IEEE - Aerospace and Electronic Systems - January 2023 - 30

Synthetic Aperture Radar During the 50 Years of the Aerospace and Electronic Systems Society
download them (without charge), and use the sentinel application
toolbox (SNAP) to carry out sophisticated processing and
fusion of data. Copious examples are provided, and the toolboxes
can be extended through user generated Python tools.
An exciting move that certain of these free datasets are
carried by cloud suppliers (Amazon, Google, etc.) means
that SNAP instantiated in the cloud is freed from large data
download, and is readily available to users. This paradigm
is rapidly expanding into data cubes, i.e., highly organized
layers of data with clear ontology, making the task of the
EO analysis easier and open to AI applications. The next
section discusses evolving standards that will allow EO
users easy access to data from different senses to aid in
developing algorithms or applying artificial intelligence to
the classification or estimation ofsurface parameters.
STANDARDIZATION ACTIVITIES
The Aerospace and Electronic Systems Society's community
has established an IEEE standard for the are used to define radar
performance [37]. The IEEE Signal Processing Society has
started on a new project [38] to establish standards for SAR.
This committee is including subjects, such as channel sounding,
synthetic aperture sonar, in the deliberations. It is too early to
say whether this standardization effort will include many ofthe
day today performance criteria used in SAR, such as, noise
equivalent sigma zero, integrated sidelobe level, and so on.
The use ofSAR data faces large number ofdifferent systems
each one with its own data formats. These can be simple
differences in how the numbers of stored in files, but more
fundamental differences, such as polarimetric standards, complicate
the issue. The CEO is committee has been defining
standards that are referred to as " analysis ready data. " The
objective here is that since the data providers will conform to
these common standardsmaking interoperability much easier.
Already a large number of these standards have been written
or are in advanced state [39].
Hopefully we will reach a stage when this observation
practitioner be able to chop and change between sensors
both radar and optical to put together algorithms to extract
information from the terrain being imaged. Applications,
such as soil moisture biomass all growth rates of crops and
so on come to mind.
CONCLUSION
In this article, we have seen the growth of SAR from its
origins in World War II where coherent radar allowed the
phase of signals to be recorded. The concept of holograms
led to early experiments to implement a holographic or
imaging radar. The early experiments with airborne platforms
soon gave way to satellite systems, and these have
grown in complexity and numbers over the last years. In
particular the new space phenomena means that smaller,
30
private companies can offer both optical and radar satellites
to the public, and the use of these data to extract
information for a number of industries continues to grow.
The early difficulty of processing carried out with
optical systems, i.e., lenses, gave way, as digital technology
improved, to complete digital systems. Although realtime
processing systems exist for airborne SAR, the goal
of achieving satellite image processing in real time
remains a little in the future. No doubt that this will be
achieved, possibly as an information extraction process.
Philosophically the amount of information stored in the
raw versus the processed image does not change in today's
image algorithms. For example, the position and classification
of targets, such as ships or aircraft will be discerned
directly, areas occupied by forest types and crop types
will be exported as vectors determined using AI.
Difficulties lie ahead ofcourse with a growing congestion
of the electromagnetic spectrum. The radar bands are
under continuous pressure from the communications
industry and together with the radio astronomers, the sensing
of the Earth surface might become challenging. This is
not helped by the proliferation of small, new space, SAR
systems. They will have to be some form of co-operation
between these sensors in the future. The work that has
being carried out in whitespace communications will be
an import important precursor to such work [chapter
shannon].
In summary, the last 50 years of SAR has seen the
emergence of a very strong industry that will provide
important information to almost all of the industries
involved in our future existence.
REFERENCES
[1] H.J.Kramer, Observation of the Earth and Its Environment:
Survey ofMissions and Sensors, 3rd ed. Berlin, Germany:Springer,
Dec. 2012.
[2] D. Gabor, " Holography, 1948-1971. " Accessed: Aug. 8,
2022. [Online]. Available: https://www.nobelprize.org/
uploads/2018/06/gabor-lecture.pdf
[3] S. W. Lasswell, " History of SAR at Lockheed Martin (previously
Goodyear Aerospace), " Proc. SPIE 5788, Radar
Sensor Technol. IX, 2005, pp. 1-12.
[4] J. D. Greshem, " Project Quill: Radar in space. " Accessed:
Aug. 8, 2022. [Online]. Available: https://www.
defensemedianetwork.com/stories/project-quill-radar-inspace/
[5]
J. F. Vesecky and R. H. Stewart, " The observation of ocean
surface phenomena using imagery from the SEASAT synthetic
aperture radar: An assessment, " J. Geophys. Res.,vol. 87,
no. C5, 1982, Art. no. 3397, doi: 10.1029/JC087iC05p03397.
[6] " SeaSat. " Accessed: Aug. 3, 2022. [Online]. Available:
http://https://directory.eoportal.org/web/eoportal/satellitemissions/s/seasat
IEEE
A&E SYSTEMS MAGAZINE
JANUARY 2023

https://www.nobelprize.org/uploads/2018/06/gabor-lecture.pdf https://www.nobelprize.org/uploads/2018/06/gabor-lecture.pdf https://www.defensemedianetwork.com/stories/project-quill-radar-in-space/ https://www.defensemedianetwork.com/stories/project-quill-radar-in-space/ https://www.defensemedianetwork.com/stories/project-quill-radar-in-space/ http://dx.doi.org/10.1029/JC087iC05p03397 http://https://directory.eoportal.org/web/eoportal/satellite-missions/s/seasat http://https://directory.eoportal.org/web/eoportal/satellite-missions/s/seasat

IEEE - Aerospace and Electronic Systems - January 2023

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