Geoscience Reference
In-Depth Information
An obvious extension of the algorithms described in this paper involves radar imaging of
moderately overspread targets, ESF being a good example. Such targets can be investigated
using aperiodic or incremental-lag pulses (e.g. Chau et al. (2004); Uppala & Sahr (1994);
Virtanen et al. (2009)). This produces temporal lagged-products with nonuniform spacing
which can be spectrally analyzed using the same methodologies developed for imaging
(Hysell et al., 2008). Moreover, the spatio-temporal lagged products arising from aperiodic
aperture synthesis imaging experiments can be analyzed together in one operation, yielding
images in range, bearing, and the added dimension of Doppler frequency seamlessly.
The
total number of distinct lagged products will be given by
N
/2,
N
being the product of
the number of sensors and the number of aperiodic pulses considered at a time. Compromises
in spectral and angular resolution will be required if the inverse problem is to remain tractable.
(
N
−
1
)
Finally, it has been our observation that the backscatter from ionospheric plasma density
irregularities in many contexts tends to be “clumpy” rather than diffuse. This information
could be exploited in the inversion scheme if the prior probability function were augmented
with a component based on an appropriate model Markov chain. Fully exploiting this
information would require processing data from multiple ranges and Doppler frequency bins
simultaneously, since the spatial organization occurs equally in bearing, range, and Doppler
frequency. That the “clumpy” targets often remain organized for long periods of time suggests
that this information should be folded in as well.
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