A strobe light on the ISS

[kelvinzero]

I just skimmed the thread. Did anyone mention the possibility of a spinning mirror? But I see Wayne's point of not creating extra light pollution.

Could we create one of those corner mirrors that reflects backwards, large enough so that a site on the ground could fire a light up and see it reflected back? Something like that on the moon would also be cool. A flashing light from the dark side of the moon would be quite cool, and not really pollution since it would be limited to the vicinity of the site that fired the beam.

The thought of something like this on the moon is sort of cool because it would be there pretty much forever. I know it has already been done on a small scale, but I guess you would need a much larger one to be visible.

Anyone know what sort of spread a laser fired through the atmosphere would have before reaching the moon?

 

[dreada5]

I think Halman's aim is good.

Not wanting to change the subject but I've often thought that by now we should be able to broadcast, around the clock (24/7) to the public what humans are doing/have accomplished in space. I don't think there is a better way to get adults and school kids interested in space than to allow them to access live views of manned spaceflight around the clock. NASA has recently started the LIVE ISS Stream http://www.nasa.gov/multimedia/nasatv/index.html?param=station, but when it works I think it should be more like http://www.earthcam.com/usa/newyork/timessquare/. ESA have also started running the mars express webcam http://webservices.esa.int/blog/; I think this is good and is probably all people can expect from a mission hundreds of millions of miles away.

My point is in this information age, we should by now be able to provide on-demand, high quality videostreams of LEO/ISS operations and lunar missions to the public, they should be able to see impressive live images of the whole space station (not just a small section), they should be able to select a camera and see live views of earth as seen from ISS, we should even by now have live webcams on the moon's surface. Bring space to the people!

 

[Zipi]

My point is in this information age, we should by now be able to provide on-demand, high quality videostreams of LEO/ISS operations and lunar missions to the public, they should be able to see impressive live images of the whole space station (not just a small section), they should be able to select a camera and see live views of earth as seen from ISS, we should even by now have live webcams on the moon's surface. Bring space to the people!

I agree with you! Luckily some things are beginning to happen like you mentioned about the ISS live cam.... Google X prize will hopefully bring live moon images to us, but we shall see:

http://www.googlelunarxprize.org/

 

[halman]

What I would like to see happen is for a visible, artificial signal to be sent from the International Space Station during the dark portions of its orbit. By visible, I mean that if the strobe fires in your field of view, you would probably notice it, but other wise, not brilliant, not hemisphere wide coverage, no shadows need to be cast. By artificial, I mean a blinking light is going to appear artificial to most folks. I hope. Strobe intervals have to be several seconds or more to keep power requirements down, but one flash every 5 seconds would be the longest desirable interval.

By experimenting with power levels, emitters, pulse forming networks, spinning mirrors, and such, a visual signal visible to people on Earth could be developed for relatively little cost in comparison to the number of people who would ultimately see it. And it would dramatically increase the amount of time the ISS would be visible, as well as giving some continuity to the presence of the station when it goes into shadow. Reminding people that people are up there, in whatever way we can, is the best advertising we can hope for. Making an experiment out of building a signaling device that does not require large amounts of power, but would be visible to persons on Earth, is the kind of fun stuff that people could participate in, reporting when they saw the pass by the strobe light.

The space station is an ongoing, continuous presence in the environment which makes up most of the Cosmos. Space. Emptiness filled with energy. Instead of people going up, and then coming back down, a few are staying up there, some for months on end, helping us to learn how to survive in an environment opposite to every thing we have evolved in. The first commercial aspects of space exploitation, apart from the vomit comets, will come from orbital factories, making what cannot be made on Earth. We need cars that weigh less than one metric ton, including the batteries. The frames for these cars may end up coming from space, made of foamed aluminum reinforced with carbon filaments, annealed for six weeks. Or it may be building materials made of foamed ceramics, carbon reinforced, annealed, and pre-drilled.

Our future can be better than today, if we can convince ourselves to invest in the future. Being able to show people the progress we are making could be a critical factor in whether we chose our future wisely. NASA cannot buy TV ads and show people working on the Hubble. They can't skywrite. But they can have a blinking light.

 

[samkent]

Given that this strobe would only be visible during the ‘night’ portion of the orbit, it would be a significant drain on the stations batteries just to be visible from the ground. That alone will kill the whole idea.

 

[neilsox]

Two AAA cells will flash a digital camera hundreds of times, besides running the camera electronics. Perhaps one miliwatthour per flash. If the ISS stobe is 100 million times brighter at the same efficiency; it should appear just as bright at 10,000 times the distance from the camera. So 500 kilometer = 50 meters. In dim light the camera flash is noticable at 50 meters, perhaps even if you are not in the brightest part of the light beam = camera flash is is moderately directional. 10,000 times one miliwatt hour = ten watt hours. One million flashes is ten megawatt hours = the ISS batteries will be OK if the flashes are several seconds apart = 1000 flashes per hour = one million flashes in 1000 hours. Neil

 

[tadpoletriker]

It would be bright enough to take a picture at 5 meters, but it might be visible at 5000 meters or even much more. Think the events video you have seen with all those flashes going off. They do nothing for the pictures, but they sure can be seen!

JohnB

 

[halman]

Given that this strobe would only be visible during the ‘night’ portion of the orbit, it would be a significant drain on the stations batteries just to be visible from the ground. That alone will kill the whole idea.

I think that the technology exists to turn the strobe light off when the station is in sunlight, although I am not sure. A strobe light which fires only every few seconds does not consume large amounts of power compared to a strobe light which fires several times per second. The goal I seek is not to have the ISS casting shadows on the ground while it tries to take our picture, just to provide a way of following the station when it goes into shadow, as well as creating an obviously artificial effect in the sky. I am sure that there are people who have seen the ISS when it is quite bright, and did not think it was something man-made, attributing it to 'stuff that goes on in the sky by itself.' Flashing lights are not 'stuff that goes on in the sky by itself.'

The more UFO reports this generates, the better, because it would be publicity for the most important endeavor we have attempted, to live and work beyond the confines of our planet. Low Earth Orbit may only be a few miles away, but it is almost identical to what we will find in 99 percent of the Cosmos. If we can survive and thrive in LEO, than we can figure out how to survive and thrive just about anywhere in space. ("In space" I said. Not on a planet. Planets are a minute fraction of what we call the Cosmos.)

 

[halman]

Okay, let's say that the International Space Station is in shadow an average of 45 minutes an orbit, with a range of plus or minus 7 minutes. If we stipulate a flash every 5 seconds, that is 12 flashes a minute, which means the most flashes possible would be 624. If each flash is a 1000 volt flash,and was drawn from a 100 volt supply, the current would be 10 amps for the fraction of a second the flash lasts. But a Pulse Forming Network can lower the current requirements significantly, say by 50 percent. So, if we are going to draw 5 amps continuously, how big of a battery would we need to power the strobe? What is the voltage of the battery bus on the station?

 

[MeteorWayne]

I'm telling you, with a flash every 5 seconds NO ONE is going to notice it. They don't notice any of the othet satellites that flash at that rate There are several per night....

 

[halman]

Okay, let's pretend that we are watching a very bright light move across the sky. All of a sudden, it starts to get fainter, and fainter, and then it is gone. But a moment later, flash. A few seconds later. flash. Obviously, what we were watching is not a natural object, so what is it? For those of us who are cajoling friends outside to watch a pass, that flash every few seconds is a useful tool, because it helps us to explain that the station has gone into the Earth's shadow.

If it turns out that a flash every 5 seconds puts an unnoticeable drain on the stations electrical system, maybe increase the duty cycle to every 3 seconds. But I still think that it would be the cheapest advertising that NASA could buy, and still be able to call it an 'experiment.'

 

[eburacum45]

If people see a flashing light they'll think its an aircraft. Best leave it as it is, and just point it out to people when it is lit by the Sun. Show as many people as you can, especially the bit when it fades in or out as it enters or leaves the shadow.

 

[kv171]

Hai!

Good point on efficiency. I liked it. I am a newbie in your site.And you know from the very first visit to your started loving it. Thanks!



Kavi
------

FTP Software

 

[EAK09]

Let's say the strobe was a green laser, pointed downwards at the surface, and this laser had a 1 milliradian dispersal (same as a laser diode pen). Let's further assume we want the green light to be very noticable - so noticable, it is 'annoying' but not visually damaging. The FAA has defined an 'annoyance glare' level = 5E-6 watts/cm2

Based upon this, and assuming the ISS is orbiting at a 400km altitude, I calculate a 6.5 kW green laser would be required to generate a bright enough light to create a very noticable 'annoyance glare'. The spot size on earth's surface would be about 405m in diameter.

Each pair of solar power wings on the ISS generates 32.8 kW, for a total of 131 kW (ignoring the smaller backup solar wings)

Therefore, to operate a continuous green laser on the ISS bright enough to be very annoyingly noticable (even in daylight) on the earth's surface would require about 5% of the electrical generating capability of the ISS.

A laser 1/100 as bright (still very bright) would require only about 0.05% of the ISS's generating capability.

Of course, this bright green light would be visible only to people lucky (?) enough to be inside of the 405m diameter spot.

I think the laser idea is excellent. I like the idea of a green light (not very common).

I wonder, doesn't the relevance of magnitude vary completely with distance from urban center? For example, I live a good 60 miles or so south of Los Angeles and on any given night there is a good chance that fewer than a couple dozen or so stars are visible at all. In my case this is mostly a function of how much marine cover we have.

I wonder, what if the laser strobe....

(a) Covered a larger area -- kilometers rather than meters.

(b) Was intended not to come anywhere close to annoying, but rather to merely increase the number of viewers (like myself) likely to have any chance of ever seeing the ISS at all.

(c) Could be pointable -- would generally point toward larger metropolitan areas for maximum exposure. However the hubble-type children school drives could win elementary schools login access to a web site where they could enter in their own GPS coordinates to schedule usage for an upcoming pass and make an evening campout out of the event.

(d) Would flash -- with some distinct pattern -- to save electricity. I could imagine the apparatus being 80% capacitor by weight. [Anyone know if some lasers would work better with this vs. worse?]. Maybe over the course of any 10 second period, the thing might fire off 5 1/4 second bursts. If so, would that reduce power requirements by 1/8?

(e) The elementary school-type access winners (see above) could have the thing flash Morse code.

(f) Regarding usage as a percentage of total ISS power...
#1 -- the laser could be turned off during periods of high need (ex: when more crew are visiting?).
#2 -- question : how much of that 132kw is used at present anyway? With I believe three more modules on the way, I wouldn't expect all of the 132kw to be used/needed at present.

 

[EAK09]

Okay, l...... But I still think that it would be the cheapest advertising that NASA could buy, and still be able to call it an 'experiment.'

Thanks for starting this thread!
This is a digression of sorts, but I was noticing your last statement. On one hand, I wonder what type of experiments might be done with this. (In my own mind, I'm thinking of a popular science theme, possibly involving air quality minded enthusiasts with beam intensity measuring devices). On the other hand, I was curious -- do you ever sense any angst, as I do, for NASA to be calling things experiments in the first place? Personally, I notice NASA diffusely spraying a vacuous label of "in the name of science" over so many things that it makes it harder to actually find (and appreciate) the real science being done. For example, last year I thought I noticed astronauts moving stoage around the discovery module and temporarily uncovering the window there, when one of the crew returned with a camera and took a photograph. From the low res video at least, it looked like an inexpensive camera. The NASA TV narrator clearly described this as "earth science." Comments like that confuse me.

 

[halman]

Standing on my back patio a few moments ago, I noticed the anti-collision lights of an airliner. There is about a 3/4 moon to the south of where I first noticed the flashing lights, and it took about 2 minutes before the aircraft passed overhead. Presuming this was a typical commercial flight, it was probably traveling about 600 miles per hour at about 30,000 feet.

So I had to notice those strobe lights through over 10 miles of the lower atmosphere, and probably closer to 15 miles of smoke-filled air and water vapor, with the angle that I was initially viewing at. Very few people I know would have noticed them, but some would. By the time the plane was directly overhead, the lights were quite bright. Very few people I know would have noticed them then, either. but some would.

When the ISS is passing by overhead, it is visible for long periods of time, in part because our angle of view is so steep. The light reflected off of the space station does not have to travel through a lot of atmosphere to reach the Earth's surface, compared to an airliner 10 miles away. So a strobe light not much brighter than those carried on airliners would probably be visible to people on Earth. Perhaps it wouldn't catch many peoples eyes, but it would certainly get some people to ask, "What is that?"

For some reason, space fanatics don't seem to be the kinds of people who will spray paint messages on their cars, put up bill boards in their yards, or walk around down town handing out literature, like other fanatics do, so we have to make up for these shortcomings somehow. A blinking light in the night sky is not going to resurrect the space program, but it would help. Anything to raise awareness of what we are doing off-planet right now would help, and a strobe light on the ISS seems to me to be about the cheapest advertising the program could get.