Landsat 8 currently acquires up to 740 images per day — up from the 550 images per day acquired in 2013.
Priorities assigned to each scene and special request help distribute the acquisitions.
Day-lit images are defined as images with sun elevations greater than five degrees. If fewer than 740 images per day exist, all candidates can be scheduled. If more than 740 candidate scenes exist, then images are excluded as a function of cloud cover prediction and long term cloud cover statistics. If the cloud cover prediction is better than the long-term average then the priority is increased. If an acquisition is rejected, a missed opportunity priority will take effect to increase the probability of future acquisitions.
Figure 1 illustrates the priorities of Landsat 8 scenes as of August 7, 2017. The lower priority scenes are more likely to be rejected to meet the daily limit, while the highest priority scenes are only rejected for maneuvers or rare calibration events.
Figure 2 illustrates the distribution of candidate scenes during 2017. The green region represents the scenes that were acquired. The orange region represents scenes that did not meet the day-lit criteria. The yellow regions represent special request images that are rejected due to cloud cover thresholds. The blue regions represent images that cannot be acquired due to resource reservations, such as maneuvers or calibration activities. The black horizontal line is the 740 image daily limit. The red region represents the scenes that were rejected due to the daily limit. Most rejected scenes are over Antarctica where the sidelap between paths permits revisit times of up to once every two days.