Parasol
PARASOL is a CNES satellite of the Myriade series, flying within the A-Train and embarking the 3rd POLDER (POLarization and Directionality of the Earth’s Reflectances) instrument.
The aim of its mission is to characterise the radiative properties of clouds and aerosols by making the best use of the complementarity with the other instruments of the A-train constellation such as the CERES and MODIS radiometers on-board the AQUA satellite, the CALIPSO lidar and the CloudSat radar. In addition to these sensors, PARASOL carries out polarised and multi-directional reflectance measurements of the Earth/atmosphere system.
First of all, the data provided by the microsatellite makes it possible to specify the quantity and size distribution of aerosols over the ocean, as well as their turbidity index over land and to evaluate the radiative forcing in the solar domain. In addition, it contributes to the detection of clouds, the determination of their thermodynamic phase, their altitude and the estimation of the reflected flux in the solar domain. The integrated water vapour content can also be estimated.
In the A-Train, the synergy between the AQUA, CALIPSO, CLOUDSAT and PARASOL missions guides the choice of orbit parameters, which are:
- Heliosynchronous orbit
- Altitude: 705 km,
- Inclination: 98.1°
- Local time crossing the equator: 1:33 pm (up to December 2009 and then orbit drift)
Since November 16, 2011, PARASOL was placed in an orbit 9.5 km under the A-train and continues its nominal mission observing clouds and aerosols.
Due to the orbital drift, in July 2012 the local time crossing the equator was 3:00 PM.
Satellite
PARASOL satellite is composed of a microsatellite spacecraft bus of the Myriade series and a payload based on the POLDER instrument.
It was launched by Ariane 5 on December 18, 2004, as an auxiliary passenger of the Helios 2A military reconnaissance satellite. It operated until October 11, 2013 when its initial life span was expected 2 years.
The Myriade platform
PARASOL is the second in CNES’s Myriade series of microsatellites, it uses the same spacecraft bus as the DEMETER microsatellite which is probing electromagnetic disturbances related to earthquakes.
The main structure is a 60-cm cube opening out on each side for easy access to equipment. With its payload, the satellite stands about 80 cm tall, topped by a solar generator consisting of two articulated panels which, when deployed, is 1.70 m long (electrical power 180 W). Its weight at launch is 120 kg.
The attitude control system, precise to within 0.1°, is built around a star sensor, four reaction wheels and three magnetic torquers. Four one-Newton hydrazine thrusters control the satellite’s orbit.
The playload
The PARASOL payload includes:
- a computer and a 16 Gb mass storage unit,
- high-speed telemetry equipment,
- the POLDER instrument.
The PARASOL payload has 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
The POLDER-3 instrument of PARASOL is very similar to the POLDER instruments on-board the Japanese platform ADEOS and ADEOS-2. The only evolutions involve the orientation of the CCD array and the choice of the spectral bands.
With regards to the original POLDER instrument, the orientation of the telecentric lens matrix (284×364 pixels) has been rotated by 90° in order to shift the emphasis from daily global coverage to multidirectional imaging. Up to 16 successive acquisitions of the same point on ground with different viewing conditions are available.
Also, in order to make observations that can be compared with data from the CALIPSO lidar, a 1020 nm spectral band has been added.
The polarized 443 band of POLDER 1&2 has been replaced by a polarized 490 band.
Products
Level-1 and Level-2 products are daylight orbit passes whereas Level-3 products are global scale, daily and monthly syntheses (averages and statistics).
The processing of Level 1 was carried out by the CNES. The scientific processing of aerosol, clouds, radiation and water vapour products was done by the ICARE Data and Services Center of AERIS.
All products are archived and distributed by ICARE.
The products available in the catalog cover the period from March 4, 2005 to October 11, 2013.
PARASOL has capitalized on POLDER 1&2 heritage and major improvements have been achieved thanks to the second generation POLDER algorithms, such as the retrieval aerosol fine fraction over land or the refinement of cloud phase (a reprocessing of the POLDER 1&2 dataset has also been done at the end of 2007)