McIDAS Programmer's Manual
Version 2015
[Search Manual] [Table of Contents] [Go to Previous] [Go to Next]
The AVHRR (Advanced Very High Resolution Radiometer) instrument is a 5channel scanning radiometer. It generates data in HRPT, LAC and GAC modes.
The band information for the AVHRR sensor is provided in Appendix B, Satellite Information. 
The AVHRR navigation block is divided into 128 words.
The calibration block is not used. Instead, calibration is done dynamically on a linebyline basis to accommodate changing orbital conditions in the AVHRR/3 instrument. Therefore, the calibration data is contained in the data line prefixes. Refer to theTIRO and AVHR line prefix descriptions below, and Appendix D, POES AVHRR Calibration Information for additional information.
Because NOAA12 and 14 AVHRR use the older TIRO calibration while the NOAA15 AVHRR uses the newer AVHR calibration, changes have been made in the McIDASX area structure between the NOAA14 areas and the NOAA15 areas.
The AVHRR data block consists of data lines, each consisting of a line prefix and line data. The TIRO and AVHR line prefixes are different.
The TIRO line prefix for the data block contains the information below.
Region  Description 

8 bytes; values 1 through 5 (left to right), with three pad zeros in successive bytes, indicate the order the bands will appear in each pixel in the subsequent data section 
The TIRO line prefix is defined as follows:
The AVHR line prefix for the data block contains the information below.
Region  Description 

8 bytes; values 1 through 5 (left to right), with three pad zeros in successive bytes, indicate the order the bands will appear in each pixel in the subsequent data section 
The AVHR line prefix for the data block is defined as folllows.
The AVH3 calibration block is defined as follows.
Section  Byte Address  Description (preKLM data)  Description (KLM data) 

CAL 
0 
* Slope, Band 1 
** Slope #1, Band 1 

4 
Intercept, Band 1 
Intercept #1, Band 1 

8 
0 
Slope #2, Band 1 

12 
0 
Intercept #2, Band 1 

16 
Slope, Band 2 
Slope #1, Band 2 

20 
Intercept, Band 2 
Intercept #1, Band 2 

24 
0 
Slope #2, Band 2 

28 
0 
Intercept #2, Band 2 

32 
0 
Slope #1, Band 3a 

36 
0 
Intercept #1, Band 3a 

40 
0 
Slope #2, Band 3a 

44 
0 
Intercept #2, Band 3a 

48 
Slope, Band 3 
Slope, Band 3b 

52 
Intercept, Band 3 
Intercept, Band 3b 

56 
0 
Nonlinear Correction, Band 3b 

60 
Slope, Band 4 
Slope, Band 4 

64 
Intercept, Band 4 
Intercept, Band 4 

68 
0 
Nonlinear Correction, Band 4 

72 
Slope, Band 5 1 
Slope, Band 5 

76 
Intercept, Band 5 
Intercept, Band 5 

80 
0 
Nonlinear Correction, Band 5 
*  For preKLM data, slope is scaled by 2^30; intercept is scaled by 2^22.
**  For KLM data, slope is scaled by 1.E+07; intercept is scaled by 1.E+06 for vis/near IR; Slope/Intercept/Nonlinear terms are scaled by 1.E+06 for IR.
For a complete description of the AVHRR instruments on the satellites and their calibration, see the NOAAKLM User's Guide at http://www2.ncdc.noaa.gov/docs/klm or http://www2.ncdc.noaa.gov/docs/intro.htm. For instruments prior to 1988, see NOAA Technical Memorandum NESS 107, 1988 (now obsolete) or http://noaasis.noaa.gov/NOAASIS/ml/calibration.html. 
AVHRR data is transmitted as 10 bits and stored as 16 bits. The 10bit data is formatted as follows, with x representing a data bit and the rest being zerofilled after shifting.
The 16bit values from each of the five channels covering the same geographic area are stored interleaved in one image. The lines of data are stored in a timeordered sequence and as the satellite scans right to left.
[Search Manual] [Table of Contents] [Go to Previous] [Go to Next]