Depacketizing of CCSDS Level-0 Data: The packets of each group are depacketized and aligned to recover the unpacketized instrument source data by using a sequential counter, flags in the primary header and time tags in the secondary header. In the instrument source data format, the spectral band information is multiplexed with the image in BIP (Band Interleaved by Pixel) format as shown in Figure 2-2. Each swath line of image data is appended by the instrument supplement data and spacecraft ancillary data specific for the swath line.

Demulitplexing Instrument Source Data: The instrument source data are demultiplexed to separate image data for every spectral band into BSQ (Band Sequential) format. Here, we have the data rearranged in three groups, that is, the VNIR data group, the SWIR data group and the TIR data group. Each data group consists of the image data for each spectral band, the supplement data and the ancillary data. For only the TIR data group, the short term calibration obtained at the beginning of each observation is included. The supplementary data are necessary for all of the data groups to make it possible to process them independently. In this stage the image data are not divided into scenes but kept in one continuous observation unit, that is, a long strip of image data for more flexible scene selection. This data set is defined as Level-0A data which is a tentative product only used during processing.

Image Data Stagger Realignment: For SWIR and TIR image data the Level-0 pixel addresses are changed, so that all pixels for each band lie on one line, compensating for the staggered configuration described below. This realignment process is carried out not only to have more exactly aligned image data without resampling for the image matching process but also to simplify subsequent processes.

The SWIR subsystem uses electronically scanned linear detector arrays for each band to obtain one data line simultaneously in the cross-track direction for each scan period. These detector arrays are separated for odd and even numbered detectors with a staggered configuration as shown in Figure 2-3(a). The realignment for SWIR pixel addresses is carried out to compensate for the difference from the center line between the odd and the even lines. The stagger offset value to the center line can be set to ± 1 pixel with a good approximation.

TIR images are obtained by mechanical scanning with 10 detectors for each spectral band, that is, 50 detectors in total. Ten detectors for each band are arranged with the staggered configuration in the cross-track direction as shown in Figure 2-3(b). The realignment for TIR pixel addresses is carried out to compensate for the difference from the center line between the odd and the even lines. The stagger offset value to the center line can be set to ± 4 pixels with a good approximation.