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[~nicedice@unaffiliated/nicedice] has joined ##hplusroadmap 11:19 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has quit [Read error: Connection reset by peer] 11:20 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has joined ##hplusroadmap 11:25 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has quit [Read error: Connection reset by peer] 11:25 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has joined ##hplusroadmap 11:31 -!- juri_ [~juri@205.166.94.162] has joined ##hplusroadmap 11:38 < fltrz> maaku, thanks, thats interesting! my major motivation for the solar LIDAR idea is to detect small objects with unused (at night) solar panels 11:41 < fltrz> it won't generate pretty pictures, but for assessing potential future impacts or for mining objects we need to be able to predict their motion a long time in advance 11:42 < fltrz> so instead of astronomical imaging Detection and Ranging are more relevant (and the large deployment of solar can enable ridiculously huge detector apertures) 11:43 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has quit [Ping timeout: 252 seconds] 11:47 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has joined ##hplusroadmap 11:57 < streety> I've not been following the discussion but would solar panels produce any signal from the weak light received at night? 12:08 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has quit [Ping timeout: 245 seconds] 12:09 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has joined ##hplusroadmap 12:25 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has quit [Read error: Connection reset by peer] 12:26 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has joined ##hplusroadmap 12:35 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has quit [Read error: Connection reset by peer] 12:36 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has joined ##hplusroadmap 12:39 -!- nicedice_ [~nicedice@unaffiliated/nicedice] has quit [Read error: Connection reset by peer] 12:40 -!- nicedice_ 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timeout: 240 seconds] 15:15 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has joined ##hplusroadmap 15:17 < fenn> fltrz because of the inverse square law you get really low signal strength the further out your reflecting object is; have you calculated how big of a (solar panel) detector area you need to equal the gain of a narrow field of view telescope? 15:18 < fenn> also i was thinking about using a laser pulse to illuminate the hypothetical objects, then it really would be LIDAR 15:19 < fenn> i'd think a man-made omnidirectional laser pulse could be higher power (for a few microseconds) than the average variation in solar intensity 15:28 -!- TripFandango [~trip@141.226.9.200] has quit [Read error: Connection reset by peer] 15:29 -!- TripFandango [~trip@141.226.9.200] has joined ##hplusroadmap 15:49 -!- TC [~talinck@cpe-174-97-113-184.cinci.res.rr.com] has quit [Ping timeout: 246 seconds] 16:05 -!- sachy [~sachy@78.108.102.220] has quit [Quit: Leaving.] 16:14 -!- justanotheruser [~justanoth@unaffiliated/justanotheruser] has quit [Ping timeout: 246 seconds] 16:29 -!- justanotheruser [~justanoth@unaffiliated/justanotheruser] has joined ##hplusroadmap 16:39 < fltrz> streety, why wouldn't it? the pixel sensors in a camera sensor are just miniature solar panels. at night the solar panels would be reverse biased just like photodiodes in photoconductive mode 16:40 < fltrz> fenn, comparatively both optical telescopes as the LIDAR setup suffer from the same inverse square laws regarding distance from the sun and distance to the observer 16:41 < fltrz> a telescope does not provide gain, the larger the cross section or area of reflector/refractor the larger the bucket with which to catch photons 16:43 < fltrz> regarding illumination, when both superpowers considered bombing the moon for demonstration purpouses, they both quickly realized that a the light from a nuclear weapon on the moon would be imperceptible, but generating enough lunar dust to reflect sunlight would be perceptible 16:44 < fltrz> so even though the fluctuations in sunlight may be imperceptibly small in a relative sense, it may still be grand in an absolute sense 16:46 < fltrz> also, since it does not really need aiming, the dimmer an object reflects light, it merely means recording for a longer time (i.e. as long as humanity) for the blip to stand out in trajectory parameter space 16:54 < fltrz> "as long as humanity preserves the solar panel recordings" 16:54 < fltrz> the gain of a telescope is merely the aperture area compared to the aperture of your eyes pupils 16:54 < fltrz> obviously for a very long fraction of the foreseeable future the sum total of deployed solar panels will remain larger than the sum total of optical imaging telescopes 16:54 < superkuh> Better luck looking at what cherenkov telescopes do. 16:54 < superkuh> And other non-imaging solutions. 16:54 < streety> Solar panels are designed/optimized for producing electricity in sunlight, might there be internal resistances that would obscure any signal. There would also be thermal noise. I thought many of the cameras used for astronomy used cooled detectors 16:54 < fltrz> the internal resistance is of no interest (and equally undesirable for imaging and power generation) 16:54 < fltrz> streety, the cooled detectors are for infrared imaging 16:54 < fltrz> thats independent of astronomy (i.e. thermal imaging of objects on earth also requires cooling) 16:54 < fltrz> I'm just pointing out that if we are going to have massive deployments of solar panels, we might as well realize their dual use as a LIDAR sensor 16:55 < superkuh> Right... just put an ADC on every panel, run all the cable, install all the computers and storage for thousands of megabyte/s streams. Easy. 16:55 < superkuh> This is sarcasm. 16:57 < fltrz> cherenkov telescopes for high energy particles? I don't think they can help much with detecting small objects within solar system, but they should prove very useful for extragalactic observation 16:58 < superkuh> The detection is from light. Not high energy particles. The high energy particles create the light. 16:58 < superkuh> Very low levels of light. 16:58 < superkuh> The arrays are design to cover the entire sky. 16:58 < fltrz> superkuh, for a single PV park, you only need one resultant output stream (since all the panels are within say 6km) and USB sound card is pretty much nothing compared to price of inverters etc 16:58 < superkuh> Oh, so now all the panels are sampled coherently? 16:59 < superkuh> Because if you just sample the DC power you get nothing. And the DC power goes over non-impedance controlled cabling. 16:59 < fltrz> you can connect the panels in parallel 16:59 < superkuh> So unless you sample directly at each panel you get nothing. 16:59 < fltrz> I thought I mentioned from start it would be AC coupled? 17:00 < superkuh> At each panel? 17:00 < superkuh> Do that and now you have to make the ADCs coherent. 17:00 < superkuh> And thats $$$. 17:00 < superkuh> And pretty hard to do at large distances. 17:00 < fltrz> superkuh, its audiorate ADC, literally soundcards 17:03 < streety> I don't think cooled detectors are exclusively used for IR. I'm not familiar with astronomy but cooled cameras are quite commonly used in biological microscopes. I would be amazed if astronomy did not see similar benefits 17:06 < fltrz> sure they eliminate dark current 17:06 < streety> is that not an issue with your proposal? 17:06 < fltrz> my proposal does not generate images, its DAR detection and ranging 17:08 < fltrz> any noise on top (i.e. blinking airplane lights, artificial light polution from cities etc) will simply not correlate with the solar variation recorded on the day side 17:08 < streety> I don't understand. You still need to detect very weak signals. If the noise is greater than the signal there is nothing to correlate 17:09 < fltrz> I'm not sure if you are willfully ignoring linear systems theory or unaware of it? 17:10 < streety> I genuinely don't understand so assume I am unaware. Is there a particular keyword/phrase I should focus on in this context? 17:11 < fltrz> streety, perhaps I should write it out first as a document with illustrations and equations 17:12 < streety> If you do I will read it 17:14 < fltrz> with correlation I mean the coefficient that results by integrating over time: the product of an incoming noise signal (from reverse biased solar panels at night time) with a delayed reference noise signal (from pyranometers pointed at the sun in daytime) 17:14 < fltrz> for correct values of delay, the resulting number will show a peak as a function of delay 17:16 < fltrz> suppose the following straight line configuration: sun - earth - object, where object is one light second away, then the night side observer will observe a 2 second delayed "echo" of the solar variation recorded by people on the day side 17:17 < fltrz> you can add noise to the observation signal, but if its uncorrelated to the solar fluctuation the integral will eliminate it 17:19 < fltrz> some objects are such dim reflectors that they reflect less light than the stars behind it, so with normal optical telescopes you have no hope of separating it from distant starlight, but fluctuations in distant starlight are uncorrelated to our sun 17:20 < fltrz> so by pointing the reference pyranometers at our sun, we filter and select specifically for objects illuminated by the sun (since the start of recording) 17:24 -!- Kingsy0 [~Kingsy@106.104.45.138] has joined ##hplusroadmap 17:27 -!- Kingsy0 [~Kingsy@106.104.45.138] has quit [Remote host closed the connection] 17:28 < streety> I think I understand the concept. I'm still concerned about noise. I accept you could handle a lot by using long time periods and multiple detectors but there must be a point when it is beyond what can be handled 17:30 < streety> are you aiming for just detection and range or azimuth and altitude as well? 17:30 -!- sektor [~sektor@95.87.234.241] has quit [Ping timeout: 244 seconds] 17:32 < fltrz> you can roughly determine azimuth and altitude by noticing the change in correlation strength for a static solar panel as the earth rotates 17:33 < fltrz> also the object is moving and changing distance, so the correlation delay is changing slowly depending on its (and our) orbit parameters in the solar system 17:34 < fltrz> from this you can deduce its position 17:34 < streety> I thought you might be able to use trilateration from multiple panels spread across the night side of the earth 17:36 < streety> the change in position would presumably impact the length of the measurement you can make and the amount of noise you can compensate for 17:36 < fltrz> and then optionally aim optical telescopes equiped with expensive super high framerate cameras and perform the same trick: the raw video recording seems to show just the normal star view, but after processing the stars disappear and the reflector for the chosed depth becomes visible (assuming the optical telescope's area and observation time is long enough) 17:37 < fltrz> streety, yes that should be possible by having metadata for each audio stream (the PV park's GPS location, and GPS time reference as audio sample index numbers) 17:40 < fltrz> the resolution is 6.25km for 44.8kHz and 1.5 km for 192 kHz audio 17:41 < fltrz> thats the depth resolution, so the angular resolution for origin depends on the spatial separation between the different PV parks 17:45 -!- ebowden_ [~ebowden@unaffiliated/ebowden] has quit [Remote host closed the connection] 17:49 < streety> that would make sense. What would the basic kit look like. An audio card, GPS disciplined oscillator, anything else? The panels still seem like the weak link. 17:49 -!- helleshin [~talinck@cpe-174-97-113-184.cinci.res.rr.com] has joined ##hplusroadmap 17:53 < fltrz> the panels themselves are not the weak link, weaker links are probably network infrastructure (although most inverters in commercial solar parks have some network infrastructure in place anyway to monitor individual module performance), conventions/standards for daytime/nighttime switchover, The GPS & audio card(s) sound right, but probably also a battery for reverse biasing the panels at night. And of course modified photodiode 17:53 < fltrz> pyranometers for audioband AC-coupled measurement during the day 17:56 < fltrz> as long as the scientific utilization does not interfere with commercial energy production of the plant I don't think PV park operators would mind (and if they protest, regulations mandating provisions for access by the astronomy community should be easily passed, as long as the rules ensure respect of the commercial property and equipment) 17:58 < fltrz> btw pyranometer is roughly fancy talk for light sensor during the day (the expensive part about pyranometers is mostly their callibration for the DC scale) 18:00 < superkuh> There's also ##astronomy and ##optics if you're looking for more input. 18:01 < fltrz> superkuh, yeah I think I will join ##astronomy, I have a hard time finding DC-coupled audiorate pyranometer recordings (with flat audiorate bandwidth) 18:01 < fltrz> of course the long timescale solar cycles are well documented 18:07 < fltrz> superkuh, I am thinking I should make a clear proposal document with pictures and equations in latex/pdf before bothering ##astronomy 18:09 < streety> AC-coupled measurement? Is AC alternating current or something else? 18:11 < fltrz> yes alternating current: the relative size of fluctuations will be much smaller than the average intensity of the sun (that does not mean the absolute fluctuations are small) 18:12 < fltrz> suppose you made DC coupled measurement of solar intensity, then we are wasting ADC bit depth on the DC component 18:12 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has quit [Ping timeout: 240 seconds] 18:14 < streety> I see, ignore any slow changes as it is the fast changes that are of interest. I had not heard AC-coupled before for this use 18:16 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has joined ##hplusroadmap 18:25 < fltrz> yes, by ignoring the DC component, you can electronically amplify the smaller variations at much larger gains. If you leave the DC component in you would start clipping on the ADC's range (the maximum and minimum values)) 18:27 -!- ebowden [~ebowden@unaffiliated/ebowden] has joined ##hplusroadmap 18:31 < fenn> it's another way of saying band-pass filter 18:31 < fltrz> right 18:41 < fltrz> an easy proof of concept would be a single photodiode + variable gain audio amplifier, a cheap telescope and a soundcard. Point the telescope to say mars for a couple of hours, and increase the gain until a small fraction of the samples are clipping the ADC range 18:41 < fltrz> the different moons will be at different depths so the autocorrelation should show peaks corresponding to their depth difference 18:42 < fltrz> this test is easier than actually measuring the direct solar variation since that needs coordination between multiple people on different continents 18:43 -!- Freejack20 [~Freejack@pc-121-48-44-190.cm.vtr.net] has joined ##hplusroadmap 18:44 < fltrz> once this is proven to work, we can consider further investigation of the idea 18:48 -!- Freejack20 [~Freejack@pc-121-48-44-190.cm.vtr.net] has quit [Remote host closed the connection] 18:49 < fltrz> in theory it could also help detect exoplanets by autocorrelating the light from a distant star 18:49 < fltrz> but don't take my word on that last one 18:51 < fltrz> (since its impossible to remove the full intensity direct solar variation from the reflector solar variation, we are forced to lose bit depth resolution when observing exoplanets around distant stars) 18:55 < fenn> do you need observing stations around the globe even for a proof of concept? 18:55 < fenn> if you looked at something big and about 12 light hours away you could autocorrelate 18:56 < fenn> er, duh, nevermind 18:56 * fenn reads 18:57 < fltrz> for the moons around mars you don't need stations around the world, correct for objects that just happen to be an integer multiple of 12 light hours away you also don't need multiple stations (assuming a climate without clouds, say a desert) 18:57 < fltrz> but if there are occasional clouds, then multiple redundant daylight stations, and multiple redundant nighttime stations are required 18:58 < fenn> why don't we have active RADAR surveys for asteroids already? 18:58 < fenn> is it a wavelength and dish size problem? 18:59 < fltrz> I believe it's a power issue, and yes also wavelength in the sense that gaussian beams disperse beyond their waist 18:59 < fenn> your idea ought to work with solar RF emissions just as well 19:00 < fltrz> fenn, in theory yes, but I see no large-scale radiowave detector to freeride on (unless we somehow use power lines as antennas, but since power is in constant use these will be very noisy)) 19:01 < fltrz> while the huge photodiodes go unused at night 19:02 < fltrz> (and are correctly pointed towards the ecliptic for their daytime use) 19:02 < fenn> are they still pointed at the ecliptic at night? the earth rotational axis is out of plane 19:03 < fltrz> for a static panel: if it is perfectly directed at summer noon sun altitude, then it is perfectly directed at night ecliptic during the winter 19:04 < fenn> i would guess the solar panels are pointed away from the ecliptic at twice the angle from the sun's current position to local "up" 19:04 < fltrz> the variation is simply the same as the seasonal solar "height" variation 19:04 < fenn> (at night) 19:04 < fltrz> anyway, its only a cos(alpha) factor, imho not really worth worrying about 19:04 < fenn> ok 19:06 < fenn> i figured since they pay dudes to drive around in trucks and wash the panels off, they also pay dudes to go around and rotate the panels to point at the sun's seasonal height average 19:07 < fenn> with active tracking you could just rotate them wherever you want 19:07 < fltrz> I don't know if they repoint static panels, but would sure like to know. 19:08 < fltrz> correct the PV parks can probably point them however they want, which makes it a more interesting site for the first versions, as soon as it is night, and for the rest of the night, you can keep tracking the direction opposite the sun 19:09 < fltrz> slowly over a year scanning the full circle 19:09 < fltrz> they are still omnidirectional in the cos(alpha) sense though 19:09 < fenn> it it computationally feasible to integrate the light signal over orbital parameter space? 19:11 < fltrz> fenn, I am not 100% sure if the algorithms are available, but I believe it would become feasible with enough attention to the problem 19:11 < fenn> each body would be a point that should stand out from the sea of noise given enough time 19:11 < fltrz> correct 19:11 < fenn> also it could give you ideas about where to point your laser search light 19:11 < fltrz> so even if it underperforms, if we preserve the results the next generations can reap the fruits 19:13 < fenn> i don't really understand what it is that SETI@Home is/was doing that was so hard to compute 19:13 < fltrz> to be honest I have no idea at all what exactly SETI@home was computing 19:13 < fenn> "data are then parsed into small chunks in frequency and time, and analyzed, using software, to search for any signals" yeah, wow, great 19:14 < fenn> USING SOFTWARE! 19:14 -!- Cory [~Cory@unaffiliated/cory] has joined ##hplusroadmap 19:15 < fltrz> I guess it would depend on their definition of "signal" 19:16 < fenn> shortly after that it says they're looking for: spikes in power spectra, gaussian rises and falls in transmission power, triplet spikes, pulsing signals, and autocorrelation 19:20 < fltrz> searching for signs of intelligence seems like a very hard and open ended problem, I don't have the audacity nor the knowledge to contribute in that area 19:21 < fenn> mrdata was working on the inverse problem, how to send a short message that stands out from background noise 19:21 < fenn> his main concern was compensating for doppler shift from earth moving around the sun 19:21 < fenn> since that would be the major unknown parameter on the receiving end 19:22 < fenn> the more precisely you can compensate it, the higher the possible gain 19:22 < fenn> unfortunately we don't have space-based transmitters available for hobbyists to send messages to space 19:23 < fltrz> doppler shift can be bypassed by working at lower modulation frequencies (it's why I propose using audiorate ADCs), but then the message becomes longer 19:23 < fenn> well mostly the message is "we are here!" which is like 1 bit 19:24 < fenn> and you can send another message in parallel that has a different encoding 19:27 < fltrz> https://en.wikipedia.org/wiki/Chelyabinsk_meteor#Injuries_and_damage << if the passive solar LIDAR turns out to be feasible, there can be economic incentives for doing so as well, to protect assets like windows etc over a large area. The first nations to deploy can sell to other nations or withhold such knowledge at the last minute 19:27 < fenn> the passive asteroid surface is also sending a "we are here" message, but it is not compensated for doppler shift 19:29 < fenn> how do you withhold asteroid orbits at the last minute? you'd have to withhold up until the last minute and then decide to continue withholding after the last minute 19:30 < fltrz> I think if I had to design a message at the top of my head, I would send a gaussian blip of 2 sine waves, many processes like distortion create harmonics, but you wouldn't expect a second co-occuring frequency component to have f2 = f1 * sqrt(2) 19:31 < fltrz> its perhaps the simplest irrational number 19:33 < fenn> being irrational makes it difficult to generate precisely 19:34 < fenn> you can't do a simple PLL for instance 19:34 < fltrz> fenn, right I meant suppose the west had secretly built out passive solar LIDAR (assuming it is feasible!) then we could offer advance notification for a certain yearly price, nations that don't pay receive no advance warning (unless perhaps the last minute to prove advance knowledge when its to late to open all the windows over a large area) 19:35 < fenn> meh you could do the same for many early warning systems such as earthquake or weather, but nobody is selling that kind of service 19:35 < fltrz> fenn, irrational up to some accuracy, if its accurate up to say 10 bits (the third digit), I would still be surprised to see the 2 simultaneous frequency blips co-occur 19:36 < fltrz> well the weather and earthquake alert services are arguably selling this information 19:37 < fenn> i'm not aware of any that are not also government funded public services 19:37 < fltrz> but I agree that the national borders would probably be irrelevant 19:38 < fltrz> you can compare it somewhat to the early mechanical tide calculators during wartime 19:39 < fenn> "Early Warning Labs" is one company that takes warning data from USGS and sends alerts to mobile phones, but that's hardly doing anything 19:39 < fltrz> yeah I agree 19:40 < fltrz> so its mostly just useful for astronomy, and perhaps in the far future for decelerating and mining asteroids 19:42 < fenn> .title http://youtu.be/xJsUDcSc6hE 19:42 < yoleaux> Asteroid Discovery - 1980-2012 - UHDTV - YouTube 19:43 < fenn> .title http://youtu.be/BKKg4lZ_o-Y 19:43 < yoleaux> Asteroid Discovery - 1970-2015 - 8K resolution - YouTube 19:43 < fenn> as if you could play 8k 19:43 -!- ebowden [~ebowden@unaffiliated/ebowden] has quit [Remote host closed the connection] 19:53 < fltrz> thanks those are nice visualizations! 19:59 -!- l_wl [~l_wl@pool-71-191-33-241.washdc.fios.verizon.net] has joined ##hplusroadmap 20:12 -!- ebowden [~ebowden@unaffiliated/ebowden] has joined ##hplusroadmap 20:23 -!- l_wl [~l_wl@pool-71-191-33-241.washdc.fios.verizon.net] has quit [] 20:29 < fenn> https://www.cnet.com/news/20-million-historical-artifacts-destroyed-in-brazil-national-museum-fire/ 20:50 -!- Cory [~Cory@unaffiliated/cory] has quit [Ping timeout: 244 seconds] 20:54 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has quit [Ping timeout: 252 seconds] 20:55 -!- kuldeep [~kuldeep@unaffiliated/kuldeepdhaka] has joined ##hplusroadmap 20:57 -!- Storyteller [~Storytell@unaffiliated/storyteller] has joined ##hplusroadmap 20:58 < fltrz> "On the day of the impact, Bloomberg News reported that the United Nations Office for Outer Space Affairs had suggested the investigation of creating an "Action Team on Near-Earth Objects", a proposed global asteroid warning network system, in face of 2012 DA14's approach" huh? impact and flyby on same date? 21:01 -!- Cory [~Cory@unaffiliated/cory] has joined ##hplusroadmap 21:01 -!- Storyteller [~Storytell@unaffiliated/storyteller] has left ##hplusroadmap [] 21:12 -!- hehelleshin [~talinck@cpe-174-97-113-184.cinci.res.rr.com] has joined ##hplusroadmap 21:17 -!- helleshin [~talinck@cpe-174-97-113-184.cinci.res.rr.com] has quit [Ping timeout: 252 seconds] 21:20 -!- justanotheruser [~justanoth@unaffiliated/justanotheruser] has quit [Ping timeout: 245 seconds] 21:34 -!- justanotheruser [~justanoth@unaffiliated/justanotheruser] has joined ##hplusroadmap 22:12 < fltrz> fenn, regarding feasibility of integrating over orbital parameter space, I think in practice (at least initially) one would simply explore delay space (naive fourier transform correlation would assue a constant delay), i.e. delay=a, delay=a+b*t, delay=a+b*t+c*t^2 etc... eventually someone would work out good analytic approximations for the delay as a function of both reflector orbit parameters, earth orbit parameters and station 22:12 < fltrz> GPS location... 22:13 < fenn> "U.S. government sensor data also provides an approximate path for the Chelyabinsk impactor. A similar calculation can be made from analysis of video records of the event; both methods yield similar results. This path through the atmosphere reinforces that the fireball was not associated with asteroid 2012 DA14, which made a very close flyby of Earth just over 16 hours later. This is known 22:13 < fenn> because the two objects approached the Earth from completely different directions and had entirely different orbits around the sun. And, their compositions are dissimilar." 22:14 < fenn> now i wonder what sort of sensors they are talking about 22:14 < fenn> radar satellites? seismic sensors? 22:14 < fltrz> then given such analytic form of delay function its correlation math 22:15 < fenn> why are you using a polynomial? 22:15 < fltrz> I assume radar, once the object is close enough the reflections become noticable (at least in hindsight) 22:17 < fltrz> fenn, because the [sun-reflector-earth distance minus sun-earth distance] changes day by day 22:17 < mrdata> SETI@home is looking for the kind of signal i want to send 22:17 < fenn> what's the maximum degree of polynomial? 22:17 < mrdata> extremely narrow band beacon 22:18 < fltrz> fenn, not sure, but the more accurate the polynomial, the longer the integration time is adding constructively 22:19 < fenn> polynomial series are a poor way to model sine functions if you already know it's a sine function 22:19 < fltrz> the polynomial would be until more accurate analytic forms allow unlimited accumulation of data 22:19 < mrdata> fltrz, what are you doing? 22:19 < fltrz> mrdata, not yet doing, investigating possibility of passive solar LIDAR 22:20 < fenn> mrdata read the logs, you'll find it interesting 22:20 < mrdata> i dont have a clue what passive solar LIDAR even means 22:20 < fenn> http://gnusha.org/logs/2018-09-01.log 22:22 < fltrz> the sun's optical radiation is not exactly constant (on long timescales we have solar cycles), assuming there is similarily audiorate variation of solar intensity (in the absolute sense large, but probably small in the relative sense relative to average intensity) 22:22 < fltrz> active LIDAR is detection and ranging of objects by a variation of a controlled light source (usually sine or square wave) 22:23 < fltrz> at night all the solar panels (photodiodes) go unused 22:23 < mrdata> fenn, i cant browse web atm; but5 if those are channel logs i have scrollback 22:24 < mrdata> fltrz, what would you be ranging 22:24 < fltrz> mrdata, I think I started the discussion yesterday with the sentence " does anyone know of publicly available pyranometer dataset?" 22:24 < fltrz> the distance to faint objects within our solar system 22:25 < mrdata> dont you need to focus the light? 22:25 < maaku> fltrz: I'm interested in your solar LIDAR idea for crypto currency purposes. it's potentially useful for solar-system wide consensus systems, with the sun acting as a random oracle anyone can verify 22:26 < fltrz> it's DAR not immaging, so there won't be pretty pictures for the magazines :( but the aperture of a couple of PV parks would easily dwarf any optical telescope 22:26 < fenn> detection and ranging 22:27 < fltrz> maaku, I think solar variation is only "in common" in a relatively narrow cone emanating from the sun 22:27 < fltrz> the other side sees... the other side of the sun 22:28 < fenn> you could see bounce light off of a) a planet or b) an artificial passive reflector that's too bright to economically falsify 22:28 < mrdata> the PV panels integrate the light they receive; and they have leakage current 22:28 < fltrz> maaku, why do you need a random oracle that anyone can verify? it seems like Silvio Micali's Algorand can already do this? 22:29 < mrdata> so right now, though, the moon is above the horizon here 22:29 < fltrz> mrdata, what do you mean with "integrate the light" ? of course I propose reverse biasing the solar panels to draw the charge away for measurement 22:31 < mrdata> fltrz, so photons knock electrons into the conduction band, and this raises the potential; but in darkness, thats not by much. those electrons roll around and settle back into spots they got knocked out of 22:31 < fltrz> mrdata, I am not proposing to use a normal PV setup as-is, and somehow measure their night time power output, after day time there should be a switchover to other circuitry that reverse biases and amplifies the current generated in the photodiode 22:32 < fltrz> mrdata, you seem to be describing photoVOLTAIC mode, for light sensing you use photoCONDUCTIVE mode. your complaint is entirely valid for photovoltaic mode 22:33 < mrdata> then i'm not understanding you 22:33 < mrdata> the PV panel is a diode 22:33 < fltrz> correct 22:33 < fltrz> just like BPw34 is a photodiode 22:33 < mrdata> in PV mode it is "reverse biased" 22:34 < mrdata> you are forward biasing it? 22:34 < fltrz> nono in power generation mode the solar panel is on the other side as in photoconductive mode 22:35 < fltrz> photoconductive is reverse biased 22:35 < maaku> fltrz: a solar telescope is capable of seeing a lot more than just the tiny angle pointed at it 22:35 < mrdata> i thought you could damage panels by running current through them when theyre dark 22:36 < fltrz> mrdata, you can, if you forward bias them! 22:36 < maaku> fenn: i didn't read all the gian scrollback, but are you aware of the arecibo observatory's active radar? 22:37 < maaku> it's routine to do active radar observation of asteroids and other solarr system objects 22:37 < mrdata> so the panels have bypass diodes installed to prevent this problem 22:37 < mrdata> i dont get how you config this for your use 22:38 < mrdata> i still dont get how it will work 22:38 < fenn> maaku no i haven't heard very much about active observations. presumably that was the same system used to send the 'arecibo message' way back when 22:38 < fltrz> maaku, what do you mean with more than the tiny angle pointed at it? every photon that ends up on the camera sensor of the telescope was caught as a light ray striking the refractor lens or reflector mirror 22:39 < mrdata> fltrz, do you have a panel to experiment with? 22:39 < fltrz> mrdata, if you have some basic electronics equipment I suggest you order a few BPW34 photodiodes and opamps to play around with, you will understand what I propose 22:40 < mrdata> there's going to be a lot of light pollution, clouds, etc 22:40 < fltrz> mrdata, I will experiment with a telescope and photodiode pointed at mars first 22:40 < mrdata> fltrz, please show me a schematic then 22:42 < fltrz> https://en.wikipedia.org/wiki/Photodiode#Principle_of_operation 22:43 < fltrz> U+ --|<-- outputnode --^^R^^-- U- or ground 22:43 < fltrz> if there is no light current wont flow through the photodiode 22:45 < fltrz> as soon as a photon separates an electron hole pair, they are swept out of the PN junction region by the applied potential, the photocurrent passes through the resistor generating a emasurable signal at the output node 22:45 < fltrz> the --|<-- is the photodiode or solar panel 22:47 < fltrz> light pollution, clouds etc are also a problem for the usual imaging telescopes. but since we are measuring solar noise we can filter out uncorrelated stray light from light pollution 22:49 < mrdata> ok so lets say you want to range planet 9 22:49 < mrdata> how much light do you expect to get 22:50 < fltrz> that depends on multiple factors: it is still investigation for me because I don't know the RMS noise of solar light as a function of frequenncy 22:50 < fltrz> so it also depends on bandwidth of measurement 22:51 < fltrz> so obviously the RMS power will be lower than the DC average power from the sun, but with all the solar panels going unused at night... 22:52 < mrdata> it's somewhere around 500 to 1200 AU, so expect return signal in 9 days 22:53 < mrdata> but all other light sources drown it out 22:53 < mrdata> including stars 22:53 < fltrz> the amount of light from planet 9 will be the same amount of light from planet 9 multiplied with the fraction of power in the considered frequency band compared to DC power. And also proportional to total aperture area (solar park PV area) 22:53 < mrdata> we're talking a few dozen visual magnitudes 22:55 < fltrz> mrdata, thats why you correlate with the solar output from 9 days ago, which eliminates the other stars from the background 22:55 < fltrz> since the fluctuations in the distant star light is uncorrelated to fluctuations on our sun 22:56 < mrdata> so, if youre experimenting with this, i suppose you can use the moon to start 22:56 < mrdata> since it's brighter 22:56 < fltrz> yes, thats what I considered first 22:56 < mrdata> did you mention any of this in ##astronomy? 22:56 < fltrz> say at a time when both sun and moon are visible 22:56 < fltrz> mrdata, no not yet 22:57 < mrdata> some of the folks there have quite good handle on fundamental limits 22:57 < fltrz> I'd like some pyranometer data first, or make some measurments myself before bothering the serious people 22:57 < mrdata> ok 22:58 < fltrz> thing is, I just don't find audiorate pyranometer data, and google is trying to sell me pyranometers 22:58 < fltrz> so I'll just have to build my own... 22:58 < fltrz> then I realized pointing a photodiode+telescope at mars should work as well 22:59 < fltrz> using autocorrelation should reveal peaks corresponding to depth difference of the moons 22:59 < mrdata> that should test your sensitivity well, if it works 22:59 < fenn> hey, ##hplusroadmap is serious business! 23:00 < fltrz> sorry! I'll get my coat ;) 23:01 < fenn> mars has pretty tiny moons 23:01 < mrdata> yes 23:01 < fltrz> mrdata, it also avoids me needing a collaborator on the day side of the earth, for an experiment that may amount to nothing 23:01 < fenn> maybe easier to separate out the signals if you pick a binary near earth asteroid 23:01 < fenn> about 10% of NEO are binaries 23:01 < fltrz> thats also a good idea, but I'll have a hard time locating and tracking a binary without first also making a star tracker 23:02 < mrdata> mars and the moon are at least easy to find 23:05 < fltrz> apparently hplusroadmap really is more serious given that I only got a youtube link for AC/DC when asking for both AC and DC coupled audiorate pyranometer recordings 23:05 < fltrz> that was in ##astronomy 23:05 < fltrz> to be fair I didn't explain my idea there 23:08 < mrdata> fltrz, oh! that was lando who gave you that link; he is the channel's pet troll 23:09 < fenn> how about using ISS and the moon 23:09 < fenn> not many observation opportunities, but it will be two sun-reflecting objects in the sky at the same time 23:10 < fenn> also the moon has earthshine which is another correlated delay 23:10 < fltrz> oh I see 23:11 < mrdata> i will be astonished if you can autocorrelate the moon with mars and use that to range mars 23:11 < fltrz> fenn, yes those are all good ideas 23:13 < fltrz> to be honest the required correlation duration goes up with the size of the object (since the moons and mars are many many kilometers of depth from closes point to the rim) 23:13 < fltrz> which effectively forms a lowpass filter 23:14 < fltrz> while asteroids are much smaller and most may fall under the 6km limit for single sample duration of 48kHz audio 23:15 < fenn> c/moonradius = 172Hz 23:15 < fltrz> so I'd actually really prefer testing on binary asteroids or ISS... but that would require building a tracker first 23:15 < fltrz> fenn, yeah 23:16 < fenn> so that's 278 samples 23:16 < fenn> i think 44kHz is more common 23:16 < fltrz> yeah the impulse response of the moon is that many samples 23:16 < maaku> fenn: "active observations" was what aricibo was actually mde to do, except a lot closer to home (spy satellites) 23:18 < fltrz> so from ~20Hz to 172Hz leaves roughly 150Hz of bandwidth for the RMS noise... while smaller objects can utilize a higher bandwidth of the solar noise 23:23 < mrdata> 44kHz sampling is audio CD quality but 48 kHz is professional 23:23 < maaku> fltrz: I mean that signal off the sun is not directional. if your scope is capable of resolving the surface of the sun, you could resolve the whole ~175 degree field of view, which could be use to coordinate with anyone in your side of the system 23:24 < fltrz> I have 192kHz on most of my computers (not an audio phile and most of my hardware is about 8 years old) 23:25 < mrdata> maybe look at things through a tube before you widen the field of view to the entire hemisphere 23:25 < fltrz> maaku, this is for the cryptocurrency application right? can you explain how it would be used? 23:26 < maaku> fenn: regarding US government sensor data I presume they are talking about this : https://www.lockheedmartin.com/en-us/products/sbirs.html 23:27 < maaku> designed to pick up ICBM rocket plumes, but also detects just about everything entering the atmosphere 23:28 < fenn> ah yes i have heard of that 23:28 < maaku> it's my understanding that they had a hell of a time removing this "noise" 23:28 < fenn> always get it confused with "small business innovation research" 23:28 < maaku> me too 23:29 < mrdata> what is this noise you speak of 23:30 < maaku> mrdata: meteors 23:31 < mrdata> seems to me that data classification is needed then 23:32 < fltrz> until next generation ICBMs start mimicking meteor strikes 23:33 < fenn> starting from orbit would be a violation of the outer space treaty 23:33 < mrdata> they already have a chart, https://i1.wp.com/www.sott.net/image/image/s3/73829/full/weather_balloon_or_UFO.jpg 23:35 < maaku> mrdata: the system it replaced was from the 1980's (70's design). computational capabilities made classification difficulty 23:36 < mrdata> mhm.. 23:36 < maaku> there's an apocryphal story that when it was first turned on (the DSP, not SBIRS) the system was indicating multiple simultaneous launches 23:37 < fenn> fltrz: $25 USB digital television tuners have 25 MHz (?) of bandwidth and 7 bit sample depth https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ 23:38 < fenn> no idea what the bandwidth of a solar panel diode is 23:38 < mrdata> maaku, and one person saved us from apocalypse by insisting it was a glitch? 23:38 < maaku> not sure if that' strue, although there is a true one about the first time the russians turn their version on they got strong infrared reflections of minnesota lakes, near known ICBM installations. nearly ended the world 23:38 < mrdata> it's a great story 23:38 < maaku> i mean not sure if the US meteors-look-like-attack one is true, but the Russian lake-reflection one is 23:40 -!- Gurkenglas [~Gurkengla@unaffiliated/gurkenglas] has quit [Ping timeout: 244 seconds] 23:42 < fenn> fltrz: one application would be to use the sun as a way to verify what the current time is, in order to prevent attacks that rely on spoofed network time 23:45 < fltrz> fenn, I know about the RTLSDR dongles, I have one (though I don't use it as often as I should), unless theres a new generation of USB tuner dongles with raw output I thik the bandwidth is more like 2.5 MHz. The corresponding depth resolution is 120 meters, so that may slowly approach the limits of PV park size (or at least require multiple ADCs per park if the future PV parks are of such scales)) 23:46 < fltrz> fenn, bandwidth of solar panel is probably fine (sure huge capacitance is proportional to area, but required load resistor is inversely proportional since we have more photocurrent, so apart from routing the frequency response should be similar-ish) 23:47 < nmz787> https://hackaday.com/2018/08/31/max1000-tutorial-is-quite-persistent/ 23:47 < nmz787> .title 23:47 < yoleaux> Learn FPGA with this Persistence of Vision Hack | Hackaday 23:50 < fltrz> fenn, I'm not sure I see how a neutral random oracle helps in verifying against spoofed time? I'd have to see the simplified protocol proposal to understand the attack model/scenario 23:52 < fenn> fltrz: a bit above my paygrade but this is what i'm referring to: https://people.xiph.org/~greg/decentralized-time.txt 23:54 < nmz787> just bought that FPGA for $29 w/free overnight shipping --- Log closed Mon Sep 03 00:00:19 2018