A satellite integrity monitoring method and device under ground-based joint observation

Abstract

The present invention discloses a satellite integrity monitoring method and device under joint observation between the earth and the sky, the method comprising: obtaining satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data; processing the satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data to obtain a space-to-ground integrated monitoring network; the space-to-ground integrated monitoring network comprises an inter-satellite monitoring network, a satellite-borne observation network and a satellite-to-ground monitoring network; using the space-to-ground integrated monitoring network, processing a target satellite to obtain a satellite integrity monitoring result; the satellite integrity monitoring result comprises a first satellite integrity monitoring result and a second satellite integrity monitoring result. The present invention can realize the integrity monitoring of the entire arc segment of an on-orbit satellite by constructing a space-to-ground integrated monitoring network and combining the optimization of satellite-borne observation network link data.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation technology, and in particular to a satellite integrity monitoring method and device under ground-ground combined observation. Background Art

[0002] In July 2020, the BeiDou Global Navigation Satellite System (BDS-3) was announced to be officially operational. It has the ability to provide basic navigation services to global users and has achieved reliable engineering applications. However, in terms of integrity monitoring, it is still limited by ground station layout, inter-satellite communication capacity, etc., making it difficult to achieve real-time monitoring and feedback of all information.

[0003] Low-orbit satellites have the characteristics of fast movement speed and rapid change in relative distance from Beidou satellites. They are not limited by geographical and political factors and are safe, autonomous and controllable. Using them as high-precision space-based monitoring stations for navigation satellites has become a research hotspot in the aerospace field at home and abroad in recent years. Their advantages are reflected in: 1) making up for the limitations of the satellite-to-ground and inter-satellite monitoring network. By introducing low-orbit aircraft equipped with satellite-borne monitoring receivers as mobile monitoring stations, combined with the advantages of low-orbit inter-satellite high-speed communication, it can effectively make up for the shortcomings of the satellite-to-ground observation network, effectively increase the tracking and monitoring arc, and support the rapid return of integrity information of the current effective identification system service status; 2) improving the availability of integrity parameters. By utilizing the data transmission capabilities of inter-satellite links and low-orbit satellites, various types of observation data can be transmitted to the ground master control station in real time, realizing real-time calculation of various integrity parameters, and greatly reducing the proportion of integrity identification parameters showing "not monitored". Therefore, it is of great significance to improve system-level integrity monitoring by comprehensively utilizing satellite-ground, inter-satellite and satellite-borne observation data to build an integrated space-ground and ground-based integrity monitoring system and realize real-time monitoring of various integrity-related parameters. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a satellite integrity monitoring method and device under joint ground-ground observation, which is used to solve the limitations of the satellite-ground and inter-satellite monitoring network and the redundancy problem of massive low-orbit satellite-borne observation data, and realize the integrity monitoring of the entire arc segment of the on-orbit satellite.

[0005] In order to solve the above technical problems, a first aspect of an embodiment of the present invention discloses a satellite integrity monitoring method under joint observation of ground and space, the method comprising:

[0006] S1, obtaining satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data;

[0007] S2, processing the satellite-to-ground observation link data, the inter-satellite observation link data and the satellite-borne observation link data to obtain a ground-to-space integrated monitoring network;

[0008] The integrated space-ground monitoring network includes an intersatellite monitoring network, a satellite-borne observation network and a satellite-ground monitoring network;

[0009] S3, using the integrated ground-ground monitoring network to process the target satellite to obtain satellite integrity monitoring results;

[0010] The satellite integrity monitoring result includes a first satellite integrity monitoring result and a second satellite integrity monitoring result.

[0011] As an optional implementation manner, in the first aspect of the embodiment of the present invention, the using of the integrated ground-ground monitoring network to process the target satellite to obtain a satellite integrity monitoring result includes:

[0012] S31, processing the onboard observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain a minimum onboard observation unit;

[0013] S32, constructing an orbit determination and solution observation unit for the satellite-ground and satellite-borne observation networks according to the observation conditions of the target satellite by the satellite-ground and satellite-borne observation networks;

[0014] S33, using the orbit determination and solution observation unit to solve the orbit of the target satellite to obtain a first satellite integrity monitoring result;

[0015] S34, performing integrity assessment on the target satellite according to the monitoring results of the minimum onboard observation unit and the orbit determination and solution observation unit, and obtaining a second satellite integrity monitoring result.

[0016] As an optional implementation manner, in the first aspect of the embodiment of the present invention, the processing of the satellite-borne observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain the minimum satellite-borne observation unit includes:

[0017] S311, gridding all areas where satellites fly around the earth according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain grid areas;

[0018] S312, performing a coverage dynamic analysis on the grid area using a satellite-borne monitoring receiver to obtain a dynamic analysis result;

[0019] S313, processing the dynamic analysis result to obtain a minimum satellite-borne observation unit.

[0020] As an optional implementation manner, in the first aspect of the embodiment of the present invention, the construction of the orbit determination and solution observation unit of the satellite-ground satellite-borne observation network combined with the minimum satellite-borne observation unit includes:

[0021] S321, using a low-orbit satellite onboard monitoring receiver and a ground monitoring receiver, processing the space observation angle of the target satellite to obtain the number of onboard observation links and the number of satellite-to-ground observation links;

[0022] S322, processing the number of satellite-borne observation links and the number of satellite-to-ground observation links to obtain a satellite dilution of precision factor;

[0023] S323, processing the satellite precision reduction factor to obtain an orbit determination and solution observation unit for a satellite-ground and satellite-borne observation network.

[0024] As an optional implementation manner, in the first aspect of the embodiment of the present invention, the performing integrity determination on the target satellite according to the positional relationship between the target satellite and the satellite-to-ground monitoring network to obtain the second satellite integrity monitoring result includes:

[0025] S341, when the target satellite is located in the visible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined by using the satellite-to-ground observation network data to obtain a second satellite integrity monitoring result;

[0026] S342, when the target satellite is located in an invisible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined using the inter-satellite monitoring network data and the satellite-borne observation network data to obtain a second satellite integrity monitoring result.

[0027] As an optional implementation, in the first aspect of the embodiment of the present invention, when the target satellite is located in the visible area of ​​the satellite-to-ground observation network, using the satellite-to-ground observation network data to perform integrity determination on the target satellite to obtain the second satellite integrity monitoring result includes:

[0028] S3411, obtaining the target satellite broadcast ephemeris and ground station coordinates;

[0029] S3412, processing the target satellite broadcast ephemeris and the ground station coordinates to obtain the distance R from the target satellite to the center of the earth OS , the distance from the ground station to the center of the earth R OG and the distance R from the target satellite to the ground station GS ;

[0030] S3413, the distance R from the target satellite to the center of the earth OS , the distance R from the ground station to the center of the earth OG and the distance R from the target satellite to the ground station GS Processing is performed to obtain the satellite-to-ground observation elevation angle α;

[0031] The expression of the satellite-to-earth observation elevation angle α is:

[0032]

[0033] S3414, when the satellite-to-earth observation elevation angle α satisfies α min ≤α≤α max When the target satellite is in the visible area of ​​the satellite-earth observation network, α min is the minimum value of the satellite-to-earth observation elevation angle α, max is the maximum value of the satellite-to-earth observation elevation angle α;

[0034] S3415, acquiring signal domain information of the target satellite and information domain information of the target satellite;

[0035] S3416, processing the signal domain information of the target satellite and the information domain information of the target satellite to obtain multi-source fused signal domain information and multi-source fused information domain information;

[0036] S3417, performing integrity determination on the multi-source fused signal domain information and the multi-source fused information domain information to obtain a second satellite integrity monitoring result.

[0037] As an optional implementation manner, in the first aspect of the embodiment of the present invention, when the target satellite is located in an invisible area of ​​the satellite-to-ground observation network, using the inter-satellite monitoring network data and the satellite-borne observation network data to perform integrity determination on the target satellite to obtain a second satellite integrity monitoring result includes:

[0038] S3421, processing the intersatellite monitoring network data to obtain the residual of the autonomous orbit determination result of the target satellite and the residual of the intersatellite ranging between the target satellite and other navigation satellites;

[0039] S3422, processing the residual of the autonomous orbit determination result of the target satellite, the residual of the inter-satellite ranging between the target satellite and other navigation satellites, and the integrity-related information in the N-fold satellite basic navigation message sent back by the minimum onboard observation unit to obtain the second satellite integrity monitoring result.

[0040] As an optional implementation, in the first aspect of the embodiment of the present invention, the intersatellite monitoring network includes links between the target satellite and other navigation satellites and low-orbit intersatellite links;

[0041] The link between the target satellite and other navigation satellites is used to generate inter-satellite pseudo-range phase observation data within the planned time slot and to interact with on-board autonomous navigation messages;

[0042] The low-orbit inter-satellite link is used to realize the mutual transmission of satellite-borne pseudo-range phase observation data and navigation messages;

[0043] The onboard observation network includes low-orbit satellites, which are used to realize onboard pseudo-range phase observation of navigation satellites and receive navigation messages, and transmit the received information back to the ground master control station through the low-orbit onboard communication link;

[0044] The satellite-to-ground monitoring network includes a master control station, an injection station and a monitoring station;

[0045] The master control station is used to complete the real-time reception and fusion processing of various types of returned observation data, and complete the generation and injection of navigation messages;

[0046] The injection station is used to receive and inject the navigation message generated by the master control station, receive satellite-to-ground, inter-satellite, and satellite-borne pseudo-range phase observation data and navigation messages, and transmit the satellite-to-ground, inter-satellite, and satellite-borne pseudo-range phase observation data and navigation messages back to the master control station;

[0047] The monitoring station is used to receive satellite-to-ground, inter-satellite and satellite-borne pseudo-range phase observation data and navigation messages, and transmit the satellite-to-ground, inter-satellite and satellite-borne pseudo-range phase observation data and navigation messages back to the main control station.

[0048] A second aspect of an embodiment of the present invention discloses a satellite integrity monitoring device under joint observation of ground and space, the device comprising:

[0049] A data acquisition module is used to acquire satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data;

[0050] A space-ground integrated monitoring network construction module is used to process the satellite-ground observation link data, the inter-satellite observation link data and the satellite-borne observation link data to obtain a space-ground integrated monitoring network;

[0051] The integrated space-ground monitoring network includes an intersatellite monitoring network, a satellite-borne observation network and a satellite-ground monitoring network;

[0052] A satellite integrity monitoring module is used to process the target satellite using the integrated ground-ground monitoring network to obtain satellite integrity monitoring results;

[0053] The satellite integrity monitoring result includes a first satellite integrity monitoring result and a second satellite integrity monitoring result.

[0054] As an optional implementation manner, in the second aspect of the embodiment of the present invention, the use of the integrated ground-ground monitoring network to process the target satellite to obtain a satellite integrity monitoring result includes:

[0055] S31, processing the onboard observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain a minimum onboard observation unit;

[0056] S32, constructing an orbit determination and solution observation unit for the satellite-ground and satellite-borne observation networks according to the observation conditions of the target satellite by the satellite-ground and satellite-borne observation networks;

[0057] S33, using the orbit determination and solution observation unit to solve the orbit of the target satellite to obtain a first satellite integrity monitoring result;

[0058] S34, performing integrity assessment on the target satellite according to the monitoring results of the minimum onboard observation unit and the orbit determination and solution observation unit, and obtaining a second satellite integrity monitoring result.

[0059] As an optional implementation manner, in the second aspect of the embodiment of the present invention, the processing of the satellite-borne observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain the minimum satellite-borne observation unit includes:

[0060] S311, gridding all areas where satellites fly around the earth according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain grid areas;

[0061] S312, performing a coverage dynamic analysis on the grid area using a satellite-borne monitoring receiver to obtain a dynamic analysis result;

[0062] S313, processing the dynamic analysis result to obtain a minimum satellite-borne observation unit.

[0063] As an optional implementation manner, in the second aspect of the embodiment of the present invention, the construction of the orbit determination and solution observation unit of the satellite-ground satellite-borne observation network combined with the minimum satellite-borne observation unit includes:

[0064] S321, using a low-orbit satellite onboard monitoring receiver and a ground monitoring receiver, processing the space observation angle of the target satellite to obtain the number of onboard observation links and the number of satellite-to-ground observation links;

[0065] S322, processing the number of satellite-borne observation links and the number of satellite-to-ground observation links to obtain a satellite dilution of precision factor;

[0066] S323, processing the satellite precision reduction factor to obtain an orbit determination and solution observation unit for a satellite-ground and satellite-borne observation network.

[0067] As an optional implementation manner, in the second aspect of the embodiment of the present invention, the performing integrity determination on the target satellite according to the positional relationship between the target satellite and the satellite-to-ground monitoring network to obtain the second satellite integrity monitoring result includes:

[0068] S341, when the target satellite is located in the visible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined by using the satellite-to-ground observation network data to obtain a second satellite integrity monitoring result;

[0069] S342, when the target satellite is located in an invisible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined using the inter-satellite monitoring network data and the satellite-borne observation network data to obtain a second satellite integrity monitoring result.

[0070] As an optional implementation, in the second aspect of the embodiment of the present invention, when the target satellite is located in the visible area of ​​the satellite-to-ground observation network, using the satellite-to-ground observation network data to perform integrity determination on the target satellite to obtain the second satellite integrity monitoring result includes:

[0071] S3411, obtaining the target satellite broadcast ephemeris and ground station coordinates;

[0072] S3412, processing the target satellite broadcast ephemeris and the ground station coordinates to obtain the distance R from the target satellite to the center of the earth OS , the distance from the ground station to the center of the earth R OG and the distance R from the target satellite to the ground station GS ;

[0073] S3413, the distance R from the target satellite to the center of the earth OS , the distance R from the ground station to the center of the earth OG and the distance R from the target satellite to the ground station GS Processing is performed to obtain the satellite-to-ground observation elevation angle α;

[0074] The expression of the satellite-to-earth observation elevation angle α is:

[0075]

[0076] S3414, when the satellite-to-earth observation elevation angle α satisfies α min ≤α≤α max When the target satellite is in the visible area of ​​the satellite-earth observation network, α min is the minimum value of the satellite-to-earth observation elevation angle α, max is the maximum value of the satellite-to-earth observation elevation angle α;

[0077] S3415, acquiring signal domain information of the target satellite and information domain information of the target satellite;

[0078] S3416, processing the signal domain information of the target satellite and the information domain information of the target satellite to obtain multi-source fused signal domain information and multi-source fused information domain information;

[0079] S3417, performing integrity determination on the multi-source fused signal domain information and the multi-source fused information domain information to obtain a second satellite integrity monitoring result.

[0080] As an optional implementation manner, in the second aspect of the embodiment of the present invention, when the target satellite is located in an invisible area of ​​the satellite-to-ground observation network, using the inter-satellite monitoring network data and the satellite-borne observation network data to perform integrity determination on the target satellite to obtain a second satellite integrity monitoring result includes:

[0081] S3421, processing the intersatellite monitoring network data to obtain the residual of the autonomous orbit determination result of the target satellite and the residual of the intersatellite ranging between the target satellite and other navigation satellites;

[0082] S3422, processing the residual of the autonomous orbit determination result of the target satellite, the residual of the inter-satellite ranging between the target satellite and other navigation satellites, and the integrity-related information in the N-fold satellite basic navigation message sent back by the minimum onboard observation unit to obtain the second satellite integrity monitoring result.

[0083] As an optional implementation, in the second aspect of the embodiment of the present invention, the intersatellite monitoring network includes links between the target satellite and other navigation satellites and low-orbit intersatellite links;

[0084] The link between the target satellite and other navigation satellites is used to generate inter-satellite pseudo-range phase observation data within the planned time slot and to interact with on-board autonomous navigation messages;

[0085] The low-orbit inter-satellite link is used to realize the mutual transmission of satellite-borne pseudo-range phase observation data and navigation messages;

[0086] The onboard observation network includes low-orbit satellites, which are used to realize onboard pseudo-range phase observation of navigation satellites and receive navigation messages, and transmit the received information back to the ground master control station through the low-orbit onboard communication link;

[0087] The satellite-to-ground monitoring network includes a master control station, an injection station and a monitoring station;

[0088] The master control station is used to complete the real-time reception and fusion processing of various types of returned observation data, and complete the generation and injection of navigation messages;

[0089] The injection station is used to receive and inject the navigation message generated by the master control station, receive satellite-to-ground, inter-satellite, and satellite-borne pseudo-range phase observation data and navigation messages, and transmit the satellite-to-ground, inter-satellite, and satellite-borne pseudo-range phase observation data and navigation messages back to the master control station;

[0090] The monitoring station is used to receive satellite-to-ground, inter-satellite and satellite-borne pseudo-range phase observation data and navigation messages, and transmit the satellite-to-ground, inter-satellite and satellite-borne pseudo-range phase observation data and navigation messages back to the main control station.

[0091] The third aspect of the present invention discloses another satellite integrity monitoring device under joint observation of ground and space, the device comprising:

[0092] A memory storing executable program code;

[0093] a processor coupled to the memory;

[0094] The processor calls the executable program code stored in the memory to execute part or all of the steps in the satellite integrity monitoring method under ground-based joint observation disclosed in the first aspect of the embodiment of the present invention.

[0095] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0096] The present invention enriches the satellite integrity monitoring method, comprehensively utilizes satellite-to-ground, satellite-borne and inter-satellite observation data, realizes real-time monitoring of the entire arc segment of on-orbit satellites, can make up for the limitations of the existing satellite-to-ground and inter-satellite monitoring network, and effectively improves the availability of integrity parameters.

[0097] The method of the present invention optimizes the observation data of ground monitoring receivers and low-orbit satellite-borne monitoring receivers, effectively eliminates the observation link data with poor observation geometry conditions, reduces the dimension of the normal equation in the satellite orbit determination solution process, and thus improves the efficiency of satellite orbit determination solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0099] Figure 1 It is a flowchart of a satellite integrity monitoring method under ground-based joint observation disclosed in an embodiment of the present invention;

[0100] Figure 2 It is a flowchart of another satellite integrity monitoring method under ground-based joint observation disclosed in an embodiment of the present invention;

[0101] Figure 3 It is a schematic diagram of the principle of integrated ground-based monitoring disclosed in an embodiment of the present invention;

[0102] Figure 4 is a schematic diagram of a target satellite disclosed in an embodiment of the present invention being located in a visible area of ​​a satellite-to-ground observation network;

[0103] Figure 5 It is a structural schematic diagram of a satellite integrity monitoring device under ground-based joint observation disclosed in an embodiment of the present invention;

[0104] Figure 6It is a structural schematic diagram of another satellite integrity monitoring device under ground-based joint observation disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0105] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0106] The terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, device, product or equipment that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or equipment.

[0107] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0108] The present invention discloses a satellite integrity monitoring method and device under joint observation between the earth and the sky, the method comprising: acquiring satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data; processing the satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data to obtain a space-to-ground integrated monitoring network; the space-to-ground integrated monitoring network comprises an inter-satellite monitoring network, a satellite-borne observation network and a satellite-to-ground monitoring network; using the space-to-ground integrated monitoring network, processing the target satellite to obtain a satellite integrity monitoring result; the satellite integrity monitoring result comprises a first satellite integrity monitoring result and a second satellite integrity monitoring result. The present invention can realize the integrity monitoring of the entire arc segment of an in-orbit satellite by constructing a space-to-ground integrated monitoring network, combined with the optimization of satellite-borne observation network link data. The following are detailed descriptions respectively.

[0109] Embodiment 1

[0110] See also Figure 1 , Figure 11 is a flow chart of a satellite integrity monitoring method under ground-based joint observation disclosed in an embodiment of the present invention. Figure 1 The satellite integrity monitoring method under the combined observation of the ground and the sky is applied to the field of satellite navigation technology to realize the integrity monitoring of the entire arc segment of the on-orbit satellite, which is not limited in the embodiments of the present invention. Figure 1 As shown, the satellite integrity monitoring method under the joint observation of the ground and the sky may include the following operations:

[0111] S1, obtaining satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data;

[0112] S2, processing the satellite-to-ground observation link data, the inter-satellite observation link data and the satellite-borne observation link data to obtain a ground-to-space integrated monitoring network;

[0113] The integrated space-ground monitoring network includes an intersatellite monitoring network, a satellite-borne observation network and a satellite-ground monitoring network;

[0114] S3, using the integrated ground-ground monitoring network to process the target satellite to obtain satellite integrity monitoring results;

[0115] The satellite integrity monitoring result includes a first satellite integrity monitoring result and a second satellite integrity monitoring result.

[0116] Optionally, the using the integrated ground-ground monitoring network to process the target satellite to obtain a satellite integrity monitoring result includes:

[0117] S31, processing the onboard observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain a minimum onboard observation unit;

[0118] S32, constructing an orbit determination and solution observation unit for the satellite-ground and satellite-borne observation networks according to the observation conditions of the target satellite by the satellite-ground and satellite-borne observation networks;

[0119] S33, using the orbit determination and solution observation unit to solve the orbit of the target satellite to obtain a first satellite integrity monitoring result;

[0120] S34, performing integrity assessment on the target satellite according to the monitoring results of the minimum onboard observation unit and the orbit determination and solution observation unit, and obtaining a second satellite integrity monitoring result.

[0121] Optionally, the processing of the satellite-borne observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain a minimum satellite-borne observation unit includes:

[0122] S311, gridding all areas where satellites fly around the earth according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain grid areas;

[0123] S312, performing a coverage dynamic analysis on the grid area using a satellite-borne monitoring receiver to obtain a dynamic analysis result;

[0124] S313, processing the dynamic analysis result to obtain a minimum satellite-borne observation unit.

[0125] Optionally, constructing an orbit determination and solution observation unit for a satellite-ground satellite-borne observation network based on the minimum satellite-borne observation unit includes:

[0126] S321, using a low-orbit satellite onboard monitoring receiver and a ground monitoring receiver, processing the space observation angle of the target satellite to obtain the number of onboard observation links and the number of satellite-to-ground observation links;

[0127] S322, processing the number of satellite-borne observation links and the number of satellite-to-ground observation links to obtain a satellite dilution of precision factor;

[0128] S323, processing the satellite precision reduction factor to obtain an orbit determination and solution observation unit for a satellite-ground and satellite-borne observation network.

[0129] Optionally, performing integrity determination on the target satellite according to the positional relationship between the target satellite and the satellite-to-ground monitoring network to obtain a second satellite integrity monitoring result includes:

[0130] S341, when the target satellite is located in the visible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined by using the satellite-to-ground observation network data to obtain a second satellite integrity monitoring result;

[0131] S342, when the target satellite is located in an invisible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined using the inter-satellite monitoring network data and the satellite-borne observation network data to obtain a second satellite integrity monitoring result.

[0132] Optionally, when the target satellite is located in a visible area of ​​the satellite-to-ground observation network, using the satellite-to-ground observation network data to perform integrity determination on the target satellite to obtain a second satellite integrity monitoring result includes:

[0133] S3411, obtaining the target satellite broadcast ephemeris and ground station coordinates;

[0134] S3412, processing the target satellite broadcast ephemeris and the ground station coordinates to obtain the distance R from the target satellite to the center of the earth OS , the distance from the ground station to the center of the earth R OG and the distance R from the target satellite to the ground station GS ;

[0135] S3413, the distance R from the target satellite to the center of the earth OS, the distance R from the ground station to the center of the earth OG and the distance R from the target satellite to the ground station GS Processing is performed to obtain the satellite-to-ground observation elevation angle α;

[0136] The expression of the satellite-to-earth observation elevation angle α is:

[0137]

[0138] S3414, when the satellite-to-earth observation elevation angle α satisfies α min ≤α≤α max When the target satellite is in the visible area of ​​the satellite-earth observation network, α min is the minimum value of the satellite-to-earth observation elevation angle α, max is the maximum value of the satellite-to-earth observation elevation angle α;

[0139] S3415, acquiring signal domain information of the target satellite and information domain information of the target satellite;

[0140] S3416, processing the signal domain information of the target satellite and the information domain information of the target satellite to obtain multi-source fused signal domain information and multi-source fused information domain information;

[0141] S3417, performing integrity determination on the multi-source fused signal domain information and the multi-source fused information domain information to obtain a second satellite integrity monitoring result.

[0142] Optionally, when the target satellite is located in an invisible area of ​​the satellite-to-ground observation network, using the intersatellite monitoring network data and the satellite-borne observation network data to perform integrity determination on the target satellite to obtain a second satellite integrity monitoring result includes:

[0143] S3421, processing the intersatellite monitoring network data to obtain the residual of the autonomous orbit determination result of the target satellite and the residual of the intersatellite ranging between the target satellite and other navigation satellites;

[0144] S3422, processing the residual of the autonomous orbit determination result of the target satellite, the residual of the inter-satellite ranging between the target satellite and other navigation satellites, and the integrity-related information in the N-fold satellite basic navigation message sent back by the minimum onboard observation unit to obtain the second satellite integrity monitoring result.

[0145] Optionally, the intersatellite monitoring network includes links between the target satellite and other navigation satellites and low-orbit intersatellite links;

[0146] The link between the target satellite and other navigation satellites is used to generate inter-satellite pseudo-range phase observation data within the planned time slot and to interact with on-board autonomous navigation messages;

[0147] The low-orbit inter-satellite link is used to realize the mutual transmission of satellite-borne pseudo-range phase observation data and navigation messages;

[0148] The onboard observation network includes low-orbit satellites, which are used to realize onboard pseudo-range phase observation of navigation satellites and receive navigation messages, and transmit the received information back to the ground master control station through the low-orbit onboard communication link;

[0149] The satellite-to-ground monitoring network includes a master control station, an injection station and a monitoring station;

[0150] The master control station is used to complete the real-time reception and fusion processing of various types of returned observation data, and complete the generation and injection of navigation messages;

[0151] The injection station is used to receive and inject the navigation message generated by the master control station, receive satellite-to-ground, inter-satellite, and satellite-borne pseudo-range phase observation data and navigation messages, and transmit the satellite-to-ground, inter-satellite, and satellite-borne pseudo-range phase observation data and navigation messages back to the master control station;

[0152] The monitoring station is used to receive satellite-to-ground, inter-satellite and satellite-borne pseudo-range phase observation data and navigation messages, and transmit the satellite-to-ground, inter-satellite and satellite-borne pseudo-range phase observation data and navigation messages back to the main control station.

[0153] It can be seen that the present invention enriches the satellite integrity monitoring method, comprehensively utilizes satellite-to-ground, satellite-borne, and inter-satellite observation data, and realizes real-time monitoring of the entire arc segment of in-orbit satellites. It can make up for the limitations of the existing satellite-to-ground and inter-satellite monitoring network and effectively improve the availability of integrity parameters.

[0154] Embodiment 2

[0155] See also Figure 2 , Figure 2 1 is a flow chart of another satellite integrity monitoring method under ground-based joint observation disclosed in an embodiment of the present invention. Figure 2 The satellite integrity monitoring method under the combined observation of the ground and the sky is applied to the field of satellite navigation technology to realize the integrity monitoring of the entire arc segment of the on-orbit satellite, which is not limited in the embodiments of the present invention. Figure 2 As shown, the satellite integrity monitoring method under the joint observation of the ground and the sky may include the following operations:

[0156] Step S1, comprehensively utilize satellite-to-ground, inter-satellite, and satellite-borne observation link data to build a ground-to-space integrated monitoring network.

[0157] Figure 3 It is a schematic diagram of the principle of integrated ground-based monitoring disclosed in an embodiment of the present invention;

[0158] "Tian" refers to the intersatellite monitoring network and the satellite-borne monitoring network. The intersatellite monitoring network is mainly composed of links between target satellites and other navigation satellites and low-orbit intersatellite links. Among them, the link between the target satellite and other navigation satellites mainly realizes the interaction of intersatellite pseudo-range phase observation data and on-board autonomous navigation messages within the planned time slot; the low-orbit intersatellite link mainly realizes the mutual transmission of satellite-borne pseudo-range phase observation data and navigation messages.

[0159] The satellite-based monitoring network is mainly composed of low-orbit satellites, which mainly realize the satellite-based pseudo-range phase observation of navigation satellites and the reception of navigation messages, and transmit the received information back to the ground master control station through the low-orbit satellite-based communication link.

[0160] "Ground" refers to the satellite-ground monitoring network, which is mainly composed of a master control station, an injection station and a monitoring station. The master control station is mainly responsible for completing the real-time reception and fusion processing of various types of returned observation data, and completing the generation and injection of navigation messages; the injection station is mainly responsible for receiving and injecting the navigation messages generated by the master control station, and is also responsible for receiving satellite-to-ground, inter-satellite, and satellite-borne pseudo-range phase observation data and navigation messages, and transmitting them back to the master control station; the monitoring station is mainly responsible for receiving satellite-to-ground, inter-satellite, and satellite-borne pseudo-range phase observation data and navigation messages, and transmitting them back to the master control station.

[0161] Step S2, constructing the smallest satellite-borne observation unit in the satellite-borne observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation, for returning the navigation message of the target satellite.

[0162] That is to say, all areas where satellites fly around the earth are gridded according to the satellite orbit altitude, and combined with the deployment of low-orbit constellations, a dynamic analysis of the coverage of all grid points by satellite-borne monitoring receivers is performed. If 100% real-time N (N is a natural number) coverage of all grid points can be achieved under satellite-borne observation conditions, the minimum low-orbit constellation combination that can achieve N-fold coverage is further selected through enumeration to form a minimum satellite-borne observation unit for the return of navigation messages from the target satellite. Otherwise, the minimum satellite-borne observation unit is the satellite-borne observation unit of the current low-orbit constellation composition.

[0163] Step S3, using the ground-space joint observation geometry optimization method, constructs an orbit determination and solution observation unit that combines the ground-space and satellite-borne observation networks to quickly solve the orbit of the target satellite. If the residual error of the satellite orbit measurement exceeds the threshold, the satellite is judged to be not intact, otherwise the satellite is intact.

[0164] That is to say, firstly, the number of onboard and satellite-to-ground observation links is calculated based on the spatial observation angle of the low-orbit satellite onboard monitoring receiver and the ground monitoring receiver to the target satellite; secondly, if the sum of the number of effective onboard observation links m and the number of effective satellite-to-ground observation links n is greater than or equal to k, then The satellite precision reduction factors under different combinations are calculated, otherwise the observation link optimization is not performed. Finally, according to the combination priority principle with satellite-to-ground observation links, the satellite precision reduction factors under all combinations are sorted in order from small to large, and the top-ranked combined observation data are preferentially selected as the observation geometry optimization scheme for the real-time solution of the space-ground joint orbit determination, and the selected satellite-to-ground and satellite-borne observation links are used as the observation units for orbit determination.

[0165] Step S4, when the target satellite is within the visible area of ​​the satellite-to-ground observation network, integrity determination is performed using the satellite-to-ground observation network data; otherwise, integrity determination is performed using the inter-satellite and satellite-borne observation network data.

[0166] Step S4.1, when the target satellite is in the visible area of ​​the satellite-earth observation network:

[0167] Specifically, Figure 4 This is a schematic diagram of the target satellite in the visible area of ​​the satellite-ground observation network. By obtaining the target satellite broadcast ephemeris and ground station coordinates, the distance R from the target satellite to the center of the earth can be obtained. OS , the distance from the ground station to the center of the earth R OG And the distance R from the target satellite to the ground station GS , then the satellite-to-ground observation elevation angle α between the target satellite-ground monitoring station line of sight and the ground horizontal line where the ground monitoring station is located is:

[0168]

[0169] When α min ≤α≤α max When , the target satellite is in the visible area of ​​the satellite-to-earth observation network, otherwise the target satellite is not in the visible area of ​​the satellite-to-earth observation network.

[0170] Step S4.1.1, collect the signal domain information and information domain information of the satellite, where the signal domain information refers to the satellite-to-ground downlink observation data sent back by each ground monitoring station; the information domain information refers to the basic navigation message and the differential enhanced navigation message.

[0171] Step S4.1.2, the signal domain information and the information domain information are sorted according to the recovery time and the observation time. For the same type of information at the same observation time, only the set of information with the recovery time priority of the master control station is retained to realize the fusion of multi-source signal domain data and multi-source information domain data.

[0172] Step S4.1.3, analyze whether the satellite clock working status, frequency modulation, phase modulation, signal delay, power, frequency, phase and other information in the multi-source fused signal domain information indicate an abnormality, and analyze whether the integrity-related information in the multi-domain fused information domain indicates an abnormality. If one of the information indicates an abnormality, the satellite is determined to be not intact, otherwise the satellite is intact.

[0173] Specifically, the integrity parameter information broadcast by the new system signal of the Beidou satellite navigation system BDS-3 public frequency point mainly includes two types of parameters: global basic integrity in basic navigation message and satellite-based augmentation integrity parameters in differential augmentation message. Among them, the global basic integrity parameters include satellite health status (HS), satellite integrity status indicator, space signal accuracy index (Signal in space accuracy indicator, SISAI) and space signal monitoring accuracy index (Signal in space monitoring accuracy indicator, SISMAI), and satellite health information (Health) in the almanac; the satellite-based augmentation integrity parameters mainly include UDREI (User differential range error indicator, UDREI), GIVEI (Grid, point ionospheric vertical delay error index, GIVEI), dual frequency range error indicator (Dual frequency range error indicator, DFREI) and dual frequency range error change indicator (Dual frequency range error indicator, DFRECI) and degradation parameters.

[0174] HS is used to identify whether the satellite can be used for basic navigation services; the basic integrity status of the satellite is described by three parameters: message integrity identifier (DIF), signal integrity identifier (SIF) and system alert identifier (AIF); SISAI is used to describe the orbit and clock error prediction accuracy broadcast in the basic navigation message, which can be further decomposed into two parts: ephemeris prediction accuracy SISAoe, which mainly reflects the prediction accuracy of the satellite orbit tangent and normal directions; clock error prediction accuracy SISAoc, which mainly reflects the satellite orbit path. The accuracy of the prediction of direction and clock error includes SISAocb (comprehensive estimation of the time deviation and orbit radial deviation of the satellite clock and Beidou), SISAoc1 (accuracy estimation of the fixed deviation of the satellite clock), and SISAoc2 (accuracy estimation of the frequency deviation of the satellite clock); SISMAI is used to describe the accuracy of the estimation error of the spatial signal accuracy using the zero-mean Gaussian distribution model, which is consistent with the meaning of RURAI; the degradation parameter is used to reflect the user ranging accuracy limit of the user differential distance error after slow-varying and fast-varying differential correction within a certain time period and within the effective service area.

[0175] Step S4.2, when the navigation satellite is in the invisible area of ​​the satellite-earth observation network:

[0176] Step S4.2.1, using the inter-satellite two-way ranging information and autonomous navigation message information between the target satellite and other navigation satellites in the inter-satellite monitoring network, calculate the residual of the target satellite's autonomous orbit determination result and the inter-satellite ranging residual between the target satellite and other navigation satellites. If one of the calculation results exceeds the threshold, the satellite is judged to be not intact, otherwise the satellite is intact.

[0177] Step S4.2.2, analyze whether the integrity-related information in the N basic satellite navigation messages sent back by the smallest onboard observation unit indicates an abnormality. If there are N / 2 or more identical information indicating satellite abnormalities, the satellite is determined to be not intact, otherwise the satellite is intact.

[0178] Embodiment 3

[0179] See also Figure 5 , Figure 5 : is a schematic diagram of the structure of a satellite integrity monitoring device under ground-based joint observation disclosed in an embodiment of the present invention. Figure 5 The satellite integrity monitoring device under the combined observation of the earth and the sky is applied to the field of satellite navigation technology to realize the integrity monitoring of the entire arc segment of the on-orbit satellite, which is not limited in the embodiments of the present invention. Figure 5 As shown, the satellite integrity monitoring device under the combined observation of the earth and the sky may include the following operations:

[0180] S301, a data acquisition module, used to acquire satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data;

[0181] S302, a space-ground integrated monitoring network construction module, used to process the satellite-to-ground observation link data, the inter-satellite observation link data and the satellite-borne observation link data to obtain a space-ground integrated monitoring network;

[0182] The integrated space-ground monitoring network includes an intersatellite monitoring network, a satellite-borne observation network and a satellite-ground monitoring network;

[0183] S303, a satellite integrity monitoring module, used to process the target satellite using the integrated ground-ground monitoring network to obtain a satellite integrity monitoring result;

[0184] The satellite integrity monitoring result includes a first satellite integrity monitoring result and a second satellite integrity monitoring result.

[0185] Embodiment 4

[0186] See also Figure 6 , Figure 6 : is a schematic diagram of the structure of another satellite integrity monitoring device under ground-based joint observation disclosed in an embodiment of the present invention. Figure 6The satellite integrity monitoring device under the combined observation of the earth and the sky is applied to the field of satellite navigation technology to realize the integrity monitoring of the entire arc segment of the on-orbit satellite, which is not limited in the embodiments of the present invention. Figure 6 As shown, the satellite integrity monitoring device under the combined observation of the earth and the sky may include the following operations:

[0187] A memory 401 storing executable program codes;

[0188] a processor 402 coupled to the memory 401;

[0189] The processor 402 calls the executable program code stored in the memory 401 to execute the steps of the satellite integrity monitoring method under the ground-ground joint observation described in the first and second embodiments.

[0190] The device embodiments described above are only illustrative, wherein the modules described as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules, i.e., they may be located in one place, or they may be distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those of ordinary skill in the art may understand and implement it without creative work.

[0191] Through the specific description of the above embodiments, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the above technical solution can be essentially or partly contributed to the prior art in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, and the storage medium includes a read-only memory (ROM), a random access memory (RAM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), a one-time programmable read-only memory (OTPROM), an electronically erasable rewritable read-only memory (EEPROM), a compact disc (CD-ROM) or other optical disc storage, magnetic disk storage, magnetic tape storage, or any other computer-readable medium that can be used to carry or store data.

[0192] Finally, it should be noted that the satellite integrity monitoring method and device under the joint observation of the sky and the earth disclosed in the embodiment of the present invention discloses only the preferred embodiment of the present invention, which is only used to illustrate the technical scheme of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical schemes recorded in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not make the essence of the corresponding technical schemes deviate from the spirit and scope of the technical schemes of the embodiments of the present invention.

Claims

1. A satellite integrity monitoring method under ground-based joint observation, characterized in that: The method comprises: S1, obtaining satellite-to-ground observation link data, inter-satellite observation link data and onboard observation link data; S2, processing the satellite-to-ground observation link data, the inter-satellite observation link data and the satellite-borne observation link data to obtain a ground-to-space integrated monitoring network; The integrated space-ground monitoring network includes an intersatellite monitoring network, a satellite-borne observation network and a satellite-ground monitoring network; The intersatellite monitoring network includes links between the target satellite and other navigation satellites and low-orbit intersatellite links; The link between the target satellite and other navigation satellites is used to generate inter-satellite pseudo-range phase observation data within the planned time slot and to interact with on-board autonomous navigation messages; The low-orbit inter-satellite link is used to realize the mutual transmission of satellite-borne pseudo-range phase observation data and navigation messages; The onboard observation network includes low-orbit satellites, which are used to realize onboard pseudo-range phase observation of navigation satellites and receive navigation messages, and transmit the received information back to the ground master control station through the low-orbit onboard communication link; The satellite-to-ground monitoring network includes a master control station, an injection station and a monitoring station; S3, using the integrated ground-ground monitoring network to process the target satellite to obtain satellite integrity monitoring results, including: S31, processing the onboard observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain a minimum onboard observation unit; S32, constructing an orbit determination and solution observation unit for the satellite-ground and satellite-borne observation networks according to the observation conditions of the target satellite by the satellite-ground and satellite-borne observation networks; S33, using the orbit determination and solution observation unit to solve the orbit of the target satellite to obtain a first satellite integrity monitoring result; S34, performing integrity assessment on the target satellite according to the monitoring results of the minimum onboard observation unit and the orbit determination solution observation unit, and obtaining a second satellite integrity monitoring result; The satellite integrity monitoring result includes a first satellite integrity monitoring result and a second satellite integrity monitoring result.

2. The satellite integrity monitoring method under ground-based joint observation according to claim 1, characterized in that: The processing of the satellite-borne observation network according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain the minimum satellite-borne observation unit includes: S311, gridding all areas where satellites fly around the earth according to the orbital position of the target satellite and the deployment of the low-orbit constellation to obtain grid areas; S312, performing a coverage dynamic analysis on the grid area using a satellite-borne monitoring receiver to obtain a dynamic analysis result; S313, processing the dynamic analysis result to obtain a minimum satellite-borne observation unit.

3. The satellite integrity monitoring method under ground-based joint observation according to claim 1, characterized in that: The step of constructing an orbit determination and solution observation unit for a satellite-ground satellite-borne observation network based on the minimum satellite-borne observation unit includes: S321, using a low-orbit satellite onboard monitoring receiver and a ground monitoring receiver, processing the space observation angle of the target satellite to obtain the number of onboard observation links and the number of satellite-to-ground observation links; S322, processing the number of satellite-borne observation links and the number of satellite-to-ground observation links to obtain a satellite dilution of precision factor; S323, processing the satellite precision reduction factor to obtain an orbit determination and solution observation unit for a satellite-ground and satellite-borne observation network.

4. The satellite integrity monitoring method under ground-based joint observation according to claim 1, characterized in that: The step of determining the integrity of the target satellite based on the monitoring results of the minimum onboard observation unit and the orbit determination and solution observation unit to obtain the second satellite integrity monitoring result includes: S341, when the target satellite is located in the visible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined by using the satellite-to-ground observation network data to obtain a second satellite integrity monitoring result; S342, when the target satellite is located in an invisible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined using the inter-satellite monitoring network data and the satellite-borne observation network data to obtain a second satellite integrity monitoring result.

5. The satellite integrity monitoring method under ground-based joint observation according to claim 4 is characterized in that: When the target satellite is located in the visible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined by using the satellite-to-ground observation network data to obtain the second satellite integrity monitoring result, including: S3411, obtaining the target satellite broadcast ephemeris and ground station coordinates; S3412, processing the target satellite broadcast ephemeris and the ground station coordinates to obtain the distance R from the target satellite to the center of the earth OS , the distance from the ground station to the center of the earth R OG and the distance R from the target satellite to the ground station GS ; S3413, the distance R from the target satellite to the center of the earth OS , the distance from the ground station to the center of the earth R OG and the distance R from the target satellite to the ground station GS Processing is performed to obtain the satellite-to-ground observation elevation angle α; The expression of the satellite-to-earth observation elevation angle α is: S3414, when the satellite-to-earth observation elevation angle α satisfies α min ≤α≤α max When the target satellite is in the visible area of ​​the satellite-earth observation network, α min is the minimum value of the satellite-to-earth observation elevation angle α, max is the maximum value of the satellite-to-earth observation elevation angle α; S3415, acquiring signal domain information of the target satellite and information domain information of the target satellite; S3416, processing the signal domain information of the target satellite and the information domain information of the target satellite to obtain multi-source fused signal domain information and multi-source fused information domain information; S3417, performing integrity determination on the multi-source fused signal domain information and the multi-source fused information domain information to obtain a second satellite integrity monitoring result.

6. The satellite integrity monitoring method under ground-based joint observation according to claim 4 is characterized in that: When the target satellite is located in an invisible area of ​​the satellite-to-ground observation network, the integrity of the target satellite is determined by using the intersatellite monitoring network data and the satellite-borne observation network data to obtain the second satellite integrity monitoring result, including: S3421, processing the intersatellite monitoring network data to obtain the residual of the autonomous orbit determination result of the target satellite and the residual of the intersatellite ranging between the target satellite and other navigation satellites; S3422, processing the residual of the autonomous orbit determination result of the target satellite, the residual of the inter-satellite ranging between the target satellite and other navigation satellites, and the integrity-related information in the N-fold satellite basic navigation message sent back by the minimum onboard observation unit to obtain the second satellite integrity monitoring result.

7. A satellite integrity monitoring device under joint observation of ground and space, characterized in that: The device comprises: A data acquisition module is used to acquire satellite-to-ground observation link data, inter-satellite observation link data and satellite-borne observation link data; A space-ground integrated monitoring network construction module is used to process the satellite-ground observation link data, the inter-satellite observation link data and the satellite-borne observation link data to obtain a space-ground integrated monitoring network; The integrated space-ground monitoring network includes an intersatellite monitoring network, a satellite-borne observation network and a satellite-ground monitoring network; A satellite integrity monitoring module is used to process the target satellite using the integrated ground-ground monitoring network to obtain satellite integrity monitoring results; The satellite integrity monitoring result includes a first satellite integrity monitoring result and a second satellite integrity monitoring result; The satellite integrity monitoring device under the joint observation of the ground and the sky is used to execute the satellite integrity monitoring method under the joint observation of the ground and the sky as described in any one of claims 1-6.

8. A satellite integrity monitoring device under joint observation of ground and space, characterized in that: The device comprises: A memory storing executable program code; a processor coupled to the memory; The processor calls the executable program code stored in the memory to execute the satellite integrity monitoring method under ground-ground joint observation as described in any one of claims 1-6.

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