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Can satellites help find missing flight MH370?

China has released several satellite images its officials say could be wreckage from the missing Malaysia Airlines flight MH370 with 239 people onboard. If they are proved to be true it shows how remote…

Images released by China’s State Administration of Science, Technology and Industry for National Defense that it says are three large floating objects in an area where missing Malaysian Airlines flight MH370 vanished. AAP/SASTIND

China has released several satellite images its officials say could be wreckage from the missing Malaysia Airlines flight MH370 with 239 people onboard.

If they are proved to be true it shows how remote sensing satellites can play an important role in locating the wreckage of a crashed plane. It can be done within a couple of hours after the accident if multiple high-resolution satellites are used.

About satellites

Remote sensing satellites can be broadly classified into two categories – optical and radar satellites.

Optical satellites can now deliver unclassified images at a resolution of half a metre while radar satellites can provide unclassified images at one metre resolution.

Metallic structures such as plane wreckage can produce strong return on radar images, making them easily visible. Satellite imaging radar can also “see” through any cloud and can take images day and night.

According to China’s satellite images – taken over the suspected crash area a day after flight MH370 went missing on Saturday – the largest object shown is about 24m by 22m. This is clearly large enough to be imaged by both optical and radar satellites.

It should be noted from the images that the object is closely surrounded by cloud. Any potential wreckage would not be spotted by optical satellite if it were covered by cloud but it would still be visible on a radar image.

That’s why it makes sense to use both optical and radar satellites in any search for the location of plane wreckage.

Eye in the sky

Satellite remote sensing has many advantages over conventional air and sea search using ships and aircraft.

The satellites orbit around Earth at a height between 200km to 900km and can cover a large area, typically 100km by 100km (100,000 square kilometres – about the size of Cuba) or even 500km by 500km (250,000 square kilometres – about the size of the UK), with a single image collected in only a few seconds.

It would take an aircraft between 1.5 and 34 hours to cover the same area. A ship will take much longer.

The search much slower at sea level. Indonesian Search And Rescue (SAR) members looking for the missing flight MH370 in the Malacca straits, near Aceh Sea. EPA/ Hotli Simanjuntak

So it is much more cost effective to use remote sensing satellites to search over large areas.

Another advantage of satellites is that once in orbit the cameras and radar sensors on board are always on standby. They can be switched on immediately, as soon as the space agencies are informed of an accident, and be pointed straight at the area around the last known coordinates of the aircraft.

This also makes them much quicker to respond to incidents such as the air crash than the air and sea search vessels.

Another advantage is that satellites can take images globally without the issue around border protection so it is much easier to use them in international search.

Any limits?

Although the remote sensing satellites have the potential for global coverage some do have difficulty in imaging the two poles. That’s because they use near-polar orbits and not all of them have side-looking capability – they mostly look only down.

If an aircraft goes missing in the mountains, there is also a good chance that any wreckage may be hidden under the forest canopy. Although long wavelength radars can penetrate tree canopy, they may still have difficulty in seeing through the dense tropical forest.

In contrast, the open sea is a more favourable environment for searching a missing aircraft with satellite remote sensing, because the main features in a satellite image will be just sea water and the plane wreckage – there is less chance of confusing any wreckage with any other targets, such as trucks, trains or farm houses, as in the case of a plane crash on land.

Satellites in other disasters

Since 2008 the Geoscience and Earth Observing Systems group (GEOS), at the UNSW School of Civil & Environmental Engineering has responded, in near real-time, to a range of natural disasters using both optical and radar satellite remote sensing.

These events include major earthquakes in China and New Zealand, bushfire in Victoria and floods in Queensland, New South Wales and Victoria.

Satellite radar monitoring of NSW floods near Grafton in 2011. Processed by the Geoscience and Earth Observing Systems Group, UNSW School of Civil and Environmental Engineering. ASI

The team has repeatedly demonstrated that intelligence such as ground deformation, fire and flood extent can be extracted and delivered to relevant authorities within two hours of satellite image capture.

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8 Comments sorted by

  1. Colin Samundsett

    retired BSurv

    Delivery in about two hours of satellite image being taken; but how long might the expectation be for an optimum satellite positioning over an area of interest in order for an image to be taken?

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    1. Allan Gardiner

      Dr

      In reply to Colin Samundsett

      Sometimes there may not be any need to wait because there might already be a geostationary satellite hovering directly above the area when a crash occurs.

      Does anyone know if there was in fact a geostationary satellite or orbiting satellite above the area where flight MH370 was when it was said to have disappeared?

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    2. Linlin Ge

      Associate Professor at UNSW Australia

      In reply to Colin Samundsett

      GPS positioning satellites have been deployed as a constellation so that at least 4 satellites are visible anywhere on the Earth at anytime.

      Remote sensing satellites can be deployed in a similar fashion so that multiple satellites can observe a suspected crash site anywhere on the Earth at anytime.

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  2. Geoffrey Dell

    Associate Professor/Discipline Leader Accident Investigation and Forensics at Central Queensland University

    The potential for satellite photographs to aid finding the location of wreckage from aircraft crash sites, such as the Malaysian B777, would seem to be a quantum step forward. Replacing the need to carry out extensive area searches, of the kind we are all observing in the effort to find flight MH370, should be a step change in search and rescue methods.

    I'm usually the first to argue that technological advancement is the key to solving complex socio-technical problems. However, being something…

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  3. Allan Gardiner

    Dr

    Even switching a satellite's radar/camera on briefly every five or ten minutes could at least leave a trace where every sizeable aircraft or ocean going vessel inside the footprint was at that time. If we knew from a satellite radar image exactly where flight MH370 was five or even ten minutes before it crashed [if it did indeed crash] then the search could narrowed. This is exactly the same as the original method of using flashlights [torches] at night when batteries for them were very expensive. As you walked along in the darkness you just flashed the torch on briefly to see your way clear and then released the button. By only using the flashlight with this duty cycle the batteries would last for so long that it seemed they were lasting nearly as long as their shelf life.

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  4. Jan Burgess

    Retired

    Satellites images are very useful - but suffer from all the problems mentioned.

    Very few people seem to be aware of the satellite communication options available to airlines to avoid all these problems of lost airplanes. Something like spidertracks provide a device (starting at ~$1000) that allows real time tracking of aircraft with a position report every 1 or 2 minutes for about $1.50 per flight hour. This is peanuts in the cost of operating a jumbo or similar. The device can be independently…

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  5. michael sergent

    legal

    michael sergent

    legal
    .

    Thanks Linlin -great piece. I'm intrigued why the Australian authorities were unable to detect MH370 as it apparently approached the Western Australia coastline especially in the context of the Australian Government's paranoia about border security. Is it unrealistic to have expected detection given the distance of the search now about 1,600 klms from Perth or should the question be asked, perhaps by a good journalist, as to why it was not detected?

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