A nullsteering viewpoint of interferometric SAR
Abstract
Interferometric synthetic aperture radar (IFSAR) extends the twodimensional imaging capability of traditional synthetic aperture radar to threedimensions by using an aperture in the elevation plane to estimate the 3D structure of the target. The operation of this additional aperture can be viewed from a nullsteering point of view, rather than the traditional phase determination point of view. Knowing that IFSAR can be viewed from the nullsteering perspective allows one to take advantage of the mathematical foundation developed for nullsteering arrays. In addition, in some problems of interest in IFSAR the nullsteering perspective provides better intuition and suggests alternative solutions. One example is the problem of estimating building height where layover is present.
 Authors:
 Publication Date:
 Research Org.:
 Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
 Sponsoring Org.:
 US Department of Energy (US)
 OSTI Identifier:
 755624
 Report Number(s):
 SAND993220C
TRN: AH200021%%59
 DOE Contract Number:
 AC0494AL85000
 Resource Type:
 Conference
 Resource Relation:
 Conference: IEEE Geoscience and Remote Sensing Symposium 2000, Honolulu, HI (US), 07/24/200007/28/2000; Other Information: PBD: 2 May 2000
 Country of Publication:
 United States
 Language:
 English
 Subject:
 47 OTHER INSTRUMENTATION; RADAR; INTERFEROMETRY; THREEDIMENSIONAL CALCULATIONS; DATA ANALYSIS; BUILDINGS; HEIGHT
Citation Formats
BICKEL,DOUGLAS L. A nullsteering viewpoint of interferometric SAR. United States: N. p., 2000.
Web.
BICKEL,DOUGLAS L. A nullsteering viewpoint of interferometric SAR. United States.
BICKEL,DOUGLAS L. 2000.
"A nullsteering viewpoint of interferometric SAR". United States.
doi:. https://www.osti.gov/servlets/purl/755624.
@article{osti_755624,
title = {A nullsteering viewpoint of interferometric SAR},
author = {BICKEL,DOUGLAS L.},
abstractNote = {Interferometric synthetic aperture radar (IFSAR) extends the twodimensional imaging capability of traditional synthetic aperture radar to threedimensions by using an aperture in the elevation plane to estimate the 3D structure of the target. The operation of this additional aperture can be viewed from a nullsteering point of view, rather than the traditional phase determination point of view. Knowing that IFSAR can be viewed from the nullsteering perspective allows one to take advantage of the mathematical foundation developed for nullsteering arrays. In addition, in some problems of interest in IFSAR the nullsteering perspective provides better intuition and suggests alternative solutions. One example is the problem of estimating building height where layover is present.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2000,
month = 5
}

A brief theoretical review of adaptive null steering is presented. The basic theory is first outlined in the context of sidelobe cancellation systems as well as general antenna arrays. Various approaches to the practical implementation of adaptive null steering are then discussed. These fall into the two main categories of closedloop methods and directsolution methods. The closedloop methods are very costeffective and suitable in principle, for either analog or digital processing. However, their rate of convergence is fundamentally limited and too slow for some applications. The directsolution methods do not suffer from this problem, but tend to be suitable onlymore »

Interferometric null test of a deep parabolic reflector generating a Hertzian dipole field
We report on interferometric characterization of a deep parabolic mirror with a depth of more than five times its focal length. The interferometer is of Fizeau type; its core consists of the mirror itself, a spherical null element, and a reference flat. Because of the extreme solid angle produced by the paraboloid, the alignment of the setup appears to be very critical and needs auxiliary systems for control. Aberrations caused by misalignments are removed via fitting of suitable functionals provided by means of ray tracing simulations. It turns out that the usual misalignment approximations fail under these extreme conditions. 
Nullplane invariance of Hamiltonian nullplane dynamics.
Relativistic Hamiltonian fewbody dynamics [1,2] involves two unitary representations of the Poincare group on the Hilbert space H of physical states, with and without interactions. These two representations, U({Lambda}, a) and U{sub 0}({Lambda},a), coincide for a kinematic subgroup H. The ''Hamiltonians'' are the generators not in the Lie algebra of the kinematic subgroup. The kinematic subgroup of nullplane dynamics leaves the nullplane z {center_dot} x {triple_bond} x{sup 0} + x{sub 3} = 0 invariant. Fewbody Hamiltonians satisfying the required commutation relations can be constructed as functions of a mass operator and kinematic quantities. For more than two particles there aremore » 
The role of neutrals in the HL back transition of high density singlenull and doublenull gasfueled discharges in DIIID
The role of neutrals in triggering the HL back transition in high density ELMing Hmode plasmas is explored in doublenull (DN) and singlenull (SN) divertors. The authors propose that the neutral particle buildup below the Xpoint may play an important role in triggering the HL transition at high density. Neutral pressure in the private flux region is, in fact, significant near the HL backtransition. High density formation inside the separatrix near the Xpoint may also be a factor in triggering the HL backtransition. They have observed that the ELMing Hmode density limit in SN divertors normally occurred at or nearmore » 
A Comparison of Plasma Performance Between SingleNull and DoubleNull Configurations During Elming HMode
Tokamak plasma performance generally improves with increased shaping of the plasma cross section, such as higher elongation and higher triangularity. The stronger shaping, especially higher triangularity, leads to changes in the magnetic topology of the divertor. Because there are engineering and divertor physics issues associated with changes in the details of the divertor flux geometry, especially as the configuration transitions from a singlenull (SN) divertor to a marginally balanced doublenull (DN) divertor, we have undertaken a systematic evaluation of the plasma characteristics as the magnetic geometry is varied, particularly with respect to (1) energy confinement, (2) the response of themore »