This release contains the following files, for copying to the specified directories: .../AAPP/sources/calibration/avhrcl/avhcal.txt .../AAPP/sources/preproc/avh2hirs_maia_2.1/cor_n17.dat .../AAPP/include/timang.h Then the following sections of AAPP should be rebuilt using the INST_3 command navnoaa amsuacl amsubcl avhrcl hirscl msucl avh2hirs_maia_2.1 Furthermore, the scientic and the software description has been updated aapp3_l.doc.Z Software Description of AAPP V3 aapp3_s.doc.Z Scientific Description of AAPP V3 --------- Comments --------- About cor_n17.dat and timang.h updates -------------------------------------- HIRS NOAA17 presents a mounting "error" of one pixel. This has been shown by Mike Chalfan beginning of July 2002. The plot of the best adjustment of the 2 instruments shows that it is quite constant in scanning correction (1.70deg) and near linear in time correction (3 different slopes). The noise in the scanning correction plot is due to the discretisation of the image in pixels, and is always less than one AVHRR pixel (1mrd). In order to get the best mapping for the level1d products the correction file for NOAA17 takes the raw time corrections but a constant value for the scanning correction (1.70deg). Each day the best alignment of the 2 instruments is computed from the local HRPT data of the LANNION station. If a drift of the values is observed during the next months the monitoring will be updated. For the navigation of the HIRS level1b data a shift of 1.7degree will be applied even if the mistake is of one HIRS pixel (1.8 degree). We consider that the navigation of AVHRR is a reference because it is controlled on landmarks. From those landmarks we deduce a spacecraft attitude error, which includes the orbit extrapolation error and any misplacement of the instrument on the satellite. The attitude is also applied for the HIRS navigation and so we need to introduce the relative shift observed, 1.7deg . The correction is introduced in the include file timang.h About avhcal.txt update ----------------------- Corrected radiance corrections for the AVHRR channel 4 of NOAA-17 AAPP CMS developers