GOME2_L1_transmission
Variables
The table below lists the variables that are present in the HARP product that results from an ingestion of GOME2_L1_transmission
data.
field name 
type 
dimensions 
unit 
description 

datetime 
double 
{time} 
[seconds since 20000101] 
time of the measurement at the end of the integration time 
orbit_index 
int32 
absolute orbit number 

latitude 
double 
{time} 
[degree_north] 
center latitude of the measurement 
longitude 
double 
{time} 
[degree_east] 
center longitude of the measurement 
latitude_bounds 
double 
{time, 4} 
[degree_north] 
corner latitudes for the ground pixel of the measurement 
longitude_bounds 
double 
{time, 4} 
[degree_east] 
corner longitudes for the ground pixel of the measurement 
transmittance 
double 
{time, spectral} 
[] 
transmittance 
wavelength 
double 
{time, spectral} 
[nm] 
nominal wavelength assignment for each of the detector pixels 
integration_time 
double 
{time, spectral} 
[s] 
integration time for each pixel 
scan_subindex 
int8 
{time} 
relative index (015) of this measurement within a scan (forward+backward) 

scan_direction_type 
int8 
{time} 
scan direction for each measurement; enumeration values: forward (0), backward (1) 

cloud_top_pressure 
double 
{time} 
[hPa] 
cloud top pressure 
cloud_fraction 
double 
{time} 
[] 
cloud fraction 
solar_zenith_angle_toa 
double 
{time} 
[degree] 
solar zenith angle at top of atmosphere 
solar_azimuth_angle_toa 
double 
{time} 
[degree] 
solar azimuth angle at top of atmosphere 
viewing_zenith_angle_toa 
double 
{time} 
[degree] 
viewing zenith angle at top of atmosphere 
viewing_azimuth_angle_toa 
double 
{time} 
[degree] 
viewing azimuth angle at top of atmosphere 
index 
int32 
{time} 
zerobased index of the sample within the source product 
Ingestion options
The table below lists the available ingestion options for GOME2_L1
products.
option name 
legal values 
description 

band 
band1a, band1b, band2a, band2b, band3, band4 
only include data from the specified band (‘band1a’, ‘band1b’, ‘band2a’, ‘band2b’, ‘band3’, ‘band4’); by default data from all bands is retrieved 
data 
transmission, sun, moon, sun_reference 
retrieve the measured radiances (default), the transmission spectra (data=transmission), the sun measurement spectra (data=sun), the moon measurement spectra (data=moon) or the sun reference spectrum (data=sun_reference 
This definition is only applicable when: data=transmission
Mapping description
The GOME2 spectral data in the GOME2 L1b product is stored inside MDRs. There are separate MDRs for Earthshine, Calibration, Sun, and Moon measurements. In addition there are also ‘Dummy Records’ (DMDR) that can be present when there is lost data in the product. With HARP only Earthshine, Sun, and Moon measurements can be ingested.
Each MDR roughly contains a single scan. However, an MDR does not exactly correspond 1to1 with a GOME2 scan. This is an important fact to be aware of. The real situation is as follows:
Within a single scan (a scan takes 6 seconds) there are 16 Instrument Source Packets (covering 375ms each) coming from the satellite. Each ISP contains at most two readouts (there are two if the integration time for a band is 187.5ms (or 93.75ms)). The problem is that the two readouts of the first ISP of a scan contain the last measurement of the previous scan and the first measurement of the new scan. The second ISP contains data for measurements #2 and #3, the third for #4 and #5, etc. The last measurement of a scan will again be found in the first ISP of the next scan. Instead of shifting the data and grouping all data of a single scan together in a single MDR the Level 1a and Level 1b processors just place the MDR boundary at the start of the first ISP of a scan and terminate the MDR at the end of ISP 16. This means that in Level 1b (but also 1a) products the first measurement in an MDR will always be the last measurement of the previous scan.
Nearly all metadata for a readout (time, geolocation, viewing/solar angles, etc.) in an MDR are filled taking into account this same shift. This means that for retrieving the geolocation of the first readout of an MDR from the GEO_EARTH_ACTUAL record, one will in fact get the geolocation information of the last backscan pixel of the previous scan. However, the integration time metadata for the first readout in an MDR is not shifted this way (the GEO_EARTH information is also not shifted, by the way, and just contains the 32 geolocation pixels for the scan). As long as the integration time does not change from one scan to another this won’t impact anything, but the L1 products will contain invalid metadata for the first MDR readout if there is a change of integration time between two consecutive scans. In that case the calculated geolocation, angles, etc. of the first readout are values based on the integration time of the _new_ scan instead of the _old_ scan (e.g. the ground pixel will thus either be too large or too small). The (relative) good news to this is that, if a change in integration time occurs, the last pixel readout of the final scan with the ‘old’ integration time will never be valid and will have undefined values in the product (this is because the instrument prematurely terminates the final readout if a scan configuration change occurs). This means that the readout that has the ‘invalid’ metadata will never be a valid measurement anyway.
Because of all this, HARP will exercise the following rules during ingestion: 1) the first readout of the first MDR will always be ignored (and you will never see the last readout of the last scan, because it won’t be in the product) 2) the first readout after a change in measurement mode (i.e. earthshine vs. calibration vs. sun vs. moon) will be ignored 3) if a change in integration time occurs (for any of the bands) then the first readout (for all bands) of the next MDR will be ignored 4) if two MDRs are not continuous (i.e. there is a time gap) then the first readout of the second MDR will be ignored
GOME2 uses 6 bands for the main spectra (1A, 1B, 2A, 2B, 3, and 4). Within a scan each band can have its own integration time. There will be at most 32 readouts per scan (corresponding with an integration time of 187.5ms). If the integration time is 375ms, 750ms, 1.5s, 3s or 6s there will be 16, 8, 4, 2, or 1 measurement(s) respectively for this band in a scan. Some readouts may even cover multiple scans if the integration time is larger than 6s. HARP will combine the data for all bands into a single twodimensional pixel_readout array and uses a fixed resolution of 187.5ms for the variables. Because bands might have higher integration time this means that for those bands there will be multiple rows in the pixel_readout array for a single readout. Each of those multiple rows will be filled with the same measurement value. This comes down to breaking the measurement up into pieces of 187.5ms (the actual integration time can still be found from the integration_time variable). All metadata, such as geolocation, angles, etc. will also be ingested for this minimum integration time of 187.5ms and filtering on time and geolocation will also always be performed using the 187.5ms resolution.
If the band configuration changes somewhere during the orbit and a band filter is given, then only detector pixels that are inside the requested band for the duration of the whole orbit will be included. i.e. detector pixels that change band during the orbit will always be excluded when a band filter is given.
The table below details where and how each variable was retrieved from the input product.
field name 
mapping description 


datetime 
path 
/MDR[]/Earthshine/RECORD_HEADER/RECORD_START_TIME 
description 
The record start time is the start time of the scan and thus the start time of the second readout in the MDR. The start time for readout i (0..31) is thus RECORD_START_TIME + (i  1) * 0.1875 and the time at end of integration time (which is the time that is returned) is RECORD_START_TIME + i * 0.1875 

orbit_index 
path 
/MPHR/ORBIT_START 
latitude 
condition 
CODA product version < 12 
path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL/CENTRE_ACTUAL[INT_INDEX[band_id],]/latitude 

description 
The integration time index INT_INDEX[band_id] is the index of the band with the minimum integration time (limited to those bands that are ingested) 

condition 
CODA product version >= 12 

path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL_k[]/CENTRE_ACTUAL/latitude 

description 
The integration time index k is the index (starting with 1) of the minimum integration time such that UNIQUE_INT[k1] == min(INTEGRATION_TIMES[j]) for all bands j (0..9) that are ingeste. 

longitude 
condition 
CODA product version < 12 
path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL/CENTRE_ACTUAL[INT_INDEX[band_id],]/longitude 

description 
The integration time index INT_INDEX[band_id] is the index of the band with the minimum integration time (limited to those bands that are ingested). 

condition 
CODA product version >= 12 

path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL_k[]/CENTRE_ACTUAL/longitude 

description 
The integration time index k is the index (starting with 1) of the minimum integration time such that UNIQUE_INT[k1] == min(INTEGRATION_TIMES[j]) for all bands j (0..9) that are ingeste. 

latitude_bounds 
condition 
CODA product version < 12 
path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL/CORNER_ACTUAL[INT_INDEX[band_id],,]/latitude 

description 
The integration time index INT_INDEX[band_id] is the index of the band with the minimum integration time (limited to those bands that are ingested). The corners ABCD are reordered as BDCA. 

condition 
CODA product version >= 12 

path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL_k[]/CORNER_ACTUAL[]/latitude 

description 
The integration time index k is the index (starting with 1) of the minimum integration time such that UNIQUE_INT[k1] == min(INTEGRATION_TIMES[j]) for all bands j (0..9) that are ingeste. 

longitude_bounds 
condition 
CODA product version < 12 
path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL/CORNER_ACTUAL[INT_INDEX[band_id],,]/longitude 

description 
The integration time index INT_INDEX[band_id] is the index of the band with the minimum integration time (limited to those bands that are ingested). The corners ABCD are reordered as BDCA. 

condition 
CODA product version >= 12 

path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL_k[]/CORNER_ACTUAL[]/longitude 

description 
The integration time index k is the index (starting with 1) of the minimum integration time such that UNIQUE_INT[k1] == min(INTEGRATION_TIMES[j]) for all bands j (0..9) that are ingeste. 

transmittance 
path 
/MDR[]/Earthshine/BAND_1A[,]/RAD, /MDR[]/Earthshine/BAND_1B[,]/RAD, /MDR[]/Earthshine/BAND_2A[,]/RAD, /MDR[]/Earthshine/BAND_2B[,]/RAD, /MDR[]/Earthshine/BAND_3[,]/RAD, /MDR[]/Earthshine/BAND_4[,]/RAD 
wavelength 
path 
/MDR[]/Earthshine/WAVELENGTH_1A[], /MDR[]/Earthshine/WAVELENGTH_1B[], /MDR[]/Earthshine/WAVELENGTH_2A[], /MDR/Earthshine[]/WAVELENGTH_2B[], /MDR[]/Earthshine/WAVELENGTH_3[], /MDR[]/Earthshine/WAVELENGTH_4[] 
integration_time 
path 
/MDR[]/Earthshine/INTEGRATION_TIMES[] 
scan_direction_type 
path 
/MDR[]/Earthshine/INTEGRATION_TIMES[] 
description 
the scan direction is based on the subset counter of the measurement; 011: forward (0), 1215: backward (1) 

cloud_top_pressure 
path 
/MDR[]/Earthshine/CLOUD/FIT_1[] 
description 
If the minimum ingested integration time > 187.5ms then the corresponding cloud top pressures will be combined using logarithmic averaging. The cloud top pressure will be set to NaN if FIT_MODE in the CLOUD structure is not equal to 0 or if FIT_1 is set to a fill value (even when this holds for only one of the averaged items) 

cloud_fraction 
path 
/MDR[]/Earthshine/CLOUD/FIT_2[] 
description 
If the minimum ingested integration time > 187.5ms then the corresponding cloud fractions will be combined using averaging. The cloud fraction will be set to NaN if FIT_MODE in the CLOUD structure is not equal to 0 or if FIT_2 is set to a fill value (even when this holds for only one of the averaged items) 

solar_zenith_angle_toa 
condition 
CODA product version < 12 
path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL/SOLAR_ZENITH_ACTUAL[INT_INDEX[band_id],1,] 

description 
The integration time index INT_INDEX[band_id] is the index of the band with the minimum integration time (limited to those bands that are ingested). 

condition 
CODA product version >= 12 

path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL_k[]/SOLAR_ZENITH_ACTUAL[1] 

description 
The integration time index k is the index (starting with 1) of the minimum integration time such that UNIQUE_INT[k1] == min(INTEGRATION_TIMES[j]) for all bands j (0..9) that are ingeste. 

solar_azimuth_angle_toa 
condition 
CODA product version < 12 
path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL/SOLAR_AZIMUTH_ACTUAL[INT_INDEX[band_id],1,] 

description 
The integration time index INT_INDEX[band_id] is the index of the band with the minimum integration time (limited to those bands that are ingested). 

condition 
CODA product version >= 12 

path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL_k[]/SOLAR_AZIMUTH_ACTUAL[1] 

description 
The integration time index k is the index (starting with 1) of the minimum integration time such that UNIQUE_INT[k1] == min(INTEGRATION_TIMES[j]) for all bands j (0..9) that are ingeste. 

viewing_zenith_angle_toa 
condition 
CODA product version < 12 
path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL/SAT_ZENITH_ACTUAL[INT_INDEX[band_id],1,] 

description 
The integration time index INT_INDEX[band_id] is the index of the band with the minimum integration time (limited to those bands that are ingested). 

condition 
CODA product version >= 12 

path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL_k[]/SAT_ZENITH_ACTUAL[1] 

description 
The integration time index k is the index (starting with 1) of the minimum integration time such that UNIQUE_INT[k1] == min(INTEGRATION_TIMES[j]) for all bands j (0..9) that are ingeste. 

viewing_azimuth_angle_toa 
condition 
CODA product version < 12 
path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL/SAT_AZIMUTH_ACTUAL[INT_INDEX[band_id],1,] 

description 
The integration time index INT_INDEX[band_id] is the index of the band with the minimum integration time (limited to those bands that are ingested). 

condition 
CODA product version >= 12 

path 
/MDR[]/Earthshine/GEO_EARTH_ACTUAL_k[]/SAT_AZIMUTH_ACTUAL[1] 

description 
The integration time index k is the index (starting with 1) of the minimum integration time such that UNIQUE_INT[k1] == min(INTEGRATION_TIMES[j]) for all bands j (0..9) that are ingeste. 