BICEP Array is a degree-scale Cosmic Microwave Background (CMB) experiment that will search for primordial B-mode polarization while constraining Galactic foregrounds. BICEP Array will be comprised of four receivers to cover a broad frequency range with channels at 30/40, 95, 150 and 220/270 GHz. The first low-frequency receiver will map synchrotron emission at 30 and 40 GHz and will deploy to the South Pole at the end of 2019. In this paper, we give an overview of the BICEP Array science and instrument, with a focus on the detector module. We designed corrugations in the metal frame of the module to suppress unwanted interactions with the antenna-coupled detectors that would otherwise deform the beams of edge pixels. This design reduces the residual beam systematics and temperature-to-polarization leakage due to beam steering and shape mismatch between polarized beam pairs. We report on the simulated performance of single- and wide-band corrugations designed to minimize these effects. Our optimized design alleviates beam differential ellipticity caused by the metal frame to about 7% over 57% bandwidth (25 to 45 GHz), which is close to the level due the bare antenna itself without a metal frame. Initial laboratory measurements are also presented.
There is special synergy between NASA space instruments and medical devices, especially those that may be implanted in the human body. For example, in both cases instruments have to be small, typically have to consume little power and often have to operate in harsh environments. JPL has a long history in using this synergy to leverage from the technology developed for space missions for application in medical fields. In this talk, we discuss the general overlap of technological requirements in the medical field and space science. We will highlight some examples where JPL instrumentation and engineering has been transferred successfully.
This paper reports an attempt in improving surface soil moisture radar algorithm for Hydrosphere State Mission (Hydros). We used a Radiative Transfer Model to simulate a wide range surface dielectric, roughness, vegetation with random orientated disks database for our algorithm development under HYDROS radar sensor (L-band multi-polarizations and 40º incidence) configuration. Through analyses of the model simulated database, we developed a technique to estimate surface soil moisture. This technique includes two steps. First, it decomposes the total backscattering signals into two components - the surface scattering components (the bare surface backscattering signals attenuated by the overlaying vegetation layer) and the sum of the direct volume scattering components and surface-volume interaction components at different polarizations. From the model simulated data-base, our decomposition technique works quit well in estimation of the surface scattering components with RMSEs of 0.12, 0.25, and 0.55 dB for VV, HH, and VH polarizations, respectively. Then, we use the decomposed surface backscattering signals to estimate the soil moisture and the combined surface roughness and vegetation attenuation correction factors with all three polarizations. Test of this algorithm using all simulated data showed that an accuracy for the volumetric soil moisture estimation in terms of Root Mean Square Error (RMSE) of 4.6 % could be achievable.
Spaceborne scatterometers are active microwave radar instruments designed to acquire near-simultaneous, spatially collocated measurements of the normalized radar backscattering cross section (sigma0) of the global surface from several azimuth and/or incidence angles. The primary objective of the scatterometer mission is to measure the near-surface wind speed and direction over the global ocean using sigma0 measurements together with a wind geophysical model function. However, since sigma0 measurements are collected globally all the time, sigma0 data can also be used for global land and ice applications. In this paper, we will first present the objectives of the QSCAT mission, the instrument design, and the unique features of the Ku- band scatterometer currently in operation, called SeaWinds on QuikSCAT (QSCAT). We will then present some emerging land and ocean applications of the QSCAT data, which include (1) global snow detection and monitoring, (2) melt region mapping on the Greenland ice sheet, (3) Monsoon flood detection and monitoring, (4) soil wetness application at large scale, and (5) hurricane monitoring and tracking.
This paper summarizes the recent work in the fields of Synthetic Aperture Radar polarimetry and interferometry. These fields have seen very significant development during the last five years, and these fields are now well understood.
This paper reports preliminary results of a study using L-band SAR imagery to estimate soil moisture and surface roughness for bare fields in a mountain watershed. The small perturbation model requires that the surface roughness profile deviates only slightly from that of a smooth surface. This condition is seldom met by most natural surfaces. Thus, the classic treatment of the scattering model has only limited usage. In this study, we show a simplified model derived from the integral equation model for estimation of soil moisture and surface roughness. We then test this model using JPL L-band AIRSAR data.
In this paper, a systematic theoretical analysis of polarization filtering for a bistatic system is developed for two applications: maximization of signal to noise ratio and discrimination between two target types. The described method finds the optimum receive antenna polarization analytically but relies on a numerical approach to find the optimum transmit antenna polarization. The method uses the Stokes matrix representation, and therefore applies to analyze the partially polarized scattered field from extended targets. Examples of the technique are presented for the NASA CV990 polarimetric L-band radar. Image enhancement filters maximizing the signal-to-noise ratio are developed for different noise characteristics and different target types (urban and forest). A filter is also developed to maximize the power ratio between urban and natural targets. Results show that the filter maximizing the contrast between urban and forest area is essentially the same as the one maximizing the contrast between urban and ocean areas.
During normal SAR processing, a flat earth is assumed when performing radiometric corrections such as antenna pattern and scattering element size removal. Here we examine the effects of topographic variations on these corrections. Local slopes will cause the actual scattering element size to be different from that calculated using the flat earth assumption. It is shown that this effect, which is present for both airborne and spaceborne SAR data, may easily cause calibration errors on the order of a dB. In the case of airborne systems, the errors introduced by assuming a flat earth during antenna pattern removal are also significant; errors of several dB can easily result. The effect of topography on antenna pattern removal is expected to be negligible for spaceborne SARs.
In this paper we applied Cloude's decomposition to imaging radar polarimetry. We show in detail how the decomposition results can guide the interpretation of scattering from vegetated area. For multi-frequency polarimetric radar measurements of a clearcut area, the decomposition leads us to conclude that the vegetation is probably thin compared to even the C-band radar wavelength of 6 cm. For a forested area, we notice an increased amount of even number of reflection scattering at P-band and L-band, probably the result of penetration through the coniferous canopy resulting in trunk-ground double reflection scattering. The scattering for the forested area is still dominated by scattering from randomly oriented cylinders, however. It is found that these cylinders are thicker than in the case of clearcut areas, leading us to conclude that scattering from the branches probably dominate in this case.