they would be able to do true Mars bounce with a 150 foot dish. Thanks - 73, Russ K2TXB Datum: Thu, 27 Oct 2005 10:53:08 -0700 (PDT) It is my understanding from the published information that the Mars echo received by the SRI Int. 150-foot dish was actually transmitted from the Odyssey spacecraft. Some years ago I calculated the link budget for Earth-Mars-Earth and Earth-Venus-Earth under the most favorable conditions for each. Best I remember Mars Bounce signals are more than 60dB down from eme. Venus is more favorable by many dB. Maybe someone else has the exact data available. Derwin W5LUU Datum: Thu, 27 Oct 2005 17:50:43 +0000 Yes, the August 2003 tests revealed reflections from the orbiters (MGS & Odyssey) from the Mars surface. The plot, in the article clearly, shows the Doppler compensated signal from Odyssey (a straight line) and a separate weak reflection (with a noncompensated Doppler signature curve). As a result they have this "new" Mars Bi-Static UHF Radar Experiment. n9ab Datum: Thu, 27 Oct 2005 13:33:53 -0400 Komu: Andrew Bachler [+] CC: moon-net@list-serv.davidv.net [+] Velikost: 5 KB Zdroj | Zobrazit hlavičku | Tisk Andy - The article says that the reflection was from the surface of Mars, bounced back to Earth. W9IP Datum: Thu, 27 Oct 2005 09:34:14 -0700 Komu: moon-net@list-serv.davidv.net [+] Reply-To: retired@easystreet.com [+] Velikost: 4 KB Zdroj | Zobrazit hlavičku | Tisk Mike: Thanks for the interesting article. It struck me as strange, though, that if JPL needed to use enough power that it would produce a detectable reflection off the surface of Mars that the Odyssey spacecraft must have a pretty deaf receiver. It would be interesting to see the link budgets for the Odyssey communications link and the Mars reflection path. de Randy, W7HR Port Orchard, WA Datum: Thu, 27 Oct 2005 16:20:05 +0000 The Mars Bi-Static UHF Radar Experiment is using the Stanford University, SRI International's 46-meter (150-foot) dish for transmission, and detection by Odyssey. Andy N9AB Datum: Thu, 27 Oct 2005 18:16:23 +0200 Komu: Moon-Net [+] Reply-To: ok1dfc@seznam.cz [+] Velikost: 5 KB Zdroj | Zobrazit hlavičku | Tisk Also group of TM8EME had tested planet bouncing. It was before EME conference 1998 in Paris. I guess in May 1998. They tested successfully Venus on 1296MHz. Maybe Herve F5HRY, his father working in Nancy observatory, has any documents about. Zdenek OK1DFC Datum: Thu, 27 Oct 2005 17:47:42 +0200 I Wonder ? what is the path loss to Mars ?? OZ5IQ, Kim and tnx fr info Datum: Thu, 27 Oct 2005 06:52:06 -0800 Thanks Mike, That was an interesting article and I had not heard about them detecting Mars echo. Certainly the signal needed for the relay receiver to detect was pretty big to span the distance; must be sufficently near Mars, now, to detect the weaker echo at the s/c. Many years ago I worked at Goldstone where they did primary radar astronomy on planets like Venus and Mars (used a 100kw 14-GHz klystron from Varian and the then 210-foot dish). We participated in MGS and MRO flight tests of the 437.1 Relay Tx...that was fun! 73's, Ed - KL7UW ========================================= http://www.qsl.net/al7eb - BP40iq 144-EME: FT-847, mgf-1801/1402, 4xM2-xpol-20, 170w 432-EME: FT-847, mgf-1402, 1x21-ele (18.6 dBi), 60w ========================================= Datum: Thu, 27 Oct 2005 10:54:42 -0400 Mike, that's pretty neat! Wonder how much power they were running? 73, Russ K2TXB Datum: Thu, 27 Oct 2005 07:36:09 -0400 Here's a little piece about 70 cm Mars-bounce, accidentally detected by the Stanford dish in 2003. http://mars.jpl.nasa.gov/odyssey/spotlight/20051024.html 73, W9IP -- Michael R. Owen, Ph.D. Dept. of Geology Northern Lights Software Associates St. Lawrence University http://www.nlsa.com mowen@stlawu.edu Datum: Wed, 14 Sep 2005 12:32:52 -0400 Komu: Michael R. Owen [+] CC: Moon-Net [+] Velikost: 3 KB Zdroj | Zobrazit hlavičku | Tisk Michael R. Owen wrote: > Dear frineds, > > In case you were unaware, another spacecraft is on its way to Mars.. It > is carrying a 70-cm beacon which will be tested soon, much like the Mars > Global Surveyor in the 1990's. Information is at > http://members.verizon.net/~km1p/welcome.html All are welcome to join the mars-net mailing list for up to the minute information. Send an e-mail to mars-net-request@alum.WPI.EDU with the word "subscribe" in the body of the message. -Joe KM1P Datum: Wed, 14 Sep 2005 12:00:00 -0400 Komu: Moon-Net [+] Velikost: 4 KB Zdroj | Zobrazit hlavičku | Tisk Dear frineds, In case you were unaware, another spacecraft is on its way to Mars.. It is carrying a 70-cm beacon which will be tested soon, much like the Mars Global Surveyor in the 1990's. Information is at http://members.verizon.net/~km1p/welcome.html A good challenge for your receiving system! 73, W9IP -- Michael R. Owen, Ph.D. Dept. of Geology Northern Lights Software Associates St. Lawrence University http://www.nlsa.com mowen@stlawu.edu