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one to believe. In fact, a contiguous image area of 4700 sq. km. can be acquired on a single pass, with the
poorest GSD being 1.0 m, for an area of interest below the ground track. This imaging takes about 128 seconds,
including maneuver time. Within a single communications cone, three such contiguous areas are capable of
being imaged in a 9 minute window. For larger GSD's, larger areas can be imaged. For example, at 45 degrees
minimum elevation, or 1.3 m GSD, 10,000 contiguous sq. km can be imaged in 220 seconds, thus allowing for
two such contiguous areas in a 9 minute window. In addition, IKONOS can image long 13 km wide stripes up to
1000km long. Same pass stereo images are acquired by pointing the sensor forward of nadir for the first image,
then aft of nadir for the second image, forming a stereo pair. These stereo images are epi-polar resampled in
ground processing for visual display. Mosaic images up to 12,000 sq. km can be created. The high agility
capability of the satellite allows for rapid collection of image targets dispersed off track. For example, for
alternate targets located below the ground track and at a cross track distance of 100 km, these can be imaged at a
rate of 2.8 per minute for 11 x 11 km images. 22 x 22 km images can be imaged at a rate of 1.0 per minute for
the same conditions. Presently the IKONOS satellite is imaging an average 80 to 100K sq. km. Per day in an
average operate time of 80 minutes. The satellite is designed to operate 120 minutes per day. As more regional
operations centers, ROCS, come on line, the image collection per day will increase proportionally. Figure 1
depicts IKONOS imaging statistics through March 20, 2000. Equivalent images per minute are for the equivalent
of an 11 x 11 km image.
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Figure 1 IKONOS Imaging Statistics
2 Sensor System
21 General
The camera system, built by the Eastman Kodak Company in Rochester, NY, consists of a one meter
panchromatic and four band 4 meter GSD multispectral sensor. The camera field of view for both pan and
multispectral are 0.931 degrees and the IFOV's are 1.2 and 4.8 micro-radians for the pan and multispectral bands
respectively. At 681 km, this equates to GSD's of 0.82 and 3.26 meters. The pan and multispectral detectors
field share the optical system and are collected simultaneously within 0.5 seconds of each other. Both the pan
and multispectral imagery is collected at 11 bits per pixel and bandwidth compressed on board the satellite to 2.6
for transmission to the ground. The telescope assembly consists of a 10 meter focal length three mirror
anastigmat with on-orbit refocus capability. Both the pan and multispectral detectors incorporate anti-blooming
circuitry to limit blooming for 1.5 times the max scene radiance to 1 pixel. However, on orbit experience shows
that under unique conditions of collection geometry and reflectivity of objects within the scene, that blooming is
unavoidable. The requirement on inoperable detectors is less than or equal to 0.1 %. The IKONOS satellite
launched with all detectors operable. The requirement on system radiometric accuracy relative to full scale is 10
% absolute, meaning temporally, 10 % relative, or pixel to pixel, and a linearity of 5 %.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B1. Amsterdam 2000. 129
