POLDER/PARASOL news and events

POLDER/PARASOL full reprocessing and
new multi-sensor synergistic products – April 2017


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At the end of the PARASOL mission, CNES completed the final reprocessing of Level-1 data in 2014. ICARE completed the reprocessing of the PARASOL Level-2 and Level-3 products in 2015, using revised science codes as well as new codes provided by the French science team at LOA (University of Lille).
In addition to the HDF5 version of the products, released in 2016, global gridded Level-2 and Level-3 products are also available now in HDF5 format.
The Level-2 and Level-3 products are generated from the Level-1 data alone or in combination with other data sets. PARASOL stand-alone products include the Level-2 and Level-3 data sets and the PARASOL "CALTRACK" product (subset colocated with the CALIPSO/CALIOP subtrack).
More recently, an innovative algorithm, called "GRASP" (Generalized Retrieval of Aerosol and Surface Properties), has been developed to retrieve simultaneously many more parameters compared to the standard product. Finally, the unique synergistic "PM-L2” Level-2 product is derived from combined PARASOL and Aqua/MODIS observations.




2nd announcement
3rd International A-Train Symposium
18-21 April 2017, Pasadena Convention Center, California


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The 705-km Afternoon (A-Train) Satellite Constellation brings together a rich array of instruments to better understand Earth’s changing climate and environment. The 3rd International Symposium on the A-Train Satellite Constellation is an opportunity to learn more about the evolving capabilities of the A-Train system, and to engage other colleagues with similar interests.
To see the second official circular, click here.
Registration and abstract submission are now open. The deadline for abstract submission has been extended to December 16, 2016. There is no registration fee to attend. Additional information regarding the meeting is available on the symposium web site: https://atrain2017.org/




Release of PARASOL-MODIS unique synergy products

    Date: 2016/04
    Besides improvements brought to the standard POLDER/PARASOL Level-2 science codes (see below), a new science code has been developed, tested and validated. This code, named PM-L2, is based on the synergy between POLDER/PARASOL and MODIS/Aqua observations. Products are generated and distributed since April 2016. The output data sets are in the same grid as PARASOL standard products, at native 1/18 deg. spatial resolution for the cloud parameters and at 1/6 deg. resolution for the aerosol parameters. The algorithm makes synergetic use of the well-known specific capabilities of each sensor in the retrieval scheme, i.e. polarization for PARASOL, and large-range spectral measurements for MODIS, thus alleviating individual methodological limitations. This concept was underused thus far.
    The new data sets enable thorough analyses of cloud properties derived from each sensor individually (cloud cover, optical depth, thermodynamic phase). More importantly, they enable new parameters to emerge or to be derived with a higher level of confidence: cloud thermodynamic phase and aerosol optical thickness above cloud layers.
    Coincident colocated observations from other sensors of the A-Train constellation were also used (CALIPSO/CALIOP and CloudSat) to validate the cloud oxygen pressures and geometrical extent.
    The new aerosol and cloud parameters from PM-L2 are:
    • Cloud classification (upcoming documentation)
    • Cloud thermodynamic phase
    • Cloud top pressure (upcoming documentation)
    • Cloud geometrical thickness (upcoming documentation)
    • Aerosol optical thickness above cloud layers

    All PARASOL data sets now available in HDF format

    Date: 2016/03 - Update: 2016/09 for v1.01
    All PARASOL data products, starting from Level-1, are now available in HDF format (see online archive):
    L1_B-HDF: v1.01 - Top of the atmosphere radiances - Level-1
    OC2-HDF: v1.01 - Daily aerosol product over ocean - Level-2
    LS2-HDF: v1.01 - Daily aerosol product over land - Level-2
    RB2-HDF: v1.01 - Daily cloud, water vapor, and radiative budget - Level-2
    OC3-HDF: v1.01 - Monthly aerosol product over ocean - Level-3
    AC3-HDF: v1.01 - Monthly aerosol product over land - Level-3
    RB3-HDF: v1.01 - Monthly cloud, water vapor, and radiative budget - Level-3

    Full reprocessing of PARASOL data archive with new data sets available

    Date: 2015/09 - Update: 2016/09
    After the end of the PARASOL mission, CNES and ICARE completed a full-mission reprocessing in 2014. CNES carried out the final Level-1 PARASOL reprocessing using an improved algorithm incorporating all final in-flight radiometric calibration parameters (CNES document PARASOL_L1_final_reprocessing.pdf ). ICARE proceeded with the reprocessing of the PARASOL Level-2 and Level-3 products using revised science codes as well as new codes provided by the scientists.
    As a result, in addition to improved standard products, new, innovative atmospheric products also become available.
    The new aerosol and cloud parameters from the revised science codes are:
    • Uncertainty of AOT (Level-2 aerosol over ocean) (upcoming description)
    • Aerosol altitude (Level-2 aerosol over land) (upcoming description)
    • CLOud VErtical Structure (CLOVES) parameters : Cloud top and middle oxygen pressure, multilayer flag,
    • and cloud geometrical extent (Level-2 Earth radiation budget, water vapor and clouds)
    For aerosol retrievals over ocean, code revisions include:
    • improvement of aerosols non-spherical models
    • improvement of cloud mask
    • implementation of see-ice mask
    • update of ancillary data
    for aerosol retrievals over land:
    • implementation of higher resolution land biome map
    and for cloud and radiative budget products:
    • update of the solar irradiance.
    Scientists completed the quality control. Invalid orbits of some Level-2 products (OC2, LS2, RB2) were removed, a few minor fixes were incorporated in a new version of RB2 (v21.22), and all derived Level-3 products (OC3, AC3, RB3) were generated. The public release occurred in September 2016. Here is a summary of the latest version numbers (see also the ICARE online catalogue):
    L1_B: v03.02 - Top of the atmosphere radiances - Level-1
    OC2: v11.11 - Daily aerosol product over ocean - Level-2
    LS2: v10.11- Daily aerosol product over land - Level-2
    RB2: v21.22 - Daily cloud, water vapor, and radiative budget
    PM-L2: v3.00 - Daily aerosol and cloud product from combined PARASOL-MODIS observations - Level-2
    PR_ATM: v.12.07.2 - Daily and monthly global gridded atmosphere products - Level-3
    OC3: v11.11 - Monthly Aerosol Product over Ocean - Level 3
    AC3: v10.11 - Monthly Aerosol Product over Land - Level 3
    RB3: v08.06 - Monthly Cloud & Radiative Budget Products - Level 3
    A table with the version history and collection information of the PARASOL products will be provided in 2016.

    PARASOL Level-1 and Level-2-and-up Data Reprocessing Completion

    Date: 2015/06/08
    After 9 years in orbit, the PARASOL mission has gone well beyond the 2-year lifespan expected at the beginning of the mission. PARASOL flew nearly 5 years in formation with other instruments of the A-Train constellation of satellites, providing coincident observations (available at ICARE as well). The good quality of the measurements and innovative inversion methods lead to various global climatologies and unique atmospheric products.
    Following the end of the mission, the reprocessing of PARASOL Level-1 data and all atmosphere products using revised algorithms was carried out from April to November 2014. This is the first step of a large-scale reprocessing of all POLDER/PARASOL data. Indeed, the reprocessing of POLDER-1 and POLDER-2 will be carried out later in 2015 to get a consistent POLDER/PARASOL archive with new calibration information. Ultimately, it will improve their usefulness in climate studies.
    The new PARASOL data records (L1_B.v03.02, OC2.v11.11, LS2.v10.11) will replace the previous versions as soon as the current validation process is over (in mid-2015). The records will span the entire duration of the scientific mission, i.e. from March 12, 2005 to October 11, 2013 (8 years and 7 months).
    All ICARE PARASOL web pages are currently being revised to include the latest information on the PARASOL mission, data products and data access.

    PARASOL Level-1 and Level-2 data reprocessing underway
    September 2014


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    The PARASOL Level-1 data and all atmosphere products are currently being reprocessed from the beginning of the mission onward using revised algorithms. The Level-1 reprocessing, performed by CNES, began in April 2014 and new files are transferred to ICARE for Level-2-and-up products reprocessing. As of September 1, 2014, PARASOL data from March 2005 to mid-2008 are available at ICARE. The reprocessing of the whole PARASOL archive (until October 2013) is expected to be completed by the end of 2014.
    Changes to the Level-1 algorithm include improved radiometric calibration. For aerosol products over ocean, changes include the calculation of uncertainties, improvement of aerosol non-spherical models and cloud mask, and the implementation of a sea-ice mask. Over land, changes include the use of a higher resolution land biome map and the retrieval of the altitude of the aerosol layer. For cloud and radiative budget products, the solar irradiance was updated.

    Data services related to PARASOL will switch to the latest version of all products (L1_B.v03.02, OC2.v11.11, LS2.v10.11) when the reprocessing is complete.




    December 2013: Innovative atmospheric products
    over 8 years of PARASOL observations


    Time series of aerosol optical thickness observed by
    PARASOL. Photo credit: CNES/LOA/LSCE/ICARE.

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    During its life span of 9 years in orbit, the PARASOL mission provided 8 years and 7 months of global aerosol and cloud observations from mid-March 2005 to mid-October 2013 (see also the previous highlight on PARASOL). PARASOL was within the A-Train constellation during nearly 5 years, providing observations coincident with other instruments.

    The scientific outcome of the mission fulfills and even exceeds the original objectives of the mission. PARASOL contributed to global characterization of aerosol and cloud radiative and microphysical properties. The image on the left (Click here for the full resolution image) shows global seasonal averages of aerosol optical thickness. Many other climatologies of aerosols, clouds, water vapor, and earth radiation budget have been produced and are publicly available (see PARASOL gallery). Moreover, the good quality of the measurements and innovative inversion methods led to unique science products. Thanks to polarization, it is possible to get the size of the droplets at the top of the clouds or information on aerosols even over bright surfaces. Also, the combination of POLDER observations with other observations from the constellation, such as the lidar and/or the radar, led to new parameters not envisioned at first, e.g. the macro-physical properties of clouds (altitude and geometrical thickness) or the presence and the quantization of aerosol plumes over cloudy areas.

    The scientists are pursuing the improvement of the science algorithms using PARASOL data alone or combined with other data sets.

    The full archive of PARASOL observations will be reprocessed in 2014 and the latest version of all products will be available at the ICARE Data and Services Center.




    December 2013: The PARASOL mission ended
    after more than 8 years of service


    The last PARASOL images in natural and polarized light
    above the Kamchatka Peninsula. Photo credit: CNES.

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    These images are the last taken by PARASOL in natural (left) and polarized light (right) above the Kamchatka Peninsula. Click here for the full resolution image.

    The PARASOL mission ended on December 18, 2013, exactly 9 years after it was launched on December 18, 2004. The PARASOL scientific mission started on March 12, 2005 after a 3-month commissioning phase. In December 2009, PARASOL left the A-train orbit but kept acquiring observations in science mode while slowly drifting toward later overpass times. The science mission ended on October 11, 2013, when the decommissioning phase begun. The satellite was shut down permanently on December 18, 2013.

    The PARASOL mission is a success in demonstrating the usefulness of directional polarized measurements. Scientists now have to be patient and wait several years for polarization or directional measurements, until the 3MI mission onboard EPS-SG takes over.

    The full archive of PARASOL observations will be reprocessed in 2014 and the latest version of all products will be available at the ICARE Data and Services Center.




    Drift of PARASOL overpass time is accelerating


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    The Parasol project team informs the scientific community that the overpass time of the PARASOL mission is departing more and more rapidly from its original value (1:30 pm). The mission has gone well beyond its expected duration and the inclination of the spacecraft has not been maintained for years causing the drift to increase rapidly in the afternoon. Parasol is currently crossing the equator at approximately 3:00 pm local time. This drift does not significantly affect the quality of the products, but leads to a significant modification on solar geometries during acquisitions.

    Furthermore, please be reminded that since February 2012 there is no more overlapping at the equator with the other sensors of the A-Train constellation.




    PARASOL descend du Train / PARASOL gets off the Train


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    Après presque 5 ans de mesures simultanées avec les satellites de l'A-Train, le microsatellite PARASOL a quitté sa position au sein de la constellation à 12:48 TU, le 2 décembre 2009. La manoeuvre d'abaissement d'orbite réalisée par les équipes opérationnelles du CNES a permis d'atteindre une orbite à 3.9 km sous l'A-Train. PARASOL avait rejoint la constellation A-Train début février 2005. Depuis plusieurs mois déjà, la trace au sol de PARASOL dérivait lentement vers l'Est par rapport à celle des autres satellites de l'A-train car les réserves en carburant disponibles n'avaient pas permis de suivre les dernières manoeuvres d'inclinaison de la constellation A-train réalisées au printemps 2009. Cependant les mesures étaient encore en phase avec celles des autres capteurs. Sur la nouvelle orbite atteinte par PARASOL, cette quasi-simultanéité des mesures ne se reproduira désormais qu'à intervalles réguliers et pendant une durée limitée à quelques jours. Le CNES a décidé de positionner PARASOL un peu en dessous du A-train pour minimiser les risques en cas de défaillance du satellite et garantir ainsi la sécurité des autres satellites de la constellation. En effet, initialement prévu pour 2 ans, PARASOL atteindra ses 5 ans de mission nominale en mars 2010. PARASOL fêtera donc en solitaire son cinquième anniversaire en orbite le 18 décembre prochain mais poursuit néanmoins normalement sa mission d'observation des nuages et des aérosols.

    After collecting observations synchronous with the other satellites from the A-Train for almost 5 years, PARASOL was moved to a lower orbit (3.9 km beneath) at 12:48 UT on December 2, 2009. The maneuver was performed by the CNES flight operations teams. The microsatellite PARASOL had joined the A-Train constellation in early February 2005. PARASOL orbit tracks have been slowly drifting eastward these past few months, due to insufficient fuel supplies that prevented PARASOL to be part of the last inclination maneuver performed by the other A-Train satellites in Spring 2009. However, observations were still in phase with the other sensors. On the new orbit, observations from PARASOL will no longer be simultaneous with the other sensors, except for only a few days at regular intervals. CNES's decision to position PARASOL to a lower orbit was motivated by safety reasons to minimize the risk of collision, should PARASOL begin to fail. While the expected duration of the PARASOL mission was 2 years, it will reach 5 years in March 2010. On December 18, 2009, PARASOL will celebrate its 5th anniversary in orbit, alone, yet pursuing its mission of observation of clouds and aerosols.




    PARASOL: 4 years in orbit


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    In March 2009, ICARE celebrates the 4th anniversary of PARASOL successful operations. PARASOL is a microsatellite launched by CNES on December 18, 2004. It carries a wide-field imaging radiometer/polarimeter called POLDER (Polarization and Directionality of the Earth's Reflectances). PARASOL is part of the A-Train constellation, and contributes to an overall strategy to observe clouds and aerosols from multiple sensors on the same orbit. Originally scheduled to last 2 years, the mission was reconducted indefinitely, in consideration of the instrument good performance and scientific value. The ICARE Data and Services Center generates derived cloud and aerosol science products routinely, usually within 24-48 hours of data acquisition. Science products have been operationally produced and distributed since March 2005, at the end of the satellite commissioning phase. Other than a few scattered incidents, PARASOL did not experience any major problem, and only very few downtimes occurred. Over 4 years's worth of PARASOL data are now available in the ICARE archive.


    Complete Reprocessing of POLDER Atmosphere Products
    and New Distribution Scheme for POLDER Products


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    A reprocessing of the entire POLDER-1/POLDER-2 archive was completed in November 2007 to produce all atmosphere products (Aerosols and Clouds) with the latest generation of science algorithms used to process the PARASOL data, such that a consistent POLDER-1, POLDER-2, and POLDER-3/PARASOL archive is now available.
    On that occasion, POLDER distribution services for atmosphere products are transferred from CNES/CPP to ICARE. The ICARE Data and Services Center is now responsible for the processing, archive, and distribution of POLDER atmosphere products, in line with the PARASOL mission. From now on, all POLDER level-1 and atmosphere products may be downloaded from the ICARE website.