Frank Gerlach 
  
Characteristics of Space Imaging’s One-Meter Resolution Satellite Imagery Products 
Frank Gerlach 
Director of Product Quality and Research, Space Imaging 
fgerlach ? spaceimaging.com 
Key Words: High Resolution Imagery, Metric Accuracy, CARTERRA, IKONOS, Calibration 
ABSTRACT 
Space Imaging's IKONOS satellite provides imagery products at one-meter panchromatic, one-meter color, and 
four-meter multi-spectral ground sampled distances, GSD's. The characteristics of the satellite imaging 
capability, as related to image quality, radiometric resolution and metric accuracy are described. The selection of 
the orbit and it's parameters as they pertain to image collection efficiency and utility for the creation of precision 
cartographic image products is discussed, as is the on-orbit calibration and evaluation of the operational system 
modulation transfer function, MTF, radiometric accuracy and metric verification. A description of the one-meter 
and four-meter Carterra products offered by Space Imaging, and their attributes as they relate to interpretive, 
multi-spectral, and cartographic products are presented. 
1. Image Collection 
1.1 Orbit Geometry 
The IKONOS satellite, built by Lockheed Martin in Sunnyvale, California, was launched from Vandenberg AFB, 
California, on September 24, 1999 at 11:24 AM PDT, on board a Lockheed Martin Athena II launch vehicle, into 
a sun synchronous orbit with an inclination of 98.1 degrees to the equator at an altitude of 681 kilometers, or 423 
nautical miles, and an orbital period of 98.3 minutes. The local crossing time at the descending node is 10:30 
AM. The velocity of the satellite over the ground is 6.79 kilometers per second. The altitude was chosen to 
result in a unique daily revisit or repeat pattern from day to day. At this altitude, for an image collection at the 
equator, the ground track repeats within 10 degrees of obliquity every 11 days and within 1 degree every 140 
days. Orbit maintenance is performed as required to maintain this ground track repetition. 
1.2 Revisit and Ground Resolved Distance 
The IKONOS satellite / sensor is capable of pointing off nadir to image. Hence, if a customer can tolerate a 
larger, i.e., poorer GSD, the frequency of revisit increases. This provides for more opportunities to collect low 
cloud cover images, or more images per unit time to monitor temporal changes in scene content. As the latitude 
of interest is located farther from the equator, the number of opportunities increases, as represented in table 1 
  
  
  
  
Target Point Target Location 
GSD - meters Elevation Equator 40 Degrees 
0.84 79 11 8.5 
1.00 60 3.9 2.9 
1.18 50 2.8 2.0 
  
  
  
  
  
  
Table 1 Revisit frequency as a function of GSD and latitude. 
1.3 Image Collection Modes 
The number of detectors in the sensor focal plane dictates the instantaneous footprint, or field of view projected 
onto the Earth. At nadir, this equates to 11 km, while at 1.0 m GSD this is 13 km. However, unlike typical 
pushbroom sensors, IKONOS has the capability to either pushbroom or whiskbroom imagery. Therefore, on the 
  
128 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 
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