CN116660944A - Method and system for GPS occultation observation based on Beidou satellite signals - Google Patents

Method and system for GPS occultation observation based on Beidou satellite signals Download PDF

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Publication number
CN116660944A
CN116660944A CN202310322866.3A CN202310322866A CN116660944A CN 116660944 A CN116660944 A CN 116660944A CN 202310322866 A CN202310322866 A CN 202310322866A CN 116660944 A CN116660944 A CN 116660944A
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gps
occultation
satellite
beidou
event
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Inventor
王卓焱
王先毅
孙越强
杜起飞
白伟华
刘黎军
蔡跃荣
王冬伟
仇通胜
孟祥广
夏俊明
李伟
吴春俊
刘成
李福�
乔颢
柳聪亮
程双双
曹光伟
胡鹏
尹聪
张璐璐
张�浩
黄飞雄
谭广远
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National Space Science Center of CAS
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National Space Science Center of CAS
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Priority to CN202310322866.3A priority Critical patent/CN116660944A/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/35—Constructional details or hardware or software details of the signal processing chain
    • G01S19/37—Hardware or software details of the signal processing chain
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)
  • Radio Relay Systems (AREA)

Abstract

The invention relates to the technical field of GNSS radio occultation atmosphere detection, in particular to a method and a system for performing GPS occultation observation based on Beidou satellite signals. The method comprises the following steps: the method comprises the steps of capturing, tracking and positioning a receiver through signals received by a GNSS occultation receiver, obtaining time and position information of the GNSS occultation receiver under space-time coordinates of a Beidou satellite system, converting Beidou positioning results into GPS positioning results, resolving GPS satellite positions according to the GPS positioning results, realizing GPS occultation prediction and occultation capturing and tracking based on the GPS satellite positions, and completing GPS occultation observation. The system for carrying out GPS occultation observation by adopting the Beidou satellite signals comprises a radio frequency front end, an FPGA end and an ARM end. The invention does not need to allocate positioning channel resources to the GPS system independently, saves system resources and saves operation time.

Description

Method and system for GPS occultation observation based on Beidou satellite signals
Technical Field
The invention relates to the technical field of GNSS radio occultation atmosphere detection, in particular to a method and a system for performing GPS occultation observation based on Beidou satellite signals.
Background
The GNSS (Global navigation satellite System ) occultation observer is used for occultation remote sensing detection, can provide globalization, all-weather and high vertical resolution atmospheric profile information, has wide application in aspects of weather, astronomy and the like, but the current GNSS occultation observer is developed towards low cost miniaturization and high integration, and the microminiature GNSS occultation observer usually adopts low-cost components, has limited hardware operand and resource, and can cause operand exceeding, insufficient resource and abnormal operation of the instrument if the traditional occultation tracking method is directly applied to the observer.
In the traditional method, when GPS (global positioning system ) and Beidou satellite occultation are observed, a positioning antenna is required to capture, track and de-telegraph the GPS and the Beidou signals, then a GNSS occultation receiver, a GPS satellite and a Beidou satellite are subjected to positioning and resolving, then satellite occultation events are predicted according to the relative positions of the receiver, the GPS satellite and the Beidou satellite, and pseudo-range phases and carrier frequencies of the satellite are predicted to be put into a tracking loop to realize fine tracking. In the process, a GNSS occultation receiver is often required to respectively realize tracking and positioning calculation of the GPS and the Beidou dual system, a large amount of time and resources are required to be occupied to process a positioning calculation result, a fixed time and coordinate conversion relation exists between the actual GPS and the Beidou system, mutual conversion can be carried out through an algorithm, and repeated calculation causes a large amount of time and resource waste.
Disclosure of Invention
The invention aims to solve the problems in the traditional method, and considers that a fixed conversion relation exists between a GPS and a Beidou system in practice, the invention provides a method for carrying out positioning calculation by using the Beidou system alone, then converting the Beidou positioning result into a GPS positioning result, and calculating the position of a GPS satellite according to the result, thereby realizing GPS occultation prediction, capturing and tracking and completing GPS occultation event observation. The method can remove the GPS positioning resolving module from the system, and only a small amount of GPS channels are reserved for receiving GPS satellite ephemeris/almanac information, so that hardware resources are saved, and the system operation efficiency is improved; the Beidou system is a self-controlled navigation system with complete intellectual property rights in China and can provide reliable positioning service, so that the reliability and the safety of the integral receiver can be obviously improved after the method is adopted.
In order to achieve the above purpose, the present invention is realized by the following technical scheme.
The invention provides a GPS occultation observation method based on Beidou satellite signals, which comprises the following steps:
the method comprises the steps of capturing, tracking and positioning a receiver through signals received by a GNSS occultation receiver, obtaining time and position information of the GNSS occultation receiver under space-time coordinates of a Beidou satellite system, converting Beidou positioning results into GPS positioning results, resolving GPS satellite positions according to the GPS positioning results, realizing GPS occultation prediction and occultation capturing and tracking based on the GPS satellite positions, and completing GPS occultation observation.
As one of the improvements of the above technical solutions, the method specifically includes:
step 1, receiving and processing a positioning radio frequency analog signal through a positioning antenna of a GNSS occultation receiver to obtain a positioning intermediate frequency digital signal;
step 2, correlating the positioning intermediate frequency digital signal with a local code and a carrier wave of a Beidou satellite system, acquiring a correlation peak value, capturing and tracking each satellite of the Beidou satellite system, measuring the pseudo range of each satellite of the Beidou satellite system, and acquiring real-time ephemeris or almanac and BDT-GNSS time synchronization parameters of each satellite of the Beidou satellite system; calculating the position of the GNSS occultation receiver according to the Beidou satellite pseudo-range information, ephemeris or almanac information;
step 3, correlating the positioning intermediate frequency digital signals with the local pseudo codes and carriers of all GPS satellites to obtain correlation peaks, capturing and tracking all GPS satellites, measuring the pseudo range of the GPS satellites, and obtaining the real-time ephemeris or almanac of all GPS satellites;
step 4, calculating GPS time at the current moment by utilizing a conversion relation between a Beidou system and a GPS system according to BDT-GNSS time synchronization information and Beidou time information obtained by measuring the current moment, and calculating real-time positions of all GPS satellites according to ephemeris or almanac of all GPS satellites and the GPS time information obtained by conversion;
step 5, judging whether each GPS satellite is in a satellite-masking state according to the obtained GNSS satellite-masking receiver position and each GPS satellite position, and generating a GPS satellite-masking prediction table;
and step 6, updating the satellite-occulting event state according to the GPS satellite-occulting prediction table obtained in the step 5, and completing GPS satellite-occulting observation.
As an improvement of the foregoing solution, in the step 3, acquiring a real-time ephemeris or almanac of each GPS satellite includes:
when the real-time ephemeris or almanac of a certain GPS satellite is obtained, the tracking channel resources occupied by the satellite are released, so that the real-time ephemeris or almanac of the other GPS satellites is received.
As one of the improvements of the above technical solution, in the step 4, the current time GPS time t GPS The calculation formula of (2) is as follows:
t GPS ＝t BD -Δt Systems
wherein Δt is Systems The calculation formula is as follows for the difference between the Beidou system time second and the GPS system time second at the current moment:
Δt Systems ＝A 0BGTO +A 1BGTO [t BD -t 0BGTO +604800(WN-WN BGTO )]+A 2BGTO [t BD -t 0BGTO +604800(WN-WN BGTO )] 2
wherein A is 0BGTO 、A 1BGTO 、A 2BGTO And WN BGTO Are BDT-GNSS time synchronization parameter broadcasting parameters, t BD And WN is the current Beidou moment and week.
As an improvement of the foregoing technical solution, the step 5 specifically includes:
step 5-1, calculating elevation angle Elev and tangential point height T of each GPS satellite per second according to the obtained position of the GNSS occultation receiver and the positions of each GPS satellite ph Relative azimuth R AZM And makes the following judgment:
elevation angle of star Elev, tangent point height T ph Relative azimuth R AZM When the satellite-masking judgment conditions are within the range of the satellite-masking judgment setting conditions, the satellite-masking judgment conditions are effective satellite-masking events;
elevation angle of star Elev, tangent point height T ph And relative azimuth R AZM If any one of the two is not in the range of the occultation judging and setting conditions, the occultation event is a failure occultation event;
step 5-2, updating the GPS occultation event prediction table to the present second according to the last second occultation eventIn (a) and (b); meanwhile, the GPS occultation event prediction table from last second GPS occultation event to last second GPS occultation event is buffered +.>Is a kind of medium.
As an improvement of the foregoing technical solution, the step 6 specifically includes:
step 6-1. According to the GPS occultation event prediction table of this secondAnd last second GPS occultation event prediction table +.>The satellite occultation event state identifiers of the GPS satellites in the present second and the last second are subjected to difference, and judgment is carried out according to the difference result, specifically:
when the satellite difference result is 1, the satellite occultation event is a newly added GPS occultation event in the second;
when the satellite difference result is-1, the satellite occultation event is a failure GPS occultation event in the second;
when the satellite difference result is 0, further judging whether the satellite occultation event of the second is an effective GPS occultation event, if the satellite occultation event of the second is an effective GPS occultation event, indicating that the satellite occultation event of the second is an existing occultation event; if the satellite occultation event is an invalid GPS occultation event, the satellite occultation event does not exist in the satellite.
Step 6-2, updating the state of the occultation event according to the judging result to finish GPS occultation observation, specifically comprising the following steps:
when judging that the GPS satellite occultation event is a newly added occultation event, further judging whether an idle GPS occultation tracking channel exists or not: if yes, distributing the newly added occultation event into the channel, starting occultation event capturing and tracking, and collecting occultation observation data; if the idle channel does not exist, the new mark of the occultation event is kept until the idle channel distributes the idle channel or the occultation event is invalid;
when judging that the satellite occultation event is invalid, stopping receiving the satellite occultation event, releasing and initializing the GPS satellite occultation tracking channel, setting the GPS satellite occultation tracking channel to be idle, and waiting for newly adding the satellite occultation event for use;
and when judging that the existing occultation event exists, keeping tracking the occultation event, and continuously collecting occultation data.
The invention also provides a system for carrying out GPS occultation observation based on the Beidou satellite signals, which comprises:
the radio frequency front end module is used for processing the positioning radio frequency signals received by the positioning antenna of the GNSS occultation receiver to obtain positioning intermediate frequency digital signals;
the signal processing module is used for correlating the positioning intermediate frequency digital signal with a local code and a carrier wave of the Beidou satellite system, acquiring a correlation peak value, capturing and tracking each satellite of the Beidou satellite system, measuring the pseudo range of each satellite of the Beidou satellite system, acquiring real-time ephemeris or almanac and BDT-GNSS time synchronization parameters of each satellite of the Beidou satellite system, and calculating the position of the GNSS occultation receiver according to the pseudo range information, ephemeris or almanac information of the Beidou satellite; the method is also used for correlating the positioning intermediate frequency digital signals with GPS satellite local pseudo codes and carriers to obtain correlation peaks, capturing and tracking each GPS satellite, measuring each GPS satellite pseudo range and obtaining real-time ephemeris or almanac of each GPS satellite;
the conversion module is used for calculating GPS time at the current moment by utilizing the conversion relation between a Beidou system and a GPS system according to BDT-GNSS time synchronization information and Beidou time information obtained by measuring the current moment, and calculating the real-time position of each GPS satellite according to each GPS satellite ephemeris or almanac and the GPS time information obtained by conversion; and
the occultation sampling module is used for judging whether each GPS satellite is in an occultation state according to the obtained GNSS occultation receiver position and each GPS satellite position and generating a GPS occultation prediction table; and the satellite occultation state updating module is also used for updating the satellite occultation event state according to the GPS satellite occultation prediction table to finish GPS satellite occultation observation.
As one of the improvements of the above technical solutions, the signal processing module includes:
the Beidou signal processing unit is used for correlating the positioning intermediate frequency digital signal with a local code and a carrier wave of a Beidou satellite system, acquiring a correlation peak value, capturing and tracking a Beidou satellite, measuring a Beidou satellite pseudo-range, acquiring real-time ephemeris or almanac and BDT-GNSS time synchronization parameters of the Beidou satellite, and calculating the position of the GNSS occultation receiver according to the Beidou satellite pseudo-range information, the ephemeris or almanac information; and
and the GPS signal processing unit is used for correlating the positioning intermediate frequency digital signal with a GPS satellite local pseudo code and a carrier wave to obtain a correlation peak value, capturing and tracking each GPS satellite, measuring the pseudo range of each GPS satellite and obtaining the real-time ephemeris or almanac of each GPS satellite.
As one of the improvements of the above technical scheme, the signal processing module is realized based on an FPGA chip.
As one of the improvement of the technical scheme, the conversion module and the occultation sampling module are realized based on an ARM chip.
Compared with the prior art, the invention has the advantages that:
1. according to the method for calculating the GPS position information by using the Beidou positioning result, provided by the invention, on the premise of not reducing the performance of an observer, the GPS system is not required to be independently allocated with positioning channel resources, the step of calculating the GPS positioning result by a traditional receiver is reduced, the system resources are saved, the operation time is saved, and the saved time/space can be allocated to Beidou positioning tracking/occultation observation, so that the positioning precision and the occultation event observation quantity are improved; the Beidou system has completely independent intellectual property rights, and is safer and more controllable;
2. compared with the method for independently calculating the positioning results of the GPS system and the Beidou system in the traditional method, the method provided by the invention is simple and effective, and does not need to carry out hardware modification.
Drawings
FIG. 1 is a flow chart of a method for GPS occultation observation by Beidou satellite signals;
fig. 2 is a system structure diagram of the invention for carrying out GPS occultation observation by using Beidou satellite signals.
Detailed Description
The invention provides a method for GPS occultation observation based on Beidou satellite signals in a micro GNSS occultation observation system. The method utilizes the Beidou direct signal to track and position, calculates the position of the receiver, and calculates the GPS occultation event by receiving GPS ephemeris/almanac information, thereby realizing the GPS occultation event tracking observation based on Beidou positioning. The method fully utilizes the mutual compatibility of the Beidou and GPS signals, reduces the system resource consumption required by GPS direct signal positioning, reduces the dependence of a receiver system on the GPS signals, is beneficial to the design targets of low resource, low power consumption and high integration level of the microminiature GNSS occultation observation system, can be applied to the microminiature GNSS occultation observation field, and has wide application prospect. The method has simple and clear design structure, is suitable for the microminiature GNSS occultation receiver, and does not need to carry out special hardware change.
The technical scheme of the invention is described in detail below with reference to the accompanying drawings and examples.
Example 1
As shown in fig. 1, a flowchart of a method for performing GPS occultation observation by using a beidou satellite signal is provided.
The method provided by the invention comprises the following steps:
(1) Beidou signal positioning and resolving method
And the front-end radio frequency unit receives the positioning antenna signal and performs down-conversion so as to capture, track and solve ephemeris/almanac of the Beidou positioning signal, and calculate the position of a receiver and the position of a Beidou satellite.
(2) Beidou occultation event prediction
And judging whether to trigger the Beidou satellite masking conditions according to the calculated receiver position and the Beidou satellite position, and generating a Beidou satellite masking event prediction table according to the Beidou satellite masking conditions.
(3) Beidou occultation event capturing and tracking device
According to the Beidou occultation event prediction table obtained in the step (2), updating the state of the Beidou occultation event table, and if the Beidou occultation event is a newly added occultation event, tracking the distribution channel; and if the event is a failure occultation event, releasing the channel thereof, and ending the observation.
(4) Beidou star-masking data packaging and transmitting device
And packing Beidou occultation observation data every second, storing information such as carrier phase, pseudo range, I/Q path integral value and the like, and transmitting the information through LVDS for subsequent occultation inversion calculation.
(5) Acquiring GPS ephemeris/almanac
And receiving GPS signals through positioning antenna signals, thereby acquiring real-time ephemeris/almanac of each GPS satellite, releasing a channel occupied by the satellite after the acquisition is completed, and using the channel for other GPS satellites which do not acquire the ephemeris/almanac.
(6) Beidou positioning result conversion GPS positioning result
Calculating GPS time at the current moment by utilizing a conversion relation between a Beidou system and a GPS system according to BDT-GNSS time synchronization information in a message received by a GNSS occultation receiver and Beidou time information obtained by measuring the current moment, and calculating the real-time position of a GPS satellite according to the GPS ephemeris/almanac received in the step (5) and the GPS time information obtained by conversion.
(7) GPS occultation event prediction
And (3) judging whether each GPS satellite is in a satellite-occulting state according to the GPS system position and the GPS satellite position obtained by calculation in the step (6), and generating a GPS satellite-occulting prediction table.
(8) GPS occultation event capture tracking
Updating the state of the occultation event according to the Beidou occultation event prediction table obtained in the step (7), and if the occultation event is a newly added occultation event, tracking the distribution channel; and if the event is a failure occultation event, releasing the channel thereof, and ending the observation.
(9) Beidou star-masking data packaging and transmitting device
Every second, the Beidou occultation observation data are packaged, information such as carrier phase, pseudo range, I/Q path integral value and the like is stored, the information is sent to a star system through an LVDS interface, and the information is received through a ground station and then used for subsequent occultation inversion calculation.
In particular, the method comprises the steps of,
the step (1) comprises: receiving a positioning signal through a positioning antenna, down-converting the received radio frequency signal by utilizing a front-end radio frequency unit to obtain an analog intermediate frequency signal, converting the analog intermediate frequency signal into an intermediate frequency digital signal through an AD sampling module, inputting the digital signal into a baseband board FPGA, generating a local code and a carrier wave of a Beidou system with the baseband board for correlation, and transmitting a capturing result to an ARM end to obtain a correlation peak value, thereby further realizing capturing, tracking and message decoding; and calculating the position of the GNSS occultation receiver under the Beidou coordinate system and the Beidou satellite position according to the measured Beidou satellite pseudo-range information, time information and ephemeris/almanac information, and calculating various information such as Beidou satellite carriers, pseudo code phases and the like according to the Beidou satellite position and the GNSS occultation receiver position for subsequent occultation prediction and occultation capture.
The step (2) comprises the following steps: and calculating information such as an elevation angle, an azimuth angle, a tangential point height, a relative azimuth angle and the like of the Beidou satellite at the ARM end every second according to the GNSS receiver position and the Beidou satellite position calculated at the current moment, judging the satellite masking conditions of the Beidou satellites by utilizing the information, writing a masking event judgment result into a masking event prediction table TblBDp of the current second, and simultaneously storing the Beidou masking event generated in the last second into a masking event prediction table TblBDe of the previous second.
The step (3) comprises the following steps: comparing the present second and the previous second Beidou occultation event prediction tables TblBDp and TblBDe generated in the step (2), determining newly added, existing and invalid occultation events, distributing the newly added occultation events to the occultation tracking observation channel, and deleting the invalid occultation events from the tracking channel.
The step (4) comprises: and packing the Beidou occultation event measurement results in the second every second, and transmitting the results to a star processing system for caching through an LVDS interface at the end of the second.
The step (5) comprises the following steps: and (3) correlating the intermediate frequency signals which are converted by the A/D and transmitted to the FPGA end of the baseband board with the local pseudo codes and the carrier waves of the GPS satellites to obtain correlation peaks, capturing and tracking the GPS satellites, measuring pseudo ranges, and receiving ephemeris and almanac of the GPS satellites.
The step (6) comprises: and (3) converting the Beidou system time information obtained in the step (1) into a GPS (global positioning system) at an ARM end. The method specifically comprises the following steps: analyzing BDT-GNSS time synchronization (BGTO) information broadcasted by the Beidou third-generation satellites, and converting Beidou time at the current moment calculated by the GNSS occultation receiver into GPS time by utilizing the information algorithm; converting the position of the GNSS receiver under the Beidou coordinate system calculated by the Beidou system into a geocentric inertial coordinate system, calculating the positions of all GPS satellites by using the positioning information, the GPS satellite ephemeris information obtained in the step (5) and the GPS time obtained by conversion, and using the GPS satellite ephemeris information and the GPS time obtained by conversion in the step (7) for GPS occultation prediction.
The step (7) comprises: judging the position of the GNSS occultation receiver calculated in the step (1) and the position of the GPS satellite calculated in the step (6) at the ARM end every second, calculating the elevation angle, azimuth angle, tangential point height, relative azimuth angle, predicted carrier frequency, code phase and other information of the GPS satellite, judging satellite occultation conditions of the GPS satellite according to the information, writing the occultation event judgment result into an occultation event prediction table TblGPSp of the current second, and simultaneously, storing the occultation event generated in the last second into a occultation event prediction table TblGPSe of the previous second.
The step (8) comprises: and (3) comparing the present second and the previous second GPS occultation event prediction tables TblGPSp and TblGPSe generated in the step (7), determining newly added, existing and invalid GPS occultation events, distributing the newly added occultation events to a GPS occultation tracking observation channel, inputting information such as the predicted carrier frequency, the code phase and the like of the GPS satellites corresponding to the occultation events so as to start occultation observation, and deleting the invalid occultation events from the tracking channel.
The step (9) comprises: packing GPS occultation event measurement results in the second every second, and transmitting the results to a star processing system for caching through an LVDS interface at the end of the second; and the Beidou occultation measurement result are transmitted to a ground system through a ground station for subsequent inversion calculation.
Example 2
The invention provides a system for GPS occultation observation by adopting Beidou satellite signals, which comprises: the device comprises a radio frequency front end module, a signal processing module, a conversion module and a occultation sampling module.
The radio frequency front end module is used for processing the positioning radio frequency signals received by the positioning antenna of the GNSS occultation receiver to obtain positioning intermediate frequency digital signals;
the signal processing module includes: the GPS signal processing unit is used for receiving the GPS signals; the Beidou signal processing unit is used for correlating the positioning intermediate frequency digital signal with a local code and a carrier wave of a Beidou satellite system, acquiring a correlation peak value, capturing and tracking a Beidou satellite, measuring a Beidou satellite pseudo-range, acquiring real-time ephemeris or almanac and BDT-GNSS time synchronization parameters of the Beidou satellite, and calculating the position of the GNSS occultation receiver according to the Beidou satellite pseudo-range information, the ephemeris or almanac information; and the GPS signal processing unit is used for correlating the positioning intermediate frequency digital signal with a GPS satellite local pseudo code and a carrier wave to obtain a correlation peak value, capturing and tracking each GPS satellite, measuring the pseudo range of each GPS satellite and obtaining the real-time ephemeris or almanac of each GPS satellite.
The conversion module is used for calculating GPS time at the current moment by utilizing the conversion relation between a Beidou system and a GPS system according to BDT-GNSS time synchronization information and Beidou time information obtained by measuring the current moment, and calculating the real-time position of each GPS satellite according to each GPS satellite ephemeris or almanac and the GPS time information obtained by conversion;
the occultation sampling module is used for judging whether each GPS satellite is in an occultation state according to the obtained GNSS occultation receiver position and each GPS satellite position and generating a GPS occultation prediction table; and the satellite occultation state updating module is also used for updating the satellite occultation event state according to the GPS satellite occultation prediction table to finish GPS satellite occultation observation.
The signal processing module is realized based on an FPGA chip, and the conversion module and the star masking sampling module are realized based on an ARM chip.
Fig. 2 is a design block diagram of a system for performing GPS occultation observation by using beidou satellite signals (hereinafter referred to as GNSS occultation observer) according to embodiment 2 of the present invention, including three parts of a radio frequency front end, an FPGA end and an ARM end.
In order to make the purpose and the technical scheme of the invention clearer, the method for carrying out GPS occultation observation based on Beidou satellite signals in the microminiature GNSS occultation observation system provided by the invention is explained in detail below with reference to the attached drawings and the embodiment.
The structure of the GNSS occultation observer is shown in figure 2, and consists of a radio frequency front end, a baseband board FPGA and a baseband board ARM. The front end of the radio frequency comprises a positioning antenna module, a forward occultation antenna module and a backward occultation antenna module; in order to miniaturize the receiver, the baseband board FPGA and the baseband board ARM can be realized by adopting an SOC integrated chip.
The GNSS occultation observer is illustrated by taking the received Beidou signal as a Beidou third-generation B1C signal and the GPS signal as a GPS L1 signal as an example. The carrier frequencies of the two signals are 1575.42Mhz, firstly, the positioning antenna receives the frequency point signals and filters and down-converts the signals to obtain intermediate frequency signals, the intermediate frequency signals are input to a baseband FPGA end, and then the analog intermediate frequency signals are converted into digital intermediate frequency signals r through an AD sampling module IF 。
At the time of obtaining intermediate frequency signal r IF Then, local carrier wave and Beidou B1C local pseudo code are generated at the FPGA end and are matched with r IF And (3) carrying out correlation, stripping B1C pseudo codes and carrier information in the intermediate frequency signals, sending the processed signals to an ARM end, acquiring a correlation peak value to achieve capture, putting a capture result into a positioning tracking loop, acquiring an I/Q path integral result according to integral time, obtaining Beidou B-CNAV1 text information through I/Q path integral identification after stable tracking is achieved, extracting parameters such as time parameters, ephemeris, almanac, BDT-GNSS time synchronization information and the like, and storing the parameters. The current time Beidou time can be obtained after system time parameters SOH (hour-second count), HOW (Zhou Naxiao time count) and WN (whole week count) are calculated, and parameters such as ephemeris, almanac and various error corrections are extracted from the telegraph text, so that the GNSS occultation observer position and each Beidou satellite constellation position are calculated.
After the position calculation is completed, the Beidou satellite masking event prediction can be performed, and the elevation angle Elev and the tangential point height T of each Beidou satellite per second can be calculated according to the GNSS satellite masking observer and the position calculation result of the Beidou satellite constellation ph Relative azimuth R AZM If the three are in the condition range of the table 1, the three are considered to be effective occultation events, otherwise, the three are invalid occultation events, and the three are updated to the Beidou occultation event prediction table Tbl of the second according to the last occultation event BDp In (a) and (b); and buffering the last second Beidou satellite-masking event to the last second Beidou satellite-masking event prediction table Tbl BDe Is a kind of medium.
Table 1 Star-masking Range judgment Table
After the Beidou occultation event prediction result is obtained, the Beidou occultation event prediction table is subjected to difference, and then the second new addition, the existing occultation event and the invalid occultation event can be determined:
aiming at the judgment result of the occultation event, the following operations are carried out:
newly added occultation event
Firstly judging whether an idle Beidou occultation tracking channel exists, if so, distributing a newly added occultation event into the channel, starting occultation event capturing and tracking, and collecting occultation observation data; if there is no free channel, the occultation event is marked as new and tracking is not started until the free channel is allocated for the occultation event or the occultation event is invalid.
Existing occultation event
Keeping track, continuously collecting occultation data.
Failure occultation event
If the occultation event existing in the occultation channel is not in the occultation prediction table, the occultation event is considered to be invalid, at the moment, the occultation event is stopped being received, the Beidou occultation channel is released and initialized, and the channel state is set to be idle, so that the occultation event is newly added for use.
Absence of occultation event
No operation is performed.
After the judgment operation of the occultation event is completed, the newly added occultation event is captured, the existing occultation event keeps tracking, information such as carrier phase, I/Q (input/output) path integration, carrier-to-noise ratio and pseudo range is collected, the information is cached according to the speed of 100Hz, and the information is packaged according to a time stamp and is sent to a star system through a bus.
For GPS system, intermediate frequency signal r IF And (3) carrying out correlation between the FPGA end and the local carrier and the GPS L1C/A code, and sending the correlation result to the ARM end, so as to realize the tracking of GPS direct signals and acquire GPS ephemeris/almanac information.
According to the BDT-GNSS time synchronization parameter part in the Beidou B-CNAV1 text information, the solved Beidou time can be converted into GPS time:
Δt Systems ＝A 0BGTO +A 1BGTO [t BD -t 0BGTO +604800(WN-WN BGTO )]+A 2BGTO [t BD -t 0BGTO +604800(WN-WN BGTO )] 2
wherein A is 0BGTO ～A 2BGTO And WN BGTO Are BDT-GNSS time synchronization parameter broadcasting parameters, t BD For the current Beidou time second, WN is the current Beidou time week, and deltat is calculated Systems The difference between the time second of the Beidou system at the current moment and the time second of the GPS system can be calculated as the time second of the GPS system
t GPS ＝t BD -Δt Systems
The conversion relation can be utilized to obtain GPS time seconds at the current moment on the premise of not analyzing the GPS telegraph text, the Beidou system is utilized to calculate and obtain the position information of the GNSS occultation observer and the GPS ephemeris almanac, and the GPS satellite constellation position information is calculated and used for GPS occultation prediction.
Similar to the Beidou satellite-occultation prediction method, the GNSS satellite-occultation observer calculates the elevation angle Elev and the tangential point height T of each GPS satellite per second ph Relative azimuth R AZM If the three are in the table condition range, the three are considered to be effective occultation events, otherwise, the three are invalid occultation events, and the GPS occultation event prediction table Tbl is updated to the present second according to the last occultation event GPSp In (a) and (b); and buffering the last-second GPS occultation event to the last-second GPS occultation event prediction table Tbl GPSe Is a kind of medium.
The GPS occultation event is also subjected to difference, so that the operating condition of the GPS occultation event can be obtained:
and aiming at the judgment result of the occultation event, the rest operation is the same as that of the Beidou occultation event, and the received observation information is packaged and stored at the rate of 100 Hz.
After receiving the Beidou and GPS occultation data information per second, the star system caches the Beidou and GPS occultation data information and downloads the data information to a ground receiving station at appropriate time for subsequent inversion.
It should be noted that the above embodiment is only a preferred embodiment of the present invention for performing GPS occultation observation based on the Beidou satellite signal in the micro-GNSS occultation observation system, and the preferred embodiment is not intended to limit the scope of the present invention. All algorithms and their corresponding system designs disclosed herein are capable of various combined interception or substitution of features with the same or similar purpose and effect. It should be noted that various modifications and variations, such as adding, deleting, replacing or combining certain steps or functional units/modules, can be made by those skilled in the art without departing from the principles and spirit of the present invention, and such modifications and variations are also within the scope of the present invention.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and are not limiting. Although the present invention has been described in detail with reference to the embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the appended claims.

Claims (10)

1. A method for performing GPS occultation observation based on beidou satellite signals, the method comprising:
the method comprises the steps of capturing, tracking and positioning a receiver through signals received by a GNSS occultation receiver, obtaining time and position information of the GNSS occultation receiver under space-time coordinates of a Beidou satellite system, converting Beidou positioning results into GPS positioning results, resolving GPS satellite positions according to the GPS positioning results, realizing GPS occultation prediction and occultation capturing and tracking based on the GPS satellite positions, and completing GPS occultation observation.
2. The method for performing GPS occultation observation based on Beidou satellite signals according to claim 1, which is characterized by specifically comprising the following steps:
step 1, receiving and processing a positioning radio frequency analog signal through a positioning antenna of a GNSS occultation receiver to obtain a positioning intermediate frequency digital signal;
step 2, correlating the positioning intermediate frequency digital signal with a local code and a carrier wave of a Beidou satellite system, acquiring a correlation peak value, capturing and tracking each satellite of the Beidou satellite system, measuring the pseudo range of each satellite of the Beidou satellite system, and acquiring real-time ephemeris or almanac and BDT-GNSS time synchronization parameters of each satellite of the Beidou satellite system; calculating the position of the GNSS occultation receiver according to the Beidou satellite pseudo-range information, ephemeris or almanac information;
step 3, correlating the positioning intermediate frequency digital signals with the local pseudo codes and carriers of all GPS satellites to obtain correlation peaks, capturing and tracking all GPS satellites, measuring the pseudo range of the GPS satellites, and obtaining the real-time ephemeris or almanac of all GPS satellites;
step 4, calculating GPS time at the current moment by utilizing a conversion relation between a Beidou system and a GPS system according to BDT-GNSS time synchronization information and Beidou time information obtained by measuring the current moment, and calculating real-time positions of all GPS satellites according to ephemeris or almanac of all GPS satellites and the GPS time information obtained by conversion;
step 5, judging whether each GPS satellite is in a satellite-masking state according to the obtained GNSS satellite-masking receiver position and each GPS satellite position, and generating a GPS satellite-masking prediction table;
and step 6, updating the satellite-occulting event state according to the GPS satellite-occulting prediction table obtained in the step 5, and completing GPS satellite-occulting observation.
3. The method for performing GPS occultation observation based on Beidou satellite signals according to claim 2, wherein in the step 3, acquiring real-time ephemeris or almanac of each GPS satellite includes:
when the real-time ephemeris or almanac of a certain GPS satellite is obtained, the tracking channel resources occupied by the satellite are released, so that the real-time ephemeris or almanac of the other GPS satellites is received.
4. The method for performing GPS occultation observation based on Beidou satellite signals according to claim 2, wherein in the step 4, the current moment GPS time t GPS The calculation formula of (2) is as follows:
t GPS ＝t BD -t Systems
wherein t is Systems The calculation formula is as follows for the difference between the Beidou system time second and the GPS system time second at the current moment:
t Systems ＝A 0BGTO +A 1BGTO [t BD -t 0BGTO +604800(WN-WN BGTO )]+A 2BGTO [t BD -t 0BGTO +604800(WN-WN BGTO )] 2
wherein A is 0BGTO 、A 1BGTO 、A 2BGTO And WN BGTO Are BDT-GNSS time synchronization parameter broadcasting parameters, t BD And WN is the current Beidou moment and week.
5. The method for performing GPS occultation observation based on the beidou satellite signal according to claim 2, wherein the step 5 specifically includes:
step 5-1, calculating elevation angle Elev and tangential point height T of each GPS satellite per second according to the obtained position of the GNSS occultation receiver and the positions of each GPS satellite ph Relative azimuth R AZM And makes the following judgment:
elevation angle of star Elev, tangent point height T ph Relative azimuth R AZM When the satellite-masking judgment conditions are within the range of the satellite-masking judgment setting conditions, the satellite-masking judgment conditions are effective satellite-masking events;
elevation angle of star Elev, tangent point height T ph And relative azimuth R AZM If any one of the two is not in the range of the occultation judging and setting conditions, the occultation event is a failure occultation event;
step 5-2. Occultation according to last secondGPS occultation event prediction table for updating event to present secondIn (a) and (b); meanwhile, the GPS occultation event prediction table from last second GPS occultation event to last second GPS occultation event is buffered +.>Is a kind of medium.
6. The method for performing GPS occultation observation based on Beidou satellite signals according to claim 5, wherein the step 6 specifically includes:
step 6-1. According to the GPS occultation event prediction table of this secondAnd last second GPS occultation event prediction table +.>The satellite occultation event state identifiers of the GPS satellites in the present second and the last second are subjected to difference, and judgment is carried out according to the difference result, specifically:
when the satellite difference result is 1, the satellite occultation event is a newly added GPS occultation event in the second;
when the satellite difference result is-1, the satellite occultation event is a failure GPS occultation event in the second;
when the satellite difference result is 0, further judging whether the satellite occultation event of the second is an effective GPS occultation event, if the satellite occultation event of the second is an effective GPS occultation event, indicating that the satellite occultation event of the second is an existing occultation event; if the satellite occultation event is an invalid GPS occultation event, indicating that the satellite does not have the occultation event in the second;
step 6-2, updating the state of the occultation event according to the judging result to finish GPS occultation observation, specifically comprising the following steps:
when judging that the GPS satellite occultation event is a newly added occultation event, further judging whether an idle GPS occultation tracking channel exists or not: if yes, distributing the newly added occultation event into the channel, starting occultation event capturing and tracking, and collecting occultation observation data; if the idle channel does not exist, the new mark of the occultation event is kept until the idle channel distributes the idle channel or the occultation event is invalid;
when judging that the satellite occultation event is invalid, stopping receiving the satellite occultation event, releasing and initializing the GPS satellite occultation tracking channel, setting the GPS satellite occultation tracking channel to be idle, and waiting for newly adding the satellite occultation event for use;
and when judging that the existing occultation event exists, keeping tracking the occultation event, and continuously collecting occultation data.
7. A system for performing GPS occultation observation based on beidou satellite signals, the system comprising:
the radio frequency front end module is used for processing the positioning radio frequency signals received by the positioning antenna of the GNSS occultation receiver to obtain positioning intermediate frequency digital signals;
the signal processing module is used for correlating the positioning intermediate frequency digital signal with a local code and a carrier wave of the Beidou satellite system, acquiring a correlation peak value, capturing and tracking each satellite of the Beidou satellite system, measuring the pseudo range of each satellite of the Beidou satellite system, acquiring real-time ephemeris or almanac and BDT-GNSS time synchronization parameters of each satellite of the Beidou satellite system, and calculating the position of the GNSS occultation receiver according to the pseudo range information, ephemeris or almanac information of the Beidou satellite; the method is also used for correlating the positioning intermediate frequency digital signals with GPS satellite local pseudo codes and carriers to obtain correlation peaks, capturing and tracking each GPS satellite, measuring each GPS satellite pseudo range and obtaining real-time ephemeris or almanac of each GPS satellite;
the conversion module is used for calculating GPS time at the current moment by utilizing the conversion relation between a Beidou system and a GPS system according to BDT-GNSS time synchronization information and Beidou time information obtained by measuring the current moment, and calculating the real-time position of each GPS satellite according to each GPS satellite ephemeris or almanac and the GPS time information obtained by conversion; and
the occultation sampling module is used for judging whether each GPS satellite is in an occultation state according to the obtained GNSS occultation receiver position and each GPS satellite position and generating a GPS occultation prediction table; and the satellite occultation state updating module is also used for updating the satellite occultation event state according to the GPS satellite occultation prediction table to finish GPS satellite occultation observation.
8. The system for performing GPS occultation observation based on Beidou satellite signals of claim 7, wherein the signal processing module includes:
the Beidou signal processing unit is used for correlating the positioning intermediate frequency digital signal with a local code and a carrier wave of a Beidou satellite system, acquiring a correlation peak value, capturing and tracking a Beidou satellite, measuring a Beidou satellite pseudo-range, acquiring real-time ephemeris or almanac and BDT-GNSS time synchronization parameters of the Beidou satellite, and calculating the position of the GNSS occultation receiver according to the Beidou satellite pseudo-range information, the ephemeris or almanac information; and
and the GPS signal processing unit is used for correlating the positioning intermediate frequency digital signal with a GPS satellite local pseudo code and a carrier wave to obtain a correlation peak value, capturing and tracking each GPS satellite, measuring the pseudo range of each GPS satellite and obtaining the real-time ephemeris or almanac of each GPS satellite.
9. The system for performing GPS occultation observation based on Beidou satellite signals according to claim 7, wherein the signal processing module is realized based on an FPGA chip.
10. The system for performing GPS occultation observation based on Beidou satellite signals according to claim 7, wherein the conversion module and the occultation sampling module are realized based on ARM chips.
CN202310322866.3A 2023-03-29 2023-03-29 Method and system for GPS occultation observation based on Beidou satellite signals Pending CN116660944A (en)

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CN117784186A (en) * 2024-02-22 2024-03-29 中国科学院国家空间科学中心 Occultation reflection detector and configuration method
CN117930296A (en) * 2024-03-22 2024-04-26 中国科学院国家空间科学中心 Star-masking data processing method and system

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CN117743275A (en) * 2024-02-19 2024-03-22 天津云遥宇航科技有限公司 Star-masking orbit data application system and method based on SGP4 forecasting model
CN117743275B (en) * 2024-02-19 2024-05-28 天津云遥宇航科技有限公司 Method for occultation orbit data application system based on SGP4 forecasting model
CN117784186A (en) * 2024-02-22 2024-03-29 中国科学院国家空间科学中心 Occultation reflection detector and configuration method
CN117784186B (en) * 2024-02-22 2024-05-24 中国科学院国家空间科学中心 Configuration Method of Occultation Reflection Detector
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