Future trends and expected technological evolution - A possible scenario for the long term
From INVESaTWIKI
Future trends and expected technological evolution - A possible scenario for the long term
Certainly small satellites are there for ever, or at least for long, but a number of problems are
to be solved if we want to transform technical experiments, or lucky opportunities, in real
and sustained business.
The question of launch of the small satellites is not an easy one. Today the piggy backing on
Ariane or other large launcher has proven very valuable for some missions and nearly all
experiments or demonstrations, but doesn’t seem an easy one for operational missions using
small satellites, especially when considering the replacement of a failed satellite. Small
launcher are basically of two types : those made in « west » that unfortunately one could
consider as rather expensive, and those made in « east » that some consider as a not reliable
source on the long term (for price or availability). But this may change with more and more
launches done; the confidence and selection will have advanced.
Also the question of real take off of « mass markets » for remote sensing is another difficult
topic. It seems now that the demand is oriented towards better availability of information
acquired by satellites than better accuracy. If this is confirmed then the small satellites are in
good position to serve the needs. As a matter of fact, the smaller the satellite the cheaper it
is; and the cheaper the satellites, the more we can launch for a given amount of funding.
Therefore it is possible to place in orbit more satellites and having a « constellation », to
observe the earth more frequently and then deliver the image more rapidly.
The final user we aim at convincing to use satellites produced data is not buying bits or
images, he is buying « information » usable directly by him. Meteorology is providing
specialized forecast the user understands, not only data adapted to engineers.
So we must develop better and better softwares to process raw data and build services
adapted to user needs.
Also in the speed of data delivery , intervene the ease of access to existing data, stored in
archives, and the response time of space systems to new request of informations. There the
question of accessing the satellites to command a new picture is major and the more
satellites, the easier it will normally be, provided that the telecommand of satellites is
organized in such a way that one can access the satellites very quickly and one has not to
wait one or more orbit. The solutions are in this field or to provides intersatellites link such
as TDRSS or to set up a network of earth stations.
But on another direction, instead of going to smaller and smaller and have more satellites to
provides an affordable frequent service, one can imagine to develop bigger geostationary
satellites, one or two for Europe would be enough, able to observe at any time a region
underneath the satellite. Such a satellite with geometric resolution comparable to LEO
satellites is not today easy to design and build but will certainly be launched one day.
In fact the nice solution could be perhaps, to have both type of satellites in orbit : A
geostationary satellite of moderate resolution but able to constantly observe a region and
instruct a constellation of small satellites in LEO, of high resolution but narrow swath, to
observe zones without clouds and zones where a change has been noticed.
In a first step, tomorrow, it would be possible to put in orbit a geostationary satellite able
to picture the earth with a resolution of 10 m or so, and a constellation of microsats of 1
m, and close to 10 km swath.
In a near future, may be a GEO satellite of 2 to 5 m resolution and LEO of less than one
meter resolution and wider swath.
And later the same thing in visible and infrared, plus constellations of small radars.
From what has been said in the preceding paragraph, one can derive a scenario for the future of Earth observation satellite:
- Constellation of mini (and/or micro) satellites in Low Earth Orbit (LEO).
- Geostationary satellites. In this case, given the higher distance to the ground, the telescope size must be bigger than in LEO. It results in bigger satellites.
- Resolution in the submetric range (not more) with field of view as wide as possible.
- More sensitive detectors.
- On-board sophisticated compression technics.
- Networks of stations to receive the image as soon as it is captured by the satellite and then transmission through telecom network for immediate delivery to the processing centre or the final user.
- Sophisticated tools for processing data (including the data banks existing). [1]
References
[1] D.Hernandez
"Possible scenario for future mission in Earth observation".
