Payload
The Parasol Payload is composed of a set of elements and sub-systems based on the Polder instrument developed for a launch on board the Japanese platform ADEOS and ADEOS-2. The main evolutions involve the spectral bands.
The Parasol payload will have the following characteristics :
total mass | about 30 kg |
volume | about 0.5 x 0.5 x 0.3 m3 |
Power consumption (imaging mode) | 77 W |
Mean power | 29 W |
data rate | 880 bits/s |
It consist basically of a digital camera composed of a 284x364 pixels CCD detection matrix, a wide field of view telecentric optics (± 51° along the great axis) and of a rotating wheel carrying spectral and polarized filters.
There are 15 filters (plus an obscurity current measure), and could cover a spectral domain ranging from 443 to 1020 nm. For some wave length, 3 filters measure the linear polarization of the incoming light in three directions separated by 120°, thus allowing to supply the Stokes parameters and the total radiance. Moreover, the acquisition of an image sequence every 20 secondes enable the observation of one natural target from different directions.
Compared to Polder, the telecentric optics array has been turned 90 degrees to favour multidirectional viewing over daily global coverage. Likewise, a 1020-nm waveband has been added to conduct observations for comparison with data acquired by the lidar on Calipso, one of its companion satellites.
The Polder 443 P band was replaced by the 490 P band and the Polder 490 band was replaced by the 1020 band.
The radiometric performances of the Parasol payload are similar to the Polder ones. The vicarious calibration methods, based on the observation of natural targets (no calibration system on board), are also the same than the Polder ones.
The Parasol spectral bands
In order to correct from absorption effects, spectral sensitivities
of all Parasol bands are given in the spectrum file.
Polder channels | Bandwidth | Parasol channels | Rationale |
443P | 20 nm | cancelled | Polarization moved to 490 nm |
443 | 20 nm | 443 no change but high dynamic | Cloud detection, Drop of ocean color applications |
490 | 20 nm | 490P addition of polarization | Aerosol retrieval, Cloud pressure |
565 | 20 nm | 565 high dynamic | Lidar at 532 nm |
670P | 20 nm | 670P no change | Aerosol retrieval, Cloud properties |
865P | 40 nm | 865P no change | Aerosol retrieval, Cloud properties |
763 | 10 nm | 763 no change | Cloud oxygen pressure by Differential absorption technique in Oxygen A band |
765 | 40 nm | 765 no change | |
910 | 20 nm | 910 no change | Water vapor retrieval |
/ | 20 nm | 1020 new channel | Lidar at 1064nm, Aerosol retrieval |