Can anyone explain this plane's BLUE SHADOW ?

Placemark deleted as this post pre-dates it. http://bbs.keyhole.com/ubb/showthreaded.php/Number/37789

Beno

Probably has something to do with the plane's movement and the way the CCD sensors gather the light.

Attached is another example of blue planes. In this one though, the aircraft is a 747 over the state of Maine having just crossed the Atlantic Ocean when it is still at 40,000 or more feet and traveling around 600mph. It is very clear this is not a shadow as the vapor trails are visible in both the high resolution image and the lower resolution blue image. We must be dealing with a double exposure but why are the two images different.

In the UK image the twin engine (737?) plane appears to have just left Birmingham airport and is at a lower altitude. But has the same dual resolution image associated with it.

Researching the possibility I have the following data points. On the keyhole/Google Earth images the high resolution area are 11 kilometers wide and the shortest length is 11 kilometers. The high resolution appears to be 1 meter and the typical resolution 3 meters.

The only Satellite imaging manufacturer I discovered of such systems was Ikonos. Whose sites have identical images that you one can find by yourself with Google.

This being the case we know that the most likely satellite has the following Facts associated with it.

Launched - 24th September 1999 Vandenberg Air Force Base , California
Orbit- 98.1 degree, sun synchronous
Speed on orbit- 7.5 km per second (4.7 miles per second)
Speed over ground- 6.8Kilometers per second (4.2 Miles) per second
Number of revolutions Around Earth- 14.7 every 24 hours
Orbit Time- 98 minutes
Altitude- 681 Kilometers (423 miles)
Resolution- 1 meter both color & Panchromatic
3 meters Multi-spectral
Image swath 11.3 Kilometers (7.0 miles)
Equator crossing time 10:30 am Solar Time
Dynamic range 11 bits per pixel
Image bands Panchromatic, Blue, Green. Red, Near infra red

The Clues
In the 747 image we have some the blue image is lower resolution than the primary image. The primary is probably 1 meter and the blue image 3 meters.

Why different resolutions?
The second image could be from the near infrared imager, which is probably both slower and at a different position within the satellite. Moving objects would not align when processed as a composite. These artifacts would be allowed for when looking at earth bound stationary object. The ground image is moving past the camera at 105,000ft per second compared to the plane doing 880 ft per second.

Why would the image be blue?
Assuming the second image is from an infra red imager and a plane at 40,000 ft (747 image) then the skin of the aircraft could be anywhere between -25 and -50 degrees Centigrade. Usually with IR imaging blue represents cold and red hot. Note there are some red areas in both The US and UK plane images indicating hot spots.

Why are the blue images not in the same relative positions for the US versus UK plane?
The 747 blue plane�s image is to the North West, while the plane is traveling West and party South and for the UK plane it is to the South East with the plane traveling South East.

I was thrown by the fact the blue image was not in the same relative location. The planes are flying in opposite directions. My theory is the satellite circumscribes the Earth such that is always 10:30 am local time. The Earth is rotating once every 24hours and the satellite 15 times a day it will therefore pass over some locations traveling from the south and some from the North. In the USA image it is likely coming from the South to North passing the color imager first and then the IR and in the UK image the Satellite is traveling from North to South so it catches the full color Imager first and then the IR imager.

It is interesting to note that the USA plane and its Blue partner are at their respective centers 144 ft apart while the UK plane is about 132ft apart. The UK plane is only 4.5 mile out and probably not at its final altitude.

Second thoughts on Blue Shadow

I just realized that my theory of the imaging satellite passing from South to North versus North to South cannot be correct. The South to North travel is on the sunlit side of the earth and the North to South therefore must be the night side of the earth. If it is 10: 30 am on the equator and the satellite makes a revolution every 98 minutes then all visible images are between 9:41 and 11:19 am while on the dark side it will be between 9:41pm and 11:19 pm. This has caused me to rethink how the two exposures occur.

The other speculation that there were two cameras involved in this composite image may also be incorrect. However what is not a wrong conclusion there is a double exposure.

The full color 1 meter camera on this satellite uses 3 linear array sensor CCDs that are approximately 12,000 pixels wide. The optics split the light into the three components (red, green and blue) and projects them onto the linear sensors. The motion of the satellite provides scanning in the direct of travel while electronics scan the array from left to right. This is analogous to how a flat-bed home PC scanner operates.

The slowest the CCD array can scan and capture a full swath of land must is equivalent time it takes the satellite to travel one meter; which is 1,000,000/7500 = 150 microseconds.

A 747 is 70 meters long if traveling parallel to the sensor it would occupy 70 pixels and take 60 CCD scans to cover the 60 ft wing span. The equivalent of 9 milliseconds by which time the 747 would have flown a further 2.3 meters.

It is clear that the double exposure is not due to the planes motion relative to the sensor.

Anybody else have some theories.

attached is another example again a 747