Instruments

The AAPP – ATOVS (Advanced TIROS Operational Vertical Sounder) and AVHRR (Advanced High Resolution Radiometer) Processing Package – performs the end-to-end processing of Sounding and Imager Data from the HRPT (High Resolution Picture Transmission) direct readout data stream of the TIROS-N/NOAA satellites and also their successors of the NOAA-KLM satellite series, from 1998 onwards. AAPP also processes data from the European METOP satellites

The data of the following instruments can be processed:

TIROS-N

• HIRS/2
• MSU
• AVHRR/2

NOAA-KLM

• HIRS/3
• AMSU-A
• AMSU-B
• AVHRR/3

NOAA-NN’

• HIRS/4
• AMSU-A
• MHS
• AVHRR/3

METOP

• HIRS/4
• AMSU-A
• MHS
• AVHRR/3
• IASI

NPP

• ATMS
• CrIS
• VIIRS (to be added later)

FY3

• MWTS and MWTS-2
• MWHS and MWHS-2
• IRAS
• MWRI

For the NOAA satellites, AAPP performs the following tasks:

• decommutation of the instrument data from the HRPT data frame
• extraction of the calibration information
• navigation of the data
• calibration of the data
• pre-processing of the data (cloud mask included)
• mapping of the data of the sounder instruments on a common instrument grid (HIRS, AMSU, MHS or IASI)
• deriving a set of statistical parameters from the AVHRR data in the HIRS FOVs

For METOP, AAPP ingests “EPS Level 0” files (one file per instrument), then performs navigation, calibration and pre-processing as above.

In the case of IASI, level 1 processing is performed by the OPS-LRS (Operational Software – Local Reception Station), which is an optional extension to AAPP and is based on the OPS software provided to EUMETSAT by CNES.

For NPP, the starting points for AAPP are Sensor Data Record files (SDR). For direct readout, you will need an external program, such as University of Wisconsin’s CSPP package, or NASA’s IPOPP package, to generate the SDR files. The same applies to FY-3, for which the China Meteorological Administration provide a processing package for direct readout use.

Supplementary Modules perform the processing of Orbital information and provide the following services:

• decoding of TBUS/TLE/SPOT Messages
• creation of a TBUS/TLE/SPOT data base
• creation of a data base of on board clock errors
• analysis of antenna reception conflicts
• antenna tracking coordinates

In the course of the processing the following files are created for each instrument:

• level 1a = instrument counts
• level 1b = instrument counts, navigation and calibration information appended
• level 1c = instrument reflectance factors or brightness temperatures, navigation and calibration information appended
• level 1d = instrument reflectance factors or brightness temperatures, mapped on one common instrument grid, navigation, calibration and contamination information appended

From the Navigation step the resulting files are created:

• TBUS/TLE/SPOT files
• ephemeris files
• clock error files
• tracking files

Inversion Packages

The output of AAPP is taken as input by level 2 processing packages that derive temperature and humidity profiles from the NOAA satellite instruments data by inverting the radiation transfer through the Earth’s atmosphere.

One such package developed and distributed by the University of Wisconsin-Madison is called “International ATOVS Processing Package” (IAPP). Details can be found on the IAPP Webpage. IAPP takes, as its main input, HIRS level 1d files from AAPP in little-endian byte order. If your input is big-endian (e.g. level 1d from EUMETSAT’s EARS-ATOVS service) you will need to byte swap! We can provide a script that will do this – contact the Helpdesk.