Why don't commercial airplanes carry Earth-observing instruments?

Question

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?

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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.

Answer 5

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.

Answer 6

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.

Answer 7

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.

Answer 8

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/

Answer 9

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.).

Answer 10

• 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.

Answer 11

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.

Answer 12

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.

Answer 13

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.

Answer 14

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.

Answer 15

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.