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: Robert Clark (rgregoryclark_at_yahoo.com)
Date: 02/07/05 

Date: 7 Feb 2005 15:07:03 -0800

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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