NASA has chosen to develop three small satellite missions designed to explore the Earth's dynamic systems under its Earth System Science Pathfinders (ESSP) program, one of which will be managed by the Jet Propulsion Laboratory.

JPL will provide mission management and payload development for CloudSat, an Earth-orbiting radar that was chosen as one of two alternative missions. The principal investigator for CloudSat is Dr. Graeme Stephens at Colorado State University.

CloudSat is a mission focused on understanding the role that thick clouds play in the Earth's radiation budget -- a balance of solar energy reaching the Earth and lost to space that ultimately controls the temperature of the Earth. CloudSat would use an advanced cloud-profiling radar to provide information on the vertical structure of highly dynamic tropical cloud systems. This new radar would enable measurements of cloud properties for the first time on a global basis, revolutionizing our understanding of cloud-related issues. CloudSat would launch in 2003.

CloudSat will fill a significant gap in the existing and planned Earth observation missions by measuring the vertical profile of clouds using active remote sensing (94-GHz radar) and a profiling oxygen A-band spectrometer/imager. CloudSat information will be enhanced by formation flying with the IceSat lidar, a NASA ice and cloud mission set to launch in 2001.

The estimated mission cost of CloudSat would be $144.6 million, with NASA contributing $119.6 million. Collaboration with Canada is being explored for the provision of critical components for CloudSat's cloud-profiling radar.

In addition to CloudSat, NASA has chosen one additional concept, the Volcanic Ash Mission (Volcam), as an alternate mission. Volcam would monitor volcanic clouds and aerosols from a geostationary orbit. CloudSat and Volcam will go through an extended development and technology assessment before NASA selects one as a primary mission and one as an alternate.

At the same time, NASA selected the Pathfinder Instruments for Cloud and Aerosol Spaceborne Observations - Climatologie Etendue des Nuages et des Aerosols, or Picasso-Cena mission, for development as a primary mission. Picasso-Cena, led by NASA's Langley Research Center, Hampton, VA, will fly instruments designed to address the role of clouds and small atmospheric particles known as aerosols and their impact on Earth's radiation budget.

These missions join NASA's two current ESSP missions, the Vegetation Canopy Lidar (VCL), which will launch in 2000, and the JPL-managed Gravity Recovery and Climate Experiment (GRACE), which will launch in 2001. The VCL mission will provide the first global inventory of the vertical structure of forests across Earth using a multi-beam laser-device. GRACE employs a satellite-to-satellite microwave tracking system between the two satellites to measure the Earth's gravity field and its time variability over five years.

The philosophy of the ESSP program is to achieve maximum science value while complementing existing or planned flight missions. The principal investigator is responsible for developing the flight mission hardware from selection to a launch-ready condition within 36 months, with minimal direct NASA oversight. The principal investigator and mission team are responsible for accomplishing the stated scientific objectives and delivering resulting data to the broader Earth science community and general public as expediently as possible.

JPL is a division of the California Institute of Technology.

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