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NAMMA Second Generation Airborne Precipitation Radar Table of Contents
The Second Generation Airborne Precipitation Radar (APR-2) is a dual-frequency (14 GHz & 35 GHz), Doppler, dual-polarization radar system that includes digital, real-time pulse compression, extremely compact RF electronics, and a large deployable dual-frequency cylindrical parabolic antenna subsystem. This system measures radar reflectivity and doppler velocity at both the Ku- and Ka-band. The APR-2 radar flew on the NASA DC-8 aircraft during the NAMMA field experiment. It was designed to emulate the GPM core satellite's Ku- and Ka-band radars. The main reason to build and deploy the APR-2 was to gain knowledge that could subsequently be applied to the design and use of spaceborne rain radars. CampaignThese data files were generated during support of the NASA African Monsoon Multidisciplinary Analyses (NAMMA) campaign, a field research investigation sponsored by the Science Mission Directorate of the National Aeronautics and Space Administration (NASA). This mission was based in the Cape Verde Islands, 350 miles off the coast of Senegal in west Africa. Commencing in August 2006, NASA scientists employed surface observation networks and aircraft to characterize the evolution and structure of African Easterly Waves (AEWs) and Mesoscale Convective Systems over continental western Africa, and their associated impacts on regional water and energy budgets. For more information about the NAMMA Campaign, go to the NAMMA web site: http://namma.nsstc.nasa.gov/
The APR-2 system includes a real-time pulse compression processor, a fully-functional control and timing unit, and a very compact LO/IF module, all of which could be used in spaceborne applications. The cylindrical reflector antenna and linear feed array for the spaceborne PR-2 have been replaced by traveling wave tube amplifiers (TWTAs), front-end electronics, and an offset parabolic reflector antenna with mechanical scanning. The APR-2 operational geometry is shown in Figure 1 below; it looks downward and scans its beam across-track, with each scan beginning at 25 degrees to the left of nadir and ending at 25 degrees to the right. It uses the same scanning antenna reflector as that used for the Airborne Rain Mapping Radar (ARMAR), which consists of a 0.4 m offset reflector antenna with a mechanically scanned flat plate. The APR-2 antenna feed is a dual-frequency feed (13.4 and 35.6 GHz) and the aperture at 35.6 GHz is under-illuminated to provide matched beams at the two frequencies. This choice results in poor Doppler accuracy at Ka-band, but is needed for rain retrieval.
APR-2 Parameters are shown in Table 1 below:
Table 1 Additional information on the development and specifics of APR-2 can be viewed at this Jet Propulsion Lab web site: http://trmm.jpl.nasa.gov/apr.html File Naming ConventionEach HDF (Hierarchical Data Format) data file will have a corresponding jpg (JPEG Interchange Format) browse file. There is also an animation file included in AVI format (Audio Video Interleave). Sample data, browse and video files are shown below:
where, Data Format These data files are in HDF (Hierarchical Data Format) format and are similar to that from the TRMM Precipitation Radar. Measurements included within the data files are:
The data producer has provided a word document, NAMMA06_APR2_Format_HDFv41.doc, which explains the data format in detail, and also addresses known problems and other issues. These data can be read with most any HDF reader, thus no sample read software is supplied by the data producer. More information about HDF may be found at the HDF group homepage. Contact InformationUsers are invited to address questions and provide feedback to the contact below.
To order these data or for further information, please contact:
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