Briefly, SLAR imagery can be obtained day or night and can penetrate
all but the heaviest rain storms., The imagery is of very small scale --
ranging from 1:500,000 to 1:250,000; however, geometric accuracies are
of the order of + one percent even 48 Km from the aircraft. On Project
Radam, the average error in geometric positioning was + 66m.
The availability of this imagery for making land use maps and de-
termining where forests, streams and rivers really lie is providing
tropical countries the first complete inventory of their resources --
albeit at a fairly coarse resolution (~20m).
Aircraft multispectral and thermal scanners
The biggest advances made in the development of multispectral
scanners (MSS) has been in the design of the instrument which permits
all reflected and emitted energy to be collected through a single aper-
ture. Thus, each picture element (pixel) in the scene has one instan-
taneous field of view and permits perfect comparison of each waveband
of energy with respect to all other wavebands. This new design permits
signature analyses to be made because all energy data including thermal,
are recorded on computer compatible tape (CCT). Some success has been
attained in making thermatic maps of land use from such MSS data col-
lected by aircraft, LANDSAT, and SKYLAB (Weber et al, 1972).
Charge coupled detectors
The charge coupled detector (CCD) concept offers a major breakthrough
in the field of solid state image sensor development (Amelio, 1974).
The typical diode spectral response is that of silicon with sensitivity
extending from the blue to the near IR (fig. 2). This new device while
still experimental shows considerable promise for high altitude aircraft
and spacecraft imagers. Advantages include: no mechanical scanning,
built-in geometric accuracy, high quantum efficiency of silicon for
visible and near IR wavebands, high resolution, good stability and low
voltage operation.
CCD arrays represent an imaging technique that make use of linear
arrays of solid state detectors operating in what is called a "push-
broom scan mode". In such a system, a detector array is used to image
the scene in the cross track direction, and spacecraft motion is used
to provide the orthoganal scan component (fig. 3).
The resolution capabilities of the system look promising; for ex-
ample, some laboratory images have been made of urban scenes which
image about 56 line pairs per mm. On a projected Space Shuttle mission,
the designers of CCD arrays predict a ground resolution of 7.5m from
920km of altitude over a 185km cross track scene.
Fairchild Camera and Instrument Company 3/ is currently producing a
solid state CCD television camera (MV-101) having a 100 x 100 element
3/ Trade names and commercial enterprises or products are mentioned
in this report solely for information. No endorsement by the
author is implied.
