McIDAS Programmer's Manual

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GMS

The following section describes the navigation and calibration for the visible and infrared channels of the Geostationary Meteorological Satellites, GMS-4 and GMS-5. GMS-4 has one channel of visible and one channel of infrared data. GMS-5 has two channels for visible and two channels for infrared data; only one channel of each is used. The remaining two channels are reserved for backup.

 

 

The tables referenced in this section are from the document Revision of GMS Stretched-VISSR Data Format , Japan Meteorological Agency, October 1993.

GMS navigation block

The following three tables list the words used in the GMS navigation block. These are 1-byte words. The first table lists all the words in the GMS navigation block and the following two tables list the words used in the attitude prediction data sub-blocks and the orbit prediction data sub-blocks.

The Type column in the tables below shows scaled integers in the format R*M.N. The R indicates real numbers, M is the number of bytes and N is the exponent.

 

 

The GMS data is also formatted using the navigation block format of GOES-7 data. The section GOES-7 AAA navigation block describes the GOES-7 navigation block.

 

Word

Type

Description

1-6

R*6.8

observation start time (MJD)

7-10

R*4.8

VIS channel stepping angle along line (rad)

11-14

R*4.8

IR channel stepping angle along line (rad)

15-18

R*4.10

VIS channel sampling angle along pixel (rad)

19-22

R*4.10

IR channel sampling angle along pixel (rad)

23-26

R*4.4

VIS channel center line number of VISSR frame

27-30

R*4.4

IR1 channel center line number of VISSR frame

31-34

R*4.4

VIS channel center pixel number of VISSR frame

35-38

R*4.4

IR1 channel center pixel number of VISSR frame

39-42

R*4.0

number of sensors of VIS channel

43-46

R*4.0

number of sensors of IR channel

47-50

R*4.0

VIS total line number of VISSR frame

51-54

R*4.0

IR total line number of VISSR frame

55-58

R*4.0

VIS pixel number of one line

59-62

R*4.0

IR pixel number of one line

63-66

R*4.10

VISSR misalignment angle around x-axis (rad)

67-70

R*4.10

VISSR misalignment angle around y-axis (rad)

71-74

R*4.10

VISSR misalignment angle around z-axis (rad)






75-78
79-82
83-86
87-90
91-94
95-98
99-102
103-106
107-110






R*4.7
R*4.10
R*4.10
R*4.10
R*4.7
R*4.10
R*4.10
R*4.10
R*4.7

These words are modified as a function of the horizon
points. See words 11-14 in Table A.1 in the document
Revision of GMS Stretched-VISSR Data Format

element of VISSR misalignment matrix
row 1 and column 1
row 2 and column 1
row 3 and column 1
row 1 and column 2
row 2 and column 2
row 3 and column 2
row 1 and column 3
row 2 and column 3
row 3 and column 3

111-114

R*4.4

IR2 channel center line of VISSR frame

115-118

R*4.4

IR3 channel center line number of VISSR frame

119-122

R*4.4

IR2 channel center pixel number of VISSR frame

123-126

R*4.4

IR3 channel center pixel number of VISSR frame

127-240

 

not used

241-246

R*6.8

daily mean of Satellite Spin Rate (rpm)

247-256

 

not used

257-617

 

attitude prediction data sub-blocks 1 through 10 (10 similar attitude prediction data sub-blocks are repeated). See the table below.

618-2352

 

orbit prediction data sub-blocks 1 through 8 (eight similar orbit prediction data sub-blocks are repeated); see the table below.

The table below describes an attitude data prediction sub-block. The GMS navigation block contains ten attitude data prediction sub-blocks that occupy words 257-617. Each block occupies 36 words.

Word

Type

Description

1-6

R*6.8

prediction time (UTC represented in MJD)

7-12

BCD*6

anno domini represented by BCD (YYMMDDHHmmSS: year, month, day, hour, minute, second)

13-18

R*6.8

angle between z-axis and satellite spin axis projected on yz-plane in mean of 1950.0 coordinates (rad)

19-24

R*6.11

angle between satellite spin axis and yz-plane in mean of 1950.0 coordinates (rad)

25-30

R*6.8

dihedral Angle between the Sun and the Earth measured clockwise seeing from North (rad)

31-36

R*6.8

spin Rate: spin speed of satellite (rpm)

The table describes the orbit prediction data sub-block. The GMS navigation block contains eight orbit prediction sub-blocks that occupy words 618-2352. Each block occupies 182 words.

Word

Type

Description

1-6

R*6.8

prediction time (UTC represented in MJD)

7-48

 

not used

49-54

R*6.6

x component of satellite position in Earth-fixed coordinates (m)

55-60

R*6.6

y component of satellite position in Earth-fixed coordinates (m)

61-66

 

not used

67-84

 

not used

85-90

R*6.8

Greenwich sidereal time in true of data coordinates (deg)

91-102

 

not used

103-108

R*6.8

right ascension from the satellite to the sun in the Earth-fixed coordinates (deg)

109-114

R*6.8

declination from the satellite to the sun in the Earth-fixed coordinates (deg)

115-128

 

not used

 

129-134
135-140
141-146
147-152
153-158
159-164
165-170
171-176
177-182

 

R*6.12
R*6.14
R*6.14
R*6.14
R*6.12
R*6.16
R*6.12
R*6.16
R*6.12

Element of nutation and precession matrix
row 1 and column 1
row 2 and column 1
row 3 and column 1
row 1 and column 2
row 2 and column 2
row 3 and column 2
row 1 and column 3
row 2 and column 3
row 3 and column 3

GMS calibration block

The GMS calibration block contains both directory and data conversion tables located in sub-blocks that follow the directory. The 128-word directory block, shown below, indicates the locations of the six sub-blocks. The starting byte offset for each sub-block varies with the data; therefore, it is shown as a variable in the directory below.

Word

Value

Description

0

GMS5

4-byte ASCII identifier

1

0x58

directory block length in bytes

2

COEF

4-byte ASCII identifier for sub-block 1

3

 

starting byte offset from word 0

4

4VIS or 5VIS

identifies sub-block 2

5

 

starting byte offset from word 0

6

4IR or 5IR1

identifies sub-block 3

7

 

starting byte offset from word 0

8

5IR2

identifies sub-block 4

9

 

starting byte offset from word 0

10

5IR3

identifies sub-block 5

11

 

starting byte offset from word 0

12

SPAR

identifies spares block, sub block 6

13

 

starting byte offset from word 0

14-21

 

not used

22-85

 

Words 1 to 256 of GMS 4-or -5 calibration block; see the table below

86-127

 

reserved for future tables (GMS-6, etc.)

The table below describes the calibration data sub-blocks, not all of which may be filled. The calibration data, which follows the directory, has a length of 6400 bytes.

 

See table A-7 in the Revision of GMS stretched-VISSR data format document for a complete description of the data block.

Byte

Descriptions

1-4

calibration information ID

5-10

data generated date (YYYYMMDDHHmm)

11

sensor selection

12-256

sub-block 1; infrared radiance calculations

257-1280

sub-block 2; visible level-to-albedo conversion tables; four 64-level tables for VIS1 through VIS4 detectors

1281-2304

sub-block 3; IR1 level-to-temperature conversion table

2305-3328

sub-block 4; IR2 level-to-temperature conversion table

3329-4352

sub-block 5; IR3 level-to-temperature conversion table

4353-6400

sub-block 6; spares

The prefixes for each scan line of visible data must contain a code indicating the detector used. The first four bytes of the documentation section should contain the following information.

Code

Description

00000000

not a visible band

6C6C0000

detector 1 of the visible band

B4B40000

detector 2 of the visible band

D8D80000

detector 3 of the visible band

FCFC0000

detector 4 of the visible band

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