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NASA Creating Laser Communication System For Mars
techtribune writes "NASA is in the process of developing a new technology under project Laser Communications Relay Demonstration or LCRD which will allow them to provide faster means of communications from Mars. The Mars Reconnaissance Orbiter (MRO) currently can only send at speeds of around 6 Mbps or about like a DSL modem here on Earth. At this rate, it can take upwards to 90 minutes to transmit a single high resolution image to Earth from Mars. With the MRO outfitted with the new technology it would be able to transmit the same high resolution image back to Earth at over 100 Mbps and only taking about 5 minutes to do so."
Just don't mis-aim the laser. I'd hate for my city to blow up like in Sim City 2000 when the orbiting solar plant's beam goes off-kilter...
Do not look into laser with remaining eye.
What if it's cloudy?
That's still faster than most connections in the US! That's not bad at all!
From the summary:
At this rate, it can take upwards to 90 minutes to transmit a single high resolution image to Earth from Mars
At least part of this 90 minute transmission time is due to the maximum speed of light, not the date rate. According to NASA, it takes 10 to 20 minutes to get a signal from Mars to Earth:
How long does it take for a signal to be sent from Earth to Mars?
Signals to/from Mars travel at the speed of light (186,000 miles per second, or 300,000 kilometers per second). It takes between 10 and 20 minutes for a signal to travel from Earth to Mars, depending on the relative position of the planets at that time.
Math is hard, please help me.
6Mbps ~ 600KBs
600KB/s * 60 seconds/min * 90 minutes == ~3.2GB
So if the image is a raw 32 bit TIFF we're looking at at image of 28k x 28k pixels. Me thinks someone should introduce them to JPG compression.
The speed isn't the issue. A sufficiently well focused and powerful laser (or multiple lasers) could probably push as much bandwidth as you need. The problem is the latency.
The distance between Earth and Mars varies from between roughly 56 and 399 million kilometres. That's a minimum round-trip time of ~374,000ms and a maximum round trip time of ~2,600,000ms, ignoring the speed of light in atmosphere. Somebody's going to make a killing selling Squid boxes when we get around to colonizing the place.
If Comcast or a cell phone company manages it, they could pay for the space station from the profits on bandwith!
Gently reply
At those speeds, I cant imagine that there isnt some lost/corrupted data. Does retransmission factor into the 90 minute time, or are they using so many redundant signals that theres no need for a TCP-like packed received ack? Whenever communication between Earth and Mars comes up I just have to wonder how long it's going to be until we find a way to communicate faster than light using something like quantum nonlocality. Otherwise were going to need two internets once we finally colonize that rusted out wasteland. (No really, it is all rusted out...that orange color comes from iron oxide, aka rust)
Wrong. The 10 to 20 minutes you speak of is the latency, however this 90 minute figure is probably arrived at by taking the size of the image and dividing by the 6mbps transfer rate. It will take 10-20 minutes after the first bits leave Mars and arrive at Earth, however after Earth sees the first bit they will still have to wait 90 minutes to see the last bit.
-Buck
If they can make it faster, I'd be pretty impressed. That dang light speed limit really bugs me.
Please do not read this sig. Thank you.
I'm just speculating, but a risk-averse JPL may be concerned about using a JPEG because the extra work of compressing the raw image to a JPEG would be one more failure item on already very-complicated space probes.
Like I said, that's just my theory -- a quick google of "space probe image compression" didn't turn up anything for me; maybe others would have luck.
Discrediting my theory is a note on the Galileo Wikipedia entry regarding the use of data compression to improve throughput after the high-gain antenna was discovered as damaged:
Through implementation of sophisticated data compression techniques, arraying of several Deep Space Network antennas and sensitivity upgrades of receivers used to listen to Galileo's signal, data throughput was increased to a maximum of 160 bits per second.
Science images are NEVER EVER compressed in JPEG. In fact they probably don't even use the TIFF format either. Almost all science images in astronomy are done in the FITS format which I think was developed by NASA. This is because not only does the image need to be lossless raw data in order to be used for proper scientific measurements, but also much metadata must be included with the frame for some kinds of science observations.
Common metadata will include the position of the camera (where the orbiter was when the picture was taken), the camera's orientation (which way it was looking at the time), the exact time when the image was taken, the image exposure time, the camera's CCD temperature, whether on-chip binning has been carried out, the camera's readout noise, the camera's gain, etc. All of this information is necessary for some kinds of science and therefore NASA doesn't want to lose any of this information.
-Buck
Nice planning on the communication system. Nice to see good solid planning, development and R&D. It's what NASA is good at. They also design pretty good rockets, rockets that used to take us places. Now that we have a better network, lets build the SLS and quit relying vaporcraft to get us there. Let,s quit cutting funding, and make it a priority to travel to are causing a brai Mars. We put a human on the moon and can do it again. The SLS can get us there.. we still have the brain power to go to Mars, but our politicians and misguided and overly hopeful privatization plans.... Less than one tenth of one percent of our budget is spent on space... For all of you wanting to save money, if privatizing space makes sense, why not privatize our national security, epa, and social security?? We need a heavy lifter!
No TFS is right. You're talking about latency. The summary talks about bandwidth. Latency and bandwidth are two completely different things. The time it talks for the recipient to download the image from transfer start to end is 90 minutes, no matter if you send the image from mars, jupiter or alpha centauri. Unless you use TCP.
Wrong.
Hmm...okay, why?
however this 90 minute figure is probably arrived at by taking the size of the image and dividing by the 6mbps transfer rate.
So let me correct that for you:
Probably Wrong.
why would they want a probe orbiting Mars to communicate with sharks?
ELOI, ELOI, LAMA SABACHTHANI!?
As the US internet speeds lag, leave it to NASA to show that they can communicate faster with other planets.
So we have finally realized that lasers make sense for long-distance communications. Isn't this likely to have been realized by aliens a long time ago? I think this is why SETI hasn't found alien signals. The aliens use laser or possibly something better. We are unlikely to detect any civilizations more advanced than our own over radio.
Ray Seyfarth, ray.seyfarth@gmail.com, http://rayseyfarth.blogspot.com
Higher bandwidth doesn't mean faster, it means more data over the same time. Both means are still limited by the speed of light.
The Kruger Dunning explains most post on
The most rural american internet connection gets a bandwidth upgrade, how come we can't get 100Mbps in the states.
We don't even know if the Martians use big-endian encodings yet.
I'm not sure what the big deal is. I've seen this decades ago.
Granted the end points were stationary relative to each other and the distances were slightly shorter.
But all you'd really need is a 50MW laser and a phase-conjugate tracking system.
. This is because not only does the image need to be lossless raw data in order to be used for proper scientific measurements, but also much metadata must be included with the frame for some kinds of science observations.
Pedantically speaking, TIFF also allows for arbitrary metadata. And all sorts of other bizarre crap. FITS is a much older format and part of the reason it is used is historical.
The main reason it is used is that it is a format specifically designed for archival use. It is a very simple format and one can easily write an image parser and writer from scratch which will happily accept and be accepted by most systems (so that ignores the more obscure non image options). I have done so.
NASA quite rightly expect FITS images to be readable in 100 years time. This is reasonable since you could probably write that parser in a couple of days without even having access to the spec. TIFF by comparison is not a simple file format.
t's also not a bad format. Lossless compression will get you at most 3x on a natural image with 8 bits per channel, but more like 1.5-2, and often is not worth the bother, especially as support for TIFF compression is somewhat spotty once it moves into more than 8 bits per channel.
one marginally irritating thing about FITS is that it is in column-major format (yay @ fortran) rather than row major, where as most capture hardware and other image formats are row-major. So, loaading/saving FITS images often requires a quadrupal for-loop (endian/channels/rows/cols) to rearrange the data.
But back on topic: 6mpbs over 400e6 km is amazing!
SJW n. One who posts facts.
Delay, not latency.
The Kruger Dunning explains most post on
6Mbps * 60 sec = 360 Mb/m = 45 MiB/min * 60min = 2.7GiB/hr. Are they saying they're transmitting images that exceed 2.7GiB per image? Assuming 8 bits per "color" and a 6 channel "color", that's a 450M-pixel image. Even at 12b/channel, it's a 300M-pixel image, or 20K x 15K (4:3 aspect ratio) resolution image. Call me skeptical, but I think there has been a mistake.
make imaginary.friends COUNT=100 VISIBLE=false
Well, that is not entirely true. Once thing is onboard data compression, and another data archival. There are lossy image coding standards specially targeted at spacecrafts (e.g. CCSDS 121 http://public.ccsds.org/sites/cwe/rids/Lists/1220R2/NASAUSOverview.aspx). While there is certainly a lossless data compression need, given the usual bandwidth constraints, having a larger, even if not perfect, image is a valid use case. In this last case, having a coding loss below the instrument tolerance often helps convince scientist.
Any possibility of licensing spectrum to the Russians, the Chinese, or other countries that want to send probes to Mars? Fractional T-1 to Mars in exchange for a Soyuz ride or something...
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
Are they saying they're transmitting images that exceed 2.7GiB per image?
Yep. When I did remote sensing work we had to update the TIFF library to support the BigTIFF format (> 4GB). It's not that uncommon. 32 bits per channel is also not uncommon. Sometimes even a double per channel. Hyperspectral images also have way more than 6 channels.
My home Internet connection is still only 4 Mbps. I'm totally jealous of those Martians right now. Also, "in about like"? Seriously, who edits these summaries? A twelve-ye... never mind.
Anyone have a link to the details? I'd love to see how they solved problems like atmospheric disturbances and dispersion. A cartoon of a satellite doesn't tell us jack shit about how it works.
"Well, good luck finding a judge that doesn't run a bestiality site."
There are plenty of lossless image compression techniques. There are even standardized file formats that could be used. For instance JPEG2000 can use CDF 5/3 wavelet compression (lossless) and supports user defined XML metadata boxes. In other words 100% reversible image compression plus whatever metadata payload they wanted to include.
Two of my imaginary friends reproduced once
"Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured."
From wikipedia.
Your point is valid, except that the HIRISE imager on the MRO only produces images of 16.4Gb (2.05 GB) before compression, 5Gb (630MB) after compression in red, and 1/5 of that for blue/green channels. It's only a 3 channel device. The CTX camera is lower resolution with only a single channel. MARCI operates in 7 channels, but it's also low resolution.
The MCS spectrometer operates in 9 channels, but is very low resolution.
That leaves the CRISM spectrometer as the only imager on MRO with a large number of channels. It can image 50 or 544 channels depending upon the mode. But again, it's comparatively low resolution (~ 1/40 that of HIRISE, which means about 1/1600th as many pixels in a given area), which more than offsets the increase in number of channels.
make imaginary.friends COUNT=100 VISIBLE=false
Is this bi-directional? If I'm going to spend a year going out there I'm sure as hell going to download some "images" from earth!
My mod points just expired. You are SOOOOOO right on the money. If we are going to the moon, asteroids, Mars, etc, we really need big 2-way comm (will not be fast, but pipe can be big).
I prefer the "u" in honour as it seems to be missing these days.
Um, Unless you were kidding, the transit time is a measure of LAG, not transfer speed. The original statement, that it can take 90 minutes to transmit an image to Earth, is a measure of the transfer speed, IE, when the message finishes leaving the orbiter. When Earth actually receives it is a different question. So the 10 to 20 minute speed of light lag would be in addition to the the 90 minute estimate.
Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
Faster != bandwidth++;
Radio communications in the frequency ranges that are currently used are pretty nigh on close to the speed of light. Sure there will be a slight increase in "speed" but it will unlikely be more than a few seconds difference at such a short distance in light travel.
TFA is referring to bandwidth.
The line should read "which will allow them to provide greater means of communications from Mars"
Since a lot of the meta-data like photon lists, data-cubes, etc. stored inside of FITS images are usually not part of the original format specification and requires the original code in whatever language the creator chose to create it in I really doubt most of it will be readable in 100 years. The image, maybe.
Math looks good (although upper case "K" is Kelvin - you need lower case "k" for kilo...), but I suspect there's a large dose of redundancy and Error-correction information included in that 6Mbps. It's not like you can have an efficient retry protocol with a 20 minute ping time. So, there'd be less than 3.2GB of useful data sent. Probably between 50% and 70% would be actual image.
they clearly aren't including the limit considering the new one takes 5 mins instead of 90.
"The space elevator will be built about 50 years after everyone stops laughing." - Arthur C. Clarke ~1980
Speed of light has nothing to do with it. It's not transmitted with an Ack/Nak protocol from Mars. It's just the few Mbps in a solid stream of transfer frames.
From Wikipedia for HiRise (the MRO camera) A single uncompressed image uses up to 28 Gb. However, these images are transmitted compressed,with a typical max size of 11.2 Gigabits. These images are released to the general public on the HiRISE website via a new format called JPEG 2000.
I note that JPEG2000 can be run in a lossless form, just like TIFF.
At 2 Mbps, that's about 90 minutes.
They probably can't do 6Mbps when Mars is farthest from Earth, but when it's only 0.5 AU away at closest approach, that's reasonable.
First this, next, an Ansible.
There's some misinformation here. MRO will provide downlink rates of as high as 2Mbps peak to MSL, for two short comm passes a Sol on the order of 20 minutes, cutting in at as low as 32kbps at 10 degrees elevation using ADR keyed to at or below a given SNR. And an image takes nowhere near 90 minutes to downlink, not even close, not even single HiRise images. The highest def images on MSL are 1600x1200 and clock in at under 2MByte, 1 byte to a pixel. I'm not sure where these inflated figures come from.
latency will suck though
There is an error in your calculation. It should be:
6Mbps = 6 000 000 bps = 750 000 B/s = 732.42 KiB/s
So, it is more like this:
732.42 KiB/s * 60 seconds = 42.91 MiB/s
42.91 MiB/min * 60 minutes = 2.51 GiB/hour
But, that is not taking any latency into account. A ping of 40 minutes round time is HORRIBLE, and if their protocol is anything like TCP, it would take 40 minutes to transmit a single round trip "packet" which is only about 1500 bytes big. I do realize that they're using something else which is a lot more asynchronous, but the lag is still gonna slow it down a lot regardless.
PS: Only realized halfway through my pedantic calculation that you have converted into bytes from bits...
I haven't read the article, but I'm pretty sure the 5 minutes only refers to how long it will take the data to be be sent, not received. Latency on interplanetary communications is a bitch.
Average distance between Earth and Mars: 230 * 10^6 km (from Wikipedia)
230 * 10^6 km / c = 12.78 minutes (via Google)
Most human behaviour can be explained in terms of identity.
OIC, they've hired an MBA... ;-)
LOLOMGWTFBBQ
Yeah, let's decide a compression algorithm what's an important detail on extraterrestrial pictures.
Wouldn't a disruption in the integrity of the laser beam disrupt all communications?
So anything that got in the way of the laser would get in the way of communications?
Great Mars has internets that are four times faster than my home connection now. I wish I was martian.
Who would have figured that packet collisions will likely be caused by asteroids and meteorites.
...and I live a few miles from the nearest telephone exchange
Welcome to 21st Century rural Britain...broadband officially slower than interplanetary communications!