51 results about "Synchronous orbit" patented technology

The invention provides a solar synchronous orbit quick response SAR satellite load platform integrated configuration, which comprises a satellite body, an SAR antenna, a solar array, a phased array data transmission antenna, a star sensor and a body-mounted solar cell, the satellite body is in a quadrangular prism shape, the cross section of the satellite body is an isosceles trapezoid, the satellite body comprises a group of opposite parallel surfaces and a group of opposite inclined surfaces, the phased array data transmission antenna and the star sensor are respectively arranged on two parallel surfaces, and the SAR antenna and the solar array are respectively arranged on two inclined surfaces; the body-mounted solar cell piece and the solar array are installed on the same inclined plane and located on the inner side of the solar array, and the solar array comprises two solar array plates and has an unfolded state and a folded state. According to the method, load platform integration is taken as a design thought, so that the AIT process of the SAR satellite and the time required by AIT are greatly shortened; meanwhile, the attitude requirements of energy and load work are met, and the reliability of the initial injection stage is improved through sufficient energy.

The invention provides an intelligent quality control and inversion method for electric power meteorological multi-source data, and relates to the field of data processing. In the method, a multi-view polarized brightness temperature vector structure is constructed by using original brightness temperature observation data acquired by a plurality of satellite-borne microwave radiometers in a near-synchronous orbit intersection area, and a multi-dimensional radiation transmission equation set driven by an earth ellipsoid path integral model is input to generate a brightness temperature prediction result; an inversion optimization model is constructed based on view angle invariant residual constraint, initialization is carried out based on historical data and ground data, and variational inversion solving is carried out to obtain a joint inversion result; and evaluating the credibility through a profile quality vector, and finally supporting stability early warning and load correction in electric power meteorology. By implementing the technical scheme provided by the invention, the quality control and inversion precision of the power meteorological multi-source data profile can be improved.

A method of sun-synchronous orbit design for remote sensing satellite based on revisit characteristics is proposed. The relationship between revisit and ground synchronization is established by Q value. The mathematical model of Q is established by node revisit sequence in a certain interval. Then the coverage rate is obtained by the mixed node access sequence and coverage area of orbit altitude and observation angle. Finally, the coverage rate of remote sensing satellite in sun-synchronous orbit is demonstrated from three aspects of time-varying coverage rate, minimum coverage time and minimum observation angle, which provides a reference for the design of sun-synchronous orbit of remote sensing satellite.

The invention provides a non-sun-synchronous orbit satellite energy optimal attitude sailboard control method and system. The method comprises the steps that S1, the illumination angle of each orbit in the satellite life period is calculated according to collected orbit parameters; s2, calculating the illumination area half angle and the illumination duration under the illumination angle of each track; s3, calculating the illumination energy of each track of the sailboard driving shaft under the combination of different swinging positions and different flight attitudes of the satellite; s4, comparing illumination energy of each track, and preferably selecting a combination of a posture with the maximum energy in each period and a sailboard driving position; and S5, obtaining a control strategy for the attitude of all orbital circles of satellites and the position of a sailboard driving shaft in the whole life period of the satellites. By comparing various feasible in-orbit attitude and sailboard position combinations, a sailboard position and attitude control method with optimal energy can be obtained through optimization, the in-orbit receiving energy of a two-dimensional driving solar sailboard satellite is improved, the required sailboard area is reduced under the same power consumption requirement, and the weight of the whole satellite is reduced.

The application discloses a high-throughput satellite access method and system based on 5G NR. The method is as follows: a beacon signal and a random access channel are arranged on a global signaling beam of a high-throughput satellite; a satellite terminal requests a service beam service of the high-throughput satellite through the random access channel; all satellite terminals share the random access channel, and resource competition is realized through a random backoff competition mechanism; the satellite terminal adjusts an antenna pointing direction and reports user position information by using the global signaling beam; a satellite system adjusts a variable service beam pointing direction according to the user position information, and provides access service for the user; the satellite system provides a 5G broadcast signal for the user through the service beam, and completes broadcast reception and random access of the 5G satellite system. The system realizes the high-throughput satellite access method based on 5G NR. The application realizes satellite terminal access based on 5G standards without affecting an existing synchronous orbit high-throughput satellite architecture.

The present invention discloses a method and system for transmitting in a combined geosynchronous orbit and low-orbit double-layer satellite network. The method includes the following steps: S1, a geosynchronous orbit (GEO) satellite transmits signals to low-earth orbit (LEO) satellites and cellular users; S2, the LEO satellites and cellular users receive the signals transmitted by the GEO satellite; S3, the LEO satellites use the decode-and-forward relay protocol and adaptive non-orthogonal multiple access (NOMA) to send signals to the cellular users; S4, the cellular users receive the signals relayed by the LEO satellites and combine the signals from the GEO satellite and the LEO satellite using the maximum ratio combining method. The power allocation factor of the adaptive non-orthogonal multiple access technology proposed by the present invention is dynamically adjusted according to the channel state, satellite elevation angle, and co-channel interference, and can achieve differential power allocation for different users' dynamic channels, improving the spectrum utilization rate and power allocation fairness.

The invention discloses a synchronous orbit electric propulsion satellite short-range game control method based on differential game, which comprises the following steps: under an LVLH coordinate system, establishing a near-circular orbit relative motion dynamic model of spacecrafts of both pursuit and escape parties, and further determining a state space form in a spacecraft pursuit and escape game process; based on a state space form in a spacecraft pursuit game process, introducing a Hamiltonian function, and constructing a short-distance pursuit game model with optimal time; introducing a co-state equation, and describing a short-range pursuit game process as a two-point boundary value problem; and converting the problem into a parameter optimization problem, and carrying out optimization solution on the problem by utilizing an improved difference method so as to realize short-range game control.

A method for planning a drift-and-survey mission for a geostationary orbit space target monitoring and imaging satellite is disclosed. The initial time and corresponding initial position of the observation satellite's roving mission are determined based on requirements, as well as the approach observation time and corresponding approach observation position. At the first maneuver time, the observation satellite moves to the first maneuver position, and a first velocity increment is applied to the initial velocity vector at this point, causing the observation satellite to maneuver tangentially along the orbit to obtain the velocity vector after the first maneuver. At the second maneuver time, the observation satellite moves to the second maneuver position, and a second velocity increment is applied to the initial velocity vector at this point, causing the observation satellite to maneuver tangentially along the orbit to obtain the velocity vector after the second maneuver. At the approach observation time, the observation satellite is at the approach observation position and observes the target satellite under front lighting conditions using the observation vector. This invention can improve roving efficiency and flexibility, realize drift-and-survey observation of targets on different surfaces, save propellant, and improve satellite performance.

The invention provides a communication method, a communication device and a communication system, which are applied to the field of communication. The present application is applicable to a communication system comprising a UE and a satellite, the satellite being a synchronous orbit satellite. The communication method comprises the following steps: UE calculates a TA change value by combining own position information, wherein the TA change value comprises a TA added value and a TA reduced value; and the TA change value is reported while the TA is reported to the satellite, so that the satellite / base station can determine the potential conflict area based on the TA change value, and the potential conflict area can be determined by the satellite / base station when the satellite / base station configures transmission resources (including uplink transmission and downlink transmission) or schedules data (such as preferentially transmitting high-priority data). Therefore, the purpose of avoiding the conflict between uplink transmission and downlink transmission is achieved, and the influence caused by the conflict area is reduced to the minimum extent.

The application discloses a time-difference-based synchronous orbit satellite fast maneuvering detection method, and aims at the problem of maneuvering detection of synchronous orbit satellites under a radio monitoring system. The difference between the time-difference measurement value of satellite signals arriving at two receiving stations and the theoretical value calculated by a predicted ephemeris can be approximately a linear function of satellite position error. The difference between two different time points is used as a test statistic to detect whether the satellite has maneuvered. The application greatly reduces the number of estimated parameters and the demand for observation arc length, and only needs two receiving stations to observe a short arc segment for several minutes to realize fast maneuvering detection of the synchronous orbit satellite, thereby reducing the system complexity and improving the timeliness of the system.

The invention provides an inter-station satellite bidirectional time forecasting method, and belongs to the technical field of time calibration and forecasting. According to the method, a synchronous orbit GEO satellite is used as a forwarding node of a space segment, two stations respectively carry out BPSK modulation on local time mark signals to form frequency signals, and the frequency signals are transmitted to an opposite end through power amplification. In the data processing process, an inter-station time comparison result is calculated according to an existing model, then modeling and learning training are carried out on measured data by using an LSTM model, and finally a predicted inter-station time comparison sequence is output to be used for correcting inter-station time deviation of the next period and forecast of various clock differences.

The present invention provides an imaging method, device and electronic equipment for suppressing moving targets by a geosynchronous orbit synthetic aperture radar, which are applied to the fields of synthetic aperture radar signal processing and artificial intelligence technology. The method comprises: receiving echo data sent by a synthetic aperture radar; performing aperture segmentation on the echo data to obtain a plurality of sub-aperture data; performing the following operations on each sub-aperture data: performing range compression and back-projection on the sub-aperture data to obtain an imaging result of the sub-aperture data; determining phase information and amplitude information of the sub-aperture data based on the imaging result; determining a background image of the sub-aperture data based on the amplitude information; combining the phase information and the background image to obtain complex-valued data of the sub-aperture data; and coherently fusing the complex-valued data of a plurality of sub-aperture data to obtain a target image.

The invention provides a synchronous orbit SAR moving ship detection imaging method, device and equipment and a medium, relates to the technical field of satellite detection imaging, and is applied to a geosynchronous orbit synthetic aperture radar carried on a satellite platform. The method comprises the following steps: dividing a full-aperture echo signal into a plurality of sub-aperture echo signals of optimal sub-apertures along azimuth time; sequentially carrying out distance compression and platform motion compensation based on a scene center reference signal on each sub-aperture echo signal, and eliminating linear distance migration caused by a tangential component of a ship translation speed in the sub-aperture echo signals; focusing the sub-aperture echo signal after eliminating the linear range migration through phase compensation and azimuth coherent accumulation to obtain a focused image of the moving ship target; and processing the focused image by adopting a constant false alarm detection algorithm, and outputting a final detection result of the moving ship target.

The application discloses an autonomous program control system level test method, and proposes a solution method for the correctness, effectiveness, safety and integrity of satellite active stage operation period satellite-rocket separation program control, autonomous flight program control, synchronous orbit stage operation period machine cutting program control, and emergency program control task verification. Based on satellite 1553B bus data simulation function and automatic test, satellite program control execution process is simulated and forwarded, satellite autonomous instruction sequence during program control execution is analyzed or intercepted, satellite program control process safety risk hidden danger is guaranteed, and effective verification of satellite autonomous program control function and comprehensive interpretation of instruction telemetry are realized.

The present invention provides a satellite system and method for collaborative detection and imaging of low-orbit targets from a low-orbit orbit. The satellite system includes three sun-synchronous orbit reconnaissance satellites with orbital altitudes of 600km, 800km, and 1000km. The satellite carries a camera payload with optical imaging and detection capabilities. The satellite has three working modes: flyby imaging, fly-by imaging, and joint detection and positioning mode. The advantage is that it can perform real-time multi-angle detection of satellites within the orbital altitude range of 500 to 1100km, provide high-precision positioning and orbit determination of targets; and perform high-frequency flyby imaging, and the minimum imaging distance is short (less than or equal to 100km), the imaging effect is good, and it has multiple observation angles. It can quickly form a fly-by imaging configuration for sun-synchronous orbit satellites within the orbital altitude range of 500 to 1100km, and perform fly-by imaging of targets.

The application discloses a geosynchronous orbit SAR sea surface wave imaging quality evaluation method and belongs to the technical field of geosynchronous orbit space correlation SAR sea surface wave imaging quality evaluation. The application obtains a sea surface wave echo signal, performs distance direction matching filtering and space correlation processing on the sea surface wave echo signal, generates an imaging result by using a back projection algorithm, calculates image intensity and a sea wave spectrum main energy direction slope, and finally quantifies imaging quality by using a space correlation evaluation factor. The evaluation factor can effectively represent the space coherence of sea surface wave imaging, and the larger the value is, the better the imaging quality is. The application solves the problem of insufficient applicability of existing evaluation methods in sea surface wave imaging due to low contrast and weak texture features, significantly improves the accuracy of geosynchronous orbit SAR sea surface wave imaging quality evaluation, and provides reliable technical support for marine environment monitoring.

The application provides a satellite configuration and switching method of a multi-band planar phased array antenna, which comprises a satellite platform 1, a flat panel antenna group and a solar cell array 5, the flat panel antenna group comprises multiple flat panel antennas of different frequency bands and is connected to the top plate of the satellite platform 1, the solar cell array 5 is connected to the bottom plate of the satellite platform 1, when in a launching state, the multiple flat panel antennas of different frequency bands are all folded and close to the first side surface, and the solar cell array 5 is folded and close to the second side surface; when in a flying state, the multiple flat panel antennas of different frequency bands are all unfolded until the multiple flat panel antennas of different frequency bands and the top plate of the satellite platform 1 are located in the same plane, and the solar cell array 5 is unfolded until the solar cell array 5 and the bottom plate of the satellite platform 1 are located in the same plane. The satellite configuration has stable structure and can bear large-size and large-mass load, and has high adaptability to satellites with flat panel type effective load in the current sun-synchronous orbit and low-inclination orbit.

The invention provides a sun-synchronous orbit inclination angle adjusting method and device, and the method comprises the steps: determining a position relation between an initial orbit and a target orbit, enabling two intersection points of the initial orbit and the target orbit to be located above an equator, and taking one of the intersection points as a satellite orbit transfer point; determining an orbital transfer angle required for adjusting the satellite from the initial orbital plane to the target orbital plane; according to the system state of the satellite and the task target, the single ignition duration of the satellite and the ignition moment and shutdown moment of the satellite are comprehensively determined; determining a satellite ignition direction; the speed increment of satellite monopulse ignition is analyzed and calculated, and the total impulse required for changing the inclination angle of the satellite orbit is determined according to the speed increment; the total satellite ignition orbit number is analyzed and calculated according to the total impulse and the actual impulse generated by each time of ignition; and based on the satellite orbital transfer point, the satellite ignition direction, the satellite ignition time and the shutdown time, the satellite is controlled to carry out secondary ignition orbital transfer, and then inclination angle adjustment is completed.

The geosynchronous orbit debris inclination vector evolution calculation method disclosed by the application comprises the following steps: firstly, calculating the influence of the J2 term of the earth's non-spherical perturbation on the change rate of the inclination debris, calculating the angular frequency of the geosynchronous orbit debris inclination vector, the period of the precession and the angular rate of the precession under the influence of the J2 term; then, calculating the frequency of the geosynchronous orbit debris inclination vector precession, the period of the precession and the angular rate of the precession caused by the sun's gravity and the moon's gravity respectively; finally, synthesizing and calculating the different angular frequencies, the periods of the inverse precession and the angular rates of the precession. The geosynchronous orbit debris inclination vector evolution calculation method disclosed by the application separately calculates the effects of the J2 term of the earth and the sun and the moon, and compared with the traditional geosynchronous orbit debris inclination vector evolution calculation method which adopts complete numerical calculation, the method has the advantages of fast calculation speed and can be used for the analysis and calculation of the long-term evolution of the geosynchronous orbit debris orbit.

The application discloses a positioning method and system based on Beidou PPP-B2b, and comprises the following steps: acquiring PPP-B2b orbit correction numbers broadcast by Beidou No.3 system geosynchronous orbit satellites; establishing a first full-network state space error estimation model of corresponding estimated parameters of satellite clock errors of multiple satellites, multiple satellites and multiple reference station servers according to the PPP-B2b orbit correction numbers; introducing reference constraints to the first full-network state space error estimation model, and redefining parameters to solve the satellite clock errors and the corresponding estimated parameters, so that positioning is performed according to the solved satellite clock errors. The application can quickly solve the satellite clock errors, improve the precision and reliability of the satellite clock errors, and realize wide-area real-time precise positioning.

An autonomous mission planning method for ultra-low sun-synchronous orbit optical remote sensing satellites includes the following steps: extrapolating the satellite orbit considering atmospheric drag and thrust effects; planning orbit maintenance arcs according to an autonomous orbit maintenance strategy; planning imaging and data transmission arcs respectively according to imaging and data transmission mission requirements; eliminating overlapping orbit maintenance, imaging, and data transmission arcs based on priority; estimating whether the planned arcs meet the energy requirements; if not, eliminating the planned arcs; updating the surface-to-mass ratio based on the planned arcs, and replanning using the updated surface-to-mass ratio until the planned arcs remain unchanged compared to the previous one; completing the autonomous mission planning for the next few orbits. This invention uses electric propulsion for autonomous orbit maintenance as a key constraint in mission planning, prioritizing satellite energy for orbit maintenance, and on this basis, maximizing the performance of imaging and data transmission missions.

The invention discloses a co-orbit satellite system and 5GNR system coexistence interference simulation method and device, and is used for solving the problems of complex simulation system and low simulation efficiency in the prior art, and the method comprises the steps: S11, constructing an interference evaluation scene; s12, configuring related parameters of a synchronous orbit satellite system, a 5GNR system, a 5GNR user terminal, a satellite user terminal and the like according to the interference scene; s13, distributing 5GNR base stations in the coverage area of the satellite network according to the configuration parameters; s14, distributing satellite network users and 5GNR user terminals, and establishing association between the users and the base station; and S15, calculating signal to interference plus noise ratios of the single system and the heterogeneous system, and performing interference assessment by adopting a throughput loss method. According to the method, the complexity of evaluation between large-scale heterogeneous systems can be reduced, the evaluation process between the large-scale heterogeneous systems is simplified, the simulation efficiency is high, and the practicability is high.

The invention discloses a geosynchronous orbit SAR (Synthetic Aperture Radar) sea surface wave imaging quality evaluation method, and belongs to the technical field of geosynchronous orbit space correlation SAR sea surface wave imaging quality evaluation. The method comprises the following steps: acquiring a sea surface wave echo signal, generating an imaging result by using a backward projection algorithm after range-direction matched filtering and spatial correlation processing, calculating image intensity and a sea wave spectrum main energy direction slope, and finally quantifying imaging quality through a spatial correlation evaluation factor. The evaluation factor can effectively represent the spatial coherence of sea surface wave imaging, and the larger the value is, the better the imaging quality is. According to the method, the problem of insufficient applicability caused by low contrast and weak texture features in sea surface wave imaging of an existing evaluation method is solved, the accuracy of geosynchronous orbit SAR sea surface wave imaging quality evaluation is remarkably improved, and reliable technical support is provided for marine environment monitoring.

This invention provides a method and apparatus for adjusting the inclination of a sun-synchronous orbit. The method includes: determining the positional relationship between an initial orbit and a target orbit, such that the two intersection points of the initial orbit and the target orbit are located above the equator, and using one of the intersection points as the satellite's orbit change point; determining the orbit change angle required for the satellite to adjust from the initial orbital plane to the target orbital plane; comprehensively determining the satellite's single ignition duration, ignition time, and shutdown time based on the satellite's system status and mission objectives; determining the satellite's ignition direction; analytically calculating the velocity increment of the satellite's single pulse ignition, and determining the total impulse required to change the satellite's orbit inclination based on the velocity increment; analytically calculating the total number of satellite ignitions based on the total impulse and the actual impulse generated by each ignition; and controlling the satellite to perform a single ignition orbit change to complete the inclination adjustment based on the satellite's orbit change point, ignition direction, ignition time, and shutdown time.

The invention discloses a remote drifting game control method for synchronous orbit electric propulsion satellites. The method comprises the steps that the synchronous orbit electric propulsion satellites are divided into cooperative targets and non-cooperative targets; carrying out remote floating approaching control on the cooperative target by adopting a transverse thrust control method; for a non-cooperative target, establishing an absolute dynamic model considering J2 perturbation, constructing a time-optimal pursuit game saddle point strategy problem of introducing a Hamilton function based on the absolute dynamic model, and converting the time-optimal pursuit game saddle point strategy problem into a two-point boundary value problem; and converting a two-point boundary value problem into an unconstrained parameter optimization problem, performing global search and local optimization solution on the unconstrained parameter optimization problem, and performing remote drifting game control on the non-cooperative target according to an optimal solution. According to the invention, the low-cost floating game control of the geosynchronous orbit electric propulsion satellite is realized by designing a game control strategy with high success rate approaching.

The application discloses a synchronous orbit synthetic aperture radar satellite on-board guidance attitude calculation method and belongs to the field of satellite attitude control. The method comprises the following steps: calculating the guidance attitude of a satellite at a current time in a yaw-pitch guidance mode; calculating the guidance attitude of a payload beam pointing direction in a pitch-roll guidance mode by using the guidance attitude of the payload beam pointing direction in the yaw-pitch guidance mode; and calculating the final guidance attitude in the pitch-roll guidance process under the constraint of a payload beam installation bias to correct the payload installation bias; and based on the final guidance attitudes at the current time and the last time, the attitude guidance angular rate and the attitude guidance angular acceleration are determined by using a differential calculation mode to combine the orbit parameters to calculate the pitch-roll guidance attitude quaternion at the current time, so that the Doppler frequency of a ground imaging target center point of the satellite is zero. The application can eliminate the influence of a large yaw angle and the influence of a payload installation beam bias and complete satellite attitude guidance.

The application provides a geosynchronous orbit high-energy electron flux prediction method, a model and a model construction method, and relates to the field of electron flux prediction; the geosynchronous orbit high-energy electron flux prediction method comprises the following steps: constructing a geosynchronous orbit high-energy electron flux prediction model; inputting the following parameters into the geosynchronous orbit high-energy electron flux prediction model: a time point T, spatial coordinates of a spatial point in a radiation belt, and average solar wind speed in a time range of [T-a hours, T-b hours]; calculating high-energy electron flux at the geosynchronous orbit height passing through the spatial point in a quiet period; judging whether the spatial point at the geosynchronous orbit height is in a storm time or not, and outputting high-energy electron flux at the geosynchronous orbit height passing through the spatial point in the quiet period or the storm time. The high-energy electron flux prediction method provided by the application can automatically switch the flux prediction mode in the quiet period or the storm time, and significantly improves the prediction accuracy under different geomagnetic activity conditions.

The invention relates to the technical field of satellite orbits, in particular to a sun-synchronous orbit dip angle offset calculation method and device, equipment and a medium. According to the method, an orbit perturbation equation containing earth non-spherical gravity and atmospheric damping perturbation is constructed, and the influence of semi-major axis attenuation caused by atmospheric resistance on the inclination angle offset is considered. According to the method, the influence of atmospheric damping on the orbit height and different orbit height maintaining strategies are comprehensively considered, more accurate orbit injection parameters are calculated in combination with the prior art, and a more reliable guarantee is provided for subsequent on-orbit normal operation of a spacecraft. In the initial stage of orbit design, more accurate spacecraft orbit injection parameters can be calculated by introducing more perturbation models. The orbit height maintaining strategy is also considered, which means that the later-stage spacecraft in-orbit operation and maintenance cost is also considered, the engineering implementation is more reliable, the result is more accurate, and meanwhile, flexible adjustment can be realized by fully combining actual conditions.

This invention discloses a method for implementing a geostationary orbit sparse spotting SAR imaging mode. The method involves constructing a schematic diagram of the wavefront selection for a geostationary orbit spotting SAR system; designing the wavefront of the geostationary orbit sparse spotting SAR imaging mode and calculating the mode parameters; calculating the yaw angle required for zero-Doppler attitude guidance of the geostationary orbit SAR satellite; constructing a radiation pattern model of the array antenna for the geostationary orbit sparse spotting SAR imaging mode; and conducting performance analysis of the geostationary orbit sparse spotting SAR imaging mode. This invention combines sparse microwave imaging with a geostationary orbit spotting SAR mode. Based on the existing SAR system, it uses a more accurate zebra pattern and appropriate wavefront design to obtain a larger mapping bandwidth, achieving the high-resolution, wide-swath observation objective of geostationary orbit spotting SAR. Simultaneously, it improves system performance by reducing range ambiguity and suppressing the influence of antenna rotation on orientation ambiguity.

The present invention discloses a method for planning a detailed inspection mission of a geosynchronous orbit target imaging satellite, the method comprising: dividing the mission orbit into an approaching segment, a phase adjustment segment, an outbound detailed inspection segment, a U-turn segment, a return detailed inspection segment, and a distance segment; determining the maneuvering time of the first orbital maneuver, the second orbital maneuver, the third orbital maneuver, the fourth orbital maneuver, and the fifth orbital maneuver; determining the speed increment of the first orbital maneuver, the second orbital maneuver, the third orbital maneuver, the fourth orbital maneuver, and the fifth orbital maneuver. The present invention does not have a long-term approaching state with the target, which is conducive to concealing the observation intention, reducing the intensity of the on-orbit game, avoiding legal disputes, and at the same time avoiding the target's awareness and evasion of observation as much as possible, which is conducive to achieving the observation purpose.