Input/output data specification for the TROPOMI L01b data processor
issue 9.0.0, 2018-04-01 – released
S5P-KNMI-L01B-0012-SD
Page 17 of 109
Band DEM Binning factor Across-track
ground pixel size
1 UV 8. . . 16 28 . . . 68 km
2 UV 1. . . 2 3.5 . . . 8.5 km
3 UVIS 1. . . 2 3.5 . . . 8.5 km
4 UVIS 1. . . 2 3.5 . . . 8.5 km
5 NIR 1. . . 2 3.5 . . . 8.5 km
6 NIR 1. . . 2 3.5 . . . 8.5 km
7 SWIR n/a 7 . . . 34 km
8 SWIR n/a 7 . . . 34 km
Table 2: Binning factors and across-track ground pixel sizes for Earth radiance measurements
4.3.3 Solar irradiance measurements
The Sun is visible in TROPOMI’s solar irradiance port every orbit for a period of approximately 1.5 minutes
around orbit phases 0.75
1
. Every 15 orbits - approximately once every calendar day - TROPOMI will be
commanded to perform a solar irradiance measurement. As the main purpose of the solar irradiance mea-
surement is to calculate top-of-atmosphere reflectance, the solar irradiance measurement follows the same
binning scheme as the Earth radiance measurements. The remaining parameters will be optimized for the
best signal-to-noise ratio. The signal-to-noise ratio is improved even further by averaging the solar irradiance
measurements within the L01b Processor.
4.3.4 Background measurements
The background signal for measurements will be calibrated in-orbit. For this to work, every measurement
should have accompanying background measurements in the same orbit. These background measurements
are performed using the exact same settings as the measurement they accompany. A different IcID for the
background measurement ensures that on-ground it is being processed as a background measurement. The
background measurements are performed on the eclipse side of the orbit.
4.3.5 Calibration measurements
Calibration measurements will be performed on the night side of the orbit, outside the SAA. The binning
scheme that is used for a calibration measurement depends on the objective of that measurement. Calibration
measurements that have a strong relation with Earth radiance measurements will use the same binning scheme
as Earth radiance measurements. Most calibration measurements however will use a so-called unbinned
scheme, that reads out all the pixels of the detector. For these measurements, the co-addition period may be
slightly longer than for Earth radiance measurements, to avoid data rate bottlenecks within the instrument or
the platform.
Since for instrument operations, the orbits are defined without any seasonal dependency, only a small part
of the orbit is guaranteed to be unaffected by the SAA throughout the seasons. This part of the orbit will be
used for calibration measurements, while the remainder of the orbit where the spacecraft is in eclipse will
be used for background measurements. This is shown in Figure 3. These background measurements are
susceptible for proton radiation too, but the L01b Processor will use a filter to avoid background measurements
taken in the SAA being used for in-orbit calibration
1
The orbit phase is defined as
1/(2π)
times the angle in radians traversed by the spacecraft since spacecraft midnight as seen from the
center of the Earth. Spacecraft midnight is the point on the night side of the Earth where the spacecraft crosses the orbital plane of the
Earth about the Sun. This makes the orbit phase a quantity that runs from 0 to 1, while the spacecraft moves between each spacecraft
midnight.