Technological advantage of the use of satellite based technology
From INVESaTWIKI
ASSESSMENT OF TECHNOLOGICAL ADVANTAGE OF THE USE OF SATELLITE BASED TECHNOLOGY IN THE FIELD OF EARTH OBSERVATION
During the last 5-10 years there has been a significant increase in the quantity, quality and diversity of satellite observations. Although satellite data is slightly less accurate than conventional observations such as radio sonde observations, their great advantage is their broad geographical coverage. While the data assimilation system has to spread out the information in space of radio sonde observations, this is less of an undertaking with satellite observations.
Another advantage is that the use of satellite data ensures that the elusive small amplitude-large scale errors over the oceans are corrected for, something which isolated measurements would have difficulties to do. Although the amplitude of the analysis increments are weak, their large-scale nature becomes important after some days integration when they have "cascaded" into smaller scales, which might develop and affect synoptic scale weather systems.
Consequently there is now a strong benefit from satellite data and the influence of other conventional data types are becoming less critical. In particular over the Southern Hemisphere, where there is a lack of conventional data, satellite data has had a large impact on the scores which are now almost as good as in the Northern Hemisphere. However there are limitations in the use of satellite data over land surfaces. Over desertic areas and frozen regions, at the state of the art, is particularly difficult to use tropospheric channels due to the inaccurate knowledge of the underlying surface emissivity. On global scale these are areas were overall we assimilate less data, like it is shown in Figure 2.
From the top : a) infrared lower tropospheric channel from AQUA satellite, b) microwave lower tropospheric channel from three satellites (AMSU-A ch. 5 from NOAA-15, NOAA-16m AQUA), c) composite of conventional observations (surface + radiosoundings + aircrafts) and atmospheric winds derived by satellites. As it is apparent, despite a good global coverage there are land areas (Sahara, Siberia, Arctic and Antarctic) where the data coverage in the low troposphere is still sparse. [1]
ASSESSMENT OF TECHNOLOGICAL ADVANTAGE OF THE USE OF SATELLITE BASED TECHNOLOGY IN THE FIELD OF GNSS
Electronic navigation systems employing artificial satellites as radio signal sources and position references. Satellites have the advantage that their signals have line-of-sight propagation to almost an entire hemisphere of the Earth. These systems have become the preeminent radio navigation systems and are gradually replacing ground-based systems such as Loran and Omega. Two main types of satellite navigation systems have been developed, Doppler systems and differential-time-of-arrival systems.
In addition to providing navigation service to aircraft, vehicles, and watercraft, many other uses have become practical because of the accuracy, global coverage, and low cost of satellite navigation receivers. Small, inexpensive, handheld receivers are available for use in hiker, boating, and other recreational activities. In other applications, the receiver is combined with a communication system or a geographic database. Surveying has been revolutionized by a very accurate type of differential system. A surveying system can take advantage of the fact that it is not moving for the duration of its measurements. This yields very precise position estimates relative to a local reference point. The tectonic motion of the Earth's crust around fault lines has been measured with an accuracy of 1 cm (0.4 in.) or less.
In automobile systems, the navigation receiver is combined with a display and a digitized map which is stored on a CD-ROM. Vehicle tracking systems use satellite navigation to determine a vehicle's position, which is then periodically reported to a central location by using a cellular telephone or some other communications system. Variations of this concept have been employed to track livestock, weather balloons, wildlife migration, and many other things. The ability to easily record the exact location at any point makes satellite navigation receivers ideal for mapping environmental data such as soil conditions, forest growth patterns, and pollution. Such data are used to monitor environmental damage. In aircraft navigation systems, satellite navigation is often combined with an inertial navigation system. The inertial system improves short-term accuracy, particularly during a maneuver. The satellite navigation maintains accuracy over the long term. [2]
ASSESSMENT OF TECHNOLOGICAL ADVANTAGE OF THE USE OF SATELLITE BASED TECHNOLOGY IN THE FIELD OF TELECOMMUNICATIONS
Advantage of satellite data system
Despite the rapid innovation of terrestrial technologies, satellites still hold a number of advantages over terrestrial counterparts. The benefits include the following: ubiquitous coverage, simplicity, bandwidth flexibility, rapid deployment, reliability, inexpensive installation, fewer outages and scalability.
Potential Disadvantages of Satellite Data Systems
There are drawbacks and issues associated with satellite technology. Some of the limitations can be accepted, while others will require a change in the way applications are used or operated and, in some cases, which application is used. The limitations may make satellite systems unsuitable for a limited set of applications.
Just as satellite maintains certain advantages over terrestrial technologies, it has certain disadvantages
as well, particularly when compared to current fiber optic circuits.
Several of the disadvantages of satellites can be resolved operationally through the addition of
ground technology. Security issues are mitigated through encryption technologies, the most common
being Conditional Access Systems (CAS) which encrypt digital video signals to protect against
pirated use of broadcast video networks. Latency is addressed on an application-by-application
basis, either by careful network planning or the use of third party hardware and software designed
to minimize the effects of latency. Overcoming the limited bandwidth and orbital slot disadvantages
is a much greater challenge, and the driving factor behind the emerging broadband satellite designs. Within the last decade, the advances in fiber optic technologies have so dramatically
increased the capacity of fiber lines, that satellites no longer have the ability to provide cable restoration
(backup) services to major international carriers.
Other potential disavantage of satellite data systems are related to the quality of service, the location and the applications. [3],[4]
References
[1] P.Curtis, F.Knops
"The state & health of the european and canadian EO service industry".
[2] A.J.Gavin, S.Scarda, K.Sheridan, J.I.Herrero
"Polaris: a software tool to support GNSS-based application design".
[3] more.net
"An Introduction to Satellite-based Data Services".
[4] Pioneer Consulting
"Abridged executive summary".
