R. Keith Raney

The m-chi decomposition of hybrid dual-polarimetric radar data

The Mini-RF and Mini-SAR instruments are the first compact polarimetric space-based imaging radars. Their architecture is hybrid-polarimetric, transmitting (quasi-) circular polarization, and receiving orthogonal linear polarizations and their relative phase. The four Stokes parameters that are necessary and sufficient to fully characterize the observed backscattered EM field are calculated from the received linearly polarized data. The Stokes parameters can be used to formulate an m-chi decomposition of the scene, which is a new technique. This method facilitates unambiguous interpretation of surface features according to single (odd) or double (even) bounce signatures in the polarized portion of the reflections, and characterization of the randomly polarized constituents. The m-chi decomposition has proven to be robust in the event that the transmitted field is not perfectly circularly polarized. Analysis of lunar data suggests that an m-chi-psi three-component decomposition strategy should provide additional backscatter classification finesse. These methods are directly applicable to data anticipated from Earth-observing compact-polarimetric radars.

DESDynI adopts hybrid polarity SAR architecture

DESDynl-Deformation, Ecosystem Structure, and Dynamics of Ice-is one of the first-tier missions recommended in The National Research Councils Earth Science 2007 Decadal Survey. DESDynIs L-band synthetic aperture radar (SAR) is designed to measure terrain surface deformation and forest biomass, hence its quadrature-polarimetric SAR mode. The objective to provide quantitative information on a global scale imposes severe requirements on the radar to maximize coverage and to sustain reliable operational calibration. These requirements are best served by the hybrid-polarity architecture, in which the radar transmits in circular polarization, and receives on two orthogonal linear polarizations, coherently, retaining their relative phase. This architecture offers many significant advantages over conventional all-linearly-polarized SARs. This paper reviews those advantages, summarizes key attributes of hybrid-polarity dual- and quadrature-polarized SARs including conditions under which the signal-to-noise ratio is conserved, and describes the evolution of this architecture from first principles.

POES COMPANION : OBJECTIVES, METHODOLOGY, AND BENEFITS

Abstract POES Companion is a small satellite that would carry an atmospheric sounding instrument identical to one on a nearby operational polar orbiting spacecraft. The spacing between the two satellites would be controlled and variable. The mission is designed to establish the upper bound on the distance between the two satellites within which data from the instruments are statistically equivalent, and further would demonstrate that two neighboring spacecraft can be managed safely and efficiently. POES Companion will validate new Companion options outlined in this paper that could substantially reduce costs attributable to satellite-based atmospheric sounders for both operational and research programs.

Delay/Doppler compensation: a new concept for radar altimetry

This new satellite radar altimeter concept uses on-board real-time partially coherent processing to realize an along-track impulse response shape and position which are not degraded by terrain slope or elevation. The key innovation is delay compensation, analogous to range curvature correction in a burst mode synthetic aperture radar. The detected outputs of many bursts are incoherently integrated to accumulate more than one hundred equivalent looks. The along-track footprint size is on the order of 200 - 300 meters. The radar equation for the delay/Doppler radar altimeter has an h(-5/2) dependence on height, which is more efficient than the corresponding h(-3) factor for a pulse-limited altimeter. The radiometric response obtained by the new approach would be 10 dB stronger than that of the TOPEX/POSEIDON altimeter, for example, if the same hardware were used in the delay/Doppler mode. The concept is a candidate small satellite instrument for earth observation, with particular suitability for precision altimetry of coastal and polar ice sheets.

A technology path to distributed remote sensing

Abstract The Johns Hopkins University Applied Physics Laboratory (APL) has been engaged for over 40 years in Earth science missions spanning geodesy to atmospheric science. In parallel, APLs Advanced Technology Program is supporting research in autonomy, scalable architectures, miniaturization, and instrument innovation. These are key technologies for the development of affordable observation programs that could benefit from distributed remote sensing. This paper brings these applications and technology themes together in the form of an innovative, three-satellite remote sensing scenario. This pathfinding mission fills an important scientific niche, and relies on state-of-the-art small-satellite technology.

Hybrid-polarity SAR architecture

A synthetic aperture radar (SAR) often is constrained to transmit only one polarization. Within this constraint, two aggressive measurement objectives are 1) full characterization and exploitation of the backscattered field, and 2) invariance to geometrical orientations of features in the scene. Full characterization implies coherent dual-polarization to support the four Stokes parameters. These are rotationally invariant with respect backscatterer orientation if and only if the transmission is circularly polarized. Given that the data products are the Stokes parameters, the receivers can use any orthogonal polarization basis. A SAR in hybrid-polarity architecture (CL-pol) transmits circular polarization and receives two orthogonal mutually coherent linear polarizations, which is one manifestation of compact polarimetry. The resulting radar is relatively simple to implement, and has unique self-calibration features and low susceptibility to noise and cross-channel errors. It is the architecture of choice for two lunar radars scheduled for launch in 2008. Data from a CL-pol SAR yield to decomposition strategies such as the m-delta method introduced in this paper.