McIDAS Programmer's Manual
Version 2003

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GOES-7

GOES-7 produced data in two different modes:

Most GOES-7 data after 24 March 1987 (Julian day 87083) is AAA. This section documents the mode AAA for the IR and VAS instruments. Word 52 of the area directory contains the source type AAA.

The VAS senses the atmosphere for a given spatial location in up to 12 different IR spectral bands and one visible band. All or some of the IR bands may be included in a single VAS type area. The visible, however, may be contained in a separate area of VISR type. As a result, it may require two areas to contain the total information transmitted by the satellite during a given time period.

GOES-7 AAA directory block

Word Value Description

14

 

number of spectral bands

19

 

band filter map; a bit is set to one for each band appearing in the area

52

AAA

image source type; 4 bytes ASCII

53

RAW

calibration type; 4 bytes ASCII

GOES-7 AAA data block

The line prefix consists of a 4-byte validity code, 512 bytes of IR common documentation, and 116 bytes of VAS calibration information organized as follows.

Bytes Description

4

day, yyddd

4

time of the scan, hhmmss

4

scan number (satellite coordinate line number)

104

13 eight-byte groups (1 per possible band) each containing:
channel number - 2-byte binary integer (see the table on the next page)
number of spins - 2-byte binary integer
unused - 4 bytes

The line prefix also contains 4, 8, 12 or 16 bytes of band list information; one byte for each band plus up to three bytes to round to the nearest whole word.

The structure of a VAS area is complicated by two facts:

What does appear on a given line is indicated in the band list section, which acts as an index for the line. Only the leftmost n bytes of the band list contain nonzero data, with n being the actual number of bands contained in each element of the line. The I th byte of the band list corresponds to the I th 16-bit pixel in each element of the line. Unused band list bytes are filled with binary zeros; the data in the unused pixel locations may not be zero, but in any case should be ignored.

The channel numbers range from 1 to 38; channel 39 exists but has never been put into service. Each is described in the table below.

Channel Detector Size Location Spectral band

1

HGCDTE

large

upper

1

2

HGCDTE

large

upper

2

3

HGCDTE

large

upper

3

4

HGCDTE

large

upper

4

5

HGCDTE

large

upper

5

6

INSB

large

upper

6

7

HGCDTE

large

upper

7

8

HGCDTE

large

upper

8

9

HGCDTE

large

upper

9

10

HGCDTE

large

upper

10

11

INSB

large

upper

11

12

INSB

large

upper

12

13

HGCDTE

large

lower

1

14

HGCDTE

large

lower

2

15

HGCDTE

large

lower

3

16

HGCDTE

large

lower

4

17

HGCDTE

large

lower

5

18

INSB

large

lower

6

19

HGCDTE

large

lower

7

20

HGCDTE

large

lower

8

21

HGCDTE

large

lower

9

22

HGCDTE

large

lower

10

23

INSB

large

lower

11

24

INSB

large

lower

12

25

HGCDTE

small

upper

3

26

HGCDTE

small

upper

4

27

HGCDTE

small

upper

5

28

HGCDTE

small

upper

7

29

HGCDTE

small

upper

8

30

HGCDTE

small

upper

9

31

HGCDTE

small

upper

10

32

HGCDTE

small

lower

3

33

HGCDTE

small

lower

4

34

HGCDTE

small

lower

5

35

HGCDTE

small

lower

7

36

HGCDTE

small

lower

8

37

HGCDTE

small

lower

9

38

HGCDTE

small

lower

10

For a given spectral band, only one detector size is used in an area. However, two channels representing different positions of the detector for a particular band may appear in a single area although they may not appear on the same line. For example, channels 8 and 20 may appear in the same area, but not channels 8 and 36.

GOES-7 AAA navigation block

Unless otherwise noted, the words in the GOES-7 navigation block are twos-complement binary integers.

Word Value Description

1

GOES

navigation type (ASCII characters)

2

 

satellite ID, year, and Julian day, ssyyddd

3

 

nominal start time of the image, hhmmss

4 - 12
4
5
6
7
8
9
10
11
12


1

orbit parameters
orbit type
epoch date (ETIMY), yymmdd
epoch time (ETIMH), hhmmss
semimajor axis (SEMIMA), km * 100
orbital eccentricity (ECCEN) * 1000000 (unitless)
orbital inclination (ORBINC), deg * 1000
mean anomaly (MEANA), deg * 1000
argument of perigee (PERIGEE), deg * 1000
right ascension of ascending node (ASNODE), deg * 1000

13 - 15
13
14
15

 

attitude parameters
declination of satellite axis (DECLIN), dddmmss (+=north)
right ascension of satellite axis (RASCEN), dddmmss
picture center line number (PICLIN)

16

 

spin period (SPINP); the satellite period, in microseconds, or the spin rate in revolutions/minute

17 - 20
17
18


19
20

 

frame geometry
total sweep angle, line direction (DEGLIN), dddmmss
number of scan lines (LINTOT), nnlllll where nn is the
number of sensors and lllll is the number of scans; total
number of lines is nn * lllll
total sweep angle, element direction (DEGELE), dddmmss
number of elements in a scan line (ELETOT)

21 - 30
21
22
23
24
25
26
27
28
29
30











0

camera geometry
forward-leaning (PITCH), dddmmss
sideways-leaning (YAW), dddmmss
rotation (ROLL), dddmmss
reserved
east/west adjustment (IAJUST) in visible elements (+ or -)
time computed by IAJUST from the first valid landmark of the day (IAJTIM), hhmmss
reserved
angle between VISSR and sun sensor (ISEANG), dddmmss
reserved for later implementation of *SKEW*
reserved

31 - 38
31
32
33
34
35
36
37
38

 

betas for this area
scan line of the first beta
time of the first beta scan line (beginning), hhmmss
time of the first beta scan line (continued), milliseconds*10
beta count 1
scan line of the second beta
time of the second beta scan line (beginning), hhmmss
time of the second beta scan line (cont.), milliseconds*10
beta count 2

39-128
39

40
41-120
121-128

 

gammas for this area
gamma, element offset * 100; this is the nominal offset at
time zero of this day
gamma-dot, element drift per hour * 100
reserved
memo; up to 32 ASCII characters of comments

GOES-7 AAA calibration block

The calibration block is composed of the following data.

Word Value Description

1

 

sensor source number

2

 

date, yyddd

3

 

time, hhmmss

4 - 9

 

radiance equation coefficients, array IAB(2,38)

80 - 117

 

radiance equation coefficients scale factors, IFAB(38)

118-128

0

 

Transforming the VAS raw IR values into brightness temperatures is accomplished via the intermediate computation of calibrated VAS radiances. The array IAB contains two coefficients for each of the 38 channels; IFAB contains one scale factor for each channel.

If the channel is ICHAN, compute the radiance for the raw value P using:

AB1 = IAB (1,ICHAN)
AB2 = IAB (2,ICHAN)
FAB = 2.**(15-IFAB (ICHAN))
R = (AB2 * P /32. - AB1) / FAB

The raw value P is divided by 32 because the data is stored as 15-bit numbers, but the coefficients expect 10-bit numbers.


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