ALOS Data Users Handbook

ALOS Data Users Handbookb) Nadir ViewTable 3.4-8 Extraction Start Pixel Position Data of Nadir ViewData added in AUX Data HK Telemetry Output DataCCDImage Buffer Address Absolute Pixel PositionCCD No.of each CCD [Word][Byte]1 0’H 000’H to 9BF’H 1 to 49922 1’H 000’H to 9BF’H 4993 to 99843 2’H 000’H to 9BF’H 9985 to 149764 3’H 000’H to 9BF’H 14977 to 199685 4’H 000’H to 9BF’H 19969 to 249606 5’H 000’H to 9BF’H 24961 to 29952Example: When the data added in the AUX data is [2020’H], the HK telemetry outputdata are calculated as [9984 + 64 + 1] based on [CCD3] and [020’H], to become[10049].The relationship between pixel position and image buffer address is as follows:Pixel position = Image buffer address x 2 + 1When acquiring stereoscopic data using the three PRISM telescopes, it is necessary to correct the effect of theEarth’s rotation in order to fit the swath width of the forward, nadir, and backward views. PRISM has two typesof correction method for Earth rotation: the PRISM Earth rotation correction function and a method that uses theyaw steering of the satellite. These two functions are used complementarily.In Observation Mode 1, one of the following operations is selected so that there is an overlap between theobservation areas of the forward, the nadir, and the backward views.- When yaw steering is carried out: Earth rotation correction function OFF- When yaw steering is not carried out: Earth rotation correction function ONThe relationship between pixel position and image buffer address is as follows:Observation Mode 2 (Nadir 70km + Backward 35km simultaneously) uses the same methods for Earth rotationcorrection as Mode 1. Depending on the pointing angle of the backward view, it may not be necessary to use theEarth rotation correction function because the swath width of the nadir view has more margin than that of thebackward view.Observation Mode 3 (Nadir 70km) observes only the nadir. Regardless of whether the yaw steering is used, boththe ON and OFF Earth rotation correction functions can be selected. This also applies to the Calibration Mode.3-39