The Broadband Radiometer (BBR) is a passive sensor with broadband channels in the shortwave band and the shortwave-to-longwave bands. While CPR, ATLID, and MSI are sensors that retrieve physical quantities related to clouds and aerosols, the BBR determines the radiative energy balance at the upper edge of the atmosphere. The BBR provides clues to approach the quantitative relationship between clouds and aerosols and the radiation budget.
From BBR data, radiation fluxes at the top of the atmosphere are calculated for both shortwave (SW) and longwave (LW) signals. The fluxes for longwave data are derived from the difference between the shortwave and the shortwave-to-longwave bands. The choice of bands reflects the difference in wavelength between solar and terrestrial radiation.
To derive the radiation flux at the top of the atmosphere, it is necessary to consider the global directional integration of the radiance in the line of sight, which is the quantity directly measured by the BBR. Since clouds and other objects are three-dimensional and radiance varies depending on the direction of observation, obtaining radiance flux from data in only one direction can produce large errors. To reduce them, the BBR has three optical systems, which can acquire observation data from three directions (nadir view, forward view, and backward view) for a single point.
BBR observations provide radiance data from three-way views, which are combined with MSI data to calculate shortwave and longwave radiation fluxes at the upper edge of the atmosphere. In addition, vertical profile data from CPR and ATLID are combined to obtain the shortwave and longwave heating rates for each layer for every 500 m in height.
The BBR data are provided as a 4-sensor synergistic radiation balance product. The ESA will produce the BBR stand-alone products, L1b and L2a.
| Sensor type | Broadband radiometer |
|---|---|
| Developer | European Space Agency (ESA) |
| Channel | 150 km (Left side of the flight direction: approx. 115 km, Right side of the flight direction: approx. 35 km) |
| 0.25μm-50μm | |
| Dynamic range | SW: 0–450 Wm-2sr-1 |
| LW: 0-130 Wm-2sr-1 | |
| Accuracy |
SW: 2.0 Wm-2sr-1 LW: 1.5 Wm-2sr-1 |
| Footprint (IFOV) | 10 × 10 km |
| Sampling | 1 km |
