This is the layout of the .l_mpl_binary level 1c spectra files
used as input for scia_retrieval_2d.
The purpose is to save disk space compared to plain ascii spectra files
and the format is basically using the binary representation of the numbers.
This format is currently not very portable and relies on
float and int being 32 bits (4 bytes) and endianness is not considered.
However, these limitations should not be important
as long as the binary files are prepared on the same machine on which
the retrieval code is run on.
Loading is handled in LimbNadir_IO.cpp by:
int Load_Limb_l_mpl_binary()| address | size | description |
|---|---|---|
| 0x0000 | (31 x 100) x char | text header containing metadata (number of header lines x 100 chars) (Looks for a hash # at the beginning of each 100 characters read and adjusts the number of header lines if the first character differs.) |
| 0x0c1c | int | number of tangent points nalt |
| 0x0c20 | int | number of spectral points npix |
| 0x0c24 | 5 x int | orbit state tuple: (orbit, state_in_orbit, state_id, nr_of_profiles, actual_profile) |
| 0x0c38 | 6 x int | date tuple: (year, month, day, hour, minute, second) |
| 0x0c50 | 10 x float | centre and corner latitudes and longitudes:(centre_lat, centre_lon, corner0_lat, corner0_lon, ..., corner3_lat, corner3_lon) |
| 0x0c78 | float | fractional phase of the orbit [0, 1) orbit_phase |
| 0x0c7c | npix x float |
spectral wavelengths |
0x0c7c + npix x sizeof(float) |
nalt x limb_data |
tangent point limb data |
limb_data:
| number | size | description |
|---|---|---|
| 0 | float | sub satellite point latitude |
| 1 | float | sub satellite point longitude |
| 2 | float | tangent point latitude |
| 3 | float | tangent point longitude |
| 4 | float | tangent point altitude |
| 5 | float | tangent point solar zenith angle |
| 6 | float | tangent point solar azimuth angle |
| 7 | float | tangent point line-of-sight angle |
| 8 | float | top-of-atmosphere solar zenith angle |
| 9 | float | top-of-atmosphere solar azimuth angle |
| 10 | float | top-of-atmosphere line-of-sight angle |
| 11 | float | satellite solar zenith angle |
| 12 | float | satellite solar azimuth angle |
| 13 | float | satellite line-of-sight angle |
| 14 | float | satellite altitude |
| 15 | float | Earth radius |
| 16 | npix x float |
spectral radiance values |
| 17 | npix x float |
spectral radiance relative uncertainties |