The National Oceanic and Atmospheric Administration (NOAA) have been flying microwave sounders since 1975 on
Polar Operational Environmental Satellites (POES). Microwave observations have made significant contributions to the
understanding of the atmosphere and earth surface. This has helped in improving weather and storm tracking forecasts.
However, NOAA's Geostationary Operational Environmental Satellites (GOES) have microwave requirements that can
not be met due to the unavailability of proven technologies. Several studies of a Geostationary Microwave Sounder
(GMS) have been conducted. Among those, are the Geostationary Microwave Sounder (GEM) that uses a mechanically
steered solid dish antenna and the Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) that utilizes a
sparse aperture array. Both designs take advantage of the latest developments in sensor technology. NASA/Jet
Propulsion Lab (JPL) has recently successfully built and tested a prototype ground-based GeoSTAR at 50 GHz
frequency with promising test results. Current GOES IR Sounders are limited to cloud top observations. Therefore, a
sounding suite of IR and Microwave should be able to provide observations under clear as well as cloudy conditions all
the time. This paper presents the results of the Geostationary Microwave Sounder studies, user requirements,
frequencies, technologies, limitations, and implementation strategies.
The National Oceanographic and Atmospheric Administration (NOAA) is now considering a microwave radiometer for the new series of Geostationary Operational Environmental Satellites (GOES) to be launched starting in 2012. GOES-R is expected to begin operations around 2014 and will provide significant advances in Earth coverage, environmental data, and prediction capabilities. GOES' unique vantage point in fixed geostationary orbit provides continuous, near-real-time updates (observations) of weather and environmental conditions for the Americas and large portions of the Atlantic and Pacific Oceans. In general, GOES-R sensor improvements arise from more frequent updates, finer spatial/spectral resolution, and an expanded field of view. Infrared (IR) atmospheric sounders are designed to provide excellent observations in clear conditions. Critical information within clouds and under cloud cover, however, is not available in the IR spectrum. Microwave sounders can provide synergistic coverage by their ability to observe energy through clouds. NASA's Earth Observing System (EOS) AQUA with the Advanced Microwave Sounder Unit (AMSU) and Atmospheric IR Sounder (AIRS) has illustrated the benefits of combining infrared and microwave sounder data. The benefits provided by polar microwave sounders can be extended to geostationary satellites. The combination of the Hyperspectral Environmental Suite (HES) IR sounder and Geostationary Microwave Sounder (GMS) can likewise provide complete geostationary sounder coverage and precipitation measurements.through our hemisphere. Three different sounders designs have been proposed for the GOES-R Geostationary Microwave Sounder (GMS); these designs would all use similar frequency bands to those of the AMSU A and B and therefore benefit from existing retrieval algorithms. Two designs use mechanically steered solid dish antennae, while a third design utilizes a sparse aperture antenna technology. All three GMS designs take advantage of the latest developments in sensor technology, algorithms, and antenna design. The joint NOAA/NASA GOES-R Program Office (GPO) is evaluating the various GMS designs for GOES-R. This paper will address the design, status, and advantages and limitations of these GMS approaches in reference to unmet meteorological requirements as part of Pre-Planned Product Improvement (P3I) on the GOES-R series of satellites.
The National Oceanic and Atmospheric Administration (NOAA) is considering a microwave radiometer for the next series of Geostationary Operational Environmental Satellites (GOES-R) to be launched starting in 2012. This paper examines the products proposed for the geostationary microwave radiometer in the light of current microwave retrieval algorithms and estimates the performance achievable from geostationary altitude with a three-meter antenna. The results suggest that hemispheric soundings and rain rates can be generated on an hourly basis with the desired accuracy and horizontal resolution, that capping inversions can be detected in conjunction with infrared soundings, that hurricane warm core temperatures can be resolved using high frequencies plus deconvolution and that ocean wind and total precipitable water products can be provided with close to the desired resolution.
There are several microwave instruments in low Earth orbit (LEO) that are used for atmospheric temperature and humidity sounding by themselves and in conjunction with companion IR sounders. These instruments have achieved a certain degree of maturity and are undergoing a redesign to minimize their size, mass, and power requirements from the previous generation instruments. An example of these instruments is the AMSU-A series, now flying on POES and Aqua spacecraft, with the IR sounders HIRS3 and AIRS respectively. These older microwave instruments are going to be replaced by the ATMS instruments that will fly on NPP and NPOESS satellites with the CrIS IR sounder. A number of enabling technologies acquired from the ATMS instrument hardware design and data processing are directly applicable to performing similar microwave sounding on a geostationary platform. Because these technologies are already in place, they are readily available for the development of a geostationary orbit (GEO) microwave instrument, thereby avoiding costly technology development and minimizing the risk of not achieving the scientific requirements. In fact, the MMIC microwave components that were developed by ATMS for size and volume reduction are directly applicable to a GEO microwave sounder.
The benefits of microwave sounders are well known. They penetrate non-precipitating cloud cover and allow for accurate soundings obtained with a collocated high spectral resolution IR sounder in up to 80% cloud cover. The key advantages of a microwave instrument in GEO will be its ability to provide high temporal resolution and uniform spatial resolution, and it will expand the utility of a collocated advanced IR sounder to cases in which partial cloud cover exists. A footprint in the order of 100 km by 100 km resolution with hemispherical coverage within one hour can be easily achieved for sounding channels in the 50 to 57 GHz range. A GEO microwave sounder will also allow mesoscale sampling of select regions.
Due to optical misalignment, visible and infrared channels of the Geostationary Operational Environmental Satellite (GOES) I-M Imager may not be properly registered. This “co-registration” error is currently estimated by comparing groups of visible and infrared observation residuals from the GOES Orbit and Attitude Tracking System (OATS). To make the channel-to-channel comparison more direct, it was proposed to compare individual observations rather than groups of observations. This has already been done for landmarks but not for stars. Stars would help determine nighttime co-registration when visible landmarks are not available. Although most stars in the GOES catalog are not detectable in the shortwave infrared channel, many are. Because stars drift west-to-east across the detectors and because of their high observation frequency, stars provide good east-west co-registration information. Due to the large detector fields-of-view, stars do not provide much information about north-south co-registration.