More than you need

This is not the TV case of Y, Cr, Cb read on:


Here are the facts for the most of the GE High resolution satellite only Images:

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
Earth rotation per orbit 24.5 degrees
Equator crossing time 10:30 am Solar Time
Local time shift pole to equator plus or minus 22.5 minutes of 10:30 am
Orbit Time 98 minutes
Altitude 681 Kilometers (423 miles)
Resolution 1 meter both color & Panchromatic
Resolution 3 meters Multi-spectral
Image swath 11.3 Kilometers (7.0 miles)
Dynamic range (Max) 11 bits per pixel
Image bands Panchromatic, Blue, Green, Red, & near infra red
Camera focal length 10 meters
Field of view 0.83 degrees
East west imagers/camera positioning plus or minus 8.3 degrees (estimate, 3 day return)
North South imagers/camera positioning plus or minus 22.5 degrees (estimate)
CCD pixel size 10 x 10 microns (estimate)
Panchromatic (grey scale imager) linear array 12,000 x 16 pixels (approx) employing TDI (Time delay integration)


The camera on this satellite employs at least 5 linear array sensor CCDs. The first for panchromatic imaging is approximately 12,000 pixels wide (0.83 meter resolution). The other 4 make up the MSI (Multi-spectral imager) of which three are approximately 4,000 pixels wide for red, green and blue and one for near infra red.

The satellite provides scanning in the direction of travel while electronics scan the CCD arrays from left to right. This is analogous to how a flat-bed home PC scanner operates.

The camera normally is tilted forward and directly in the direction of travel. It can however be rotated up to plus or minus 30 degrees in the direction of motion and plus or minus

The actual scanning protocol does not appear to be published however the slowest the CCD array can scan and capture a full swath of land must be equivalent the time it takes the satellite to travel one meter over the terrain; which is 1,000,000/6,800 = 147 microseconds.

The panchromatic CCD exposure time per pixel is too short to obtain sufficient light to support 11 bit resolution so the CCD linear array is replicated approximately 16 times allowing the same ground image to be exposed 16 times as the satellite travels forward. The electronics can then stores each pixel from each line and then add each 16 pixels charge together in the direction of travel to increase the exposure.

One can find trucks and planes on the ground that are reflecting light directly back into the imager and a castellated light triangle will be observed where each line adds to the saturation of the imager (gross over exposure).

The MSI (multi-spectral imager) is only a single linear array. This is because each pixel covers an area 3 to 4 times that of the panchromatic imager and takes 3 to 4 times as long to pass the same point on the ground resulting in a 9 to 16 time increase in equivalent exposure. The MSI imager can not reside at the same physical location in the optical path and as a consequence receives its image at a different time than the panchromatic imager this is corrected on the ground by time realigning the images.

This satellite has the ability to change the angle of view both in the direction of travel and East West. This enables the camera to take stereo images. If the Cameras is tilted East by say a few degrees and tilted forward say 15 degrees for some distance and time over the ground and then tilted few degrees to the west and then faced backward 15 degrees two different views of the same ground area can be captured during the same light conditions. From these two sets of images a 3D stereo image can be constructed.

The ability to tilt the camera at least plus or minus 8.3 degrees enables the satellite/imager to revisit the same swath 3 days later. Without tilting the camera it would take 240 days (11.3 Kilometers/orbit and 14.7 orbits/day).