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TECHNICAL SUMMARY AND COMMENTS
Orbit Information
The proposed systems are in the smallsat, lightsat
categories and are planned for polar sun synchronous
orbits to provide maximum global terrain coverage.
As imagery demands increase, each of the companies
plan to launch additional satellites to provide
constellation coverage which will increase imaging
opportunities for optimal sun angles, repetitive
coverage, stereo coverage and timely monitoring of
events. Generally, the orbits are circular, low-Earth-
orbits (LEO). Orbit altitudes and tracks have been
influenced by market considerations, such as
optimizing repetitive coverage intervals (revisits),
coverage of farming/agricultural regions, or for ground
station agreements with regional and national affiliate
distribution centers.
Sensor Information
Except for the two-dimensional pixel staring arrays of
the EarlyBird, the sensors are all of the pushbroom
type and produce 8 bit or 11 bit pixel data streams.
Their MS capabilities are similar and include the blue,
green, red bands of the visible and the near infrared
bands which, in general, replicate the bands of
Landsat and SPOT. The 11 bit pixel depth provides
high dynamic range for image manipulation and
interpretation. That is, for low contrast scenes and in
low lighting conditions (shadows) it will retain image
quality. The Resource 21 system includes a SWIR
"cirrus" band to calibrate and assist in removal of
atmospheric effects. This unique, but logical,
innovation of sensing atmospheric effects
simultaneously with acquiring imagery has long been
advocated by Dr. John MacDonald, President of
MacDonald Dettwiler & Associates.
One of the remarkable characteristics of the high
resolution systems is their ability to point to multiple
areas of interest within very short time intervals, thus
for example, enabling optimization of stereo base-
height ratios or to acquire off-track stereo imaging
when requested.
Communications/Processing/Marketing Information
All of the systems will rely on a store-and-forward
operation to allow for ground station access and
perhaps some preprocessing activities, such as data
compression. To assist precision pointing to customer
areas of interest the systems all use on-orbit GPS
positioning.
Each of the companies has a different approach for
providing imagery and imagery products to users. The
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main points are that the high resolution companies
offer imagery of spatial resolution from one to ten
magnitudes higher than is commercially available from
current space systems and which is metrically,
spectrally, and temporally precise, and which nominally
can be delivered from near-real-time to 48 hours from
image acquisition! Tables 4-8 summarize the technical
and operational aspects of these commercial systems.
As with any new systems, it should be expected that
some of these characteristics will change during
development and before launch of these systems.
Market Issues
From the commercial market viewpoint it is clear that
the technology has matured and the projected demand
for information to support GIS, mapping, natural
resource, environmental, news, Earth monitoring, etc.
warrants the risk. Market projections for this
industry’s products consistently estimate growth to be
$8 billion by the early years of the 21st century. The
bulk of initial sales will likely be to governments, since
that is where most world mapping and reconnaissance
programs are funded. However, the commercial GIS
market is expected to flourish rapidly because of the
cost effective, synoptic, accurate and repetitive
coverage these systems can provide. It is anticipated
that well over 50% of the imaging provided by the
aerial survey market will be replaced by this high
resolution satellite imagery.
Many have speculated whether the marketplace for
imagery is sufficient to sustain multiple commercial
high resolution space systems. More realistically the
issue is whether sufficient capital will remain available
to get the systems developed and launched, especially
for the multi-satellite systems. A large outlay of
capital is needed for the development to be completed
before the companies can begin to realize a revenue
stream. Several of the systems described in this article
will cost around $500 million.
Today the infrastructure for modelling, enhancing and
extracting spatial information from digital imaging
systems is quite limited in most regions of the world.
However, the years of experience from information
(mostly thematic) processing of digital remote sensing
data using Landsat, SPOT, AVHRR, etc. will assist the
transition. As noted above, there is a rapidly growing
need for temporal change data to provide information
for global, regional, national and urban infrastructure
activities. A recognized fact is that, in the rush and
glamour to utilize outer space, governments have
always given the highest priority for funding imagery
collection systems and have allocated very limited
resources for development of efficient imagery
exploitation systems. As a result many remote sensing
images have been archived and never used. These new
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996
