Next month, NASA will launch into space the most advanced laser instrument of its kind, beginning a mission to measure – in unprecedented detail – changes in the heights of Earth’s polar ice.
NASA’s Ice, Cloud and land Elevation Satellite-2 (ICESat-2) will measure the average annual elevation change of land ice covering Greenland and Antarctica to within the width of a pencil, capturing 60,000 measurements every second.
“The new observational technologies of ICESat-2 – a top recommendation of the scientific community in NASA’s first Earth science decadal survey – will advance our knowledge of how the ice sheets of Greenland and Antarctica contribute to sea level rise,” said Michael Freilich, director of the Earth Science Division in NASA’s Science Mission Directorate.
ICESat-2 will extend and improve upon NASA’s 15-year record of monitoring the change in polar ice heights, which started in 2003 with the first ICESat mission and continued in 2009 with NASA’s Operation IceBridge, an airborne research campaign that kept track of the accelerating rate of change.
A Technological Leap
ICESat-2 represents a major technological leap in our ability to measure changes in ice height. Its Advanced Topographic Laser Altimeter System (ATLAS) measures height by timing how long it takes individual light photons to travel from the spacecraft to Earth and back.
“ATLAS required us to develop new technologies to get the measurements needed by scientists to advance the research,” said Doug McLennan, ICESat-2 project manager at NASA’s Goddard Space Flight Center. “That meant we had to engineer a satellite instrument that not only will collect incredibly precise data, but also will collect more than 250 times as many height measurements as its predecessor.”
ATLAS will fire 10,000 times each second, sending hundreds of trillions of photons to the ground in six beams of green light. The roundtrip of individual laser photons from ICESat-2 to Earth’s surface and back is timed to the billionth of a second to precisely measure elevation.
With so many photons returning from multiple beams, ICESat-2 will get a much more detailed view of the ice surface than its predecessor, ICESat. In fact, if the two satellites were flown over a football field, ICESat would take only two measurements – one in each end zone – whereas ICESat-2 would collect 130 measurements between each end zone.
As it circles Earth from pole to pole, ICESat-2 will measure ice heights along the same path in the polar regions four times a year, providing seasonal and annual monitoring of ice elevation changes.
Tracking Ice Melt
Hundreds of billions of tons of land ice melt or flow into the oceans annually, contributing to sea level rise worldwide. In recent years, contributions of melt from the ice sheets of Greenland and Antarctica alone have raised global sea level by more than a millimeter a year, accounting for approximately one-third of observed sea level rise, and the rate is increasing.
ICESat-2 data documenting the ongoing height change of ice sheets will help researchers narrow the range of uncertainty in forecasts of future sea level rise and connect those changes to climate drivers.
ICESat-2 also will make the most precise polar-wide measurements to date of sea ice freeboard, which is the height of sea ice above the adjacent sea surface. This measurement is used to determine the thickness and volume of sea ice. Satellites routinely measure the area covered by sea ice and have observed an Arctic sea ice area decline of about 40 percent since 1980, but precise, region-wide sea ice thickness measurements will improve our understanding of the drivers of sea ice retreat and loss.
Although floating sea ice doesn’t change sea level when it melts, its loss has different consequences. The bright Arctic ice cap reflects the Sun’s heat back into space. When that ice melts away, the dark water below absorbs that heat. This alters wind and ocean circulation patterns, potentially affecting Earth’s global weather and climate.
Beyond the poles, ICESat-2 will measure the height of ocean and land surfaces, including forests. ATLAS is designed to measure both the tops of trees and the ground below, which – combined with existing datasets on forest extent – will help researchers estimate the amount of carbon stored in the world’s forests. Researchers also will investigate the height data collected on ocean waves, reservoir levels, and urban areas.
Potential data users have been working with ICESat-2 scientists to connect the mission science to societal needs. For example, ICESat-2 measurements of snow and river heights could help local governments plan for floods and droughts. Forest height maps, showing tree density and structure, could improve computer models that firefighters use to forecast wildfire behavior. Sea ice thickness measurements could be integrated into forecasts the U.S. Navy issues for navigation and sea ice conditions.
“Because ICESat-2 will provide measurements of unprecedented precision with global coverage, it will yield not only new insight into the polar regions, but also unanticipated findings across the globe,” said Thorsten Markus, an ICESat-2 project scientist at Goddard. “The capacity and opportunity for true exploration is immense.”
Will it be able to detect snow/ice with soot and how will that affect the lasers?
How do the verify satellite elevation? I would also know what the errors is.
Then we have drag caused by solar wind etc… It would be impossible to have a first order survey done imho. Are they looking for 100th’s of a foot or 10’s of feet or more in differences?
If the laser is off from perfect plumb by 1 mile, that will give an error in elevation of approx .70 feet. (curvature of the earth). This assumes a smooth non irregular ice pack on water. Of course nothing is smooth and even the irregularities will still have that error.
Even if the earth was flat, having the laser be not plumb will still impact the height measurement since the light will have to travel a longer distance both up and down.
Ever heard of GPS?
GPS does not work well for height.
LOL @ur momisugly MarkW “does not work well” : https://www.researchgate.net/publication/23877387_Measuring_Postglacial_Rebound_with_GPS_and_Absolute_Gravity
I’m curious, for the 3 folks that down voted Remy, why did you do that?
https://www.gps.gov/systems/gps/performance/accuracy/
So, acurate to a couple of feet most of the time, but could be off by up to 25 feet.
~¿~
Its actually a bit worse as GPS, for calculations, generates an probable location envelop that is NOT spherical. It is a prolate ellipsoid (watermelon shaped) with the long axis aligned with the gravity vector. Due to this GPS is more accurate with lat/long than elevation.
This is why inexpensive drones will never be delivering packages that cannot survive a 15 foot drop onto your driveway, assuming the Drone didn’t already crash into the ground.
Short of placing an altimeter on the vehicle your vertical accuracy is about +/- 5 meters using GPS alone.
Not so bad when flying about far from obstacles, but eventually it needs to land.
This is done by stationary ground-based GPS receivers for single points over a period of years. Not quite the same thing.
Which might answer your question Chris.
The question was raised about the accuracy of GPS for measuring height. Specifically how does the paper not address that?
Check out the ATBD
Does your car have auto pilot?
You don’t. You measure the difference between the ice level and the level of the sea nearby. This can be done with fair precision.
The difficulties are:
1. How deep snow is there on top of the ice (which lowers the ice freeboard)
2. There might not be any leads nearby (=no measurements on fast ice)
3. Doesn’t work in summer when there is meltwater pools on top of the ice.
Using the ocean for elevation must then account for tidal displacement.
ICE sat 1 was 5 inches
the salt flat at Salar de Uyuni is used as a calibration data set.
I imagine icesat 2 will do the same calibration
elevation: GPS and a ground base satillite laser ranging system.
calibrated against a known wide area salt flat.
Don’t worry, Michael Mann has it all in hand.
Photons travel 11.8 inches in one nanosecond.
“The roundtrip of individual laser photons from ICESat-2 to Earth’s surface and back is timed to the billionth of a second to precisely measure elevation.”
There are plenty of sites that will tell you how it’s done – bearing in mind that orbits do not track exactly the same height above the surface at all times – most are elliptical; they create a computer model of an earth and plot the position of the orbit relative to this virtual world, bearing in mind also that the orbit is mathematically predictable. This is one thing that computer models are actually very good at!
In case anybody misses the reference
Very nice touch there by Anthony !!
What an excellent project.
Fantastic information on a huge range of earth’s variables mapped down to e few metres. The data from this will be invaluable.
It won’t, however, demonstrate empirically that CO2 causes the planet to warm, far less man made CO2. Not that I imaging for a moment that is the satellites purpose.
Unfortunately, we sceptics will be overrun with ‘compelling’ data and ‘irrefutable’ evidence that man does indeed contribute enough CO2 to the atmosphere (~0.0012% of all gases) using circumstantial conditions to prove a phenomenon that just doesn’t exist.
I welcome the technology but we all know it’ll be misappropriated.
I wonder how they will falsify, er, adjust the numbers? Probably Antarctica and Greenland are rising up “faster than expected” under the reduced weight of ice?
“I wonder how they will falsify, er, adjust the numbers?”
Simple, they’ll do the same thing they do with temperature data. They’ll create a suite of models that make projections of what they want the data to show, and then adjust the empirical measurements to match their models.
Ah, yes, the “open minded” skeptics here at WUWT are already trashing the results of a new satellite measurement system even before it launches.
Chris
Drive by alert!
HotScot
Content-free post alert! Your post is the blog equivalent of a no-op command in machine language programming.
Chris
You bite every single time. LOL
call me foolish, when i see single digit iq posts i respond.
Chris, you must spend most of your time talking to yourself then.
MarkW
Damn, you got there before me. 🙂
For Chris to complain about content-free posting is rich.
MarkW
With his towering intellect, he should be above responding to “single digit iq posts”.
Apparently not.
http://www.cpom.ucl.ac.uk/csopr/seaice.html
And here is a description of the measurement problems:
http://www.cpom.ucl.ac.uk/csopr/science.html
CRYOSAT.. uses radar
ICESAT
https://www.csr.utexas.edu/glas/atbd.html
ICESAT 1
https://www.csr.utexas.edu/glas/pdf/atbd_pad_10_02.pdf
Predictions are ‘trashing’ unless in line with doctrines, when they are ‘scientific’ predictions, aren’t they?
What does your post have to do with waiting until the satellite begins generating results before disparaging them?
If there is a flaw in the design, then we don’t have to wait for the results to know that they will be worthless.
What flaw is there in the design?
If it is as accurate as they pretend, then in 60 years we will have decent data.
In NO WAY can it be compared to past data.
but you can BET that is what the alarmist fakers will try to do, (like satellite sea level data or AWS data
When talking about climate, anything LESS than 60 years, when you have KNOWN 60+ year cycles, is MEANINGLESS.
Fred, thanks for the CAPS, so we can be totally clear on exactly what you mean.
Except you’re wrong, rates of growth or decline are useful information.
That’s why we need to wait 60 years, to get an accurate read on the rate of growth, minus the many cyclical environmental factors.
Chris, please explain how “rates of growth or decline are useful information” when there is no historical data to compare with such information for at least three years but more like several decades. It is obvious what the goal of such a project is. It is to feed the orthodoxy.
Edwin, as opposed to the skeptic position, which is to throw up your hands and say “gosh, we don’t know enough, let’s do nothing.” And of course if you don’t start gathering data, you’ll never have a historical record. So your position is to do nothing, and don’t start any efforts to build knowledge and data. Got it.
They can do that because in their minds “raising questions” or merely saying
“prove it” is counted as “doing science”
arm chair science. quote popper, quote feynman, raise questions,
science job is done.
Noting all the problems with such a system is now “trashing”?
As always Chris just gets whinny when we shoot down his latest fantasy.
You didn’t note any problems. You projected problems onto the system without any evidence.
“…trashing the results of a new satellite measurement system even before it launches”
And why not? If the design specifications indicate that it is not fit for purpose, it should be pointed out before the media starts making claims that can’t be supported. Would you advocate ignoring the obvious?
What is your specific evidence that it is not fit for purpose?
I have addressed several concerns throughout these comments. However, probably the two most serious are that the document provided in a link by Mosher does not support the claim of 5 mm ‘precision.’ Secondly, I haven’t found anything addressing the issue of altitude change resulting from gravity variations over regions that can’t be verified by ground laser ranging.
we did land on the moon.
Now, if you look at ICESAT 1 you can see how they calibrated it.
You can see how they verified it against other systems
and you can comapre the models for thickness against the measurements
They have to do a lot of faking,
but since the raw data is there you could go try to prove it..
ya know do science rather than do conspiracy
“we sceptics will be overrun with ‘compelling’ data and ‘irrefutable’ evidence”
I think you’re right HS, if the “Modern (Current?) Warm Period” is anything like the previous Medieval Warm Period, it has legs. We may be in for a century (maybe two?) of warming, giving them data which will dovetail nicely with their humidification apocalypse narrative.
As always, we live in interesting times.
M.W.Plia.
Hopefully it won’t happen, but we sceptics must condemn the world to another ice age before the alarmists eventually relent and admit they are wrong.
We have wasted 40 years of productive human development on a scare that will go away quite naturally. Perhaps not soon, but it will go away.
But make no mistake, until we are entombed in another ice age, the alarmists will maintain they saved the world from AGW by insisting we turn to renewable sources of energy, no matter how pathetic and illogical we maintain wind turbines and solar arrays are now.
prediction…
They will find that they have been measuring it wrong this whole time…
..there was a lot more ice in the past
and it’s worse than we thought
….and we will get a min by min play by play every time there’s a crack
X,Y and Z axis can be a real bitch…
john 20:18
That’ll be my last sermon today. See you all Sunday!
“It won’t, however, demonstrate empirically that CO2 causes the planet to warm,”
Nothing is demonstrated empirically.
And if it doesn’t produce the results they want, they will just adjust the data.
Or ignore it. How are those Argos bouys doing these days?
Rhoda, you were suppose to have forgotten about them. They will return when the buoys are reporting the right data. ( and has been adjusted )
Or the OCO satellite data?
results they want?
Simple fact is that today we have no way to measure the thickness of ice in the arctic
other than some aircraft transects and a few sample holes drilled in the ice pack.
so you have basically 2 models: PIOMAS and DMI
figuring out how these models are wrong is important.
Steven, explain how this laser satellite will measure ice thickness? Green lasers penetrate ice and snow?
“… today we have no way to measure the thickness of ice in the arctic”
Back in the ’90s NASA was looking for methods. I proposed a method using radar ellipsometry. It never went anywhere, despite SRI showing interest in my proposal.
It is also possible to collect high-resolution stereo-photography and measure the freeboard of the ice. Those “some aircraft transects” can then be used in the same manner as the quarterly ICESat transects.
In 1967, NASA flew an experimental microwave imager over the pack ice near Point Barrow. I was on the ice, along with our Eskimo Weasel driver, boring through the pack ice to take temperatures and determine the thickness. So, there is older data available. Its a matter of knowing where to look for it.
I had no idea you had this background. Too bad we don’t have a commenter’s bio section…it would be interesting to know more about those who regularly contribute to the conversation.
rip
Despite Mosher’s denigration of the WUWT “Brain Trust,” there are a lot of commenters here who are quite qualified to criticize the science of climatology. I have purposely left off a bio’ on my nine articles because I’m a strong believer that a hypothesis should stand on the merits of the argument, and not on the CV of the person presenting.
Let’s compare the WUWT Brain Trust’s qualifications with those of Chris and Mosh. The comparative ratio is infinite, since the BT are scientists and Chris and Mosh, umm, to put it kindly, aren’t.
It’s eminently clear that WUWT has many varied and qualified commenters. And I do concur that one’s hypothesis should stand on it’s own merits. I think it can be interesting to know an individual’s background, though, especially if the reader doesn’t have the specific knowledge necessary to parse an argument…but I suppose even then it’s fraut with complications about appeals to authority and etc.
Just thinking out loud…but I love context, and knowing someone’s background can be great context sometimes.
rio
1970’s satellites began on a high-ice period (Global cooling, doancha know?). It is ironic that this satellite will begin on a low-ice period. ~70-year AMO, etc. anyone?
ya it was a conspiracy not to have laser altimeters back then
Fantastic. We will now get panic to six decimal places. Loads more data and grants to manipulate. ( Sorry – feeling a bit cynical these days)
Is the world going mad or am I suffering from a ( 18yo) Macallan deficiency?
This will be fancy light show for Al Gore I suppose… at our expense.
Still looking for the Clinton’s to paint their roof white :
https://wattsupwiththat.com/2011/07/18/clintons-solution-for-the-jobs-crisis-painters/
Maybe they can use it as as reference point!!!!
and solar panels on Al’s yacht.
Al’s next yacht?
They should call it the PAN
Then it would be the PAN asea
Top speed of that yacht must be pretty slow. What happens if you get a week’s worth of clouds?
Back to sense: I can see that this technology could be very useful monitoring the movements in active volcanoes.
“ICESat-2 will measure ice heights along the same path in the polar regions four times a year, providing seasonal and annual monitoring of ice elevation changes.” I guess there is utility in flying the same path four times per year. My question is how much area will be mapped? Will this method give appropriate data to determine ice area and volume?
It will see up to 88 N and S as it has a 92 degree inclination. So it will miss the last two degrees around the poles. It will complete an orbit about every 94 minutes, so the earth will move about 23 degrees per orbit. It will continue that precession at ~23 degrees (may be 21 to 24, but only one constant number, but with the 92 degree inclination countering the rotation I don’t want to do the math to figure it exactly) per orbit and about every 90 days finally repeat the exact track it started with.
It takes Cryosat 2 (which is already doing the same thing) about a month to get good coverage of the whole Arctic/Antarctic. Icesat might be faster or slower depending on the measurement footprint. Small footprint = better data quality data, but low coverage per orbit.
given the rate at which arctic ice moves i have to wonder how useful the data gathered will be for measuring some of what is claimed will be measured.
Based on it covering the same path 4 times a year, it must cover 360 degrees longitude every 91 days or about 4 degrees per day. According to https://nsidc.org/data/icesat/orbit_grnd_trck.html there are 14.8 orbits per day for the original ICEsat.
If central Greenland is about 75 degrees North latitude, each degree of longitude is 40,000 km x cos(75) / 360 = 29 km, so 4 degrees longitude at 75N will be 115 km. With 14.8 orbits per day, the size of the east-west grid is about 8km over central Greenland. As the article states, the number of readings along the north-south path is very high, nearly continuous.
Lasers are fairly goid at measuring small distances accurately, but…
From my real old days land surveying, we used the 100 and 200 foot metal tapes with plumb bobs on each end. We adjusted for temperature abd that worked pretty well if the persons were adept.
Then for elevation we used the philadelaphia rod and a Wild NA-2 automatic level. Did first order work mapping the coastal flood plain of New England.
Yes, the new total stations do remarkably well and I was around when HP came out with the 3810 and 3820-A.
A satellite will be a couple hundred to 20,000 miles away in orbit. The laser MUST BE PERFECTLT PLUMB taking the measurement due to the curvature of the earth. If off by several arc seconds or a minute or two, the result will be incorrect and show less ice by increased distance.
I say we need real competent boots on the ground to verify the real ice level rather than waste hundreds of millions on this costly boondoggle.
Actually, if they are off by a couple of arc seconds, they won’t receive a signal. These are pretty focused lasers on both receive and transmit. Also they will be orbiting at 500 km (269nm), so really low earth orbit.
Also the satellite is very unlikely to fall into a crevasse or get eaten by polar bears or freeze to death doing winter measurements. It can also measure both poles within 45 minutes of each other.
Ever do a traverse surveying? I’ve done a few that had 1:70,000 closures. My average was usually 1:20,000. Had my share of busts too…
The lasers we used later on required prisms to get readings on the forward tripod target (fore sight) and had them on the rear tripod Back sight). This double confirms andle and distance.
This satellite doesn’t use prismas, it just scatters light back. This is not good. I’ve used HP, Topcom and Pentax total stations and EDM’s ( electrinic distance meters). For the hell of it we tried an experiment with bicycle reflectors and other reflective materials and never got anywhere close to an accurate reading.
Even Apollo astronauts left a prism on the moon to get a fairly close distance reading.
I’m calling these guys out. Technology is great but this method to prove ice thickness will end up with poor results and add fuel to this already smouldering fire.
Boots on ground with reliable surveying gear is what’s needed.
This is just a monumental waste of time and money. I know the results can be challenged by both sides….
The only surveying I have done is for compass rose surveys for aircraft calibration. To calibrate the magnetic azimuth detector, we first had to do a full survey of the calibration site to get sure azimuth lines. We didn’t care about distance, just accurate directions.
Though sometimes the weather was bad, nothing like arctic conditions for sure.
Mapping regional geology in the 1950s and 60s in northern Canada using compass traverses, pacer and aerial photos, plus “shorelining” by canoe gave pretty good results. Two day compass and pacer traverses in Nigeria from dry stream bed “baselines” accessed by Landrover also worked.
If you got a bit off line, you tied on to a landmark visible on the aerial photo and distributed your observations along the altered line. You got pretty good at it, especially skillful at extending the direction by lining up visible natural markers with less frequent need for reshooting the line. In the forest , you consciously alternated what side of the trees you passed on as you advanced. I was always conscious of sun angle or shadow and wind angle to assist.
Making a final map showing the patterns of rock types and structures like folding, faulting (and relative directions of movement along them), strike and dip of formations, ascertaining “tops” of sedimentary and volcanic strata (from sedimentary and volcanic structures, orientation of shellfish valves – convex up! etc.) units that had been folded and overturned over hundreds of millions of years, outlining granitic and other intrusive rocks cutting them and determining relative ages – all to give you the geologic history of a region, including the third dimension, was very satisfying work. Times have changed much more radically than the climate!
john said: “Boots on ground with reliable surveying gear is what’s needed.”
Greenland is 2M km2, with a highest peak of 3,700 m2. Antarctica is 14M km2 with a highest peak of 4,900 m2. By way of comparison, Antarctica is 1.7x the size of the continental US.
How do you propose to cost effectively survey those two places 4 times per year, every year?
Easy, no more grants for AGW research at liberal arts colleges and that’s just for starters.
Right. I looked online at topographic survey charges, the figure I saw was $400/acre. Let’s be generous and say that for a massive survey it’s only $100/acre. Antarctica is 3.4B acres. So the cost would be $340B 4 times per year, or $1.4T/year. Yeah, cutting out a few billion dollars per year for climate research is going to make a big dent in that $1.4T annual cost.
The saving thing in this case is that (for sea-ice) you don’t have to do any absolute measurements, just measure the height difference of the top of the ice and the sea.
For land ice you do need the absolute altitude.
people here would say the boots on the ice were lying.
I thought they were using back scatter, not a direct reflection of the beam. Nothing down on the ice capable of doing that anyway.
here,
https://www.csr.utexas.edu/glas/pdf/atbd_pad_10_02.pdf
and amazingly they figured this out in 2002 without the collect brain trust that is WUWT
hahaha, good point. sadly, though, the collective brain trust that is WUWT is focused on knee-jerk rejection of anything that might show that AGW is occurring.
Chris,
That is inaccurate. Most of us here acknowledge that Earth is warming, and most will even attribute some small amount to human influence. The problem is to quantify what that human influence is. This particular article is about refined technology that is supposed to provide better measurement of the thickness of sea ice and the loss of continental glacier ice. I, and others, have been pointing out that the claims for accuracy have not been justified, even by information provided by Mosher. You have provided nothing.
Clyde, please point out which of your comments points out the flaws or accuracy issues with this new satellite and the laser technology it will use. All I saw was comments about the accuracy of GPS technology when used for positioning or height measurements.
Chris,
I was not the author of the discussion of GPS deficiencies. However, you might try looking at my comment of August 23, 2018 1:48 pm, August 23, 2018 2:40 pm, and August 24, 2018 10:32 am.
In the future, do your own global searches. Don’t expect me to do your ‘homework.’
“I say we need real competent boots on the ground”
In which case we need to make sure that the satellite measuring top of ice, not top of head.
How many boots in Antarctica? In Greenland? In Arctic Ocean?
Did you not also have to compensate for the steel tape’s catenary (sag)?
Yes, we had a tension scale (tensiometer) attached on one end. Depending on distance, a certain amount of tension was required.
The temp adjustment was 1/100 of a foot (+or-) for every 15 degrees F above or below 72F. I’ve done 100F down to -40.
Generally, competent personnel back then could correctly guage the tension for most surveys but those requiring first or second order results used the old spring type tensiometer.
I loved those days. Sending the field book back the the corporate office with black flies and mosquitos squished between the pages!
Oh yeah–the field book.
Rough surveying for the Dept of Highways in Canada’s hottest and dryest region. Midway between Lillooet and Lytton on the sunnyside of the bench.
At the top right-hand corner of the page we had to note those on the crew and what the weather was like.
I recall 40 days without a cloud and temps above 100 F. Guys running the Cats had a rough time.
When at school I had summer-jobs surveying. The first one was on Vancouver Island running profiles across a river.
The agency was a left over from the 1930s “New Deal” in Canada called the “Prairie Farmers Rehabilitation Agency”. Or “PFRA”.
Which we translated to: “Pray For Rain Always”.
Can’t survey when it’s raining.
As to the satellite, it will be better than the current system and the measure will likely include annual comparisons.
here is the approach with icesat 1
https://www.csr.utexas.edu/glas/pdf/atbd_pad_10_02.pdf
also there are boots on the ice collecting field data as a cross check.
jeez.
The issue is clouds. Lasers can’t penetrate clouds so they can only take measurements over cloudless areas, which means they will have to stitch together data from multiple passes, reducing the temporal accuracy of the data.
Won’t all those photons heat up the ice?
These are scientific photons. They don’t affect anything.
Scientific photons do affect one thing. Carbon trading and carbon taxes all increase exponentially, the more scientific photons that are measured.
I could see somebody making a stupid joke about how the lasers will melt the ice they are measuring.
Oops!, we dun turnt them lazers up 2 hi, so we dun melted thu sno.
Hey, Jeba, cum ova heer and hole this candill on this iees sickle, so i kin cee how tu masur thu linkth.
A Reggie, the blowtorch, replacement.
OCO2 redux.
Was thinking the exact same thing. “Houston, we have a problem, laser calibration, cooling issues, orbital decay, data transmission….oh my”
This reminded me to go look at NASA’s site again to see if they have new information, “latest images” are still from 2014.
Golly gee ma, how do they even count that many photons. /sarc
Obviously this was written by a professional writer (who took zero math and science courses).
Light travels about a foot in a billionth of a second. It’s a round trip so it sounds like one sample can resolve about half a foot. Not bad actually.
It will be accurate in time of flight to about 800 picoseconds, so plus or minus about 4.5 inches.
The light travel time will be the collected data. That data will have to be run through a model to convert it to elevation information (relativity, gravitational, temperature variations I suppose).
cB, I find it interesting you introduce the speed of light thing.
The raising of the TOA radiative cooling level (where the balance is found with incoming solar) from human activity emissions CO2 is not in question. Such is the science. The issue, or debate, concerns the phenomenon’s magnitude.
So ok, there may be some effect, but given the speed of light I doubt the approach to equilibrium is retarded enough to change the climate.
I’m with Freeman Dyson, IMHO there might be some effect at night in the colder regions of the planet, such that freezing is altered a few minutes (maybe seconds) here and there….so what?
These people (Al Gore and the alarmists) need to find a new and different hobgoblin to feed their neurotic and delusional requirements…..any ideas? Sasquach maybe?
Are you a bot?
The left owns all the bots.
But will NASA know the altitude of the orbit with the same accuracy and precision as the difference between the ground and the satellite? If not, then the information will not be all that useful!
https://www.csr.utexas.edu/glas/pdf/atbd_pad_10_02.pdf
Mosher,
I’m left with the impression that you don’t understand what you are reading. The link you provided speaks to the ATTITUDE of the ICESat-1 laser. That is, constraints on the pointing direction and the error resulting from misalignment and sloping surfaces. The article mentions a nominal altitude of 600 km for purposes of the analytical error calculations. What is of concern is the combined errors, but especially how accurately the altitude of the satellite is known. From the GLAS Measurement Requirements, “In summary, the error budget allows 10 cm instrument precision, 5 cm radial orbit position, 7.5 cm laser pointing knowledge and 2 cm or less for other error contributors.” for what appears to be a total error in precision of +/- 24.5 cm (~+/-9.6″).
What is of concern to me is whether the assumption of the 5 cm (5.0?) radial orbit position is warranted considering that the altitude will only be spot-checked rather than continuously monitored as per “The GLAS orbit position will be obtained with the Global Positioning System (GPS) and ground-based Satellite Laser Ranging (SLR).” For areas where the ice is melting, the gravitational attraction will be decreased and the satellite will rise in altitude, which will increase the distance between the ice and satellite. Thus, it will appear that the ice has melted more than it has!
Your claim below of “Icesat 1 did 5 inches” is not supported by the document whose link you provided. However, more importantly, the document doesn’t speak to my concerns of constraints on the orbital positional errors, which are probably unknowable out in the middle of Antarctica.
Icesat 1 did 5 inches
Yes for making sure laser pulses would arrive simultaneously I used that approximation (1 foot/nsec). They’re claiming freeboard measurement to 3cm so that implies path length difference of 6cm or 0.2nsec.
How will they compensate for compression or rebound of the land surface beneath the snow/ice?
They have models for that.
MarkW
That was mean.
🙂
Will they use portly or svelte models? Maybe a combination of them so they can pick out the most appealing one?
Silly boy. That’s how they will explain that although the glacier “seems” to have gained height, it’s actually lost mass because the land has rebounded from the reduced weight of ice.
..but will it show ice rising as it falls out of orbit?
Of course not, they will subtract that out with sufficient “adjustment” to maintain the expected loss of glacial ice.
Sounds as if glacial isostatic adjustment like in the sea level measurement fiasco IS GOING TO REAR ITS UGLY HEAD.
Actually not so much. That is the big problem with GRACE raw data which for Antarctica are actually not significantly different from zero, so the “catastrophic melt” there is actually 100% GIA adjustment.
Direct measurement of the height of the ice is much less affected by GIA uncertainty since the density of ice is only a third or a quarter of the density of the underlying rock.
The ugly head in this case is instead that the density of the snow for the about 300 feet down to where it turns to solid ice is known to vary geographically, but there is very limited data.
It is going to be orbiting at 500 km altitude. The stability of the orbit and the ATLAS laser system’s ability to measure its own altitude will determine the resolution of the instrument. Same problems the GRACE satellites have, just exactly how far up are they at any given time?
NASA does not like to discuss theses sort of things. Error bars that are too large embarrass them.
huh.
here is the discussion for icesat 1
https://www.csr.utexas.edu/glas/pdf/atbd_pad_10_02.pdf
They are measuring satellite altitude with a More sophisticated version of a sextant. They call theirs a “star tracker.”
They claim precision to 3 cm, and then they call 3 cm “a fraction of an inch.” The laser beam’s “footprint” on the ice is 10 meters. Obviously there will be high and low spots in a patch of ice this large.
NASA’s track record certainly leaves a lot of grounds for suspicion of false claims of precision.
err NO.
aircraft ATTITUDE is reloved with star tracking
aircraft ALTITUDE via GSP and SLR.
Psst the CIVILIAN contractors are the ones held to the spec.
Err, no. Aircraft Attitude is determined with gyros. GPS almost useless for altitude.
How will they prevent this satellite from suffering from the problems that have plagued the satellites that allegedly measure the height of the oceans?
1) How do they know the height of the satellite “to within the width of a pencil”? Gravitational changes beneath the satellite (including height of the ice) will impact the height of the orbit. And not just directly under the satellite either.
2) Ice is not smooth. How good are the algorithms for detecting crevases, water on the ice, snow, etc.?
3) Anything that impacts the density of the air will impact how fast the light travels through that air.
I remember the first gps we used surveying, back the it cost $33,000 usd back in 1984. It took days to get a close reading from several orbiting satellites. We said to heck with it and did a star shot on polaris with better results.
They have improved since but, the plumb thing bothers me a lot.
“It’s tough being a skeptic”
john 20:18
Those were the days of ‘selective availability’ for civilian use, that was cancelled in 2000.
Glaciers move, tides happen then you have useless lawyers, alarmists and politicians.
“If it ain’t plumb, the bar just got lowered”
john 20:18
MarkW
It’s ‘green’ laser beams. Infallible.
You’ve made my day, thanks.
Sorry to correct you Mark, but it’s technically “frickin’ green laser beams”
Measuring the height of ice in Greenland or Antarctica is way easier than measuring the height of water in the middle of the ocean.
Everywhere in Greenland or Antarctica is ‘reasonably close’ to some bare rock, be it a mountain top or shore line. That provides a calibration point. Out in the middle of the ocean, there are no ‘reasonably close’ calibration points.
Having ‘reasonably close’ calibration points solves a myriad of problems. Now, rather than doing absolute measurements, you’re doing a relative measurement, similar to differential GPS.
commieBob
Do satellites get sea sick?
There are ways to confuse electronic equipment that cause problems like overheating and excess battery use. My favorite is called metastability. So, in a manner of speaking, electronic equipment can get sea sick.
commieBob
Ewwwwwww. I’m not cleaning up the mess.
It’s not a problem as long as you keep the bit bucket emptied.
In searching for bit bucket I noted a huge difference between Google results and those from DuckDuckGo. In this case, DDG was far more useful.
commieBob
I use DuckDuckGo whenever possible. Unlike Google, it doesn’t track your searches. You should be able to nominate it as the default search in your browsers settings.
You are assuming that the bedrock in Greenland and elsewhere is not experiencing isostatic rebound. If it is, then it will make it look like the ice is melting more than it is. They will need differential-GPS calibration stations to do it right/
The rate of post-glacial rebound is 1 cm/yr or less.
As long as the calibration point is ‘reasonably close’ to what’s being measured, it will be rising at the same rate as the bedrock underlying the ice. In other words, it will remove the effect of post-glacial rebound from the measurement.
You are both wrong. If the bedrock is rising fast enough to maintain isostatic equilibrum it will completely hide the gravitational effects of melting ice, not make it look larger.
However it does not do that, as proven by the fact that the isostatic rebound is still going on in Canada and Scandinavia.
And there is not nearly enough calibration points close enough to accurately determine the amount of rebound. In Greenland the situation is fairly good, but even there there is a great deal of uncertainty, particularly since the rebound rate depends on local rock viscosity, which in the Greenland case is probably affected by the nearby Iceland hotspot.
GIA data for Antarctica is almost pure guesswork. And none of the GIA models fit the actual data.
In this case, the calibration points are bare pieces of rock, like mountain tops or shoreline. They act the same as surveyor’s reference markers. In the case of post-glacial rebound, they will rise along with the rest of the bedrock. The satellite measures the difference between their height and the top of the ice. It improves the accuracy by about an order of magnitude.
There are no, repeat NO, bare pieces of rock in inland East Antarctica.
For the main domes (where most of the ice is) the closest “pieces of rock” is a thousand kilometers away. Over such distances post glacial rebound can vary by more than an order of magnitude:
http://www.klimatupplysningen.se/wp-content/uploads/2017/08/nkg2005lu_stor.jpg
I was assuming that any calibration sites would be on the edge of the ice sheet and would be experiencing post-melting isostatic rebound, thereby requiring differential-GPS leveling to correct for the rebound..
“Everywhere in Greenland or Antarctica is ‘reasonably close’ to some bare rock, be it a mountain top or shore line.”
Only if you count 1000 kilometers as “reasonably close”. There is NO exposed bedrock anywhere in inland East Antarctica.
That is the big problem with GRACE data in Antarctica. Very limited GPS data, and none of the GIA models fit the data there is.
That’s why I used the quote marks. 🙂 Obviously the farther you are from a reference, the worse your accuracy.
it’s apparently close enough for extrapolating temp readings from ground based thermometers ,ask mosher.
” 3) Anything that impacts the density of the air will impact how fast the light travels through that air. ”
Were you thinking, twinkle twinkle little star?
start here
https://www.csr.utexas.edu/glas/pdf/atbd_pod_10_02.pdf
this is icesat 1.
If you find mistakes I am sure NASA will hire you.
I would call this a very thorough analysis of the problem of the orbital position, which largely justifies the estimate of +/- 5 cm radial position (although it didn’t specify whether that was 1 or 2 SD precision, or accuracy). It is far better than most climatology papers I have seen! The only thing I didn’t see explicitly addressed is topographic leveling of the elevation of the Satellite Laser Ranging (SLR) stations, which can be affected by isostatic rebound on the edges of the ice sheets. This isn’t a problem particularly in the interior of continents. But it is an EXPECTED problem on the periphery of the major ice sheets, for which this satellite was designed. Because of mantle hysteresis, or time lag, melting ice will not be be gravitationally compensated immediately, so the satellite can be expected to rise in altitude from the loss in ice. On the other hand, the SLR stations will be rising, giving a lower-bound on the distance difference between the satellite and the SLR calibration. So, unless I have missed something, there is an oversight in not providing differential-GPS leveling for elevations of SLR calibration stations on the edge of the ice sheets.
However, I’m not looking for a job.
They will “discover” that 1,1,1,2-Tetrafluoroethane increased the speed of light through the atmosphere causing erroneous measurement of deeper ice thickness. Thus requiring adjustments to the measured values.
Yawn….
They will simply “adjust” or “guess” at past numbers to make sure it shows a MASSIVE MELTING!!!!
Bruce Boelter
They used laser beams in the 1800’s to take ice measurements they can compare with, surely?
No, but there’s a bristlecone pine that has a feeling it knows how much ice was there and it told me it was a schistload more than today.
/channeling-Mann
Watch NASA ignore the findings of the new satellite and use less accurate methods when the data doesn’t give the results they desire, like they did with their satellite temperature data that didn’t show the warming the climate models predicted.
A prediction – most of the ice loss (but not all) will be a result of ‘adjustments’ to the raw data.
Lasers don’t see through clouds, which is why the LIDAR mapping used to find lost cities under the jungle canopy in Honduras was done by planes at relatively low altitude. Aggregating and matching data while compensating for missed areas due to cloud cover sounds like other-level complexity. But climate scientists are really good at making up data that doesn’t exist (infilling). Should be interesting to see how they handle this.
except its not climate scientists who do this work
ITS ENGINEERS
Steven Mosher: “except its not climate scientists who do this work … ITS ENGINEERS”
Climate scientists are not engineers. Thanks, that confirms my long-held suspicion. Can you help list the qualities that climate scientists are lacking?
Building instruments for accurate measurement is an engineering task. Interpreting the measurements and accurately factoring for instrument precision and missing measurements is the realm of statisticians and climate scientists.
It is climate scientists who are gridding and infilling global temperatures from terrestrial measurements, not engineers. They create data that doesn’t exist in the real world over large expanses of the globe to estimate global temperatures and trends. The more remote the weather station, the greater its influence on global temperatures. This is not science, it’s statistics. This abuse and misuse of statistical methods, especially in pronouncing global trends, falls squarely on the shoulders of climate scientists. It’s no surprise that there is a significant difference in the results of satellite and terrestrial measurements of temperature and sea level and their trends.
Engineers built the LIDAR but it has limitations. Lasers are incredibly accurate for measuring but they can’t measure through clouds. Statisticians and software engineers have to develop algorithms to stitch together data from multiple passes, which results in composite snapshots that reduce the temporal resolution and accuracy of the data, especially over areas that are often clouded, like high mountains. Adding complexity, to measure elevation changes over time the altitude of the LIDAR instrument must be established with high precision. Over long periods of time, the inaccuracies may not matter much and we will probably get a reasonable idea of glacier mass changes, probably (hopefully) better than the GRACE satellite measurements.
Here’s a brilliant thought: If you want satellite laser measurements to confirm a melting arctic, then make them powerful enough to melt the ice they are measuring. This way you can swear by laser precision, while hiding the fact that the lasers used were alien-death-ray strength.
You’re welcome, NASA. Just trying to help you stay consistent in your narrative.
Robert Kernodle
Pah!
All the aliens I know mock lasers as primitive and inaccurate.
And to be orbiting every 95 minutes, its gotta be hanging pretty low.
As how mirages form, don’t they need a pretty accurate temperature profile for the atmosphere they’re shooting through. Refractive Index changing the speed of light and all that shizzle?
Many many moons ago I caught a programme about the surveying of India (start with a known straight line then construct triangles) and that was when Mount Everest was discovered.
Politics of the time said they couldn’t get anywhere near it but they still took measurements to work out where it was and calculate its height. It was obviously Pretty Big.
Back in London to a room full of boys (and girls?) with log tables, pencils & paper, JUST the atmospheric correction that needed to be made altered the height by 500 feet
They got it pretty damn close considering how far away they were. Too long ago to recall the actual figure but…….
(Assuming you cannot leave India, just how close can you get to Mt Everest’s summit?)
Interesting. One billionth of a second equates to 30cm resolution on the return path, so 15cm on distance between ground and satellite per shot. The ‘pencil’ width accuracy, 5 mm, must come from the many, presumably independent, measures during a pass. However that claim of accuracy is only valid if they also know the exact position of the satellite itself to a degree better than those 5mm, otherwise the orbital uncertainties become a huge systematic error, a bias, on the measurements. I really like to see proof of that accuracy.
I was wondering if they could use orbital velocity as a proxy for satellite height.
Presumably if the satellite is orbiting over an area of high gravity, it will pull the satellite into a lower orbit, but at the same time the satellite will speed up.
The reverse would happen if the satellite was passing over an area with low gravity.
https://www.csr.utexas.edu/glas/atbd.html
See the POD.
duh.
Could that satellite use GPS?
Combination of GPS and ground based satellite laser ranging
the SLR validates the POD
https://www.csr.utexas.edu/glas/atbd.html
See the validation for Icesat 1.
you can google it
Are you being paid by the post?
Snark rather than science. MarkW’s specialty.
But the draft doesn’t address some of the issues that I and others have raised here.
“… registering increases and decreases as small as a fifth of an inch (half a centimeter).”
https://www.space.com/41596-nasa-icesat2-earth-ice-satellite-september-launch.html
As per the document (GLAS) provided by Mosher, above, the cumulative errors for the whole system are estimated to be +/- 245 mm. I’m dubious that “5 mm” can be achieved. I have not yet seen justification for the claim!
But why all this extra data?
“A laser has been used to generate small clouds on demand in lab, and real-world experiments suggest this could be a way to call down rain when it’s needed.”
https://www.newscientist.com/article/dn18848-laser-creates-clouds-over-germany/
“Rarely acknowledged in the debate on global climate change, the world’s weather can now be modified as part of a new generation of sophisticated electromagnetic weapons. Both the US and Russia have developed capabilities to manipulate the climate for military use.”
“While the substance of the 1977 Convention was reasserted in the UN Framework Convention on Climate Change (UNFCCC) signed at the 1992 Earth Summit in Rio, debate on weather modification for military use has become a scientific taboo.”
https://www.globalresearch.ca/the-ultimate-weapon-of-mass-destruction-owning-the-weather-for-military-use-2/5306386
Unprecedented? This time I believe it.