Radiometric Calibration Mode
The radiometric calibration mode product consists of the dark offset and gain coefficients that shall be used to update the OLCI radiometric calibration Auxiliary Data File (ADF) used in Earth observation mode.
This product, OL_1_RAC, which is not available to the user, includes one measurement file and one annotation file, described below. The metadata information is gathered in a SENTINEL-SAFE product manifest.
The measurement file, radiometric_coef.nc, includes the dark offset and gain coefficients and is described in the following table. Only the main variables and their dimensions are reported, not their associated attributes.
| Element name | Description | Dimension |
| Specific Dimensions | ||
| detectors | Number of instrument detectors per frame (covering the five cameras). | 1 |
| bands | Number of OLCI bands, excluding the smear band. | 1 |
| bands_total | Number of OLCI bands, including the smear band. | 1 |
| dark_pixels | Number of dark pixels for the five OLCI cameras. | 1 |
| blank_pixels | Number of blank pixels for the five OLCI cameras. | 1 |
| Included Variables | ||
| dark_offset_coefficients | Dark offset coefficients for all pixels. | bands_total detectors |
| dark_current_coefficients | Dark offset coefficients for all pixels. | bands_total detectors |
| gain_coefficients | Dark offset coefficients for all pixels. | bands detectors |
| shutter_mean_dark_pixels_time | Time average of the dark pixels of the five cameras at the 21 nominal bands plus the smear band, all acquired in shutter position. | bands_total dark_pixels |
| shutter_mean_blank_pixels_time | Time average of the blank pixels of the five cameras at the 21 nominal bands plus the smear band, all acquired in shutter position. | bands_total blank_pixels |
| diffuser_mean_dark_pixels_time | Time average of the dark pixels of the five cameras at the 21 nominal bands plus the smear band, all acquired in diffuser position. | bands_total dark_pixels |
| diffuser_mean_blank_pixels_time | Time average of the blank pixels of the five cameras at the 21 nominal bands plus the smear band, all acquired in diffuser position. | bands_total blank_pixels |
The coefficients annotation file, RC_annotation.nc, contains:
- quality information for each instrument detector, indicating if the percentage of valid pixels used in the time average of the dark offset coefficients computation is below a specific threshold and if the percentage of valid pixels used in the time average of the gain coefficients computation, is below another specific threshold
- telemetry statistics providing the minimum, maximum and mean values of measured temperatures for each sub-sequence of the calibration sequence (i.e. while the Calibration Mechanism (CM) is in shutter position, or while it is in diffuser position).