Engineering topics

Haken, Michael

Publications and source records attributed to Haken, Michael.

5 records

NASA NTRS2014

Release 2 data products from the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler

The OMPS Limb Profiler (LP) was launched on board the NASA Suomi National Polar-orbiting Partnership (SNPP) satellite in October 2011. OMPS-LP is a limb-scattering hyperspectral sensor that provides ozone profiling capability at 1.5 km vertical resolution from cloud top to 60 km altitude. The use of three parallel slits allows global coverage in approximately four days. We have recently completed a full reprocessing of all LP data products, designated as Release 2, that improves the accuracy and quality of these products. Level 1 gridded radiance (L1G) changes include intra-orbit and seasonal correction of variations in wavelength registration, revised static and intra-orbit tangent height adjustments, and simplified pixel selection from multiple images. Ozone profile retrieval changes include removal of the explicit aerosol correction, exclusion of channels contaminated by stratospheric OH emission, a revised instrument noise characterization, improved synthetic solar spectrum, improved pressure and temperature ancillary data, and a revised ozone climatology. Release 2 data products also include aerosol extinction coefficient profiles derived with the prelaunch retrieval algorithm. Our evaluation of OMPS LP Release 2 data quality is good. Zonal average ozone profile comparisons with Aura MLS data typically show good agreement, within 5-10% over the altitude range 20-50 km between 60 deg S and 60 deg N. The aerosol profiles agree well with concurrent satellite measurements such as CALIPSO and OSIRIS, and clearly detect exceptional events such as volcanic eruptions and the Chelyabinsk bolide in February 2013.

Limb scatter↗

NASA NTRS2014

OMPS Limb Profiler Instrument Performance Assessment

Following the successful launch of the Ozone Mapping and Profiler Suite (OMPS) aboard the Suomi National Polar-orbiting Partnership (SNPP) spacecraft, the NASA OMPS Limb team began an evaluation of instrument and data product performance. The focus of this paper is the instrument performance in relation to the original design criteria. Performance that is closer to expectations increases the likelihood that limb scatter measurements by SNPP OMPS and successor instruments can form the basis for accurate long-term monitoring of ozone vertical profiles. The team finds that the Limb instrument operates mostly as designed and basic performance meets or exceeds the original design criteria. Internally scattered stray light and sensor pointing knowledge are two design challenges with the potential to seriously degrade performance. A thorough prelaunch characterization of stray light supports software corrections that are accurate to within 1% in radiances up to 60 km for the wavelengths used in deriving ozone. Residual stray light errors at 1000nm, which is useful in retrievals of stratospheric aerosols, currently exceed 10%. Height registration errors in the range of 1 km to 2 km have been observed that cannot be fully explained by known error sources. An unexpected thermal sensitivity of the sensor also causes wavelengths and pointing to shift each orbit in the northern hemisphere. Spectral shifts of as much as 0.5nm in the ultraviolet and 5 nm in the visible, and up to 0.3 km shifts in registered height, must be corrected in ground processing.

ozone↗

NASA NTRS2007

Two-Dimensional Synthetic Aperture Radiometry over Land Surface During Soil Moisture Experiment in 2003 (SMEX03)

Microwave radiometry at low frequencies (L-band, approx. 1.4 GHz) has been known as an optimal solution for remote sensing of soil moisture. However, the antenna size required to achieve an appropriate resolution from space has limited the development of spaceborne L-band radiometers. This problem can be addressed by interferometric technology called aperture synthesis. The Soil Moisture and Ocean Salinity (SMOS) mission will apply this technique to monitor global-scale surface parameters in the near future. The first airborne experiment using an aircraft prototype of this approach, the Two-Dimensional Synthetic Aperture Radiometer (2D-STAR), was performed in the Soil Moisture Experiment in 2003 (SMEX03). The L-band brightness temperature data acquired in Alabama by the 2DSTAR was compared with ground-based measurements of soil moisture and with C-band data collected by the Polarimetric Scanning Radiometer (PSR). Our results demonstrate a good response of the 2D-STAR brightness temperature to changes in surface wetness, both in agricultural and forest lands. The behavior of the horizontally polarized brightness temperature data with increasing view-angle over the forest area was noticeably different than over bare soil. The results from the comparison of 2D-STAR and PSR indicate a better response of the 2D-STAR to the surface wetness under both wet and dry conditions. Our results have important implications for the performance of the future SMOS mission.

Ryu, Dongryeol↗

NASA NTRS2004

Development of the Synthetic Aperture Radiometer ESTAR and the Next Generation

ESTAR is a research instrument built to develop the technology of aperture synthesis for passive remote sensing of Earth from space. Aperture synthesis is an interferometric technology that addresses the problem of putting large antenna apertures in space to achieve the spatial resolution needed for remote sensing at long wavelengths ESTAR was a first step (synthesis only across track and only at horizontal polarization). The development has progressed to a new generation instrument that is dual polarized and does aperture synthesis in two dimensions. Among the plans for the future is technology to combine active and passive remote sensing.

LeVine, David M.↗

NASA NTRS1995

Secular variation of activity in comets 2P/Encke and 9P/Tempel 1

We compare production rates of H20 derived from International Ultraviolet Explorer (IUE) spectra from multiple apparitions of 2 comets, 2P/Encke and 9P/Tempel 1, whose orbits are in near-resonance with that of the Earth. Since model-induced errors are primarily a function of observing geometry, the close geometrical matches afforded by the resonance condition results in the cancellation of such errors when taking ratios of production rates. Giving careful attention to the variation of model parameters with solar activity, we find marginal evidence of change in 2P/Encke: a 1-sigma pre-perihelion decrease averaging 4%/revolution over 4 apparitions from 1980-1994, and a 1-sigma post-perihelion increase of 16%/revolution for 2 successive apparitions in 1984 and 1987. We find for 9P/Tempel 1, however, a 7-sigma decrease of 29%/revolution over 3 apparitions from 1983-1994, even after correcting for a tracking problem which made the fluxes systematically low. We speculate on a possible association of the character of long-term brightness variations with physical properties of the nucleus, and discuss implications for future research.

Haken, Michael↗