McIDAS Programmer's Manual
Version 2003
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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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