Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) is a Japanese-European collaborative earth observation satellite mission aimed to deepen understanding of the interaction process between clouds and aerosols and their effects on the Earth’s radiation. The outcome of this mission is expected to improve the accuracy of global climate change prediction. As one of instruments for EarthCARE, the Cloud Profiling Radar (CPR) is the world’s first space-borne Doppler cloud radar jointly developed by the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT). In Japan, the critical design review of the CPR has been completed in 2013, and CPR proto-flight model was manufactured and integrated until summer in 2015. Finally, the proto-flight test have been just started. This paper describes the design results and current status of CPR proto-flight test.
The Earth, Clouds, Aerosols and Radiation Explorer (EarthCARE) mission is joint mission between Europe and Japan
for the launch year of 2015. Mission objective is to improve scientific understanding of cloud-aerosol-radiation
interactions that is one of the biggest uncertain factors for numerical climate and weather predictions. The EarthCARE
spacecraft equips four instruments such as an ultra violet lidar (ATLID), a cloud profiling radar (CPR), a broadband
radiometer (BBR), and a multi-spectral imager (MSI) to observe aerosols, clouds and their interactions simultaneously
from the orbit. Japan aerospace exploration agency (JAXA) is responsible for development of the CPR that will be the
first space-borne W-band Doppler radar. The CPR is defined with minimum radar sensitivity of -35dBz, radiometric
accuracy of 2.7 dB, and Doppler velocity measurement accuracy of 1m/s. These specifications require highly accurate
pointing technique in orbit and high power source with large antenna dish. JAXA and National Institute of Information and Communications Technology (NICT) have been jointly developed this CPR to meet these requirements. In addition, new ground calibration technique is also being progressed for the launch of EarthCARE/CPR. This evaluation method will also be the first use for spacecraft as well as Doppler cloud radar. This paper shows the summary of the CPR design and verification status, and activity status of development of ground calibration method with a few results of experiment using current space-borne cloud radar (CloudSat, NASA).
The Tropical Rainfall Measuring Mission (TRMM) has been providing reliable global precipitation data since its launch
in 1997. It is expected that good handover to the Global Precipitation Measurement (GPM) mission at around early 2014
and GPM is expected to operate 5 years and to accumulate a reliable global long precipitation record. Currently, the dual
frequency precipitation radar (DPR), one of the major instruments onboard GPM core satellite, has been developed.
Although about twenty years global precipitation record will be obtained by the end of the GPM mission, there are still
high expectation for the longer precipitation record from the viewpoints of climate change monitoring, evaluation of the
numerical prediction models on global warming, and so on. Even the precipitation information becomes more important.
For these reasons, future precipitation measurement mission is started to study targeting the successive observation to
GPM. Mission requirements are gathered from GPM science community and are consolidated to the mission concept
during this study also the potential users and their expected requirements are defined. The most important scientific
target is the cloud-precipitation processes study, which is one of the uncovered topics in GPM mission. To fulfill this
requirement and potential users requirements, cloud and precipitation observation capability is required for this mission.
Considering the technology evolution, cloud radar (with current technology) or high sensitivity precipitation radar can
achieve the requirements. Preliminary feasibility study (accommodativeness to spacecraft) was done with the help from
JAXA’s space application program system engineering office.
The Cloud Profiling Radar (CPR) on EarthCARE satellite is the first spaceborne cloud profiling Doppler radar using Wband
frequency in order to measure vertical velocity of clouds and rain. The EarthCARE/CPR has -35dBZ in sensitivity
after 10km integration and less than 1 m/s in Doppler velocity measurement error. Because satellite velocity and beam
width spread Doppler spectrum and coherency is low, the measurement error of Doppler velocity is increased.
EarthCARE/CPR is the first Doppler radar, so we need to make simulation data for the algorithm development, but the
simulation itself is difficult in order to take into account these effects. The current method is calculated 2-dimentional
integration within illuminated area by antenna beam and hit by hit for all pulses, then it takes many computation times.
We developed the new simple calculation method, which is calculated using integrated antenna pattern, then the
computation time is decreased significantly. This paper is reported the comparison for, both methods.
The EarthCARE mission has been jointly proposed by European and Japanese scientists with the mission objective of
improving the understanding of cloud-aerosol-radiation interactions so as to include them correctly and reliably in
climate and numerical weather prediction models. This EarthCARE mission has been defined as an international
cooperative spacecraft mission between European Space Agency (ESA) and Japan Aerospace Exploration Agency
(JAXA) for the planned launch year of 2013th. The EarthCARE spacecraft equips four instruments, such as a cloud
profiling radar (CPR), an atmospheric backscatter lidar (ATLID), a multi-spectral imager (MSI) and a broadband
radiometer (BBR) to perform very accurate synergy observation to observe cloud and aerosol vertical profiles and
simultaneous radiative flux at the top of atmosphere. In this cooperation, JAXA is responsible for development of the
CPR which will be the first space-borne W-band radar with Doppler measurement capability. JAXA has developed this
Doppler radar for several years with Japanese National Institute of Information and Communications Technology
(NICT). The last year, preliminary design was finished and then fabrication and testing have been started. This
presentation shows the summary of the CPR preliminary design and reports the test status of the CPR engineering model
Global three-dimensional cloud distributions and their properties are important information to estimate the earth
radiation budget more precisely. The interactions between cloud particles and aerosols are also focused to improve
accuracies of climate model. In order to meet expectations of scientists developing climate models for global warming
problem, European and Japanese space agencies plan to launch a satellite called EarthCARE. The Cloud Profiling Radar
(CPR), which will be the first millimeter-wave Doppler radar in space, is installed on this satellite as one of main sensors
to observe clouds. This paper describes the latest design and development status of EarthCARE CPR.
The Tropical Rainfall Measuring Mission (TRMM) satellite performs 180-degree yaw maneuver (yaw-around) when the
solar beta angle which is the angle between the satellite orbit plane and the direction to the sun crosses the 0-degree The
yaw-maneuver is completed about 16 minutes (about 7000 km in flight length on the Earth) in the TRMM case. During
the yaw-around, the Precipitation Radar (PR) onboard TRMM continues nominal observation (but data processing is
limited to level-1 algorithms). Therefore very dense observation is realized during the yaw-around. Since nearly fixed
target (rain echo and surface echo) is observed by different incident angles in a short time, new information can be
obtained that cannot be obtained nominal observation. On the incident angle dependency of the sea surface echo, we can
avoid the uncertainties comes from the changes in the target. Range profiles of the sea surface echo of different incident
angles can be compared with the long-term global average data. The same approach can be used to quantitative
estimation of bright band structure such as blurring effect of the off-nadir incident angles. For convective echoes, the
non-uniform beam filling (NUBF) effect can be estimated by the different incident angle data and the data which
location is slightly offset from the center. More reliable path integrated attenuation (PIA) can be obtained from different
incident angle data and the NUBF can be estimated both by the range profiles of surface echo of off-nadir angle bin data
with an approach by Takahashi et al. (2006) and their change with the location within a footprint. Two NUBF cases are
demonstrated in this paper showing the horizontal sub-footprint size distribution of PIA. The results are confirmed by
the consistency of different angle data with slight offset location. In addition, this method is evaluated by the PIA
pattern data obtained from densely distributed (because of 180-degree yaw maneuver) data using the method similar to
the standard algorithm for TRMM/PR.