Sergei Revnivykh, Deputy Head of the GLONASS Directorate, Director of the GLONASS System Development Department, OJSC Information Satellite Systems. Academician M.F. Reshetnev "
Perhaps there is not a single branch of the economy where satellite navigation technologies have not already been used - from all types of transport to agriculture. And the application areas are constantly expanding. Moreover, for the most part, receiving devices receive signals from at least two global navigation systems - GPS and GLONASS.
State of the issue
It just so happened that the use of GLONASS in the space industry in Russia is not as great as one might expect, given the fact that the main developer of the GLONASS system is Roskosmos. Yes, already many of our spacecraft, launch vehicles, upper stages have GLONASS receivers as part of onboard equipment. But so far they are either auxiliary means or are used as part of the payload. Until now, to carry out trajectory measurements, to determine the orbits of near-earth spacecraft, synchronization, in most cases, ground-based means of the command-measuring complex are used, many of which have long been used up. In addition, the measuring instruments are located on the territory of the Russian Federation, which does not allow providing a global coverage of the entire trajectory of spacecraft, which affects the accuracy of the orbit. The use of GLONASS navigation receivers as part of the standard on-board equipment for trajectory measurements will make it possible to obtain the orbit accuracy of low-orbit spacecraft (which constitute the main part of the orbital constellation) at the level of 10 centimeters at any point of the orbit in real time. At the same time, there is no need to involve the means of the command-measuring complex in carrying out trajectory measurements, to spend funds to ensure their operability and the maintenance of personnel. It is enough to have one or two stations for receiving navigation information from the aircraft and transmitting it to the flight control center for solving planning problems. This approach changes the entire strategy of ballistic and navigation support. But, nevertheless, this technology is already well developed in the world and does not present any particular difficulty. It only requires making a decision on the transition to such a technology.
A significant number of low-orbit spacecraft are satellites for remote sensing of the Earth and solving scientific problems. With the development of technologies and means of observation, increasing the resolution, the requirements for the accuracy of binding the received target information to the coordinates of the satellite at the time of shooting are increasing. In a posteriori mode, to process images and scientific data, in many cases, the orbit accuracy needs to be known at the centimeter level.
For special spacecraft of a geodetic class (such as Lageos, Etalon), which are specially created to solve fundamental problems of studying the Earth and refining models of spacecraft motion, centimeter accuracy of orbits has already been achieved. But it should be borne in mind that these vehicles fly outside the atmosphere and are spherical in order to minimize the uncertainty of solar pressure disturbances. For trajectory measurements, a global international network of laser rangefinders is used, which is not cheap, and the operation of the tools is highly dependent on weather conditions.
ERS and science spacecraft mainly fly at altitudes up to 2000 km, have a complex geometric shape, and are fully disturbed by the atmosphere and solar pressure. It is not always possible to use laser facilities of international services. Therefore, the task of obtaining the orbits of such satellites with centimeter accuracy is very difficult. The use of special motion models and information processing methods is required. Over the past 10-15 years, significant progress has been made in world practice to solve such problems using onboard high-precision GNSS navigation receivers (mainly GPS). The pioneer in this area was the Topex-Poseidon satellite (joint NASA-CNES project, 1992-2005, altitude 1,336 km, inclination 66), the orbital accuracy of which was provided 20 years ago at a level of 10 cm (2.5 cm in radius).
In the next decade in the Russian Federation, it is planned to launch a lot of ERS spacecraft for solving applied problems for various purposes. In particular, for a number of space systems, the binding of target information with very high accuracy is required. These are the tasks of reconnaissance, mapping, monitoring of ice conditions, emergencies, meteorology, as well as a number of fundamental scientific tasks in the field of studying the Earth and the World Ocean, building a high-precision dynamic geoid model, high-precision dynamic models of the ionosphere and atmosphere. The accuracy of the position of the spacecraft is already required to know at the level of centimeters throughout the entire orbit. It's about posterior precision.
This is no longer an easy task for space ballistics. Perhaps the only way that can provide a solution to this problem is the use of measurements from the onboard GNSS navigation receiver and the corresponding means of high-precision processing of navigation information on the ground. In most cases, this is a combined GPS and GLONASS receiver. In some cases, requirements may be put forward to use only the GLONASS system.
Experiment on high-precision determination of orbits using GLONASS
In our country, the technology for obtaining high-precision coordinates using geodetic-class navigation receivers has been quite well developed for solving geodetic and geodynamic problems on the Earth's surface. This is a so-called precise point positioning technology. A feature of the technology is the following:
* for processing the measurements of the navigation receiver, the coordinates of which need to be clarified, information from the navigation frames of the GNSS signals is not used. Navigation signals are used only for range measurements, primarily based on measurements of the carrier phase of the signal;
* high-precision orbits and onboard clock corrections, which are obtained on the basis of continuous processing of measurements of the global network of GNSS navigation signals receiving stations, are used as ephemeris-time information of navigation spacecraft. Most of the solutions are now used by the International GNSS Service (IGS);
* measurements of the navigation receiver, the coordinates of which need to be determined, are processed together with high-precision ephemeris-time information using special processing methods.
As a result, the coordinates of the receiver (the phase center of the receiver antenna) can be obtained with an accuracy of a few centimeters.
For solving scientific problems, as well as for the tasks of land management, cadastre, construction in Russia, for several years now, such means have existed and are widely used. At the same time, the author has not yet had information about the means that can solve the problems of high-precision determination of the orbits of low-orbit spacecraft.
An initiative experiment carried out a few months ago showed that we have prototypes of such means, and they can be used to create standard industry-specific means of high-precision ballistic and navigation support for low-orbit spacecraft.
As a result of the experiment, the possibility of using existing prototypes for high-precision determination of the orbit of LEO spacecraft at a level of several centimeters was confirmed.
For the experiment, a flying domestic ERS "Resurs-P" No. 1 (near-circular sun-synchronous orbit with an average altitude of 475 km) was chosen, equipped with a combined navigation receiver GLONASS / GPS. To confirm the result, data processing was repeated for geodetic spacecraft of the GRACE system (joint project of NASA and DLR, 2002-2016, altitude 500 km, inclination 90), on board of which GPS receivers were installed. The features of the experiment are as follows:
* in order to assess the capabilities of the GLONASS system for determining the orbit of the Resurs-P spacecraft (general view is shown in Fig. 1), only GLONASS measurements were used (4 sets of onboard navigation receivers developed by JSC RIRV);
* to obtain the orbit of the spacecraft of the GRACE system (general view is shown in Fig. 2), only GPS measurements were used (measurements are freely available);
* High-precision ephemeris and corrections of the on-board clocks of the navigation satellites of the GLONASS and GPS systems, which were obtained at the IAC KVNO TsNIIMash on the basis of processing the measurements of the stations of the IGS global network (data are freely available), were used as assistance information. The IGS estimate of the accuracy of this data is shown in Fig. 3 and is about 2.5 cm. The location of the global network of GLONASS / GPS stations of the IGS service is shown in Fig. 4;
* a prototype of the hardware and software complex, providing high-precision determination of the orbit of low-orbit spacecraft (initiative development of JSC "GEO-MCC"). The sample also provides decoding of measurements of the onboard receivers of the Resurs-P spacecraft using high-precision ephemeris-time information and taking into account the peculiarities of the session operation of the onboard receivers. The prototype was tested according to the measurements of the spacecraft of the GRACE system.
Rice. 1. General view of the Resurs-P spacecraft.
Rice. 2. General view of the spacecraft of the GRACE system.
Rice. 3. Evaluation of the accuracy of the IAC KVNO TsNIIMash ephemeris by the IGS service. The accuracy of the assisting ephemeris information of the GLONASS navigation spacecraft (designation - IAC, dark blue dots on the graph) is 2.5 cm.
Rice. 4. Location of the global network of GLONASS / GPS stations of the international IGS service (source - http://igscb.jpl.nasa.gov/network/iglos.html).
As a result of the experiment, an unprecedented result was obtained for the domestic ballistic and navigation support of low-orbit spacecraft:
* Taking into account the assisting information and real measurements of the onboard navigation receivers of the Resurs-P spacecraft, a high-precision orbit of this spacecraft with an accuracy of 8-10 cm was obtained only from GLONASS measurements (see Fig. 5).
* In order to confirm the result during the experiment, similar calculations were carried out for geodetic spacecraft of the GRACE system, but using GPS measurements (see Fig. 6). The orbital accuracy of these spacecraft was obtained at a level of 3-5 cm, which fully coincides with the results of the leading analysis centers of the IGS service.
Rice. 5. The accuracy of the "Resurs-P" spacecraft orbit obtained from GLONASS measurements only with the use of assisting information, estimated from measurements of four sets of onboard navigation receivers.
Rice. 6. Accuracy of the orbit of the GRACE-B spacecraft obtained from GPS measurements only with the use of assisting information.
ANNKA system of the first stage
Based on the results of the experiment, the following conclusions objectively follow:
In Russia, there is a significant backlog of domestic development for solving the problems of high-precision determination of the orbits of LEO spacecraft at a competitive level with foreign information processing centers. On the basis of this groundwork, the creation of a permanent industry ballistic center for solving such problems will not require large expenditures. This center will be able to provide all interested organizations that require binding to the coordinates of information from remote sensing satellites, services for high-precision determination of the orbits of any remote sensing satellites equipped with GLONASS and / or GLONASS / GPS satellite navigation equipment. In the future, the measurements of the Chinese system BeiDou and the European Galileo can also be used.
It is shown for the first time that the GLONASS system measurements when solving high-precision problems can provide the solution accuracy practically no worse than the GPS measurements. The final accuracy depends mainly on the accuracy of the assisting ephemeris information and the accuracy of knowledge of the low-orbit spacecraft motion model.
Presentation of the results of domestic remote sensing systems with high-precision referencing to coordinates will dramatically increase its importance and competitiveness (taking into account the growth and market price) in the world market for the results of remote sensing of the Earth.
Thus, for the creation of the first stage of the Assisted Navigation system for LEO spacecraft (code name - ANNKA system) in the Russian Federation, all the components are available (or are under construction):
* there is its own basic special software that allows, independently of the GLONASS and GPS operators, to receive high-precision ephemeris-time information;
* there is a prototype of special software, on the basis of which a standard hardware and software complex for determining the orbits of LEO spacecraft with an accuracy of centimeters can be created in the shortest possible time;
* there are domestic samples of on-board navigation receivers that allow solving the problem with such accuracy;
* Roscosmos is creating its own global network of GNSS navigation signal reception stations.
The architecture of the ANNKA system for the implementation of the first stage (a posteriori mode) is shown in Fig. 7.
The system functions are as follows:
* receiving measurements from the global network to the information processing center of the ANNKA system;
* formation of high-precision ephemeris for navigation satellites of GLONASS and GPS systems (in the future - for BeiDou and Galileo systems) at the ANNKA center;
* obtaining measurements of on-board satellite navigation equipment installed on board the low-orbit ERS satellite and transferring it to the ANNKA center;
* calculation of the high-precision orbit of the remote sensing spacecraft in the center of ANNKA;
* transfer of the high-precision orbit of the remote sensing spacecraft to the data processing center of the ground-based special complex of the remote sensing system.
The system can be created in the shortest possible time, even within the framework of the existing measures of the federal target program for the maintenance, development and use of the GLONASS system.
Rice. 7. The architecture of the ANNKA system at the first stage (a posteriori mode), which ensures the determination of the orbits of LEO spacecraft at a level of 3-5 cm.
Further development
Further development of the ANNKA system in the direction of implementing the mode of high-precision determination and prediction of the orbit of low-orbit spacecraft in real time on board can radically change the entire ideology of ballistic and navigation support of such satellites and completely abandon the use of measurements of ground-based means of the command and measurement complex. It is difficult to say how much, but the operational costs of ballistic and navigation support will be reduced significantly, taking into account the payment for the work of ground facilities and personnel.
In the USA, NASA created such a system more than 10 years ago on the basis of a communication satellite system to control TDRSS spacecraft and the GDGPS global high-precision navigation system created earlier. The system was named TASS. It provides assisting information to all scientific spacecraft and remote sensing satellites in low orbits in order to solve onboard orbit determination tasks in real time at a level of 10-30 cm.
The architecture of the ANNKA system at the second stage, which provides the solution of problems of determining orbits on board with an accuracy of 10-30 cm in real time, is shown in Fig. eight:
The functions of the ANNKA system at the second stage are as follows:
* receiving measurements from stations for receiving GNSS navigation signals of the global network in real time to the ANNKA data processing center;
* formation of high-precision ephemeris for navigation spacecraft of GLONASS and GPS systems (in the future - for BeiDou and Galileo systems) in the ANNKA center in real time;
* tab of high-precision ephemeris on the SC-relay of communication systems (constantly, in real time);
* relaying of high-precision ephemeris (assisting information) by satellites-repeaters for low-orbit ERS spacecraft;
* obtaining a high-precision position of the remote sensing spacecraft on board using special satellite navigation equipment capable of processing received GNSS navigation signals together with assistance information;
* transmission of target information with high-precision referencing to the data processing center of a special ground-based remote sensing complex.
Rice. 8. The architecture of the ANNKA system at the second stage (real-time mode), which ensures the determination of the orbits of LEO spacecraft at a level of 10-30 cm in real time on board.
The analysis of existing capabilities, experimental results show that the Russian Federation has a good groundwork for creating a high-precision assisted navigation system for low-orbit spacecraft, which will significantly reduce the cost of controlling these vehicles and reduce the lag behind the leading space powers in the field of high-precision spacecraft navigation in solving urgent scientific and applied problems. In order to take the necessary step in the evolution of LEO SC control technology, it is only necessary to make an appropriate decision.
The ANNKA system of the first stage can be created as soon as possible with minimal costs.
To proceed to the second stage, it will be necessary to implement a set of measures, which should be provided for within the framework of state or federal targeted programs:
* creation of a special communication satellite system to ensure continuous control of near-earth spacecraft, either in geostationary orbit, or in inclined geosynchronous orbits;
* modernization of the hardware and software complex for the formation of assisting ephemeris information in real time;
* completion of the creation of the Russian global network of GNSS navigation signal receiving stations;
* development and organization of production of on-board navigation receivers capable of processing GNSS navigation signals together with assistance information in real time.
The implementation of these measures is serious, but quite realizable work. It can be carried out by the enterprises of the URSC taking into account the already planned activities within the framework of the Federal Space Program and within the framework of the Federal Target Program for the maintenance, development and use of the GLONASS system, taking into account the corresponding adjustments. Estimating the costs of its creation and the economic effect is a necessary stage, which should be done taking into account the planned projects for the creation of space systems of complexes for remote sensing of the Earth, satellite communication systems, space systems and scientific complexes. There is absolute confidence that these costs will pay off.
In conclusion, the author expresses his sincere gratitude to the leading specialists in the field of domestic satellite navigation Arkady Tyulyakov, Vladimir Mitrikas, Dmitry Fedorov, Ivan Skakun for organizing the experiment and providing materials for this article, the IGS international service and its leaders - Urs Hugentoble and Ruth Nilan - for the opportunity to make full use of the measurements of the global network of stations for receiving navigation signals, as well as to all those who helped and did not interfere.
the leading position of the United States as a world leader in the development and use of Earth remote sensing (ERS) systems. The main efforts of state regulation of the remote sensing industry in the United States are aimed at encouraging the development of market
mechanisms.
The fundamental document in this area is the directive on space policy on the use of commercial remote sensing systems, approved by the President of the United States
March 1994, which outlined the fundamentals of the US policy in the field of access of foreign customers to the resources of American Earth remote sensing systems.
The new policy aims to further strengthen the leadership position in
the world of American companies and covers the following areas of activity:
− licensing of the activity and functioning of the remote sensing system;
− using the resources of the remote sensing system in the interests of defense, intelligence and
other US government departments;
− access of foreign customers (government and commercial) to ERS resources, export of ERS technologies and materials;
− intergovernmental cooperation in the field of military and commercial space imagery.
The main goal of the policy is to strengthen and protect the national security of the United States and the interests of the country in the international arena by strengthening the leading position in
areas of CS ERS and the development of national industry. The objectives of the policy are to stimulate economic growth, protect the environment and strengthen
scientific and technological excellence.
The new directive also affects the commercialization of sensing systems.
On a non-commercial basis, according to experts, remote sensing technologies will not only fail to develop, but will also throw the United States (like any other country) far back from the leading positions in the world. Space imagery materials, according to the US government,
become demanded by government departments for their needs with products of remote sensing systems obtained on a commercial basis. In this case, one of the
the main goals are to relieve the National Intelligence Community of the large volume of requests for these products from various US departments. The second, but no less important task of the new government policy in the field of space is the commercialization of remote sensing systems in order to further strengthen the world's leading
provisions of American companies - operators of space sensing systems. The directive determines the procedure for licensing the activities of the remote sensing system in
interests of the Ministry of Defense, intelligence and other departments, for example, the State Department, etc. And it also sets certain restrictions for foreign customers of products
remote sensing systems and the export of technologies and materials for it and defines the basis for intergovernmental cooperation in the field of military and commercial types
The steps taken by the US government are strengthening and protecting national security and creating an enabling environment for the country in the international arena by strengthening America's leading position in the field of
Remote sensing and development of our own industry. To this end, the government of the country
immense powers have been granted to the US National Cartography and Imaging Information Administration - NIMA, which is part of the US intelligence community as a structural subdivision. NIMA is functionally responsible for the collection, distribution of species information received from the remote sensing space systems among
government departments and foreign consumers, receiving and distributing
which is produced only with the approval of the US Department of State. The Department of Commerce and NASA are charged with coordinating requests for remote sensing products in the commercial sector across areas. This provides for the use of the same species information by different departments that are interested in the same survey areas.
Civilian needs in the field of remote sensing are determined by the ministries of commerce,
Internal Affairs and the NASA Space Agency. They also allocate appropriate funds for the implementation of projects in this area. Assistance in implementation
civil government remote sensing programs are provided by NIMA. This
the organization is also the lead in the preparation of action plans for the implementation of the new space policy, in the development of which, in addition to NIMA, the ministers of defense, trade, the State Department and the director of central intelligence (concurrently and director of the CIA) participate.
Geoinnovation agency "Innoter"
It is characteristic that these issues are solved by law, in the form of discussion and adoption of laws. It is taken into account that such government means of remote sensing, such as Landsat,
Terra, Aqua and others will be used to solve defense and reconnaissance tasks when it becomes unprofitable for the operator to obtain information using commercial remote sensing systems. NIMA creates all the necessary conditions for the US industry to gain a competitive advantage over others
countries. The US government guarantees support for the development of the remote sensing systems market, it also reserves the right to limit sales of generic products to certain
countries in the interests of observing the leading role of the United States in the Earth remote sensing space assets. The directive stipulates that the CIA and the Ministry of Defense must monitor their inherent
methods and methods of the state of the development of remote sensing in other countries so that the US industry does not lose its leading position in the world in the markets for remote sensing means.
The US government does not prohibit its MoD from purchasing any species materials
from commercial firms. The direct benefit is clear: there is no need to launch a new one or to retarget an existing remote sensing satellite to the military area of interest. And the efficiency is becoming the highest. This is what the US Department of Defense is happy to do,
thereby developing commercial structures engaged in the development and
using remote sensing systems.
The main ideas of the new space policy:
− it is legally stipulated that the resources of the American Earth remote sensing spacecraft will be in
to be used to the maximum extent for solving defense, reconnaissance
tasks, ensuring internal and international security and in the interests
civil users;
− government remote sensing systems (for example, Landsat, Terra, Aqua) will
focused on tasks that cannot be effectively solved by CS operators
Remote sensing due to economic factors, interests of ensuring national
security or other reasons;
− establishment and development of long-term cooperation between
government agencies and the US aerospace industry, providing an operational mechanism for licensing activities in the field of the operation of operators of remote sensing systems and the export of technologies and materials for remote sensing;
− creating conditions that provide the US industry with a competitive advantage in the provision of remote sensing services to foreign
government and commercial customers.
Geoinnovation agency "Innoter"
The new Earth remote sensing policy is the first step of the Bush administration to revise the US space policy. It is obvious that the adoption of the document took place with the active
lobbying aerospace corporations who have embraced the new rules of the game with satisfaction. The previous policy, defined by the PDD-23 directive, contributed to the emergence and development of high definition commercial media. The new document guarantees state support for the development of the remote sensing market, and
also establishes that new commercial projects will be developed by the industry taking into account the needs for specific products identified by civil
and defense departments.
Another important aspect is that the state becomes an "international pusher"
ERS commercial information. In the structure of sales of type information of commercial operators, defense and other government customers prevailed before.
However, the scale of purchases was relatively low and the space market
ERS materials developed slowly. In recent years, after the appearance of a high-resolution (0.5-1 m) remote sensing spacecraft, the situation began to change. High and medium resolution commercial systems are now seen as a critical addition
military space systems, which makes it possible to increase the efficiency of order fulfillment
and the performance of the integrated system as a whole, to delimit functions and expand the circle of users of specific information.
Over the past 5-7 years, species imaging using commercial spacecraft has become an important source of up-to-date and high-quality species information due to
for a number of reasons:
− the resource of military surveillance systems is limited due to the expansion of the range of tasks and the number of consumers, as a result of which the efficiency of solving the tasks of survey shooting has decreased;
− commercial species production of medium and low resolution has become more accessible,
by virtue of the introduction of the principles of direct broadcasting and the growth of the supply of services in the international market;
− the market for high-resolution images (up to 1 m and better) has grown significantly, and the number of operators of commercial camera systems has increased, which has led to increased competition and reduced service costs;
− commercial specific products do not have a secrecy stamp, therefore, they are subject to wide distribution among the lower levels of the Armed Forces, the command of the allied forces, other departments (the Ministry of Foreign Affairs, the Ministry of Emergency Situations, the border service) and
even the media.
Geoinnovation agency "Innoter"
On August 31, 2006, US President George W. Bush approved the concept of the US National Space Policy, which presents
fundamental principles, goals, objectives and directions of activity of the American military-political leadership, federal ministries and departments, as well as commercial structures for the use of outer space in national interests. This document replaced the 1996 presidential directive of the same name.
The release of the "national space policy" was due to the increased importance of space systems in ensuring the national security of the United States, and
also the need to bring the implemented space policy in accordance with the new conditions of the situation.
The implementation of space programs has been declared a priority area of activity. At the same time, the American military-political leadership will
adhere to a number of fundamental principles below:
− all countries have the right to free use of outer space for peaceful purposes, allowing the United States to carry out military and intelligence activities in the national interests;
− any claims are rejected any country for the sole use of outer space, celestial bodies or their parts, as well as restriction of the rights of the United States to such activities;
− The White House seeks to cooperate with the VPR of other states within the framework of
the peaceful uses of outer space in order to expand the opportunities and achieve greater results in space exploration;
− US spacecraft must operate freely in outer space.
Therefore, the United States will view any interference with the functioning of its Constitutional Court as an infringement on their rights;
− CS, including ground and space components, as well as communication lines supporting their operation, are considered vital for the national interests of the country.
V In this regard, the United States will:
− defend their rights to the free use of outer space;
− to dissuade or deter other countries from acting or developing means to violate these rights;
Earth remote sensing method
Remote sensing is the receipt by any non-contact
methods of information about the Earth's surface, objects on it or in its depths.
Traditionally, only those methods are referred to remote sensing data.
which allow you to get from space or from the air an image of the earth
surfaces in any part of the electromagnetic spectrum (i.e. by
electromagnetic waves (EMW).
The advantages of the Earth remote sensing method are
the following:
the relevance of the data at the time of the survey (most cartographic
materials are hopelessly outdated);
high efficiency of data acquisition;
high accuracy of data processing due to the use of GPS technologies;
high information content (the use of multispectral, infrared and
radar imaging allows you to see details that are not visible on conventional
pictures);
economic feasibility (costs of obtaining information
by means of remote sensing data significantly lower than ground field work);
the ability to obtain a three-dimensional terrain model (terrain matrix) for
by using stereo mode or lidar sounding methods and,
as a result, the ability to carry out three-dimensional modeling of the site
the earth's surface (virtual reality systems).
Types of sounding by signal source:
Types of sounding at the location of the equipment:
Space photography (photographic or optoelectronic):
panchromatic (more often in one wide visible part of the spectrum) - the simplest
example black and white photography;
color (shooting in several, more often real colors on one medium);
multi-zone (simultaneous, but separate fixation of the image in different
areas of the spectrum);
radar (radar);
Aerial photography (photographic or optoelectronic):
The same types of remote sensing data as in space imagery;
Lidar (laser).
The ability to detect and measure a particular phenomenon, object or process
is determined by the resolution of the sensor.
Types of permits: Characteristics of sensors of remote sensing devices
Brief characteristics of spacecraft for data acquisition
remote sensing of the earth for commercial use Aerial photo complex integrated with GPS receiver Examples of aerial photographs of various optical resolutions
0.6 m
2m
6m Aerial photograph in optical and thermal (infrared) spectra
Left - color aerial photograph
tank farms, on the right - night
thermal image of the same
territory. Besides clear
discriminating empty (light
mugs)
and
filled with
containers, thermal image
detects leaks
from
reservoir
(3)
and
pipeline (1,2). Sensor
CAD,
shooting
Center
ecological
and
technogenic monitoring, g.
Trekhgorny. Radar satellite image
Radar images enable the detection of oil and oil products on the water surface from
with a film thickness of 50 microns. Another application of radar imagery is evaluation
moisture content of soils.
10.
Radar satellite imageRadar interferometry detects deformations from near-Earth orbit
the earth's surface in fractions of a centimeter. This image shows the deformations
arising over several months of development of the Belridge oil field in
California. The color scale shows vertical offsets from 0 (black-blue) to -
58 mm (red-brown). Processing was performed by Atlantis Scientific based on ERS1 images
11.
Ground complex for receiving and processing remote sensing data
(NKPOD) is designed to receive remote sensing data from
spacecraft, their processing and storage.
The NKPOD configuration includes:
antenna complex;
reception complex;
complex of synchronization, registration and structural
recovery;
software package.
To ensure maximum radius
review
antenna
complex
should
be installed so that the horizon is
open from the corners of the elevation 2 degrees. and higher in
any azimuth direction.
For high-quality reception, essential
is an
absence
radio interference
v
the range from 8.0 to 8.4 GHz (transmitting
radio relay, tropospheric and
other communication lines).
12.
Ground complex for receiving and processing remote sensing data (NKPOD)NKPOD provides:
Formation of applications for the planning of surveying the earth's surface and reception
data;
unpacking information with sorting by routes and allocation of arrays
video information and service information;
restoration of line-line structure of video information, decoding,
radiometric correction, filtering, dynamic transformation
range, formation of an overview image and other operations
digital primary processing;
analysis of the quality of the images obtained using expert and
software methods;
cataloging and archiving information;
geometric correction and georeference of images using data
on the parameters of the angular and linear motion of spacecraft (SC) and / or
ground control points;
licensed access to data received from many foreign ERS satellites.
Antenna and receiving complex control software
performs the following main functions:
automatic check of the functioning of the hardware part of the NKPOD;
calculation of the schedule of communication sessions, i.e. the passage of the satellite through the visibility zone
NKPOD;
automatic activation of NKPOD and data reception in accordance with
schedule;
calculation of the satellite trajectory and control of the antenna complex for
satellite tracking;
formatting of the received information stream and recording it on the hard
disk;
indication of the current state of the system and information flow;
automatic maintenance of work logs.
13.
The main areas of application of satellite systems of the global
positioning for geoinformation support of enterprises
oil and gas sector:
development of geodetic reference networks of all levels from global to
surveying, as well as carrying out leveling work for the purpose of geodetic
ensuring the activities of enterprises;
ensuring the extraction of minerals (opencast mining, drilling
work, etc.);
geodetic support of construction, laying of pipelines,
cables, overpasses, power transmission lines and other engineering and applied works;
land surveying work;
rescue and preventive work (geodetic support for
disasters and catastrophes);
environmental studies: oil spill gridding, assessment
areas of oil spills and determination of the direction of their movement;
shooting and mapping of all types - topographic, special,
thematic;
integration with GIS;
application in dispatching services;
navigation of all types - air, sea, land.
14.
The device and application of satellite systems of the globalpositioning in the oil and gas industry
Existing SGPS: GPS, GLONASS, Beidou, Galileo, IRNSS
The main elements of a satellite navigation system:
15.
GLONASSThe system is based on 24 satellites (and 2 standby) moving over
surface of the Earth in three orbital planes with an inclination of the orbital
planes 64.8 ° and a height of 19 100 km
weight - 1415 kg,
guaranteed
term
active
existence - 7 years,
features - 2 signals for civilians
consumers,
on
comparison
with
companions
the previous generation ("Glonass")
positioning accuracy
objects increased by 2.5 times,
power supply unit - 1400 W,
start of flight tests - December 10
2003 year.
domestic onboard digital computer based on
microprocessor with VAX command system
11/750
weight - 935 kg,
guaranteed
term
active
existence - 10 years,
new navigation signals in the format
CDMA format compatible systems
GPS / Galileo / Compass
by adding a CDMA signal in the range
L3, the accuracy of navigation definitions in
GLONASS format will double in
compared with satellites "Glonass-M".
completely Russian apparatus, absent
imported appliances.
16.
GLONASS accuracyAccording to SDKM data as of July 22, 2011, navigation errors
GLONASS definitions in longitude and latitude were 4.46-7.38 m at
using an average of 7-8 spacecraft (depending on the receiving point). At the same
GPS error times were 2.00-8.76 m when used on average 6-11
KA (depending on the receiving point).
When both navigation systems are used together, errors
are 2.37-4.65 m when using an average of 14-19 spacecraft (in
depending on the receiving point).
The composition of the KNS GLONASS group as of 10/13/2011:
Total OG GLONASS
28 spacecraft
Used for their intended purpose
21 spacecraft
At the stage of entering the system
2 spacecraft
Temporarily withdrawn to
maintenance
4 CA
Orbital reserve
1 spacecraft
At the stage of logout
-
17.
Equipment for receiving GLONASS signalsGlospace Navigator Screen with
displaying the plan of Moscow streets in
perspective projection and indication
observer location
NAP "GROT-M" (NIIKP, 2003)
one of the first samples
18.
GpsThe system is based on 24 satellites (and 6 standby ones) moving over
surface of the Earth with a frequency of 2 revolutions per day in 6 circular orbital
trajectories (4 satellites in each), approximately 20,180 km high with an inclination
orbital planes 55 °
GPS satellite in orbit
19.
GPS signal receiving equipment20.
Types of equipment for the reception of the SGPS signalnavigator (exact time; orientation to the cardinal points; height above level
seas; direction to a point with coordinates specified by the user; the current
speed, distance traveled, average speed; current position on
electronic map of the area; current position relative to the route);
tracker (GPS / GLONASS + GSM, transmits location and movement data,
does not display the map on the client equipment - only on the server);
logger (tracker without GSM-module, records movement data).
navigator
tracker
logger
ERS satellite "Resurs-P"
Remote sensing of the Earth (ERS) - observation of the surface by aviation and space vehicles equipped with various types of imaging equipment. The working range of wavelengths received by the survey equipment is from fractions of a micrometer (visible optical radiation) to meters (radio waves). Sensing methods can be passive, that is, use the natural reflected or secondary thermal radiation of objects on the Earth's surface, caused by solar activity, and active, using the stimulated radiation of objects initiated by an artificial source of directional action. ERS data obtained from (SC) are characterized by a high degree of dependence on the transparency of the atmosphere. Therefore, the spacecraft uses multichannel equipment of passive and active types, which register electromagnetic radiation in various ranges.
ERS equipment of the first spacecraft launched in the 1960s and 1970s. was of the trace type - the projection of the measurement area onto the Earth's surface was a line. Later, panoramic ERS equipment appeared and became widespread - scanners, the projection of the measurement area onto the Earth's surface is a strip.
Spacecraft for remote sensing of the Earth are used to study the natural resources of the Earth and to solve meteorological problems. Spacecraft for the study of natural resources are equipped mainly with optical or radar equipment. The advantages of the latter are that it allows observing the Earth's surface at any time of the day, regardless of the state of the atmosphere.
general review
Remote sensing is a method of obtaining information about an object or phenomenon without direct physical contact with this object. Remote sensing is a subsection of geography. In the modern sense, the term mainly refers to the technologies of air or space sensing of terrain with the aim of detecting, classifying and analyzing objects on the earth's surface, as well as the atmosphere and the ocean, using propagated signals (for example, electromagnetic radiation). They are divided into active (the signal is first emitted by an aircraft or a space satellite) and passive remote sensing (only the signal from other sources is recorded, for example, sunlight).
Passive remote sensing sensors register a signal emitted or reflected by an object or adjacent territory. Reflected sunlight is the most commonly used radiation source, detected by passive sensors. Examples of passive remote sensing are digital and film photography, infrared, charge-coupled devices and radiometers.
Active devices, in turn, emit a signal to scan the object and space, after which the sensor is able to detect and measure the radiation reflected or generated by backscattering by the sensing target. Examples of active remote sensing sensors are radar and lidar, which measure the time delay between emitting and registering the returned signal, thus determining the location, speed, and direction of an object.
Remote sensing provides the ability to obtain data on dangerous, hard-to-reach and fast-moving objects, and also allows observations over large areas of the terrain. Examples of remote sensing applications include monitoring deforestation (for example, in the Amazon basin), the state of glaciers in the Arctic and Antarctic, and measuring the depth of the ocean using a lot. Remote sensing is also replacing expensive and relatively slow methods of collecting information from the Earth's surface, while at the same time guaranteeing human non-interference in natural processes in the observed territories or objects.
With orbiting spacecraft, scientists have the ability to collect and transmit data in various ranges of the electromagnetic spectrum, which, combined with larger aerial and ground-based measurements and analysis, provide the necessary data spectrum to monitor current events and trends such as El Niño and others. natural phenomena, both in the short and long term. Remote sensing is also of applied value in the field of geosciences (for example, nature management), agriculture (use and conservation of natural resources), national security (monitoring of border areas).
Data acquisition techniques
The main goal of multispectral studies and analysis of the obtained data is objects and territories that emit energy, which allows them to be distinguished against the background of the environment. An overview of satellite remote sensing systems can be found in the overview table.
In general, the best time to obtain data by remote sensing methods is summer time (in particular, during these months, the sun's angle above the horizon is greatest and the day is longest). An exception to this rule is the acquisition of data using active sensors (for example, Radar, Lidar), as well as thermal data in the long wavelength range. In thermal imaging, in which the sensors measure thermal energy, it is better to use the time interval when the difference in ground temperature and air temperature is greatest. Thus, the best times for these methods are during the colder months, as well as a few hours before dawn at any time of the year.
In addition, there are some more considerations to consider. With the help of radar, for example, it is impossible to obtain an image of the bare surface of the earth with thick snow cover; the same can be said for the lidar. However, these active sensors are insensitive to light (or lack thereof), making them an excellent choice for high latitude applications (for example). In addition, both radar and lidar are capable (depending on the wavelengths used) of imaging the surface under a forest canopy, making them useful in highly overgrown regions. On the other hand, spectral data acquisition methods (both stereo imaging and multispectral methods) are applicable mainly on sunny days; data collected in low light conditions tend to have a low signal-to-noise ratio, making it difficult to process and interpret. In addition, while stereo images are capable of displaying and identifying vegetation and ecosystems, it is impossible with this method (as with multi-spectral sensing) to penetrate under the canopy of trees and obtain images of the earth's surface.
Remote sensing applications
Remote sensing is most commonly used in agriculture, geodesy, mapping, monitoring the surface of the earth and the ocean, as well as the layers of the atmosphere.
Agriculture
With the help of satellites, images of individual fields, regions and districts can be obtained with certainty in a cyclical manner. Users can receive valuable information about the state of the land, including crop identification, crop area definition, and crop status. Satellite data is used to accurately control and monitor agricultural performance at various levels. This data can be used to optimize farming and spatially oriented management of technical operations. The images can help determine the location of crops and the extent of land depletion, and can then be used to develop and implement a treatment plan to optimize the local use of agricultural chemicals. The main agricultural applications of remote sensing are as follows:
- vegetation:
- crop type classification
- crop condition assessment (crop monitoring, damage assessment)
- yield assessment
- the soil
- display of soil characteristics
- display of soil type
- soil erosion
- soil moisture
- display of tillage practice
Forest cover monitoring
Remote sensing is also used to monitor forest cover and species identification. Maps obtained in this way can cover a large area, while simultaneously displaying detailed measurements and characteristics of the area (tree type, height, density). Using remote sensing data, it is possible to identify and delineate different types of forest that would be difficult to achieve using traditional methods on the surface of the earth. Data is available in a variety of scales and resolutions to suit local or regional requirements. Requirements for the detail of the terrain display depends on the scale of the study. To display changes in forest cover (texture, density of leaves), apply:
- multispectral imagery: very high resolution data is needed to accurately identify species
- multiple images of the same territory are used to obtain information about seasonal changes of various types
- stereophotos - for differentiation of species, assessment of the density and height of trees. Stereo photographs provide a unique view of forest cover only accessible through remote sensing technology
- Radars are widely used in the humid tropics due to their ability to acquire images in all weather conditions
- Lidars allows you to get a 3-dimensional structure of the forest, to detect changes in the height of the earth's surface and objects on it. Lidar data helps estimate tree heights, crown areas, and the number of trees per unit area.
Surface monitoring
Surface monitoring is one of the most important and typical applications for remote sensing. The obtained data are used to determine the physical state of the earth's surface, for example, forests, pastures, road surfaces, etc., including the results of human activities, such as the landscape in industrial and residential areas, the state of agricultural areas, etc. Initially, a land cover classification system should be established, which usually includes land levels and classes. Levels and grades should be developed taking into account the purpose of use (national, regional or local), spatial and spectral resolution of remote sensing data, user request, and so on.
Detecting changes in the state of the earth's surface is necessary to update land cover maps and rationalize the use of natural resources. Changes are typically found when comparing multiple images containing multiple layers of data and, in some cases, comparing old maps and updated remote sensing images.
- seasonal change: agricultural land and deciduous forests change seasonally
- annual changes: changes in land surface or land-use area, such as deforestation or urban sprawl
Information about the land surface and changes in vegetation cover is directly necessary for the determination and implementation of environmental protection policies and can be used in conjunction with other data to perform complex calculations (for example, to determine the risks of erosion).
Geodesy
Airborne survey data collection was first used to detect submarines and obtain gravity data used to construct military maps. These data represent the levels of instantaneous disturbances of the Earth's gravitational field, which can be used to determine changes in the distribution of the Earth's masses, which in turn can be required for various geological studies.
Acoustic and near-acoustic applications
- Sonar: passive sonar, records sound waves emanating from other objects (ship, whale, etc.); active sonar, emits pulses of sound waves and registers the reflected signal. Used to detect, locate and measure parameters of underwater objects and terrain.
- Seismographs are a special measuring device that is used to detect and record all types of seismic waves. With the help of seismograms taken in different places of a certain territory, it is possible to determine the epicenter of an earthquake and measure its amplitude (after it has occurred) by comparing the relative intensities and the exact time of the oscillations.
- Ultrasound: Ultrasound sensors that emit high-frequency pulses and record the reflected signal. Used to detect water waves and determine the water level.
When coordinating a series of large-scale observations, most sensing systems depend on the following factors: the location of the platform and the orientation of the sensors. High quality instruments nowadays often use positional information from satellite navigation systems. Rotation and orientation are often determined by electronic compasses with an accuracy of about one to two degrees. Compasses can measure not only azimuth (i.e., the degree deviation from magnetic north), but also altitude (the value of the deviation from sea level), since the direction of the magnetic field relative to the Earth depends on the latitude at which the observation is taking place. For more accurate orientation, it is necessary to use inertial navigation, with periodic corrections by various methods, including navigation by stars or known landmarks.
Overview of the main remote sensing instruments
- Radars are mainly used in air traffic control systems, early warning systems, forest cover monitoring, agriculture and for obtaining large-scale meteorological data. Doppler radar is used by law enforcement agencies to monitor the speed of vehicles, as well as to obtain meteorological data on wind speed and direction, location and intensity of precipitation. Other types of information obtained include ionized gas data in the ionosphere. Artificial Aperture Interferometric Radar is used to obtain accurate digital elevation models of large areas.
- Satellite laser and radar altimeters provide a wide range of data. By measuring the fluctuations in ocean water level caused by gravity, these instruments display the topography of the seabed with a resolution of the order of one mile. By measuring the height and wavelength of ocean waves with altimeters, you can find out the speed and direction of the wind, as well as the speed and direction of surface ocean currents.
- Ultrasonic (acoustic) and radar sensors are used to measure sea level, ebb and flow, and determine the direction of waves in coastal sea regions.
- Light Detection and Ranging (LIDAR) technology is well known for its applications in the military field, in particular in laser navigation of projectiles. LIDAR is also used to detect and measure the concentration of various chemicals in the atmosphere, while LIDAR on board aircraft can be used to measure the height of objects and phenomena on the ground with greater accuracy than can be achieved with radar technology. Remote sensing of vegetation is also one of the main applications of LIDAR.
- Radiometers and photometers are the most common instruments used. They capture reflected and emitted radiation over a wide frequency range. The most common are visible and infrared sensors, followed by microwaves, gamma ray sensors and, less commonly, ultraviolet sensors. These instruments can also be used to detect the emission spectrum of various chemicals, providing data on their concentration in the atmosphere.
- Stereo images from aerial photography are often used to probe vegetation on the Earth's surface, as well as to generate topographic maps in the development of potential routes by analyzing terrain images, combined with modeling of environmental features obtained by ground methods.
- Multispectral platforms such as Landsat have been in active use since the 1970s. These instruments have been used to generate thematic maps by imaging multiple wavelengths of the electromagnetic spectrum (multi-spectrum) and are typically used on Earth observation satellites. Examples of such missions include the Landsat program or the IKONOS satellite. Land cover and land-use maps generated by thematic mapping can be used for mineral exploration, detection and monitoring of land use, deforestation, and the study of plant and crop health, including vast tracts of agricultural land or woodland. Landsat satellite imagery is used by regulators to monitor water quality parameters including Secchi depth, chlorophyll density and total phosphorus. Meteorological satellites are used in meteorology and climatology.
- Spectral imaging produces images in which each pixel contains complete spectral information, displaying narrow spectral ranges within a continuous spectrum. Spectral imaging devices are used to solve various problems, including those used in mineralogy, biology, military affairs, and measurements of environmental parameters.
- As part of the fight against desertification, remote sensing allows observing areas that are at risk in the long term, determining the factors of desertification, assessing the depth of their impact, as well as providing the necessary information to those responsible for making decisions on the adoption of appropriate environmental protection measures.
Data processing
With remote sensing, as a rule, digital data processing is used, since it is in this format that remote sensing data are received at the present time. In a digital format, it is easier to process and store information. A two-dimensional image in one spectral range can be represented as a matrix (two-dimensional array) of numbers I (i, j), each of which represents the intensity of radiation received by the sensor from an element of the Earth's surface, which corresponds to one pixel in the image.
The image consists of n x m pixels, each pixel has coordinates (i, j)- line number and column number. Number I (i, j)- integer and is called the gray level (or spectral brightness) of the pixel (i, j)... If the image is obtained in several ranges of the electromagnetic spectrum, then it is represented by a three-dimensional lattice consisting of numbers I (i, j, k), where k Is the number of the spectral channel. From a mathematical point of view, it is not difficult to process digital data obtained in this form.
In order to correctly reproduce the image on digital recordings supplied by information receiving points, it is necessary to know the recording format (data structure), as well as the number of rows and columns. Four formats are used that order the data as:
- sequence of zones ( Band Sequental, BSQ);
- zones alternating along lines ( Band Interleaved by Line, BIL);
- zones alternating in pixels ( Band Interleaved by Pixel, BIP);
- a sequence of zones with compression of information into a file by the method of group coding (for example, in jpg format).
V BSQ-format each area image is contained in a separate file. This is convenient when there is no need to work with all zones at once. One zone is easy to read and visualize, zone images can be loaded in any order you want.
V BIL-format zonal data is written to one file line by line, while the zones alternate along the lines: 1st line of the 1st zone, 1st line of the 2nd zone, ..., 2nd line of the 1st zone, 2nd line 2nd zone, etc. Such recording is convenient when all zones are analyzed simultaneously.
V BIP-format the zonal values of the spectral brightness of each pixel are stored sequentially: first, the values of the first pixel in each zone, then the values of the second pixel in each zone, etc. This format is called combined. It is convenient when performing pixel-by-pixel processing of a multi-zone image, for example, in classification algorithms.
Group coding used to reduce the amount of raster information. Such formats are convenient for storing large images; to work with them, you need to have a means of unpacking the data.
Image files are usually accompanied by the following additional information related to snapshots:
- description of the data file (format, number of rows and columns, resolution, etc.);
- statistical data (characteristics of brightness distribution - minimum, maximum and average value, variance);
- map projection data.
Additional information is contained either in the header of the image file or in a separate text file with the same name as the image file.
According to the degree of complexity, the following levels of CW processing provided to users differ:
- 1A - Radiometric correction of distortions caused by differences in sensitivity of individual sensors.
- 1B - radiometric correction at the processing level 1A and geometric correction of systematic sensor distortions, including panoramic distortions, distortions caused by the rotation and curvature of the Earth, fluctuations in the altitude of the satellite orbit.
- 2A shows image correction at 1B level and correction in accordance with a given geometric projection without using ground control points. For geometric correction, a global digital elevation model ( DEM, DEM) with a step of 1 km on the ground. The used geometric correction eliminates systematic sensor distortions and projects the image into a standard projection ( UTM WGS-84), using known parameters (satellite ephemeris data, spatial position, etc.).
- 2B - image correction at 1B level and correction in accordance with a given geometric projection using ground control points;
- 3 - image correction at 2B level plus correction using terrain DEM (orthorectification).
- S - image correction using the reference image.
The quality of data obtained from remote sensing depends on their spatial, spectral, radiometric and temporal resolution.
Spatial resolution
It is characterized by the size of a pixel (on the surface of the Earth) recorded in a raster image - usually ranging from 1 to 4000 meters.
Spectral resolution
Landsat data includes seven bands, including the infrared spectrum, ranging from 0.07 to 2.1 µm. The Hyperion sensor of the Earth Observing-1 apparatus is capable of registering 220 spectral bands from 0.4 to 2.5 µm, with a spectral resolution of 0.1 to 0.11 µm.
Radiometric resolution
The number of signal levels that the sensor can record. Typically ranges from 8 to 14 bits, resulting in 256 to 16 384 levels. This characteristic also depends on the noise level in the instrument.
Temporary permission
The frequency of the satellite's flight over the surface area of interest. Relevant when examining a series of images, for example, when studying the dynamics of forests. Initially, the analysis of the series was carried out for the needs of military intelligence, in particular, to track changes in infrastructure, the movements of the enemy.
To create accurate maps based on remote sensing data, a transformation that removes geometric distortion is required. An image of the Earth's surface with a device pointing straight down contains an undistorted image only in the center of the image. As you move to the edges, the distances between the points on the image and the corresponding distances on the Earth become more and more different. Correction of such distortions is performed during the photogrammetry process. Since the early 1990s, most commercial satellite imagery has been sold already corrected.
In addition, radiometric or atmospheric correction may be required. Radiometric correction converts discrete signal levels, such as 0 to 255, to their true physical values. Atmospheric correction removes spectral distortion introduced by the presence of the atmosphere.
