How can you guy’s even think about the configuration of the rover until you know how big and how much power the transmitter going to take. And as far as having a base station and a low power radio on the rover, then you would limit yourself to the line of sight. You can’t bounce radio signals off of no atmosphere.
Brian Beckius said...
How can you guy’s even think about the configuration of the rover until you know how big and how much power the transmitter going to take. And as far as having a base station and a low power radio on the rover, then you would limit yourself to the line of sight. You can’t bounce radio signals off of no atmosphere.
I think we can still plan some different ideas....we don't have to go into the 3D design phase yet.
We will be limited to line of sight anyway. Unless we have satellite that orbits the moon (which will be problematic) we will need to remember there will be time the rover is on the far side of the moon. We can program a power down system· to reserve power while the rover is in darkness.
This is ofcourse depending on how long the unit lasts. I'm trying to be optimistic.
All of this is very dependent on many different things......I know the transmitter and receiver are very important.
James,
We have to solve one thing at a time, how heavy and how much power does the transmitter and receiver require ? Thats the only thing we have to know right now .(period) We will deal with the rest as we go.
Heres what I found out, any transmitter and receiver that we can use here on earth to do the same thing will work on the moon (being that seti will be receiving the signals , they just might have to use more dishes) . My only other concern is that I'm thinking that the transmitter is going to fall in the whole Van Allen mess . I know the propeller can be made to be transmitter but nobody answerd me about if it could be a receiver.
James ,
Sorry for being so short ,the transmitter thing was starting to drive me up the wall.
Wow Brian that is an AWESOME rover. You could put that thing as it is in the completed projects section[noparse]:)[/noparse]
Congratulations[noparse]:)[/noparse]
I don't think I know enough or have enough time to participate in this, but I'll be watching these threads for progress[noparse]:)[/noparse]
Way to go Brian
Wish you the best of luck
Rafael
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You've got to play the game.
You can't win.
You can't break even, except on a very cold day.
It doesn't get that cold.
~Laws of Thermodynamics~
Brian Beckius said...
Heres what I found out, any transmitter and receiver that we can use here on earth to do the same thing will work on the moon (being that seti will be receiving the signals , they just might have to use more dishes) . My only other concern is that I'm thinking that the transmitter is going to fall in the whole Van Allen mess . I know the propeller can be made to be transmitter but nobody answerd me about if it could be a receiver.
The communications part is one of the toughest portions of the mission.· I don't have a lot of background in that area, but I have used a tracking transmittor for locating rockets.· According to the manufacturer the tracking transmitter can emit up ot 10 mW of radio power (that's milli-watts), and the signal has been received from as far as 20 miles.
The moon is 240,000 miles away, which is 12,000 times 20 miles.· The received power descrease by the square of the distance, so we would need 144 million times the power to receive the same signal.· That would be 1.44 Mega-Watts!· That looked pretty discouraging until I researched the magic of dish antennas.
According to Wikipedia, the passive gain of a dish antenna is computed from the following formula:
G =·mu * (pi * D / lambda)**2, where
mu is the effiency of the reflector -- usually about 50%
D is the diameter of the dish
lambda is the wavelength of the radio signal
The gain of a 3 meter dish at 12 GHz is 0.5 * (3.14 * 300 / 2.5)**2, which equals 71,000.· The gain of a 1 meter dish would be 1/9th of that, or about 7,900.· So if the lunar base station had a 1 meter dish and our earth station has a 3 meter dish, then the combined gain would be 71,000 * 7,900, which equals 561 million.· So the transmitter power would now only have to be 1.44/561 = 2.6 milli-watts!
From what I can tell, some amateur SETI receivers are based on the old 3 meter C-band dishes that were use 15 years ago for home satellite TV.· They can be obtained at low cost, or at no cost at all.· Low-noise converters/amplifiers are also available at a reasonable cost.· The dish on the moon could be smaller than 1 meter, but the power would have to be increased.· A quarter-watt transmitter would allow using dish of 1/10th the size, or 10 centimeters.
The power is also related to the data rate we would transmit at.· If we want to transmit real-time video at standard definition we would need a data rate around 2 mega-bits/second.· This would probably require more power than I have estimated.· If we transmit still images we could get by with a lower data rate and less power.
·· Since there's going to be what, a 2 1/2 second delay anyway, I don't think there's a great need for transmitting at video rates. I think one thing we should look at here on Earth is how the delay effects navigation and if we can get away with transmitting, say, one frame every couple seconds.
I did a little more research on data transmitters, and I found a transmitter at SparkFun that sends 9600 baud at a range of 500 meters.· Its transmit power is 10 mW.· This is about 1/60th of the range of the tracking transmitter I use, but the tracker just sends out beeps and Morse code.· The SparkFun transmitter would need 3,600 times the power (36 Watts) to be received at 20 miles.· In a simplistic model, the power is proportional to the data rate, so the tracking transmitter's data rate would correspond to less than 3 bits per second (9,600/3,600).
The Japanese lunar satellite is interesting.· It will store real-time data and send it at 1/10th the normal speed.· We would need to use a similar method.· I agree with Pharseid that a slow frame rate should be sufficient for controlling the rover.· The rover could transmit the data to the base station at real-time rates, and the base station could relay it to earth at a much slower rate.· While the rover is moving, still frame data would have higher priority over motion video.
I would hope that a 3 meter dish at the earth-based station would be large enough to send control signals and receive still images.· If the rover loses communication with the base station we should be able to send control signals directly from the earth station to the rover with enough power at the earth station.· We could put the rover in a low bit-rate mode so that we could receive data directly from it also.
The raw HD rates are very high.· The resolution of 720p is 1280x720 pixels.· There are two chroma components at half the resolution.· At 30 frames per second the total raw data rate is 1280*720*2*30 = 55 Mega-bytes/second.· HD is transmitted and recorded in a compressed format using MPEG4 or H.264.· This gets the data rate down to 2 to· 6 Mega-bits/second.
720p can also run at 60 fps.· This doubles the raw data rate, and increases the compressed rate by about 50%.· There is also a 1080-line format that can run at 30 fps in either an interlaced or progressive format.· The total resolution is 1920x1080, and the data rate is comparable to 720p at 60 fps.
Been busy all day checking on this rad hard thing , In digging threw some of nasa's docs I found that they don't allways use rad hard components if they want better performance . I can't find the exact amount of sheilding there are using , but I did find a company that can expose electronics to radiation to see if they will make it. Also I was looking at atmel's transmitter & receiver that was rad hard and I beleive the propeller can be programed the same way that they are
pharseid said...
A problem with shielding is if you shield enough to protect against the Van Allen Belt, you moderate cosmic rays and make them more damaging.
Phar,
Can you provide citation for this statement?
Brian,
Ask Parallax if they want to sponsor the initial $10,000 so we can name the team the "Propeller Team" or something.....
Can the rubber tires take the heat on the lunar surface?
I agree with having a separate Base Station lander. It is a good idea.
Bremsstrahlung is a type of "secondary radiation", in that it is produced as a result of stopping (or slowing) the primary radiation (beta particles). In some cases, e.g.32P, the Bremsstrahlung produced by shielding this radiation with the normally used dense materials (e.g.lead) is itself dangerous; in such cases, shielding must be accomplished with low density materials, e.g.Plexiglas, Lucite, plastic, wood, or water[noparse][[/noparse]1]; because the rate of deceleration of the electron is slower, the radiation given off has a longer wavelength and is therefore less penetrating.
Wow I wonder if that HD compressor is commercially available?
Raf
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You've got to play the game.
You can't win.
You can't break even, except on a very cold day.
It doesn't get that cold.
~Laws of Thermodynamics~
I didn't read the PDF word-for-word, but it appears to describe a fairly standard way for using a layered codec to handle bit errors.· I'm not sure where the innovation is in the paper.· I think it has to do with identifying sub-channels with high bit-error rates and using them for the less sensitive portion of the video stream.
Video codecs normally have a single layer.· The pixels are predicted from the previous coded frame, and only the differences are sent.· This creates a prediction loop, where you must have received all of the frames from the beginning of a sequence to decode a frame.· In MPEG, key frames are sent periodically that are not predicted from the previous frames.· This usually occurs once or twice a second depending on the frame rate and bit rate.· In H.263 and H.264 only one key frame (intra-frame) is sent at the beginning, but portions of each frame are coded without inter-frame prediction after that.
In a layered codec, there is a base layer that is identical to a single layer codec, and there are additional layers, which can increase the frame rate, increase the resolution or improve the coding quality of the base layer.· The additional layers use the base layer for prediction.· The base layer must be protected from bit errors, but the addtional layers can contain errors without accumulating a long-term error in the final image.
We could use a layered codec, but I think it is better to use an ACK/NACK protocol to ensure that we receive all of the data.· Since the delay to the moon and back is 2.5 seconds, we would need to use a method where the rover or base station store all of the packets of data while it is broadcasting them to the earth.· Any packets that are missed at the earth would be requested for retransmission.
did you have time to play with that speadsheet from AMSAT ?
At first glance the spreadsheet looked overwelming, but I played with it for a few minutes and I think I understand it now. I plugged in a few numbers, and the results didn't look that good. I'm sure that I can get better results after tweaking it a bit.
With my initial attempt I used a symmetric configuration with 10 Watt transmitters and 5.4 meter dishes (18 feet!). I used a frequency of 14 GHz. The resulting data rate is around 1200 baud. This would take about 80 days to send a Giga-byte!
The bit error rate (BER) is about 10**(-5). I didn't use any forward error correction (FEC). If we use some FEC and allow a higher BER we could increase the data rate.
Comments
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Thank's Brian
www.truckwiz.com
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
http://www.youtube.com/watch?v=1CKO67FwFhc
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Thank's Brian
www.truckwiz.com
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
We will be limited to line of sight anyway. Unless we have satellite that orbits the moon (which will be problematic) we will need to remember there will be time the rover is on the far side of the moon. We can program a power down system· to reserve power while the rover is in darkness.
This is ofcourse depending on how long the unit lasts. I'm trying to be optimistic.
All of this is very dependent on many different things......I know the transmitter and receiver are very important.
James L
We have to solve one thing at a time, how heavy and how much power does the transmitter and receiver require ? Thats the only thing we have to know right now .(period) We will deal with the rest as we go.
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Thank's Brian
www.truckwiz.com
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
· http://www.radiosky.com/tminishere.html
-phar
cool program
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Thank's Brian
www.truckwiz.com
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
James ,
Sorry for being so short ,the transmitter thing was starting to drive me up the wall.
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Thank's Brian
www.truckwiz.com
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
Congratulations[noparse]:)[/noparse]
I don't think I know enough or have enough time to participate in this, but I'll be watching these threads for progress[noparse]:)[/noparse]
Way to go Brian
Wish you the best of luck
Rafael
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
You've got to play the game.
You can't win.
You can't break even, except on a very cold day.
It doesn't get that cold.
~Laws of Thermodynamics~
The moon is 240,000 miles away, which is 12,000 times 20 miles.· The received power descrease by the square of the distance, so we would need 144 million times the power to receive the same signal.· That would be 1.44 Mega-Watts!· That looked pretty discouraging until I researched the magic of dish antennas.
According to Wikipedia, the passive gain of a dish antenna is computed from the following formula:
G =·mu * (pi * D / lambda)**2, where
mu is the effiency of the reflector -- usually about 50%
D is the diameter of the dish
lambda is the wavelength of the radio signal
The gain of a 3 meter dish at 12 GHz is 0.5 * (3.14 * 300 / 2.5)**2, which equals 71,000.· The gain of a 1 meter dish would be 1/9th of that, or about 7,900.· So if the lunar base station had a 1 meter dish and our earth station has a 3 meter dish, then the combined gain would be 71,000 * 7,900, which equals 561 million.· So the transmitter power would now only have to be 1.44/561 = 2.6 milli-watts!
From what I can tell, some amateur SETI receivers are based on the old 3 meter C-band dishes that were use 15 years ago for home satellite TV.· They can be obtained at low cost, or at no cost at all.· Low-noise converters/amplifiers are also available at a reasonable cost.· The dish on the moon could be smaller than 1 meter, but the power would have to be increased.· A quarter-watt transmitter would allow using dish of 1/10th the size, or 10 centimeters.
The power is also related to the data rate we would transmit at.· If we want to transmit real-time video at standard definition we would need a data rate around 2 mega-bits/second.· This would probably require more power than I have estimated.· If we transmit still images we could get by with a lower data rate and less power.
-phar
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Thank's Brian
www.truckwiz.com
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
http://www.selene.jaxa.jp/en/equipment/hdtv_e.htm
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Thank's Brian
www.truckwiz.com
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
The Japanese lunar satellite is interesting.· It will store real-time data and send it at 1/10th the normal speed.· We would need to use a similar method.· I agree with Pharseid that a slow frame rate should be sufficient for controlling the rover.· The rover could transmit the data to the base station at real-time rates, and the base station could relay it to earth at a much slower rate.· While the rover is moving, still frame data would have higher priority over motion video.
I would hope that a 3 meter dish at the earth-based station would be large enough to send control signals and receive still images.· If the rover loses communication with the base station we should be able to send control signals directly from the earth station to the rover with enough power at the earth station.· We could put the rover in a low bit-rate mode so that we could receive data directly from it also.
·
-phar
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
·I can't find any more info , everytime I email a question they send me the entry packet (I can see why they think they 300 interested teams).
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Thank's Brian
http://tech.groups.yahoo.com/group/lunarX/
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
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Thank's Brian
http://tech.groups.yahoo.com/group/lunarX/
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
Post Edited (Brian Beckius) : 11/25/2007 5:07:44 AM GMT
"All told, the Mooncasts will represent approximately a Gigabyte"
That is 1,073,741,824 bytes.
Even at 56k modem speed (3.3k upload) that is a 90 hour broadcast.
Just how fast can a network transmit data from the moon?
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- - - PLJack - - -
Perfection in design is not achieved when there is nothing left to add.
It is achieved when there is nothing left to take away.
-phar
I could do the actual calculation.....but it's not worth it.
James L
-phar
720p can also run at 60 fps.· This doubles the raw data rate, and increases the compressed rate by about 50%.· There is also a 1080-line format that can run at 30 fps in either an interlaced or progressive format.· The total resolution is 1920x1080, and the data rate is comparable to 720p at 60 fps.
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Thank's Brian
http://tech.groups.yahoo.com/group/lunarX/
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
Post Edited (Brian Beckius) : 11/26/2007 2:16:57 AM GMT
http://www.electronicstalk.com/news/lsi/lsi207.html
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Thank's Brian
http://tech.groups.yahoo.com/group/lunarX/
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
Bremsstrahlung is a type of "secondary radiation", in that it is produced as a result of stopping (or slowing) the primary radiation (beta particles). In some cases, e.g. 32P, the Bremsstrahlung produced by shielding this radiation with the normally used dense materials (e.g. lead) is itself dangerous; in such cases, shielding must be accomplished with low density materials, e.g. Plexiglas, Lucite, plastic, wood, or water [noparse][[/noparse]1]; because the rate of deceleration of the electron is slower, the radiation given off has a longer wavelength and is therefore less penetrating.
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Thank's Brian
http://tech.groups.yahoo.com/group/lunarX/
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
Raf
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
You've got to play the game.
You can't win.
You can't break even, except on a very cold day.
It doesn't get that cold.
~Laws of Thermodynamics~
1- HD camera (rad hard ?)
1- HD compressor board
1- ·transmitter- receiver
Anybody having trouble sleeping tonight , read the attached PDF. :-)
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Thank's Brian
http://tech.groups.yahoo.com/group/lunarX/
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
Post Edited (Brian Beckius) : 11/26/2007 5:48:37 AM GMT
Video codecs normally have a single layer.· The pixels are predicted from the previous coded frame, and only the differences are sent.· This creates a prediction loop, where you must have received all of the frames from the beginning of a sequence to decode a frame.· In MPEG, key frames are sent periodically that are not predicted from the previous frames.· This usually occurs once or twice a second depending on the frame rate and bit rate.· In H.263 and H.264 only one key frame (intra-frame) is sent at the beginning, but portions of each frame are coded without inter-frame prediction after that.
In a layered codec, there is a base layer that is identical to a single layer codec, and there are additional layers, which can increase the frame rate, increase the resolution or improve the coding quality of the base layer.· The additional layers use the base layer for prediction.· The base layer must be protected from bit errors, but the addtional layers can contain errors without accumulating a long-term error in the final image.
We could use a layered codec, but I think it is better to use an ACK/NACK protocol to ensure that we receive all of the data.· Since the delay to the moon and back is 2.5 seconds, we would need to use a method where the rover or base station store all of the packets of data while it is broadcasting them to the earth.· Any packets that are missed at the earth would be requested for retransmission.
Dave
·
did you have time to play with that speadsheet from AMSAT ?
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Thank's Brian
http://tech.groups.yahoo.com/group/lunarX/
·"Imagination is more important than knowledge..." ·· Albert Einstein
http://www.diycalculator.com/subroutines.shtml· My favorite website ( Bet you can't guess why)
With my initial attempt I used a symmetric configuration with 10 Watt transmitters and 5.4 meter dishes (18 feet!). I used a frequency of 14 GHz. The resulting data rate is around 1200 baud. This would take about 80 days to send a Giga-byte!
The bit error rate (BER) is about 10**(-5). I didn't use any forward error correction (FEC). If we use some FEC and allow a higher BER we could increase the data rate.