4 Final Report - Emits - ESA

3 Final
Report
ground coverage can be increased by acquiring the same spot several times, as already mentioned.
This is useful especially in areas, where high cloud coverage dynamics occur, hence clouds are
moving or dissolving a lot. In these areas, indicated by a high amount of cloud coverage changes,
Geo-Oculus can increase the ground coverage through multiple acquisitions of the same areas. In
result Geo-Oculus provides a higher performance in means of ground coverage than LEO systems.
These results have been correlated with the impacts of changing illumination situation, to indicate the
areas where the ground coverage can be increased most by observations with Geo-Oculus for the
handled day.
The performance evaluation of Geo-Oculus has been conducted for the Marine Applications mission,
which is accomplished as background mission. The results are considered to be representative for
these missions and also illustrate the capacity of the system for on Demand missions in the sea areas,
like Oil Slick Monitoring. For the Marine Applications, an image pattern has been implemented. The
simplified mission planning considers that the acquisition sequence is updated immediately when an
update on the cloud coverage information becomes available to the system; hence with every cloud
mask file (one new cloud mask file every 15 min) the mission plan is optimised and updated.
According to the agility of the system a certain number of acquisitions is possible within 15 min and a
selection of the images observed within the next 15 min has to be accomplished. The number of
acquisitions within 15 min is also depended to the number of parallel on-demand missions, which have
to be accomplished. The selection is based on the results of the analysis of geometrical conditions
and of cloud amount and cloud coverage changes. The current baseline foresees 4 images per 15
min. The final product is achieved by combining all the acquired images. In the analysis the
combination of the images leads to the total observed area which identifies the performance of Geo-
Oculus.
Finally the cloud coverage analysis compares the performance of Geo-Oculus with LEO Systems like
Sentinel 2 and Sentinel 3, regarding the total ground coverage which can be achieved at the handled
day. For this, different LEO swaths are implemented and superposed with the same cloud mask data,
as used for the performance evaluation for Geo-Oculus. Image 3.4-2 shows the performances of Geo-
Oculus and LEO systems by highlighting the ground coverage for one day:
Figure 3.4-2: Ground coverage within one day for Geo-Oculus (left) and LEO (Sentinel 3, right) are
highlighted blue
It can be seen that Geo-Oculus provides considerably more ground coverage (~83,3% of the
maximum possible coverage, ~55% effective) than a LEO system (Sentinel 3 ~35% of the maximum
possible coverage,~23% effective). This is due to the fact that the area for observation is accessible to
Geo-Oculus the whole day, whereas a sun-synchronous LEO mission provides commonly ~3 passes
over Europe during one day. This provides Geo-Oculus the advantage to benefit already from dynamic
Doc. No: GOC-ASG-RP-002 Page 3-25
Issue: 2
Date: 13.05.2009 Astrium GmbH