Re: Could DirecTV satellite dishes be used for the Square Kilometer Array - and a more radical proposal[Re: Can DirectTV-type satellite dishes be used for SETI?]

From: Rob Dekker (rob_at_verific.com)
Date: 02/09/05 

Date: Wed, 09 Feb 2005 06:43:56 GMT

Hi Robert,

I don't want to sound negative, but your plan is really not an alternative or even competition for the SKA.
Other people already commented on many yet unresolved issues :

 - Bandwidth is restricted to the data rate of getting signals from the dishes to the central place.
 - A non-phased array suffers significantly on sensitivity AND on narrow-beam forming
    w.r.t. a phased array (such as SKA and ATA)
 - Static DirectTV dishes diminish aiming the beam (one of the downsides of Arecibo too).
 - Cost is not only in the receiving elements. Cost calculation would need to include the entire system.

Rob

"Robert Clark" <rgregoryclark@yahoo.com> wrote in message news:832ea96d.0502071507.2bc4ff6d@posting.google.com...
> A.) According to this article $1.4 billion dollars is earmarked to be
> spent on the Square Kilometer array with completion expected by 2015:
>
> Radio Astronomy Will Get a Boost With the Square Kilometer Array.
> http://www.universetoday.com/am/publish/radio_astronomy_boost_ska.html?1592004
>
> As I stated below the primary extra components to be added to the
> DirecTV dishes to be used for radio astronomy are the feedhorn and the
> preamp. The feedhorn is simply a metal pipe of little cost. The
> SetiLeague site lists sellers of specially made preamps for SETI
> search at $150. But these are handmade. From the low number of circuit
> elements, I estimate that if mass produced at the millions of items
> level the price could come down in the range of $10 each.
> This site states the rate of growth of satellite TV subscribers is at
> 4 million per year:
>
> Satellite TV Basics.
> http://www.satellitetv-hq.com/hqguides/satellite-tv-basics.html
>
> This means the *receivers* for the SKA system if using these
> satellite dishes could be installed in 1 year at an extra cost of $10
> x 4,000,000 = $40 million dollars. Note that the feedhorn and the
> preamp could be attached at manufacture would not cost more on
> installation labor. The installation is already paid for by the
> satellite TV subscribers. To pay for the extra cost for the added
> equipment you could simply add $1 extra per month to the subscriber
> rate. Then these 4 million, .5 meter wide dishes would have a total
> collecting area of a disk 2000 x .5 m = 1000m = 1km wide, the total
> collecting area expected for the SKA. Moreover this would have the
> advantage that an additional square kilometer of collecting area would
> automatically be added every year over several years going by the
> present growth rate.
> You could also attach the extra equipment to the 25 million satellite
> systems already installed in perhaps 4 or 5 years. The number of
> satellite TV subscribers worldwide was 60 million in 2003 and is
> expected to grow to 100 million by 2008:
>
> Digital Satellite TV Platforms Continue to Gain Subscribers, and
> Profits are on the Rise.
> http://www.instat.com/press.asp?ID=1171&sku=IN0401236MB
>
> If this many .5 meter antennas were networked together, they would
> have the collecting area of a single antenna 10,000 x .5 m = 5 km
> wide.
>
> Note that the idea of using over 50 million separate, stationary
> elements is one of the proposals being considered for the SKA
> architecture:
>
> Aperture Array (AA)
> http://www.skatelescope.org/pages/design_nl.htm
>
> This method of keeping the receiving antennas fixed while detection
> directions are determined electronically is called the phased array
> approach and has the advantage that many separate targets can be
> observed simultaneously. It also has the advantage that interfering
> local signals can be suppressed. However, the Aperture Array has
> antennas close together in a predetermined configuration with the
> positions precisely determined. How could this work for the randomly
> positioned satellite dishes?
> Methods of differential GPS and carrier phase synthesis now have the
> capability of determining position to within millimeters. The method
> compares the GPS signal between a precisely known site and an unknown
> site to locate the unknown site to within centimeters. Then a
> comparison is made in the actual phase of the signals received at the
> two sites to locate the unknown site to within millimeters:
>
> CARRIER-PHASE TRACKING
> "Carrier-phase tracking provides for a more accurate range resolution
> due to the short wavelength (about 19 centimeters for L1 and 24
> centimeters for L2) and the ability of a receiver to resolve the
> carrier phase down to about 2 millimeters. This technique has primary
> application to engineering, topographic, and geodetic surveying and
> may be employed with either static or kinematic surveys. There are
> several techniques that use the carrier phase to determine a station's
> position. These include static, rapid-static, kinematic, stop-and-go
> kinematic, pseudokinematic, and on-the-fly (OTF) kinematic/Table 8-4
> lists these techniques and their required components, applications,
> and accuracies."
> http://cartome.org/FM3-34/Chapter8.htm
>
> This should be sufficient for keeping the signals for the millions of
> antennas in phase up to perhaps 3 cm wavelength, 10 Ghz frequency.
> Timing synchronization can be obtained by synchronizing from the
> common signal received by the dishes from the satellite.
> The Argus telescope at Ohio State University (this is different from
> Project Argus operated by The Seti League) may provide a model for how
> sensitive such a system can be operating from noisy populated areas:
>
> Newsgroups: sci.astro.seti
> From: Bob Dixon <dixo...@osu.edu>
> Date: Wed, 19 May 2004 12:49:02 -0400
> Subject: The Argus Telescope
> http://groups-beta.google.com/group/sci.astro.seti/browse_frm/thread/54ddf1f29f629f20/
>
> Argus Expands the Search For Life.
> By Daniel Sorid
> posted: 03:30 pm ET
> 09 June 2000
> http://www.space.com/searchforlife/seti_argus_000609.html
>
> Note though that the continent wide satellite dish system will have
> an advantage over Argus in dismissing unwanted signals in that such
> signals would only be detected by a local group of antennas not the
> continent wide system.
>
> In mentioning an estimated price for this system, I emphasized the
> estimate was for the *receiving* part of the system. But of course for
> such a system of separate receivers, it is just as important to
> combine and process the signals.
> In the thread for DirecTV being used for SETI, someone mentioned you
> might need to transfer 1 Gbps from each antenna for detections at 12
> Ghz. I seem to recall that analog signals can be tranferred in greater
> density than digital signals. Perhaps the signal received by each
> antenna can be transmitted in analog form with a stamp indicating its
> location and time of origin.
> For examples of the data density required we could look at some
> examples of systems of separate antennas that have been used to give
> combined signals in *real time*:
>
> Astronomers Demonstrate a Global Internet Telescope.
> Date Released: Friday, October 08, 2004.
> http://www.spaceref.com/news/viewpr.html?pid=15251
>
> This produced data of 32 Mbits/second for each telescope for
> observations at 1.6 Ghz. So at 16 Ghz perhaps 320 Mbps might be
> expected for each antenna. The data was sent over a high-speed
> internet network available to universities that operates at gigabits
> per second. Within a few years, the data transfer rate is expected to
> reach tens of gigabits per second.
>
> And:
>
> Prototype SETI Antenna Array Will Help Radio Astronomers Too.
> Date Released: Wednesday, June 07, 2000.
> http://www.spaceref.com/news/viewpr.html?pid=1992
>
> This is of the Argus telescope at Ohio State University. The 64
> antennas here detect signals from 400 to 2000 Mhz. The antennas
> together produce 2.56 gigabytes per second, or 20.48 gigabits per
> second. So each telescope produces 320 Mbps. This article states that
> no physical connection could economically carry that much data over
> distance however this was written in 2000. Ultra wideband technology
> (mentioned below) now has that capability.
>
> For processing the data for the proposed SKA system, I expect the
> distributed computing system used by Set@Home to be used, wherein
> millions of computers take part in the calculations. As for how the
> data can be sent by the individual antennas, there are a few possible
> ways the signals could be combined.
>
> 1.)DirecTV offers a two-way broadband satellite internet service
> called DirecWay. This allows signals to be sent from the home antennas
> back up to the transmitting satellite. However, this system currently
> has only a 100,000 subscribers in place. I want to use the millions of
> subscribers using the satellite TV systems. I think a minor low-cost
> modification of the current TV antennas would also allow them to
> transmit to the satellites used for broadband internet service. (I
> don't think the satellites used for TV service can be used to receive
> signals.)
>
> 2.)Another possibility for transferring the data from each antenna
> might be to use military satellites currently used for surveillance on
> radio transmissions, perhaps using satellites that were decommissioned
> and are no longer used for sensitive military tasks.
>
> 3.)Possibly the techniques used with amateur packet radio could be
> used. Here radio links are used to setup data networks analogously to
> how the internet sets up data transfer networks using the TCP/IP
> protocols:
>
> N6GN's Microwave Link Page
> http://www.sonic.net/~n6gn/uwavelink/uwv.html
>
> INEXPENSIVE MULTI-MEGABAUD MICROWAVE DATA LINK
> http://www.sonic.net/~n6gn/hr89/uwvarticle.html
>
> 4.)Ultra wideband (UWB) promises gigabit data transfers over both
> cable and wireless connections and should be available this year
> (2005):
>
> New chipset promises gigabit broadband on cable and wireless.
> Rupert Goodwins
> ZDNet UK
> May 11, 2004, 15:20 GMT
> http://news.zdnet.co.uk/communications/0,39020336,39154271,00.htm
>
> Ultrawideband in 2005, but only in America
> Rupert Goodwins
> ZDNet UK
> February 19, 2004, 09:45 GMT
> http://news.zdnet.co.uk/communications/wireless/0,39020348,39146644,00.htm
>
> Ultrawideband: Wireless Whoopee.
> 08:34 AM Oct. 09, 2004 PT
> "SAN FRANCISCO -- Think of it as Wi-Fi on steroids. On its way to U.S.
> living rooms and maybe even automobiles is a new type of high-speed
> wireless connection that promises downloaded data rates of up to 1
> gigabit per second -- roughly 18.5 times the speed of Wi-Fi -- to
> personal computers and other devices.
> "This ultrawideband technology, which could become available in the
> next two years, also allows the devices to send data upstream to a
> network at 480 megabits per second."
> http://www.wired.com/news/technology/0,1282,65297,00.html?tw=wn_tophead_3
>
> 5.)Some public utilities now collect their meter readings from radio
> transmitters attached to their meters. The data is collected by
> receiver on utility poles and then transmitted to a central site. This
> method could be adapted to work for collecting the data from the
> separate antennas.
>
> 6.) The above methods would require that the data transmissions be on
> specified frequencies that will not be used for detections. However,
> another method might not have this limitation:
>
> Broadband Over Power Lines?
> 01:15 PM Feb. 09, 2003 PT
> "ST. LOUIS -- Coming to a home or office near you could be an electric
> Internet: high-speed Web access via ubiquitous power lines, of all
> things, making every electrical outlet an always-on Web connection."
> http://www.wired.com/news/technology/0,1282,57605,00.html
>
> This is a new technique already being tested in small markets to
> provide interent service over power lines. The speed of transmission
> can be ramped up to 1 gigabits per second using ulta wideband
> technology.
>
> B.)This last leads me to another proposal for large scale separated
> antennas for radio astronomy: using the electrical wiring in
> households as radio antennas. Here's a post to
> rec.radio.amateur.antenna discussing this:
>
> ==========================================================================
> From: Ed Hare, W1RFI (w1rfi@arrl.net)
> Subject: Re: ISO info about using house wiring as a TV antenna
> Newsgroups: rec.radio.amateur.antenna
> Date: 2000-12-29 15:33:06 PST
>
> Richard Friday <tgirwf@bigfoot.com> wrote in message
> news:92j4h7$2b2$1@bob.news.rcn.net...
>
> > I know this post might be off-topic but could find no other newsgroup that
> > had "antenna" in its name. I'd be most appreciative if someone could point
> > to a more suitable discussion or other source of information.
> > I've seen advertised a device that claims to allow you to use the
> > electrical wiring of your house as a tv antenna. You plug this device
> > into an outlet, and then use connections it provides as your tv antenna.
> > I'm trying to find out if this actually works but have not been able to
> > find any reviews.
>
> This device will receive some signals. However, house electrical
> wiring is
> not a very good VHF antenna system for a couple of reasons:
>
> First, it is very difficult to predict the direction that the house
> wiring
> will best receive from. It is quite likely that the antenna pattern
> will
> have all sorts of peaks and nulls, sort of as if you had a rotatable
> TV
> antenna that was pointing in several directions at once. This may not
> pick
> up much of the TV signal you want to pick up or may have multiple
> responses,
> resulting in ghosts.
>
> Also, an electrical power line can be a very noisy place. All sorts of
> electronic devices on the line, from power-line equipment itself to
> every
> motor or power supply plugged in near you may create noise that will
> interfere with the signal you want to receive.
>
> If you have no other antenna choice, that device may be useable, but I
> don't
> think it will work as well as a good set of "rabbit ears" on top of
> your TV.
>
> Ed Hare, W1RFI
> ==========================================================================
>
> The disadvantage of the electrical wiring going in several different
> directions may actually be an advantage in regards to a SETI search
> since you would want the detections to be omnidirectional. If there
> are 100,000,000 homes which average 10 meters across then this would
> result in a collecting area of 10,000 x 10 meters = 100 km across.
> Since you would want to include large commercial establishments, the
> size would actually be larger than this.
>
>
>
> Bob Clark
>
>
> rgregoryclark@yahoo.com wrote in message news:<1106126272.160248.294240@z14g2000cwz.googlegroups.com>...
> > I was interested to read this on the Seti League web site:
> >
> > __________________________________________________________
> > Parasitic SETI
> > Dear Dr. SETI:
> > As a Satellite dish owner and a strong interest in SETI, I was
> > wondering if anything is available to allow the home satellite dish
> > owner to 'search' when he is not watching TV. I do a bit of programing
> > and would love to help make it so home dish owners could do this. Is it
> > possible? What would it take? Does the dish have to follow a spot or
> > can it sweep the sky from a fixed position? If this is possible it
> > could add a million listeners to the system.
> >
> > Bill T.
> >
> > The Doctor Responds:
> > Absolutely, Bill! Parasitic SETI with a home satellite TV dish is not
> > only feasilble, it's widely practiced. A second feedhorn and preamp
> > assembly are mounted next to the C-band horn/LNB at the apex of the
> > dish (see Figure 2 of this article). This assembly feeds the rest of a
> > SETI system (see our online Tech Manual). You can then sweep out the
> > sky, as described here. And yes, a million participants would be nice,
> > but our goal is a more modest 5000 stations.
> > __________________________________________________________
> > http://www.setileague.org/askdr/parasite.htm
> >
> > I believe they are referring to the 6 ft. backyard type antennas,
> > judging from the linked images on the page. But could the roof mounted
> > DirectTV and Dish Network type antennas be used for SETI?
> > The mentioned extra equipment are an extra feedhorn and a
> > preamplifier. The feedhorn can made cheaply but the preamp seems
> > expensive. If these preamps were mass produced for this purpose could
> > their per item cost be brought under $50?
> > I'm envisionig a government agency such as NSF, or a scientically
> > interested billionaire, paying satellite TV companies to attach this
> > extra equipment to their satellite dishes. Say $100 million is
> > earmarked for the program. Then you would want the extra cost to be
> > under $100 for each dish for say 1,000,000 subscribers. Judging from
> > the diagram in the online Tech Manual linked to on the page, the other
> > equipment should be doable by the equipment that comes with the
> > satellite TV system. Computer processing would be done separately at a
> > central location.
> > If you had a 1,000,000 of these .5 meter wide antennas it would have
> > the detection sensitivy of a single antenna 500 meters wide.
> > Bob Clark

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