Yes, it turns out that narrow sharp rings typically indicate one or more small satellites nearby acting as "shepards."
Saturn has at least five "Shepard Moons" - S15 bounds the outer edge of the A ring, S13 and S14
dance with the F ring, giving it a braided appearance, and S10 and S11 lie just outside the ring system.
Jupiter also has a ring satellite, J9, as does Neptune, Galatea, and I suspect that Uranus has some undiscovered ones also.
All of these satellites are small, and most if not all were discovered by the Voyager spacecraft.
More fun ring images and facts can be found on the
ringmaster
web site.
Simple (more or less) - if it orbits another body (not a star), and is not man-made, it's a moon. Size is not really a consideration - if you can detect it, it's worth cataloging.
I believe that Dactyl, the moon of the asteroid Ida, is only about 100 meters across.
The exception occurs in planetary rings, where a moon has to be bigger than the ordinary rubble of
the ring to be considered a moon.
Like all of the newly discovered moons, this little bit of rock is just another captured asteroid - its retrograde (backwards) orbit is a dead giveaway. Simulations show that most of the captured moons will eventually wander back to the asteroid belt - so this is the solar system equivalent of a one night stand.
BTW, the rings of Jupiter are close to the planet - this new moon is not. It's so far away you couldn't see it with the naked eye if you were so unwise as to stand on the surface of Europa or Io and look for it.
It is indeed the exposure - much too short to show stars. (These cameras do not have shutters to stop down.)
Late this year they will also start to do optical navigation - or optnav - which
takes long exposures to show stars relative to the
limb of the planet or a satellite. This relative spacecraft-star-planet information is a very valueable addition to the one dimensional range and Doppler (radar) information that spacecraft navigation relies upon.
Generally in opnav pictures the planet or moon is totally over-exposed, but this is how Linda Morabito discovered the volcanic eruptions on the Jovian moon IO - an enourmous fire fountain silhouted against the darkness of space - so you never know.
Because of their poor visual quality, optnav pictures are almost never released to the press.
Both Sirius and XM use S band (2.4 GigaHertz or 12 cm wavelength), which translates to line of sight only.
The joke in the Satellite biz is that XM is a nationwide chain of repeaters with some satellite fill in. There is a lot of truth to this - both of the XM satellites are in equatorial orbits, and so are always fairly low in the South over most of the US - any Southern blockage, and you need a repeater.
XM has spent hundreds of millions of dollars on the ground repeaters, and the last time they raised cash, it was to buidl more. It sounds like they have some way to go.
The Sirius system is technically superior, and uses three satellites in inclined orbits, so that one is always high in the sky over the USA.
The good side of this is that blockage is reduced. The bad side is that the satellites move around in the sky, so the blockage will vary as a function of time of day. This leads to a hard juggling act - is it worth putting up a new repeater if the signal is only blocked from 3 to 4 PM ?
There is, IMHO, no chance for Sirius & XM to survive as presently organized. XM needs over one million subscribers to break even - they have 200,000. Sirius has similar needs, but not nearly as many subscribers. Does this mean that things are hopeless ? No. Their orbital assets are real, and have real value. Just like in the case of Iridium, the initial investors will take a bath (those that didn't cash out) and the reborn companies will be able to make a profit.
Remember, in the Satellite world, bankruptcy can be part of the business model!
Multicast news services
worked well during 9/11
and there is no reason to think that they won't the
next time. Multicast is specifically designed not to "melt down" under extreme changes in audience.
The trouble is that not everyone is multicast enabled, but this shows real promise in handling news and emergency information over the Internet.
And they say that shutting it down would ''...not represent[] the interests of all the shareholders.''
Do the words "bloated" come to mind ?
How about nervey ?
How about stupid ?
In my opinion much of the dot-com money was "value-subtracting," in that they took good money and did stupid things. Enough people did this that it poisoned the ability of real businesses to make real money, because the marketplace was conditioned to assume that things that cost money actually should be free.
I cannot think of a much better example of a value-subtracting business than Liquid Audio.
Shut it down.
This is less than 1 in a million chance of impact
on
A Rock Moves In Space
·
· Score: 1
Don Yeomans of JPL says that the predicted cross-track error
ellipse at the time of impact is 10's of millions of kilometers. Since the diameter of the Earth
is 6371 km, and since the probability of impact goes as the square of the (radius / cross track orbit uncertainty), the probability of impact is less than one in 1 million.
Within a week, this will be narrowed by several orders of magnitude, so it is highly likely that the predicted impact will vanish.
Electronic music is basically not played on the regular radio.
However, there are lots of Internet radio stations that play electronic music in its various forms.
SOMAFM used to specialize in this, but it was killed by the DMCA.
DrumLogic.net
specializes in Drum and Bass.
ECKOradio
has some good downloads.
And don't forget the energy overseas. For example,
Tornado Productions
in the UK does regular live webcasts of electronic music DJ's.
Hunt around on the Internet, find some music you like, and listen to it. I do not know any better advice than that!
There has been much discussion on the various webcaster lists about going "DMCA-free" - technically, to forgo the DMCA statuatory license.
It's coming, thanks to the idiocy of the situation.
However, there is a lot of good music out there that can be freely streamed. Some Internet stations, such as
OntheI.com channel 2, have always played freely availabled music, as has
MP3.com.
It is important to remember that these stations are free of the CARP and DMCA restrictions and payments, much like open-source software is free of licensing restrictions.
I look for a new ecosystem to arise, akin to the open source movement, with music licensed freely to all, with returns coming from the sale of artifacts (DVD's, t-shirts, etc.), and concert tickets.
Our servers (on OnTheI.com) say that, of
the people who have come to our (music, not OS-related) site during June :
OS = Windows | Portion of Hits = 86.34 % OS = Macintosh | Portion of Hits = 11.08 % OS = Linux | Portion of Hits = 1.95 % OS = BSD UNIX | Portion of Hits = 0.46 % OS = SunOS | Portion of Hits = 0.17 % OS = HP-UX | Portion of Hits = 0.01 %
(where Mac OS X appears under Mac, not BSD).
A 2% share of the desktop is nothing to sneeze at.
The Deep Space Network (DSN) works well in a crisis mode, or when a spacecraft is doing something spectacular. It's not so good at the mundane day to day.
I used to work there, and then I worked for its "competition" in the US government. The DSN does a lot of non-criticial stuff that could be done cheaper elsewhere, either by other parts of the US government, or abroad, or by private industry. It has always been unwilling to off-load any of these routine tasks, even if the charge would be a fraction of what it costs the DSN to do it.
So I am not entirely sympathetic, at least until the DSN restructures and reinvents itself.
This is a direct result of poltical pressure from small webcasters, and shows that the system does respond to such pressure.
Last Thursday, before the Roundtable at the Library of Congress on the CARP recordkeeping rules, there was a "Hill Walk" organized by
Kevin Shively of
Beethoven.com and other small webcasters, who went to the Capitol and meet with legislators and their staffers to explain their position. Earlier, on May 1, the same group organized the "day of silence" on Internet radio, to show the result if the situation wasn't changed. This hearing was one result from this politcal campaign.
OOP can be oops!
on
Bitter Java
·
· Score: 1, Insightful
There is something about OOP that I have learned makes people want to over-apply it. The result is frequently bad, as project development times stretch out to infinity. I know of a number of OOP programming projects that got canceled because of implementation issues (speed of development, speed of use, etc.), and that is rare now-a-days in older programming languages.
I want to read this book. I have a feeling it may be instructive in avoiding this moral hazard of OOP.
There must be something they are not telling about, as this sounds really dumb to me.
GPS is really simple in principle. There are 24 satellites in 12 hour orbits, with orbital planes arranged so that at least 4 are up for anyone on the planet at any time. Each satellite sends its own encrypted signal (actually, 2 such) to everyone who can receive it.
The reciever decodes the signal, and checks the time lag between when each satellite's signal was received. That's it. All of the geolocation is deduced from the relative lags of the signals broadcast for all to receive.
Four satellites are needed as the receiver's clock is probably off; two signals are sent as the easily decoded civilian one has errors put in to reduce accuracy (SA - Selective Availability), while the other signal has a military grade encryption.
That's it. My signals differ from yours only based on the relative time delay between them.
So, this is subject to a replay attack - simply record the signal at the desired location and replay it to a receiver at your actual location.
This would work even for the military grade encryption, but would require a sensor at the actual target location of the geo-encryption.
To do this near to (within 4000 km or so, so that the same satellites are up) of
the target location, record the signal. Figure out the relative time delay's. Playback the signal multiple times with the appropriate lags for the other location. As the receiver uses a convolutional decoder and an omnidirectional antenna, if you do this right, the receiver
will lock onto the time shifted satellite, and
will come up with the wrong position.
The above replay attack would require a wide bandwidth (few 100 mbps) record capability and (for the time shifted version) a good ephemeris - both easily available. AND, it would work even for encryptions using the military signal.
But, you don't have to go to the trouble, as there is test equipment easily available that will do this for you (it's how you test receivers). This would not work for the encrypted military signal though.
Since these people are not stupid, my guess is they will sell a decrypt chip with with a receiver on it, and maybe use tight time delay's windows to hinder replay attacks. Give me $ 30,000 for test / record equipment, and I will break it even so.
Since this level is not out of bounds for industrial movie pirates, "This sounds dumb to me."
K Claffy gave an interesting presentation at
the last
Nanog
that illustrates the futility of the Record Companies Efforts. See, in particular, her
graph
on file sharing usage.
The result of years of litigation and bad law making :
Napster is shut down, its successors have over 5 times the file sharing volume, and are used perhaps 100 times as much as the "legitimate" pressplay and music net services.
A black hole is a term for a mass that is compact enough that it lies within an event horizon. Heuristically speaking, light cannot escape because the escape velocity from the object is faster than the speed of light, so it appears dark.
In General Relativity, given a sufficiently large mass (say, a 10 solar mass star), there is no source of rigidity strong enough to withstand gravitational collapse, so black holes will eventually form.
Big stars exist, so avoiding black holes requires either a new theory of space time (or gravitation), or a new type of matter.
These guys have opted for a new type of matter,_analogous_ to a Bose-Einstein condensate. The existance of Bose-Einstein condensates in the lab for regular matter (routine, now), says nothing about whether this exotic matter exists out there.
This is still pretty wide open from a theory vs experiment sense. Most claims for black holes are really observations of dense collections of matter. Some would be black holes for sure in General Relativity, but this is no proof.
The best source of proof for black holes will probably come from detection of Gravitational waves from their formation, which should come in the next few years from experiments such as
LIGO or
LISA
.
In most areas of the country, a single rack in a colo / exchange facility costs $ 1500 per month or less, and 3 Mbps would cost ~ $ 1200 per month. They didn't say how many racks they need, but at that bandwidth, my guess is no more than one or two.
So, they
have been getting $ 3000 per month or more of free bandwidth and rack space.
IMHO, if their work is really important, they should be able to raise $ 36K per year from the crypto community.
Slashdot Mirror
Yes, it turns out that narrow sharp rings typically indicate one or more small satellites nearby acting as "shepards."
Saturn has at least five "Shepard Moons" - S15 bounds the outer edge of the A ring, S13 and S14 dance with the F ring, giving it a braided appearance, and S10 and S11 lie just outside the ring system.
Jupiter also has a ring satellite, J9, as does Neptune, Galatea, and I suspect that Uranus has some undiscovered ones also.
All of these satellites are small, and most if not all were discovered by the Voyager spacecraft.
More fun ring images and facts can be found on the ringmaster web site.
Simple (more or less) - if it orbits another body (not a star), and is not man-made, it's a moon. Size is not really a consideration - if you can detect it, it's worth cataloging.
I believe that Dactyl, the moon of the asteroid Ida, is only about 100 meters across.
The exception occurs in planetary rings, where a moon has to be bigger than the ordinary rubble of the ring to be considered a moon.
Like all of the newly discovered moons, this little bit of rock is just another captured asteroid - its retrograde (backwards) orbit is a dead giveaway. Simulations show that most of the captured moons will eventually wander back to the asteroid belt - so this is the solar system equivalent of a one night stand.
BTW, the rings of Jupiter are close to the planet - this new moon is not. It's so far away you couldn't see it with the naked eye if you were so unwise as to stand on the surface of Europa or Io and look for it.
Does anyone think that this will actually _change_ anything ?
I would assume any actual ET sightings would be "redacted out", as the Brits would say.
It is indeed the exposure - much too short to show stars. (These cameras do not have shutters to stop down.)
Late this year they will also start to do optical navigation - or optnav - which takes long exposures to show stars relative to the limb of the planet or a satellite. This relative spacecraft-star-planet information is a very valueable addition to the one dimensional range and Doppler (radar) information that spacecraft navigation relies upon.
Generally in opnav pictures the planet or moon is totally over-exposed, but this is how Linda Morabito discovered the volcanic eruptions on the Jovian moon IO - an enourmous fire fountain silhouted against the darkness of space - so you never know.
Because of their poor visual quality, optnav pictures are almost never released to the press.
What does it mean ?
It means that Rupert Murdoch and News Corp won in its battle to keep the US satellite market open for them to try and dominate as they do in Europe.
Look for News Corp to snap up one of these payers within a year or so at firesale prices.
Both Sirius and XM use S band (2.4 GigaHertz or 12 cm wavelength), which translates to line of sight only.
The joke in the Satellite biz is that XM is a nationwide chain of repeaters with some satellite fill in. There is a lot of truth to this - both of the XM satellites are in equatorial orbits, and so are always fairly low in the South over most of the US - any Southern blockage, and you need a repeater.
XM has spent hundreds of millions of dollars on the ground repeaters, and the last time they raised cash, it was to buidl more. It sounds like they have some way to go.
The Sirius system is technically superior, and uses three satellites in inclined orbits, so that one is always high in the sky over the USA.
The good side of this is that blockage is reduced. The bad side is that the satellites move around in the sky, so the blockage will vary as a function of time of day. This leads to a hard juggling act - is it worth putting up a new repeater if the signal is only blocked from 3 to 4 PM ?
There is, IMHO, no chance for Sirius & XM to survive as presently organized. XM needs over one million subscribers to break even - they have 200,000. Sirius has similar needs, but not nearly as many subscribers. Does this mean that things are hopeless ? No. Their orbital assets are real, and have real value. Just like in the case of Iridium, the initial investors will take a bath (those that didn't cash out) and the reborn companies will be able to make a profit.
Remember, in the Satellite world, bankruptcy can be part of the business model!
Multicast news services worked well during 9/11 and there is no reason to think that they won't the next time. Multicast is specifically designed not to "melt down" under extreme changes in audience.
The trouble is that not everyone is multicast enabled, but this shows real promise in handling news and emergency information over the Internet.
Let's see -
The CEO is making $ 500K per year.
Another co-founder is also making $500K per year.
All of this on revenue of $600 K per year.
And they say that shutting it down would ''...not represent[] the interests of all the shareholders.''
Do the words "bloated" come to mind ?
How about nervey ?
How about stupid ?
In my opinion much of the dot-com money was "value-subtracting," in that they took good money and did stupid things. Enough people did this that it poisoned the ability of real businesses to make real money, because the marketplace was conditioned to assume that things that cost money actually should be free.
I cannot think of a much better example of a value-subtracting business than Liquid Audio.
Shut it down.
Don Yeomans of JPL says that the predicted cross-track error ellipse at the time of impact is 10's of millions of kilometers. Since the diameter of the Earth is 6371 km, and since the probability of impact goes as the square of the (radius / cross track orbit uncertainty), the probability of impact is less than one in 1 million.
Within a week, this will be narrowed by several orders of magnitude, so it is highly likely that the predicted impact will vanish.
Electronic music is basically not played on the regular radio. However, there are lots of Internet radio stations that play electronic music in its various forms.
SOMAFM used to specialize in this, but it was killed by the DMCA. DrumLogic.net specializes in Drum and Bass. ECKOradio has some good downloads.
And don't forget the energy overseas. For example, Tornado Productions in the UK does regular live webcasts of electronic music DJ's.
Hunt around on the Internet, find some music you like, and listen to it. I do not know any better advice than that!
There has been much discussion on the various webcaster lists about going "DMCA-free" - technically, to forgo the DMCA statuatory license. It's coming, thanks to the idiocy of the situation.
The SaveInternetRadio group and the International Webcasters Association have a lot more information about the situation. Good stations such as SOMA-FM have been forced from the air, and more are likely to fold.
However, there is a lot of good music out there that can be freely streamed. Some Internet stations, such as OntheI.com channel 2, have always played freely availabled music, as has MP3.com. It is important to remember that these stations are free of the CARP and DMCA restrictions and payments, much like open-source software is free of licensing restrictions.
I look for a new ecosystem to arise, akin to the open source movement, with music licensed freely to all, with returns coming from the sale of artifacts (DVD's, t-shirts, etc.), and concert tickets.
(where Mac OS X appears under Mac, not BSD).
A 2% share of the desktop is nothing to sneeze at.
The Deep Space Network (DSN) works well in a crisis mode, or when a spacecraft is doing something spectacular. It's not so good at the mundane day to day.
I used to work there, and then I worked for its "competition" in the US government. The DSN does a lot of non-criticial stuff that could be done cheaper elsewhere, either by other parts of the US government, or abroad, or by private industry. It has always been unwilling to off-load any of these routine tasks, even if the charge would be a fraction of what it costs the DSN to do it.
So I am not entirely sympathetic, at least until the DSN restructures and reinvents itself.
This is a direct result of poltical pressure from small webcasters, and shows that the system does respond to such pressure.
Last Thursday, before the Roundtable at the Library of Congress on the CARP recordkeeping rules, there was a "Hill Walk" organized by Kevin Shively of Beethoven.com and other small webcasters, who went to the Capitol and meet with legislators and their staffers to explain their position. Earlier, on May 1, the same group organized the "day of silence" on Internet radio, to show the result if the situation wasn't changed. This hearing was one result from this politcal campaign.
More information about this grass-roots effort can be found at SaveInternetRadio.com, and some of the best coverage is in the Radio and Internet Newsletter.
There is something about OOP that I have learned makes people want to over-apply it. The result is frequently bad, as project development times stretch out to infinity. I know of a number of OOP programming projects that got canceled because of implementation issues (speed of development, speed of use, etc.), and that is rare now-a-days in older programming languages.
I want to read this book. I have a feeling it may be instructive in avoiding this moral hazard of OOP.
IMHO, 802.11a is DOA. I can't wait for 802.11g - which should interoperate with 802.11b.
There must be something they are not telling about, as this sounds really dumb to me.
GPS is really simple in principle. There are 24 satellites in 12 hour orbits, with orbital planes arranged so that at least 4 are up for anyone on the planet at any time. Each satellite sends its own encrypted signal (actually, 2 such) to everyone who can receive it.
The reciever decodes the signal, and checks the time lag between when each satellite's signal was received. That's it. All of the geolocation is deduced from the relative lags of the signals broadcast for all to receive.
Four satellites are needed as the receiver's clock is probably off; two signals are sent as the easily decoded civilian one has errors put in to reduce accuracy (SA - Selective Availability), while the other signal has a military grade encryption.
That's it. My signals differ from yours only based on the relative time delay between them.
So, this is subject to a replay attack - simply record the signal at the desired location and replay it to a receiver at your actual location. This would work even for the military grade encryption, but would require a sensor at the actual target location of the geo-encryption.
To do this near to (within 4000 km or so, so that the same satellites are up) of the target location, record the signal. Figure out the relative time delay's. Playback the signal multiple times with the appropriate lags for the other location. As the receiver uses a convolutional decoder and an omnidirectional antenna, if you do this right, the receiver will lock onto the time shifted satellite, and will come up with the wrong position.
The above replay attack would require a wide bandwidth (few 100 mbps) record capability and (for the time shifted version) a good ephemeris - both easily available. AND, it would work even for encryptions using the military signal.
But, you don't have to go to the trouble, as there is test equipment easily available that will do this for you (it's how you test receivers). This would not work for the encrypted military signal though.
Since these people are not stupid, my guess is they will sell a decrypt chip with with a receiver on it, and maybe use tight time delay's windows to hinder replay attacks. Give me $ 30,000 for test / record equipment, and I will break it even so. Since this level is not out of bounds for industrial movie pirates, "This sounds dumb to me."
And if TEOMA really wants to get ahead of Google, they would use the Intrapet Explorer" as their browser of choice.
Any bird person would know that African Grey's are much superior to pigeons in ther web ranking abilities.
Today, AOL doesn't have any MONEY.
K Claffy gave an interesting presentation at the last Nanog that illustrates the futility of the Record Companies Efforts. See, in particular, her graph on file sharing usage.
The result of years of litigation and bad law making :
Napster is shut down, its successors have over 5 times the file sharing volume, and are used perhaps 100 times as much as the "legitimate" pressplay and music net services.
And they call it a famous victory...
A black hole is a term for a mass that is compact enough that it lies within an event horizon. Heuristically speaking, light cannot escape because the escape velocity from the object is faster than the speed of light, so it appears dark.
In General Relativity, given a sufficiently large mass (say, a 10 solar mass star), there is no source of rigidity strong enough to withstand gravitational collapse, so black holes will eventually form.
Big stars exist, so avoiding black holes requires either a new theory of space time (or gravitation), or a new type of matter.
These guys have opted for a new type of matter,_analogous_ to a Bose-Einstein condensate. The existance of Bose-Einstein condensates in the lab for regular matter (routine, now), says nothing about whether this exotic matter exists out there.
This is still pretty wide open from a theory vs experiment sense. Most claims for black holes are really observations of dense collections of matter. Some would be black holes for sure in General Relativity, but this is no proof.
The best source of proof for black holes will probably come from detection of Gravitational waves from their formation, which should come in the next few years from experiments such as LIGO or LISA .
In most areas of the country, a single rack in a colo / exchange facility costs $ 1500 per month or less, and 3 Mbps would cost ~ $ 1200 per month. They didn't say how many racks they need, but at that bandwidth, my guess is no more than one or two.
So, they have been getting $ 3000 per month or more of free bandwidth and rack space.
IMHO, if their work is really important, they should be able to raise $ 36K per year from the crypto community.