Overview

The data from MTSAT is broadcast in multiple formats, including High Resolution Imager Data (HiRID) and High Rate Information Transmission (HRIT). This chapter covers only the HRIT format. The previous chapter covers the HiRID format, also known as the GMS-5 compatibility mode.

The MTSAT satellite provides one visible image channel and four IR channels. In the HRIT format, the data rate is 3.5 Mb/second and spatial resolution at the sub-satellite point is 1 km for the visible channel and 4 km for the IR channels.

For each channel, the transmitted image data is divided into multiple separate files, called image segment files. Full Earth images consist of ten image segment files per channel, and single hemisphere images consist of five image segment files per channel. A full Earth MTSAT image is 11,000 lines by 11,000 elements for the visible channel, so one complete image consists of ten image segment files, each containing 1,100 lines by 11,000 elements. Similarly, a full Earth MTSAT IR channel image is 2,750 lines by 2,750 elements, so a complete IR image consists of ten image segment files, each 275 lines by 2,750 elements. See Figure 1 for a graphic depicting a full Earth visible or IR image and its ten segment files.

The data contained in an image segment file can be fully determined by the file name alone. The naming convention is:

ffffppppccccYYYYMMDDhhmmnnnn

Where:

ffff

is the file type (IMG_ for image data, OVL_ for map overlay)

pppp

is the projection (DK01 for full disk, DK02 for Northern Hemisphere, DK03 for Southern Hemisphere, SF01 for Small Frame image)

cccc

is the spectral channel (VIS_, IR1_, IR2_, IR3_, or IR4_, which correspond to McIDAS band numbers 1, 2, 3, 4 and 5, respectively)

YYYYMMDD

is the observation date (YYYY=year, MM=month, DD=day)

hhmm

is the observation time (hh=hour, mm=minute)

nnnn

is the image segment file number (_001 to _010)

For example, the file IMG_DK01IR1_200612312332_001 is image segment data file #1 of a full Earth disk image for infrared channel 1, observed at 23:32 UTC on 31 December 2006. Note: If the file type is OVL_, the file name consists of only the file type, the projection, and a three-character spectral channel (e.g., OVL_DK01_VIS or OVL_DK02_IR_).

Figure 1. Full Earth Image and HRIT Segment Files (from JMA HRIT Mission Specific Implementation, Issue 1.2 [pdf])

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ffff	is the file type (IMG_ for image data, OVL_ for map overlay)
pppp	is the projection (DK01 for full disk, DK02 for Northern Hemisphere, DK03 for Southern Hemisphere, SF01 for Small Frame image)
cccc	is the spectral channel (VIS_, IR1_, IR2_, IR3_, or IR4_, which correspond to McIDAS band numbers 1, 2, 3, 4 and 5, respectively)
YYYYMMDD	is the observation date (YYYY=year, MM=month, DD=day)
hhmm	is the observation time (hh=hour, mm=minute)
nnnn	is the image segment file number (_001 to _010)