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Governments and private companies spend hundreds of millions of dollars to send Earth-observing satellites to capture imagery or scan the terrain with lasers or radars.

Meanwhile, commercial planes are constantly flying around the world, and even if they do not offer global coverage, they could still carry Earth-observing instrumentation with almost no additional cost. I'm sure the data they could provide would have many scientific and commercial applications. In some cases they could be even better than satellite observations due to much shorter revisit times, less atmospheric influence and shorter round-trip times for laser and radar signals.

For example, some satellites like IceSat and IceSat-2 were designed to repeat laser altimetry observations over the same ground tracks over and over. With much interest in Greenland, the icefields in Yukon/Alaska and Antarctica. Again, in this case, commercial flight could provide very good coverage of the first two areas of interest at a fraction of the cost.

I'm a glaciologist working on the Patagonian icefields, where the persistent cloud cover renders most of the images captured by Earth-observing satellite useless. I'm evaluating the possibility of contacting authorities and airlines to collaborate in a project to put instrumentation on the planes that overfly the icefields several times a day. However, I'm sure that I'm not the first with this idea of putting instruments on commercial planes. Thus, I'm surprised that no commercial airplanes carry Earth-observing instruments.

Therefore my question:

Is there any insurmountable technical or legal limitation to equipping commercial airplanes with Earth-observing instruments?

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    $\begingroup$ I doubt the "no additional cost" thing. A system for ground observation has to be integrated into and powered by the plane's systems. Thus it is a maintenance relevant - and might even be flight security relevant - component (it has to be installed on the plane with a direct line of sight to the ground) that does induce extra cost for no benefit for the airline. $\endgroup$ – Adwaenyth Nov 29 '18 at 8:40
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    $\begingroup$ "persistent cloud cover" ... "instrumentation on the planes that overflight the icefields" This isn't an answer, but it's an issue you definitely would want to consider: Commercial airplanes typically fly above the clouds. So if there's a cloud cover, and you are working in the visual part of the spectrum, you are unlikely to get much better data from airplane-mounted equipment than from equipment in Earth orbit. (Though when conditions are favorable, you might be able to get higher resolution.) $\endgroup$ – a CVn Nov 29 '18 at 9:03
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    $\begingroup$ They probably already do carry such instruments, to help the pilots know when to to turn on the chemtrail generators. Of course everyone in the aviation industry is sworn to secrecy and will deny this. $\endgroup$ – quiet flyer Nov 29 '18 at 14:23
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    $\begingroup$ Operating a commercial service while also carrying equipment serving an intelligence gathering or espionage role would certainly introduce legal complications. Many destination countries would not generally be happy about foreign carriers spying on their country. $\endgroup$ – J... Nov 29 '18 at 15:37
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    $\begingroup$ @CamiloRada there are already dedicated companies that do such things. Most high resolution images on google earth are in fact from small planes and not satellites. Oil companies frequently contract such people for photography/lidar of interesting regions. Probably airline companies are not that interested in competing in a new industry all of the sudden. $\endgroup$ – mbrig Nov 29 '18 at 20:01

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They do! Well, at least some of them. There is for example a project called TAMDAR (Tropospheric Airborne Meteorological Data Reporting) that e.g. Icelandair is a part of. There is a document published by the Icelandic Meteorological Office about it.

Another example is MOZAIC/IAGOS: Atmospheric Research Using Commercial Airliners.

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    $\begingroup$ More broadly, the AMDAR program does this on a worldwide basis with participating airlines and national meteorological agencies. The advantage is that it works using pressure and temperature sensors that are already factory equipment on airliners, along with the communications equipment typically available, so the costs are fairly minimal (and there's some benefit to the airlines, as anything that helps weather forecasters can help them). More complicated special-purpose sensors would be quite expensive and a much harder sell. $\endgroup$ – Zach Lipton Nov 29 '18 at 10:34
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    $\begingroup$ I would not call that "Earth observing instruments". $\endgroup$ – Vladimir F Nov 29 '18 at 15:01
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    $\begingroup$ @VladimirF now I looked up the definition of "Earth observation" on Wikipedia and the first point is "Earth observations may include: numerical measurements taken by a thermometer, wind gauge, ocean buoy, altimeter or seismometer" $\endgroup$ – Florian Nov 30 '18 at 0:59
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    $\begingroup$ @Vladimir Well, ya see there's Earth, the planet and earth, the stuff we stick seeds in. Capitalization can sometimes be important. $\endgroup$ – candied_orange Dec 1 '18 at 3:34
  • $\begingroup$ flyht.com/flyhtweather $\endgroup$ – Ed Randall Dec 1 '18 at 8:25
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I work in the aviation industry, specifically repair, maintenance and engineering. While not an engineer myself, I work alongside them.

Adding anything to an airframe, internally or externally, always has a cost in time, materials and funds. Our company is in the process of modifying ERJ regional aircraft with seatside electrical outlets for passenger access. The project manager and our electrical engineer have each spent over 200 hours designing the controls and wiring for the mod, procuring materials and consulting airframe engineers. Our inspectors have consulted with the FAA to have the mod approved. Our structures and interior technicians have designed and produced new panels inside the cabin, and our electricians have installed the controls and wiring.

This project has cost our customer roughly half a million dollars, and this figure does not take into account the inevitable oversights that arise in any engineering project. These additions to the airframe must be carefully considered against the aircraft total weight and the balance on each axis of control. Now add in training time for aircrews to be aware of the mods and how to handle issues.

Your proposal will necessarily cost at least this amount, and may not be feasible if the equipment is too heavy or bulky. In light of the other comments, I conclude that this will never fly. However, the military might be tasked with this kind of job, as they already have dedicated surveillance aircraft.

Good luck in Patagonia.

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    $\begingroup$ Hi Dan, it is very interesting to hear an opinion from an insider. Thanks! that helps. However, it is still unclear to my why the economical benefits of having power outlets on the sear outweighs so clearly the benefits that could be obtained of selling imagery and terrain data for aglriculture, map providers (like google maps, here, etc.), mining, etc. All those industries currently spend millions of dollars in products that could be acquired from comercial airliners. I'm sure companies already made the cost benefit math, I wonder what makes Earth Observation such a bad idea for airlines, $\endgroup$ – Camilo Rada Nov 29 '18 at 19:41
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    $\begingroup$ @CamiloRada, as you note in your question, coverage by commercial aircraft is limited, though the re-visit time is pretty good. Commercial imagery providers get more value from having large-area coverage than they do from re-visit frequency, so the better value-for-money option is to run their own fleet of dedicated aircraft with low-frequency visits to each area. $\endgroup$ – Mark Nov 29 '18 at 22:23
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    $\begingroup$ "Adding anything to an airframe, internally or externally, always has a cost in time, materials and funds." And fuel! Anything that has mass requires fuel to fly in an airplane. While satellites requires massive amounts of fuel to get to orbit, they require virtual no fuel once on-orbit. The same is not true for aircraft. To the airlines (or any other operator of airplanes) weight = money. $\endgroup$ – reirab Nov 29 '18 at 23:51
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    $\begingroup$ Of course it has a cost. I'm sure scientists would gladly pay for that, as the cost is just a tiny fraction compared to launching a satellite or even compared to flying their own dedicated research aircraft. $\endgroup$ – gerrit Dec 2 '18 at 12:12
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    $\begingroup$ The added equipment also subtracts from the total MTOM so the plane can carry less freight - whether associated with a passenger on board or a separate paying customer. If the EO equipment is installed in any sort of external fairing, that causes drag which increases the fuel requirement which increases the fuel carried which increases the cost. $\endgroup$ – FreeMan Dec 3 '18 at 17:42
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Aside from the issues of weight and complexity, there are potential legal and political considerations regarding commercial carriage of certain kinds of observational equipment. Korean Airlines Flight 007 was shot down by a Soviet interceptor in 1983 when it inadvertently flew over Soviet territory leading the Soviets to believe it to be a military reconnaissance aircraft. Equipping commercial aircraft with photographic or laser-based earth observation instruments--even if meant to measure ice, water, clouds, or topography--could be seen as potentially hostile, leading to an elevated risk of civilian casualties.

It wouldn't have to be a shoot-down, either: a forced landing and detention of the passengers would make people much less likely to fly that airline. At a minimum, airlines might have to change routes around politically sensitive areas, leading to increased costs, even if only a few aircraft were so configured.

While major powers such as the US, Russia, and China would be unlikely to undertake excessively hostile action, one cannot always predict what a smaller nation might do.

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  • $\begingroup$ This makes a lot of sense, and is the best explanation I found so far. Still doesn't explain why is such a bad business to do it on domestic flights. I mean, within the US borders agriculture, map providers (like google maps, here, etc.), mining, and other industries spend millions of dollars on imagery and terrain data that could be acquired from comercial airliners. I'm sure companies already made the cost benefit math, I wonder what makes Earth Observation such a bad idea for airlines. $\endgroup$ – Camilo Rada Nov 29 '18 at 19:45
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    $\begingroup$ @CamiloRada in this scenario, adding the equipment makes the aircraft only usable flights that remain in domestic/international airspace. This makes the airline less flexible. The other option is to go to the additional cost of making it modular and taking it out when not allowed. $\endgroup$ – fooot Nov 29 '18 at 21:30
  • $\begingroup$ I would say the opposite. After 2001, It is more likely to be big nations rather than small nations who are worried about anything remotely related to airplanes security. $\endgroup$ – mathreadler Dec 5 '18 at 8:45
  • $\begingroup$ The Soviet shootdown of KAL007 greatly raised tensions between the US and the USSR at a time when tensions were already high. They contributed to the Soviets nearly launching World War III during Exercise Able Archer 83. As such, major powers are typically more careful to identify aircraft before shooting at it, Malaysia Flight 17 and Iran Air Flight 655 being major exceptions. In certain unstable areas, leaders can get trigger-happy and shoot at aircraft (usually smaller planes) on rumors. It happens often in Africa and has happened elsewhere, and could easily happen again. $\endgroup$ – NetworkLlama Dec 17 '18 at 16:31
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Is there any insurmountable technical or legal limitation to equip commercial airplanes with Earth Observing instruments?

This question would probably be better answered on space.se, by people who know what are the advantages of a satellite over an aircraft and the reasons why missions are not conducted on aircraft.

However several aspects indeed differ between a satellite and a commercial plane, three come to mind:

  1. The practical area visible for a given field of view: At 400 km altitude (low end of the low earth orbit) the area covered is much larger than at 10 km.

    You can have an idea by comparing what you can view through a camera on each side of a given object, when this object is at 10 m and at 400 m.

    Depending on the mission this can be decisive.

  2. The degree and frequency of vibrations: Usually, when out of the atmosphere, a satellite is very stable. A plane shows a lot of (comparatively) large amplitude vibrations due to the engines and the aerodynamic pressure, especially at high frequencies.

    This is not a trivial problem, because at 10 km you usually need a very long focal length (or a very small aperture radar array), and the effect of the vibrations is directly proportional to the focal length.

    Large sensors used for good definition and contrasted shots also increase the effect in proportion of their diameter, because if the diameter is twice, the focal length must be twice to maintain the field of view (that's why digital cameras with small sensors have short lens).

    What can be seen as a simple problem on Earth with a 50 mm lens and a full size sensor, is actually a serious one when surveying at 10 km.

    A stabilization mechanism will be required (e.g. inertial platform, or mirror/lens/aerial dynamic correction). However those mechanisms need expensive maintenance and/or calibration to be effective.

    No airline will allow repetitive maintenance windows for that. Even when paid, this won't be comparable to passenger tickets, cargo fees and on-board sales. Airliners are not, for this aspect, comparable to spy aircraft and dedicated surveying aircraft.

    Aircraft also experience permanent roll, pitch and yaw changes, but as they are relatively slow they are easy to counter with a simple stabilized platform.

  3. Area coverage: Airways are very small corridors in the sky, at specific locations.

    In contrary satellites in low orbit (which are therefore not geostationary) see the Earth rotating below them and cover easily most of the planet area (specially polar orbit ones).

Regarding the cloud coverage preventing satellite observation, the problem will be nearly the same for an airliner. It flies above the clouds, even if polar routes are lower due to the tropopause being closer to the ground.

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  • $\begingroup$ Hmmm. But the question is not about the differences between satellite capabilities and aircraft-based capabilities. It’s about technical and legal limitations of the working with airlines. Thus, this network is more appropriate than the space.se network. $\endgroup$ – Jimmy Nov 29 '18 at 14:21
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    $\begingroup$ I get your points. But you can build another even longer list of the difficulties of operating and instrument from a satellite in contrast to an airplane. The cost of the down time that an extra system might require is an interesting one. Also, regarding to coverage, many satellites don't have storage capacity and can only rely information back to earth when they are over a ground station. Therefore, they can only really observe the terrain around the ground station. For a long time brazilian, indian and corean satelites were ony observing their own countries. Still they sent a satellite. $\endgroup$ – Camilo Rada Nov 29 '18 at 19:34
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    $\begingroup$ In contrary satellites in low orbit (which are therefore not geostationary) see the Earth rotating below them and cover easily most of the planet area (specially polar orbit ones)., that's not necessarily accurate for most Earth observation satellites. A radar on a sun-synchronous satellite such as Cloudsat, has a narrow swath width (~1 km) and a repeated ground pattern, so it doesn't see the entire world either. It's true for passive sensors, and although satellites do reach all regions of the world, nadir-looking active sensors do not easily cover the entire planet. $\endgroup$ – gerrit Dec 2 '18 at 12:17
  • $\begingroup$ @gerrit: I agree partially, the fact an instrument works with small field of view doesn't mean the vehicle is not able to overfly (zenith) the whole area between latitudes allowed by the inclination. Two consecutive bands may not overlap though. E.g. Sun synchronous Terra. $\endgroup$ – mins Dec 2 '18 at 20:22
  • $\begingroup$ @mins In theory, yes — but it'd have to be commanded to overfly a specific spot for an instrument with a narrow swath width to observe it. I don't know how precise they can hit it (question for Space Exploration), the swath width of the CALIOP LIDAR is less than 100 metre. I don't know if this type of commanding happens with scientific satellites, though (it certainly does with commercial Earth observation satellites). $\endgroup$ – gerrit Dec 3 '18 at 10:58
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Space fan here, and I think you are underestimating the size of the task.

Earth has a surface area of 510 million km2.

A plane travelling at 500 km/h with a 10 km observation track can cover 5000 km2/h, or 50000 km2 per 10 hour operational day, ignoring transit to/from nearest available airport. It would need approximately 10,000 days (28 plane-years) to cover the surface of the earth. I'm not sure what the cost of operating say seven crewed planes throughout daylight hours for four years is, but I'm sure it adds up, even for a small plane. With a crew of two, we're looking at 56 pilot-years of salaries (assuming they work 10 a day hours seven days a week and never have time off!) which is running into the millions already, before you even consider fuel or maintenance.

In contrast, SpaceX publish their prices and you can charter a Falcon 9 for $62 million to put 22800 kg into low earth orbit. Your satellite only weighs 2280 kg? No problem, rideshare deals are available, so your budget would be around 6.2 million plus a markup. Just wait for a near polar rideshare (such as the SSO-A mission scheduled to launched on 3 December 2018) and once in orbit your satellite will travel at around 30000 km/h, completing three laps of the earth every four hours. The earth's circumference is 40000 km, so with a 10 km track you should be able to cover the whole equator in 4000 laps, which is 5333 hours. Accounting for day/night the job should be done in under two years with a single satellite.

As discussed in other answers, planes are an option for small areas of particular interest, but just as satellites suffer from cloud obscuration, so can planes be affected by the weather, either by obscuration or by being grounded due to unsafe conditions.

While putting equipment on existing commercial flights is an interesting idea, if the flights follow the same route on a regular basis, only the areas on common flight paths would be mapped, which may or may not coincide with areas of interest.

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  • $\begingroup$ Can you add a reference to "SSO2"? E.g., is it related to SSO-A? $\endgroup$ – Peter Mortensen Nov 30 '18 at 19:59
  • $\begingroup$ @PeterMortensen the most stable reference going forward is most likely en.wikipedia.org/wiki/… . That said, this particular mission has suffered numerous delays, probably due to the number of parties involved, and I thought it best to wait until after launch to edit it in, in case the date changed again. It would seem the correct designation is indeed SSO-A not SSO2. $\endgroup$ – Level River St Nov 30 '18 at 20:08
  • $\begingroup$ OP did not ask for global coverage, but asked for coverage of the Patagonian Icefields. Unfortunately for OP, not many commercial airliners fly over there either. As for rideshare; cubesats are too small to carry radars or lidars. $\endgroup$ – gerrit Dec 2 '18 at 12:18
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A major reason would be that Earth Observing systems are large, and would take up a significant portion of the interior space of the airliner, space that the company wishes to sell to passengers. they are also heavy, which would impact the range of the plane and trip and drive up fuel costs.

Additionally, airliners want to get from airport to airport as quickly as possible, whereas in observation missions you want to get as many passes over important areas at specific altitudes as possible.

NASA flies many airborne missions every year specifically for earth observations. Some of these are simply proving future satellite sensors, but many more are purely for gathering data on a specific parameter. They utilize their own aircraft though, because the aircraft typically need to be specially modified for the equipment, specifically with portholes cut in the belly of the frame and they then dont have to compete with the needs of a passenger service when it comes to route.

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  • $\begingroup$ Well, EO systems are not that large anymore. Every kilogram put into orbit cost a lot. So many last generation satellites are the size of a minifridge or smaller. The point of airlines wanting to go from airport to airport as quick as possible makes a lot of sense. But for instance, within the US borders coverage of commercial flights would be good, and in the US, agriculture, map providers (like google maps), mining, and other industries spend millions on imagery and terrain data that could be acquired from comercial planes. I wonder what makes Earth Observation such a bad idea for airlines $\endgroup$ – Camilo Rada Nov 29 '18 at 19:55
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    $\begingroup$ @CamiloRada No, the coverage would be very poor. The USA only has about 5,000 commercial airports with paved runways. Most of those 5,000 have flights to fewer than 10 other destinations, and many have only one commercial route, to the nearest large airport. In other first world countries (Canada, for example) the coverage would be even sparser. $\endgroup$ – alephzero Nov 29 '18 at 21:03
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Almost every morning, at almost the same time while I wait for the bus to work, there's an air plane that flies overhead. It always come from the same direction, always disappears in the same direction and if you drew a line where it flew those lines would probably probably be pretty close together, if not almost completely overlapping. If you check any website that tracks flights you will likely see that there are specific routes which a lot of planes fly.

Why am I saying this? Because it means that while the idea sounds good, the actual coverage that you get would be pretty small. Multiple planes will record the same data each day and they will record the same data day after day. There will only be a small amount of original data and a whole lot of duplicate data.

You'd be better off only installing the necessary equipment in a few planes that are specifically tasked with recording data. They will get a larger coverage, go where you want them and not record a dizzying amount of duplicate data.

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    $\begingroup$ This may not be a problem, if you find a route that happens to overfly the area of interest (OP is interested in Patagonian icefields), the cost of paying an airline sufficient money to convince them to put an instrument on their plane may still be much less than the cost of (regularly!) flying a research aircraft in the same region. $\endgroup$ – gerrit Dec 2 '18 at 12:21
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During the Cold War airliners did in fact sometimes carry cameras... but covertly, for intelligence purposes. In particular Aeroflot was known for this, but also "other national airlines" according to this article from 1981: https://www.upi.com/Archives/1981/11/21/US-intelligence-experts-say-Soviet-Aeroflot-airliners-regularly-carry/2330375166800/

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  • $\begingroup$ It was also done from US airliners flying from west Germany to west Berlin when over the area of east Germany. $\endgroup$ – Uwe Dec 3 '18 at 12:41
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To measure ice field depths and such you must know the actual position of the sensor with greater accuracy than the precision you need for the final measurement. With a satellite ballistically orbiting the earth, that's easy. With a commercial aircraft flight, that's far more difficult, especially including pitch/yaw/roll effects between the GPS, the INS and the sensor.

Further, while adding a sensor to a satellite and orbiting same is very expensive, doing so for a vast fleet of airliners may well be even more so, especially when that includes paying the airlines for the privilege of doing so, including the ongoing maintenance that satellites don't need (they seldom need washing, etc.).

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  • $\begingroup$ For height measurement, lack of accuracy in position knowledge is definitely a good point $\endgroup$ – mins Nov 29 '18 at 18:59
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    $\begingroup$ That is true, but it is a solved problem. All the surveying software currently use for UAVs (aka drones) acquired data deals with those issues with no problem, basically using correlations within the data and some ground control points. The cost of equipping planes with the instruments is a good point. But I'm not sure if it is the only or main factor. $\endgroup$ – Camilo Rada Nov 29 '18 at 20:00
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The answer to both your questions is money. With enough of it these two things are indeed possible. But, I think your question lacks enough precision to give you a valid, usable answer.

I looked up this Patagonian icefields area that you are studying on 247 flight radar. Commerical flights barely fly over your area of interest and when they do it's odd curved flight paths let alone changes in altitude. That's a lot of image pre-processing time to to verify that images taken at different times can be spatially correlated to each other. Not to mention the fact that you won't get full coverage. You note clouds being an issue, you won't necessarily get any useable data just by flying underneath them. Other than sensors like LIDAR, most sensors pick up reflected radiation. So sure, if you are using an IR sensor and flying over places like volcanoes you can get usable data. But you might not be so lucky if you sensor relies on reflected light from the sun.

Creating the sensor you want and placing in on a "Vehicle" are just engineering problems. The hard part, which I know your question left out, is how are you going to store the data, how are you going to retrieve the data, who is going to all of the data collection, where in the world are you going to host it?

I guess if you are looking for free or near free data sets, remember tanstaafl. If you've been using Landsat, TERRA, AQUA data for your studies these projects were paid for and continue to be paid for by the US government. Heck it's only been since December 2009 that you could get Landsat for free. Prior to that I believe is was around $500 US per image that only covers 170 km north-south by 183 km east-west.

I have a feeling you'd be better off finding local pilots to fly your sensors across your icefields and collection the data directly from them. It won't be cheap, but I'd hazard it would be cheaper than what you are asking for in the long run.

I can't say were I work since I'm not a "spokes person" but I've had about 18 years worth of operations experience in a part of the EOS field.

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    $\begingroup$ I disagree with that "flights barely fly over your area". I've looked at flight radar too. And I've travelled hundreds of times from Santiago (SCL) or Puerto Montt (PMC) to Punta Arenas (PUQ) and every flight pass over or just beside the icefilds. I've installed mane reapeat photography cameras (aka time-lapses) in different glaciers. Those systems have the size of a small suitcase and can take pictures autonomously for over a year. You could easily implement wireless data download. Just a camera system like those attached under the commercial planes would yield extremely useful data. $\endgroup$ – Camilo Rada Dec 1 '18 at 22:40
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I can provide some insight as an aircraft structures & stress engineer as well as private pilot. From the engineering side of things, this would require a very costly design and installation process. As others have mentioned, weight would need to be factored in for post-mod aircraft operations. Also would require a great deal of stress analysis, certification red tape, testing and possible aerodynamic re-analysis depending on the type of equipment installed. There would also be a major cost for the observation equipment alone. Anything you install on an aircraft as permanent equipment costs MUCH more than what that same electronic or camera device costs if you were to purchase it for use in some other industry. Electronic equipment for aircraft must meet thorough certification and test requirements, which adds enormous cost. As an example, a typical 21" LCD monitor was around 20k dollars last time I checked. And this isn't even the latest and greatest resolution that you'd get buying the same size monitor for $400 at Best Buy. All that extra cost is testing and certification to meet stringent regulatory requirements. Can the airline justify this cost and recover it in a timely manner by selling imagery? I highly doubt it. From the pilot side of things, you need to consider that most commercial airliners are going from airport to airport, flying the same patterns over and over. Yes you can see a great deal from 40k feet, but nothing like you can at the altitude of a satellite. There is going to be a large amount of terrain that doesn't get photographed very often, if ever, and the airlines aren't going to burn additional fuel and increase route time to go out of their way to do this. Just my 2 cents.

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    $\begingroup$ very costly, sure, but not very costly compared to a satellite design+launch or the use of a dedicated research aircraft. $\endgroup$ – gerrit Dec 2 '18 at 12:22
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  • Many carriers lease their aircraft from holding companies that would obviously forbid making novel changes to the airframe. Even for aircraft owners, cutting a hole for cameras could substantially impact the resale value.
  • Insurance would have to approve the changes. They're not going to pay a claim for an experimentally-modified aircraft
  • if anything went wrong with the equipment causing the pilot to declare an emergency, it would negatively impact the entire airline. So even if it was profitable to sell the sensor data, nobody would want to be the first to do it.
  • Who is going to maintain the equipment ? Now you're talking about retraining ground maintenance crew or adding new ones.
  • Equipment malfunctions could delay revenue-generating flights. If they prioritize pax over equipment to stay on schedule, then they're carrying dead-weight.
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In short, airliners and some other civilian aircraft have carried earth observing cameras. In the 1960's most programs were reduced. The increased use of satellites was a major factor. Additionally, at that time, and prior to, airliners tended to fly rather predictable routes, and ATC most countries would route airways and clear planes avoiding targets of interest.

There are numerous open and classified payloads which have been operated since WWII.

Furthermore, there are practical issues in that an aircraft covers a limited area, and scheduled carriers have no real control over their flight times. So cloud cover and lighting were major issues.

In addition to EO/IR observers, there were SIGINT packages which were used, and are now largely replaced by satellites.

Many survey aircraft have a variety of sensors, such as magnetometers, lidar and other instruments. However, they are deliberately flown. Your question implies the use of sensors which are not incidental to the primary purpose of the flight.

However to address the question, there are not insurmountable technical issues with aircraft based sensors. The political/legal issues are varied. For example, over polar regions significant territorial claims are virtually non-existent. Flying over Area 51 would pose some governmental limitations.

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There are a few issues with your premises.

The cost is not minimal. A National Geographic article gives a cost of roughly 33 cents for 5 pounds per flight. GOES-16 (NOAA weather satellite) without fuel weighs in at right about 6300 pounds. We can get rid of some of that, but the sensor suite surely will still be quite heavy. Likely costing over $100USD per flight.

Just for perspective, two GOES satellites take images of the entire continental US every five minutes. To get anywhere close to that, pretty much every plane would need to have a sensor suite. The sensor suite cost and maintenance need to be factored in for all these extra sensors. Even with all the flights in a day you won't get full coverage. You also risk losing data collection when weather conditions ground planes.

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  • $\begingroup$ The GOES satellites may cover the entire United States, but they've got lousy resolution: 500 meters per pixel at best. To put that in context, there are entire small towns that won't show up on GOES imagery. $\endgroup$ – Mark Dec 1 '18 at 0:27
  • $\begingroup$ The point isn't the resolution. It's that they have 100% coverage every five minutes. The airlines will get an insignificant percentage and infrequent revisits. At a cost of putting sensors in 1000s of planes. $\endgroup$ – Philip Tinney Dec 1 '18 at 0:41
  • $\begingroup$ I'm not suggesting that EO systems on comercial planes can replace GOES or MODIS. I'm just pointing that the data that could be captured from commercial planes would have a great scientific and commercial value, and I not sure why that potential haven't been exploited. I gave the example of some satellites like Icesat and I can add all he WorldView ones, for which EO systems on commercial planes could produce similar data with reduced coverage but also reduced cost. $\endgroup$ – Camilo Rada Dec 1 '18 at 22:44
  • $\begingroup$ I believe it's entirely cost. Weight and modifications to the plane would make it expensive. Most sensors would need an unimpeded view. External sensors would impact fuel efficiency. Internal sensors would need to be mounted so it can "see" the earth. That likely means modifying the hull. $\endgroup$ – Philip Tinney Dec 2 '18 at 1:13
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I'm very surprised that not a single answer to this question mentioned the magical keywords radiosonde and weather balloon.

Answer: no, there isn't, and as some of the answers noted, some commercial airplanes already do that.

To initialize numerical weather prediction (NWP) model, you need to know the temperature, pressure, relative humidity and winds at every single point of the atmosphere of planet Earth. Okay, we approximate a bit to avoid an infinite amount of data: the atmosphere of planet Earth is divided to small boxes and each box has a single value, assumed to be approximately valid for the entire box. That's a lot of initialization data, and a lot of it are far above the ground in the upper atmosphere.

Currently, weather forecasting is partially based on weather balloons, that are released at periodic times from certain locations. It's definitely possible to augment the information obtained from weather balloons by aircraft measurements. There are probably more airports than weather balloon release points, and airplanes are taking off more frequently than weather balloons are released. Thus, it's greatly beneficial to augment the information of weather balloons by aircraft measurements.

The cost is a non-issue. The weather balloons use radiosondes that are single-use devices. Install one in an airplane, and suddenly it's no longer a single-use device. The fact that these radiosondes can be frequently (many times per day) released for a single use, demonstrates that cost of installing one in an airplane is a non-issue.

The reason this information is needed is that ground-based measurement stations measure only winds, temperature, pressure, etc. at ground level. For numerical weather prediction (NWP), you need measurement data from the entire atmosphere of planet Earth. It's not enough to measure data at ground level, because the NWP model is a model of the entire atmosphere.

However, airplanes will not and cannot replace meteorological satellites. Geostationary satellites see half of the entire Earth continuously and can transmit cloudiness / temperature / etc. data at so short intervals that they are extremely useful in numerical weather prediction. A single airplane, being very close to Earth, sees only a small part of Earth. You cannot have continuous 100% coverage of Earth by merely using airplanes.

Thus, airplanes can be at most replacement for weather balloons. They will not replace satellites.

I can see a world where single-use radiosondes in weather balloons are replaced by multi-use radiosondes in aircraft for economical (too much $$$ to build and discard lots of radiosondes) and ecological (single-use prohibited) reasons. But I cannot see a world where meteorological satellites are completely eliminated. There is a reason why meteorological satellite data is the most important input for NWP.

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  • $\begingroup$ This is somewhat missing the point. OP is interested in monitoring icefields, which is orthogonal to radiosondes / weather balloons. OP could launch a research balloon with equipment attached, but that's not very practical for observing icefields. And airlines do already feed information back to NWP, not instead of radiosondes, but complementary (of course, NWP is hugely important for airlines too). $\endgroup$ – gerrit Dec 2 '18 at 12:27

protected by kevin Dec 4 '18 at 2:50

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