International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004 
  
  
1.3 Star Tracker : Used to determine the 
satellite's attitude which is needed to get precision 
poinüng during imagery collection. Sometimes, 
when collection is being occurred the Star Tracker 
can see the SUN which can cause wrong 
orientation the satellite attitude. 
1.4 Optical Sensor Assembly (OSA): the 
"camera" of the satellite. Actually, it has 10 meter 
long aperture but due to the on board attitude 
constraints it had to be shrink to the 2 meter long. 
The OSA has several mirror system to reflect the 
imagery onto the CCD arrays which transform 
imagery to voltage values. Then these voltage 
values are regenerated to create imagery again. 
OSA simultaneously collects black & white as 
well as multi-spectral imagery with the following 
specifications: 
Spatial Resolution Spectral Bands 
Black - White: 1-Mt. Blue 0.45 - 0.52 mm 
Multi-spectral:  4-Mt. Green 0.52 -0.60 mm 
Red 0.63 - 0.69 mm 
NIR 0.76 - 0.90 mm 
B & W 0.45 - 0.90 mm 
A “push broom” satellite takes images 
continuously in a strip along its ground track. 
“Tasking” is performed by the owner of the 
satellite and is controlled by turning on the 
downlink or not turning on the downlink. 
The IKONOS satellite turns *on" when it is time to 
execute a task. The satellite will turn “on” for 
either the Primary Operations Center (POC) or a 
Regional Operation Center (ROC) that has 
requested the use of the satellite. The ground 
station can then choose the exact areas needed for 
imaging. 
2. IMAGE COLLECTION 
2.1. Area of Interests 
Customer Product Orders or as we defined them 
Area of Interests are submitted by Customer 
Operations Specialists according to the customer 
requirements. They define a priority for each of the 
product order. After that, Mission Planning and 
programming is performed by Satellite Operations 
Engineers by considering these priorities. All area 
of interests is subject to the prioritization and one 
of the mission planning software criteria for 
scheduling is that and it creates opportunity for 
each priority. 
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2.2. Mission Planning 
Mission Planning provides interfaces to task the 
satelliteimaging system. For the IKONOS 
satellite, Mission Planning has capabilities to plan 
the collection of imagery within imaging windows 
assigned. by Space Imaging, and to generate 
tasking requests for direct uplink to the IKONOS 
satellite during these windows. Because 
intelligence requirements tend to be more volatile 
than the requirements for other remote sensing 
applications, this is a particularly valuable feature 
in that it permits changes to be made to the tasking 
only minutes before scheduled contacts with the 
IKONOS satellite. This near real-time tasking also 
enhances the probability of cloud-free imagery 
because changes can be made to the plan based on 
current cloud forecasts obtained from weather data 
providers. 
The field of view of IKONOS satellite for 60 
degree mono collection is 700 widths. If the 
product orders’ image region is candidate for that 
day, they would have an adjusted value for 
automatic scheduling by mission planning 
software. Satellite operations engineer has 
responsible to optimize the imaging times for the 
candidates image regions. Due to the bad weather 
conditions on affected image regions he can 
decide not to collect these image regions by zero 
out the adjusted value. 
2.3. Image Collection process 
Once the operator has finished the optimization 
the collection plan is saved. Then ground 
receiving system has returned to real time mode to 
capture the satellite signal. 
About thirty minutes prior to each contact, the 
system prepares to receive data from the satellite. 
Tests may be executed to insure the system is 
ready to receive and record the data, and that the 
antenna points to the location where the satellite is 
expected to appear above the horizon, based on 
ephemeris data provided by the operating agency. 
As the satellite rises above the horizon, the 
Antenna System acquires and tracks it until the 
end of the contact, which may be more than ten 
minutes in duration. For the IKONOS satellite, 
tasking that defines specific areas to be imaged is 
transmitted via the S-band uplink immediately 
after acquisition. When the sensor(s) on-board the 
satellite 1s activated, imagery is collected and 
transmitted via one or more Xband downlinks. 
The Antenna System receives and demodulates the 
X-band signal(s) and forwards the demodulated 
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