A geostationary microwave sounder, GeoSTAR, capable of providing continuous monitoring every 15 minutes of atmospheric temperature, water vapor, clouds, precipitation, and wind in the presence of clouds and precipitation, which will add tremendously to our ability to observe rapidly evolving dynamic atmospheric phenomena, such as hurricanes and severe storms, monsoonal moisture flow, and atmospheric rivers, has been developed at the Jet Propulsion Laboratory. GeoSTAR uses aperture synthesis to overcome the difficulty of attaining adequate spatial resolution from geostationary orbit. It is made possible with new technology that has now been developed and fully tested. Low-risk mission development can start as soon as funding becomes available. The sensor can be hosted on a commercial communications satellite, which could reduce the cost substantially. Plans have been developed at JPL for such a mission, called “GeoStorm”, focused on observing severe convective storms – tropical cyclones, mesoscale convective systems, and extratropical cyclones – with a goal of improving our understanding, modeling and prediction of these destructive phenomena. It can equally well be configured as an operational mission, where the goal is to collect data for immediate assimilation into regional forecast systems, provide “now-casting” as the storms unfold, and support post-disaster relief and recovery efforts. With key observables including vertical profiles of temperature, water vapor, wind and precipitation over a wide area, many focused applications are possible, particularly pertaining to aviation, transportation and marine operations, in both the civilian and defense domains.
The Jet Propulsion Laboratory (JPL) is best known for planetary exploration but is also heavily involved in Earth science and has in recent years become one of the premier centers for atmospheric science related to infrared and microwave satellite sounders such as the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU) and the Advanced Technology Microwave Sounder (ATMS), as well as aircraft based microwave sounders such as the High Altitude MMIC Sounding Radiometer (HAMSR) and the development of future sounders such as an infrared CubeSat system (CIRAS) and a geostationary microwave sounder (GeoSTAR). We give a brief overview of these sensors and focus on the development and assessment of sounder data products, which include vertical profiles of temperature and water vapor, cloud and surface parameters, and in the case of infrared sounders also trace gas estimates and for microwave sounders precipitation as well. The baseline AIRS data product “retrieval system” was developed by the AIRS science team and has been undergoing continuous maintenance and upgrade in close collaboration with the sounder team at JPL. To support that process, the JPL team has developed a broad range of assessment tools and techniques, which can be applied to data from other sounders as well and can range from simple “sanity check” analysis to thorough “validation” analysis. An example of the less complex testing is the preliminary assessment of products generated by new retrieval systems operating on data from the Cross-track Infrared Sounder (CrIS) and the Advanced Technology Microwave Sounder (ATMS) flying on the Suomi NPP and JPSS satellites. These retrieval systems are developed by individual investigators funded by NASA research grants and are delivered to a Sounder “Science Investigator Processing System” (SIPS) located at JPL for integration, testing and delivery to a NASA data processing center and eventual release to the public, but only limited resources are available to the SIPS for the assessment, which therefore must be relatively superficial. An example of thorough assessment is the quantification of the impact on AIRS products of the failure of the AMSU-A2 microwave sounder 2 years ago. The baseline AIRS retrieval system used initially data from the companion microwave sounders, the Humidity Sounder for Brazil (HSB), AMSU-A1 and AMSU-A2, to provide a “first guess” and support “cloud clearing”. As these instruments suddenly failed (HSB) or gradually deteriorated (AMSU), some effort was devoted to develop a version that did not depend on microwave data. It was considered somewhat inferior to the baseline system and was kept in reserve and therefore not fully assessed. When AMSU-A2 failed, this AIRS-only system became the primary version, and a substantial effort was undertaken to fully assess its performance. We discuss details of that assessment. These capabilities have resulted from substantial investments NASA has made over the years in support of AIRS and can now be applied to next-generation systems as well.
The "Precipitation and All-weather Temperature and Humidity" (PATH) mission is one of the 15 NASA "decadalsurvey"
missions recommended by the U.S. National Research Council in 2007 and will implement the first microwave
sounder in geostationary orbit. This is possible with a new sensor being developed at the Jet Propulsion Laboratory, the
Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR). Adequate spatial resolution is achieved by using
aperture synthesis instead of a large parabolic reflector as is used in conventional systems. A proof-of-concept prototype
was developed at JPL in 2005 under the NASA Instrument Incubator Program and used to demonstrate that this new
concept works well at sounding frequencies. Another IIP effort is now under way to advance key technology required for
a full space system. The maturity of the concept and technology is now such that mission development could be initiated
in 2010-11. The possibility of flying GeoSTAR as an "instrument of opportunity" on NOAA's new series of "GOES-R"
geostationary weather satellites is being actively pursued. Other low-cost options are under study as well.
PATH/GeoSTAR will provide a number of measurements that are key in monitoring and predicting hurricanes and
severe storms - including hemispheric 3-dimensional temperature, humidity and cloud liquid water fields, rain rates and
rain totals, tropospheric wind vectors, sea surface temperature, and parameters associated with deep convection and
atmospheric instability - everywhere and all the time, even in the presence of clouds - and will also provide key
measurements related to climate research.
The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new Earth remote sensing instrument
concept that has been under development at the Jet Propulsion Laboratory. First conceived in 1998 as a NASA New
Millennium Program mission and subsequently developed in 2003-2006 as a proof-of-concept prototype under the
NASA Instrument Incubator Program, it is intended to fill a serious gap in our Earth remote sensing capabilities −
namely the lack of a microwave atmospheric sounder in geostationary orbit. The importance of such observations have
been recognized by the National Academy of Sciences National Research Council, which recently released its report on
a "Decadal Survey" of NASA Earth Science activities. One of the recommended missions for the next decade is a
geostationary microwave sounder. GeoSTAR is well positioned to meet the requirements of such a mission, and because
of the substantial investment NASA has already made in GeoSTAR technology development, this concept is fast
approaching the necessary maturity for implementation in the next decade. NOAA is also keenly interested in GeoSTAR
as a potential payload on its next series of geostationary weather satellites, the GOES-R series. GeoSTAR, with its
ability to map out the three-dimensional structure of temperature, water vapor, clouds, precipitation and convective
parameters on a continual basis, will significantly enhance our ability to observe hurricanes and other severe storms. In
addition, with performance matching that of current and next generation of low-earth-orbiting microwave sounders,
GeoSTAR will also provide observations important to the study of the hydrologic cycle, atmospheric processes and
climate variability and trends. In particular, with GeoSTAR it will be possible to fully resolve the diurnal cycle. We
discuss the GeoSTAR concept and basic design, the performance of the prototype, and a number of science applications
that will be possible with GeoSTAR. The work reported on here was performed at the Jet Propulsion Laboratory,
California Institute of Technology under a contract with the National Aeronautics and Space Administration.
Recent developments in millimeter-wave receiver have enabled new remote sensing capabilities. MMIC circuits
operating at frequencies as high as 200 GHz have enabled low-cost mass producible integrated receivers suitable for
array applications. We will describe several ground-based demonstrations of this technology including development of
integrated spectral line receivers for atmospheric remote sensing, a synthetic thinned aperture radiometer for atmospheric
sounding and imaging and polarimetric array radiometers for astrophysics applications.
The Atmospheric Infrared Sounder (AIRS) sounding suite, launched in 2002, is the most advanced atmospheric
sounding system to date, with measurement accuracies far surpassing those of current operational weather satellites.
From its sun-synchronous polar orbit, the AIRS system provides more than 300,000 all-weather soundings covering
more than 90% of the globe every 24 hours. Usage of AIRS data products, available to all through the archive system
operated by NASA, is spreading throughout the atmospheric and climate research community. An ongoing validation
effort has confirmed that the system is very accurate and stable and is close to meeting the goal of providing global
temperature soundings with an accuracy of 1 K per 1-km layer and water vapor soundings with an accuracy of 20%
throughout the troposphere, surpassing the accuracy of radiosondes. This unprecedented data set is currently used for
operational weather prediction in a number of countries, yielding significant positive impact on forecast accuracy and
range. It is also enabling more detailed investigations of current issues in atmospheric and climate research. In addition
to the basic soundings related to the hydrologic cycle, AIRS also measures a number of trace gases, the latest such
product being the global distribution of carbon dioxide. We discuss some examples of recent research with AIRS data.
The Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR, is a new concept for a microwave atmospheric
sounder intended for geostationary satellites such as the GOES weather satellites operated by NOAA. A small but fully
functional prototype has recently been developed at the Jet Propulsion Laboratory to demonstrate the feasibility of using
aperture synthesis in lieu of the large solid parabolic dish antenna that is required with the conventional approach.
Spatial resolution requirements dictate such a large aperture in GEO that the conventional approach has not been
feasible, and it is only now, with the GeoSTAR approach, that a GEO microwave sounder can be contemplated.
Others have proposed GEO microwave radiometers that would operate at sub-millimeter wavelengths to circumvent the
large-aperture problem, but GeoSTAR is the only viable approach that can provide full sounding capabilities equal to or
exceeding those of the AMSU systems now operating on LEO weather satellites and which have had tremendous impact
on numerical weather forecasting. GeoSTAR will satisfy a number of important measurement objectives, many of them
identified by NOAA as unmet needs in their GOES-R pre-planned product improvements (P3I) lists and others by
NASA in their research roadmaps and as discussed in a white paper submitted to the NRC Decadal Survey. The
performance of the prototype has been outstanding, and this proof of concept represents a major breakthrough in remote
sensing capabilities. The GeoSTAR concept is now at a stage of development where an infusion into space systems can
be initiated, either on a NASA sponsored research mission or on a NOAA sponsored operational mission. GeoSTAR is
an ideal candidate for a joint "research to operations" mission, and that may be the most likely scenario. Additional
GeoSTAR related technology development and other risk reduction activities are under way, and a GeoSTAR mission is
feasible in the GOES-R/S time frame, 2012-2014.
The Earth Science and Meteorological communities are taking great interest in a new instrument released by NASA. The Atmospheric Infrared Sounder (AIRS), launched on the EOS Aqua Spacecraft on May 4, 2002, is a high spectral resolution infrared imaging spectrometer with over 2300 distinct infrared wavelengths ranging from 3.7 μm to 15.4 μm. AIRS is unique in that it provides the highest infrared spectral resolution to date while also providing coverage of over 95% of the Earth's surface every day at 15 km spatial resolution. The AIRS project is currently managed by NASA's Jet Propulsion Laboratory in Pasadena, California<sup>1</sup>. The AIRS is providing a wealth of scientific data to the Earth Science community including upper atmospheric water vapor and atmospheric composition on key greenhouse gases. It is also improving weather forecasting and the studies of processes affecting climate and weather.
The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new concept for a microwave sounder, intended to be deployed on NOAA's next generation of geostationary weather satellites, GOES-R. A ground based prototype has been developed at the Jet Propulsion Laboratory, under NASA Instrument Incubator Program sponsorship, and is currently undergoing tests and performance characterization. The initial space version of GeoSTAR will have performance characteristics equal to those of the AMSU system currently operating on polar orbiting environmental satellites, but subsequent versions will significantly outperform AMSU. In addition to all-weather temperature and humidity soundings, GeoSTAR will also provide continuous rain mapping, tropospheric wind profiling and real time storm tracking. In particular, with the aperture synthesis approach used by GeoSTAR it is possible to achieve very high spatial resolutions without having to deploy the impractically large parabolic reflector antenna that is required with the conventional approach. GeoSTAR therefore offers both a feasible way of getting a microwave sounder in GEO as well as a clear upgrade path to meet future requirements. GeoSTAR offers a number of other advantages relative to real-aperture systems as well, such as 2D spatial coverage without mechanical scanning, system robustness and fault tolerance, operational flexibility, high quality beam formation, and open ended performance expandability. The technology and system design required for GeoSTAR are rapidly maturing, and it is expected that a space demonstration mission can be developed before the first GOES-R launch. GeoSTAR will be ready for operational deployment 2-3 years after that.
The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new microwave atmospheric sounder under development. It will bring capabilities similar to those now available on low-earth orbiting environmental satellites to geostationary orbit - where such capabilities have not been available. GeoSTAR will synthesize the multi-meter aperture needed to achieve the required spatial resolution, which will overcome the obstacle that has prevented a GEO microwave sounder from being implemented until now. The synthetic aperture approach has until recently not been feasible, due to the high power needed to operate the on-board high-speed massively parallel processing system required for 2D-synthesis, as well as a number of system and calibration obstacles. The development effort under way at JPL, with important contributions from the Goddard Space Flight Center and the University of Michigan, is intended to demonstrate the measurement concept and retire much of the technology risk. To that purpose a small ground based demo version of GeoSTAR is being constructed, which will be used to characterize system performance and test various calibration methods. This prototype development, which is being sponsored by NASA through its Instrument Incubator Program, will be completed in 2005. A GeoSTAR space mission can then be initiated. In parallel with the technology development, mission architecture studies are also under way in collaboration with the NOAA Office of System Development. In particular, the feasibility of incorporating GeoSTAR on the next generation of the geostationary weather satellites, GOES-R, is being closely examined. That would fill a long standing gap in the national weather monitoring capabilities.
The Atmospheric Infrared Sounder (AIRS) was launched in May 2002. Along with two companion microwave sensors, it forms the AIRS Sounding Suite. This system is the most advanced atmospheric sounding system to date, with measurement accuracies far surpassing those available on current weather satellites. The data products are calibrated radiances from all three sensors and a number of derived geophysical parameters, including vertical temperature and humidity profiles, surface temperature, cloud fraction, cloud top pressure, and ozone burden. These products are generated under cloudy as well as clear conditions. An ongoing calibration/validation effort has confirmed that the system is very accurate and stable, and most of the geophysical parameters have been validated. AIRS is in some cases more accurate than any other source and can therefore be difficult to validate, but this offers interesting new research opportunities. The applications for the AIRS products range from numerical weather prediction to atmospheric research - where the AIRS water vapor products near the surface and in the mid to upper troposphere will make it possible to characterize and model phenomena that are key for short-term atmospheric processes, such as weather patterns, to long-term processes, such as interannual cycles (e.g., El Niño) and climate change.
The Atmospheric Infrared Sounder (AIRS), Advanced Microwave Sounding Unit (AMSU), and Humidity Sounder from Brazil (HSB) are three instruments onboard the Earth Observing System (EOS) Aqua Spacecraft. Together, they form the Aqua Infrared and Microwave Sounding Suite (AIMSS). This paper discusses the science objectives and the status of the instruments and their data products one year after launch. All instruments went through a successful activation and calibration and have produced exceptional, calibrated, Level 1B data products. The Level 1B Product Generation Executables (PGEs) have been given to NOAA and the GSFC DAAC for production and distribution of data products. After nine months of operations, the HSB instrument experienced an electrical failure of the scanner. Despite the loss of HSB, early validation results have shown the AIRS and AMSU are producing very good temperature profiles.