Simulation generation method for observation data of space-oriented terahertz telescope

Abstract

The invention discloses a space terahertz telescope-oriented observation data simulation generation method. The method comprises instrument effect simulation of observation spectrum data, cosmic space environment effect simulation of the observation spectrum data and generation of an observation data stream. HSTDM instrument effect simulation and cosmic space environment effect simulation are incorporated into a unified effect simulation framework, and an HSTDM 0-level simulation observation data stream is obtained by combining a CSST HSTDM single-point observation mode, an On-The-Fly observation mode and an HSTDM standard 0-level data format. Based on the actual demand of CSST HSTDM observation data calibration processing, a modular design thought is adopted to construct an overall framework of observation data simulation, and technical support is provided for space terahertz telescope observation data simulation generation.

Description

Technical Field

[0001] The present invention relates to the field of astronomical telescope observation technology, and in particular to a space terahertz band astronomical telescope observation data simulation technology. Background Art

[0002] The terahertz band usually refers to the frequency range of 0.1THz to 10THz, and its corresponding wavelength range is 3mm to 30μm, covering short millimeter waves to submillimeter waves (far infrared region). This electromagnetic band has not yet been fully developed and studied, and is full of potential. The terahertz band has become an ideal choice for exploring cutting-edge issues in modern astronomy due to its unique properties, such as strong molecular absorption and dispersion characteristics, high spatial resolution, ultra-wide bandwidth, and low photon energy.

[0003] The terahertz band contains abundant molecular rotation spectral lines and atomic fine structure spectral lines, which are important means to carry out research on star formation in early galaxies and star formation regions of the Milky Way, star formation in molecular clouds hidden in cold dust, temperature anisotropy measurement of microwave background radiation, celestial body formation, etc. In order to obtain these spectral line information, terahertz astronomical observations usually use two observation techniques: continuous spectrum observation and spectral line observation.

[0004] However, due to the influence of water vapor in the atmosphere, the spectral lines emitted from distant celestial bodies will be strongly absorbed by water vapor in a specific terahertz frequency band (the frequency band centered at 557GHz), and the relevant spectrum information will be lost. But for certain types of scientific observations, the lost spectrum information is of high value. Therefore, using space terahertz telescopes for scientific observations is an inevitable choice for some terahertz band observations.

[0005] On the other hand, the China Space Station Survey Telescope (CSST), a flagship project of China's space astronomy, is expected to be launched around 2027. CSST is the largest space telescope currently developed by my country, with outstanding features such as large field of view, high image quality, and wide band. Its detection sensitivity and spatial resolution are comparable to the internationally renowned Hubble Space Telescope (HST), but the scale of observation field and data acquisition will far exceed that of the Hubble Space Telescope. CSST is equipped with multiple terminal detection modules, which is very competitive and is expected to achieve major breakthroughs in research directions such as cosmology, galaxies and active galactic nuclei, the Milky Way and stars, astrometry, extrasolar planets, and solar system bodies. CSST is equipped with a High Sensitivity Terahertz Detection Module (HSTDM), the core component of which is a superconducting SIS (superconductor-insulator-superconductor) mixer operating in the frequency range of 0.41-0.51 THz (corresponding to an operating wavelength of 590-730 μm), which is used for high spectral resolution and high sensitivity spectral line observation. HSTDM will provide important opportunities for scientific discoveries in terahertz astronomy, and its influence will be far-reaching not only for the domestic but also for the global radio astronomy community.

[0006] HSTDM's scientific discoveries must rely on the telescope's pre-processed scientific data, which are obtained from HSTDM's raw observation data after careful data calibration. The processing involves a series of technical details such as HSTDM instrument effect subtraction and coordinated processing of observation data streams under all HSTDM observation modes. This data calibration process must ensure correctness and effectiveness.

[0007] In order to fully verify the correctness and effectiveness of HSTDM data calibration processing before the launch of CSST, and to promote CSSTHSTDM to produce meaningful scientific data as soon as possible after launch into orbit, so as to maximize the scientific output of HSTDM and even the entire CSST, CSST HSTDM has put forward a major demand for observation data simulation generation methods. Since there is no precedent for the launch and operation of space terahertz telescopes in my country, and there is a lack of sufficient understanding of the details of observation data calibration processing in this band, this also drives us to tackle and make breakthroughs in the simulation generation technology of observation data for space terahertz telescopes. Summary of the invention

[0008] With the steady progress of CSST research and development tasks, CSST has put forward practical needs for HSTDM observation data simulation generation technology. The present invention is based on the practical needs of CSST HSTDM observation data calibration processing and provides a modular observation data simulation generation method.

[0009] To achieve the above purpose, the technical solution provided by the present invention is:

[0010] A method for simulating and generating observation data for space terahertz telescopes includes instrument effect simulation of observation spectrum data, cosmic space environment effect simulation of observation spectrum data, and generation of observation data stream. HSTDM instrument effect simulation and cosmic space environment effect simulation are incorporated into a unified effect simulation framework, and the HSTDM level 0 simulation observation data stream is obtained by combining the CSST HSTDM single-point observation mode, the On-The-Fly observation mode, and the level 0 data format of the HSTDM standard.

[0011] To optimize the above technical solutions, the specific measures taken include:

[0012] In the unified effect simulation framework, the standard spectrum data is defined as SpecD, the head information that meets the level 0 definition is HeadI, and the observation time period simulated by the simulation data to be generated is [t i , t i +T], the total observation time length is T, the time interval between two adjacent sets of simulation data is ΔT, the total number of data sets generated is L = Ceil (T / ΔT), and the intensity of simulated cosmic ray interference is T burst , in Kelvin, the simulated local oscillator frequency f LO , the frequency interval between two adjacent channels is Δf, and the coupling coefficient simulated in the sunny area is η l , the coupling coefficient in the shaded area is η d , the number of spectrum data channels generated by simulation is N c , and according to the HSTDM observation mode, in the simulated observation period [t i , t i +T] to set single-point observation and OTF observation simulation scenarios.

[0013] Obtain the standard spectrum data SpecD with the specified name from the public astronomical database. The amplitude value dimension is Kelvin and the data length is N. s ; if N s <N c , then use the standard interpolation algorithm to interpolate SpecD to obtain a length of N c Spectrum data SpecDI; if N s >N c, then use the standard sampling algorithm to extract SpecD to obtain a length of N c Spectrum data SpecDI; if N s =N c , SpecD is used as the spectrum data SpecDI; during the interpolation or sampling process, ensure that the frequency axis corresponding to the SpecDI channel number is consistent with the frequency axis of the observation data generated by the simulation.

[0014] The instrument effect simulation of the observed spectrum data adopts at least one of a ground measurement method and an Ornstein-Uhlenbeck model method.

[0015] Furthermore, the ground-based measurement method includes:

[0016] The operating temperature of HSTDM is T c , the raw spectrum data of HSTDM output is measured under the condition that the local frequency oscillator output is enabled and there is no external RF signal, and the data set Raws = {Rawd 1， Rawd2, …Rawd N}, Raw i is the ith spectrum output, and its amplitude value is the count of the spectrum analyzer output, dimensionless; the number of spectrum data channels output each time is N c , the time interval of the output spectrum data is set to ΔT to ensure that the total number of groups N ≥ L;

[0017] Select L groups from the N groups of data in the Raws dataset and sort them in the order of output time, and use the observation period [t i , t i +T]; SRaws, a base spectrum dataset containing instrument effects;

[0018] Get the length N c Spectrum data SpecDI;

[0019] For SpecDI c The median Da is calculated from the amplitude values ​​of the outputs of the channels m , and output Da for each channel in SpecDI i Make a judgment, if Da i <Da m Then set the channel amplitude value to Da m , no operation is performed in other cases, and the length after processing is N c Standard spectrum data SpecDIP;

[0020] Get HSTDM at temperature T coldThe original spectrum data set output under cold load Rcold = {Rcold1, Rcold2, ... Rcold N}, calculate the average value Acold of N groups of spectrum data, at temperature T hot The original spectrum data set output under thermal load Rhot = {Rhot 1， Rhot2, ... Rhot N}, calculate and obtain the average value Ahot of N groups of spectrum data;

[0021] For each set of data SRaw in the dataset SRaws containing L sets of data i By formula: Obtain the spectrum data set Sds including instrument effect after cold and hot load conversion = {Sd 1， Sd2,…Sd L}, the amplitude dimension of the spectrum data is Kelvin;

[0022] Add spectrum data SpecDIP to each set of data in the spectrum data set Sds, that is, Sd i =SpecDIP+Sd i , thus the simulated observation time period is [t i , t i +T] contains the instrument effect spectrum data set SPd = {Sd 1， Sd2,…Sd L}.

[0023] Furthermore, the Ornstein-Uhlenbeck model-based method includes:

[0024] Get the length N c Spectrum data SpecDI;

[0025] The data Dat for each channel i of SpecDI i Perform iterative updates: Dat i [0] = SpecDI[i], n∈{1, 2, ..., L}, and the simulated observation period is [t i , t i +T]; where ε is the noise of normal distribution, ε~N(0,1), θ, μ, σ are all configurable parameters, θ represents the mean regression parameter, μ represents the long-term stable mean, and σ represents the variance fluctuation;

[0026] For all N cEach channel generates a series of channel outputs according to the above method, and the simulated observation time period [t i , t i +T] contains the instrument effect spectrum data set SPd = {Dat i , Dat2, ..., Dat L}.

[0027] Furthermore, the simulation of the cosmic space environment effect of the observed spectrum data includes:

[0028] In the set of integers {1, 2, ..., N c} randomly select a number n r As the spectrum channel number corresponding to the frequency band of simulated cosmic ray interference;

[0029] For each set of spectrum data in the instrument effect spectrum data set SPd, the channel number is n r The corresponding amplitude value superposition intensity is T burst interference;

[0030] For each set of spectrum data, all channels are superimposed with the cosmic microwave background radiation intensity T cmb , obtain the simulated spectrum data set SPdc after superimposing cosmic ray interference and microwave background radiation;

[0031] According to the simulated orbit information and the simulated observation time period [t i , t i +T], calculate the relative position information of the telescope, the sun and the earth, and the telescope's running speed information vel, thereby updating the header information HeadI of each group of SPdc observation data, and judging the observation time period [t i , t i +T] is the SPdc observation data in the sunny area or the shaded area. If it is in the shaded area, the amplitude value of each channel in each group of observation data under SPdc is multiplied by the coupling coefficient η d If it is in the sunny area, then the amplitude value of each channel of each group of observation data under SPdc is multiplied by the coupling coefficient η l , thus obtaining the observed spectrum data set SPdcc;

[0032] According to the telescope velocity vel corresponding to each set of data obtained, calculate its Doppler frequency offset f dop , and convert it to the offset channel number ΔN, and translate each set of spectrum data in SPdcc according to ΔN, thereby obtaining the spectrum data set SPdccd after the cosmic effect;

[0033] According to the above method, SPdccd={Spccd1, Spccd2, ..., SpccdL}Each group of spectrum data Spccd i Through the hot and cold calibration formula: Get the simulated dimensionless HSTDM raw spectrum data set {Cspcd1, Cspcd2...Cspcd L}.

[0034] Determine the observation period [t i , t i +T] is in the sunlit area or the shaded area. The method is as follows: obtain the time of the current observation data, use the CSST orbit parameters to calculate the telescope position and the sun position at the current time; calculate the angle β between the vector connecting the telescope and the center of the earth and the vector connecting the sun and the center of the earth. If β is less than 70 degrees, the telescope corresponding to the current group of observation data is in the sunlit area. If β is greater than 110 degrees, the current telescope is in the shaded area.

[0035] Furthermore, the Doppler frequency shift f is calculated dop The method is:

[0036] Project the satellite velocity vector vel to the direction of the observed target source to obtain the radial velocity value V of the satellite velocity relative to the target source in the geocentric coordinate system r1， The unit is km / s;

[0037] Calculate the galactic longitude l and galactic latitude b of the observed target source using the formula:

[0038] V r2 =V r1 +9cos(l)cos(b)+12sin(l)cos(b)+7sin(b)Calculate V r1 Radial velocity V in LSR (Local Standard of Rest) coordinate system r2 , unit is km / s;

[0039] Through the Doppler shift formula: Calculate the frequency offset f dop , where c is the speed of light, which is 299792.458 km / s, and f LO represents the simulated HSTDM local oscillator frequency;

[0040] The channel number ΔN converted to offset is calculated by the formula It is obtained that ΔN>0 means that the channel number is shifted to the right by |ΔN| units, and ΔN<0 means that the channel number is shifted to the left by |ΔN| units.

[0041] Furthermore, the generation of the observation data stream includes:

[0042] According to the observation period [t i , t i +T], set the single-point observation and OTF observation simulation scenarios, and construct the observation sequences Seqs = {seq1, seq2, ... seq L}, including five basic observation types: ON point integration, OFF point integration, internal load calibration, waiting, and telescope rotation; the methods are as follows:

[0043] For the single-point observation scenario, the three basic observations of ON point integration, OFF point integration, and internal load calibration are first combined to form the basic observation time series Pseq = {t ON ,t BLK ,t OFF}, ensure that the total execution time of the basic sequence is no greater than the relevant time τ of HSTDM, that is, T Pseq =t ON +t BLK +t OFF ≦τ, usually t ON =t OFF , t BLK The maneuvering time of the telescope from the ON point to the OFF point is determined. Then, based on the total observation time length T, the number of cycles of the basic sequence is calculated as NP = floor (T / T Pseq ), thereby constructing a periodic observation sequence {Pseq1, Pseq2,…, Pseq NP}, the rounded and truncated part is filled with the basic observation types inside the observation sequence Pseq. For the OTF observation simulation scenario, the three basic observation types of ON point scanning observation integration, OFF point observation integration, and internal load calibration are first used to form the basic observation sequence OTFseq = {t ONS ,t BLK ,t OFF}, ensuring that the total execution time of the basic sequence is no greater than the relevant time τ of the HSTDM, that is, T OTFseq =t ONS +t BLK +t OFF ≦τ, where N ON Refers to the number of scanning sample points corresponding to each OFF point. This value is determined by the OTF observation scene setting parameters. BLK The maneuvering time of the telescope from the ON point to the OFF point is determined. The correlation time τ of HSTDM is determined by performing Allan variance analysis on the output data of each channel.

[0044] The spectrum data set SPdccd is compared with the observation sequence Seqs to re-evaluate and calculate the spectrum data. The method is as follows:

[0045] Update header information HeadI i Observation type information;

[0046] If the current observation action Seq i For ON point integration, the corresponding spectrum data Cspcd is retained i ;

[0047] If the current observation action Seq i For OFF point integration, by setting N in SpecDI c The channel amplitude value is greater than the median Da m are replaced by Da m , recalculate the i-th group of data Cspcd i ;

[0048] If the current observation action Seq i For internal load calibration, at temperature T load The original spectrum data set Rlds output under load = {Rlds 1， Rlds2,…Rlds N} and set any spectrum data as the i-th group of data Cspcd i ;

[0049] If the current observation action Seq i If the telescope is in waiting state or rotating, the spectrum data has no practical meaning. i Set to empty.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention is based on the actual needs of CSST HSTDM observation data calibration and processing. It adopts a modular design concept to construct an overall framework for observation data simulation, designs an HSTDM instrument effect simulation method based on real test archives and simulation models, a cosmic space environment simulation method, and an observation data stream generation method based on HSTDM observation mode scenarios, which provides technical support for the simulation generation of observation data for space terahertz telescopes.

[0052] The present invention realizes the simulation generation of observation data streams in the HSTDM single-point observation mode and the OTF observation mode through a series of parameter settings.

[0053] The present invention provides customizable level 0 simulation observation data for the CSST HSTDM scientific data processing pipeline, effectively supporting the verification of the CSST HSTDM observation data calibration processing method. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 : Structural block diagram of the method for simulating and generating observation data for space terahertz telescopes of the present invention.

[0055] Figure 2 :Schematic diagram of HSTDM single-point observation scenario construction.

[0056] Figure 3 :Schematic diagram of OTF observation scenario construction.

[0057] Figure 4 :Structural block diagram of the simulation method of cosmic space environment effects based on observed spectrum data.

[0058] Figure 5 : Structural block diagram of the observation data stream generation method based on observation scenarios. DETAILED DESCRIPTION

[0059] The above contents of the present invention are further described in detail below in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the above contents of the present invention belong to the scope of the present invention.

[0060] The present invention proposes a method for simulating and generating observation data of space terahertz telescopes. The method is based on the actual needs of CSST HSTDM observation data calibration processing, adopts a modular design idea, incorporates HSTDM instrument effect simulation and cosmic space environment effect simulation into a unified effect simulation framework, and designs a method for generating HSTDM level 0 simulation observation data stream by combining the CSST HSTDM single-point observation mode and OTF (On-The-Fly) observation mode and the level 0 data format of the HSTDM standard. The specific steps are described as follows:

[0061] S1: A method for simulating and generating observation data for space terahertz telescopes includes instrument effect simulation of observation spectrum data, simulation of cosmic space environment effect of observation spectrum data, and generation of observation data stream; instrument effect simulation of observation spectrum data includes ground measurement-based method and Ornstein-Uhlenbeck model-based method, and one of them can be selected through configuration in actual use; the method for observing spectrum is:

[0062] The space environment effects in the data simulation include cosmic ray interference simulation, cosmic microwave background radiation simulation and Doppler frequency shift simulation; the generation of observation data stream depends on the construction of observation scene; such as Figure 1 shown.

[0063] The spectrum data that defines the standard is SpecD, the header information that meets the level 0 definition is HeadI, and the observation time period simulated by the simulation data to be generated is [ti , t i +T], the total observation time length is T, the time interval between two adjacent sets of simulation data is ΔT, the total number of data sets generated is L = Ceil (T / ΔT), and the intensity of simulated cosmic ray interference is T burst , in Kelvin, the simulated local oscillator frequency f LO , the frequency interval between two adjacent channels is Δf, and the coupling coefficient simulated in the sunny area is η l , the coupling coefficient in the shaded area is η d , the number of spectrum data channels generated by simulation is N c , and according to the HSTDM observation mode, in the simulated observation period [t i , t i +T] to set single-point observation and OTF observation simulation scenarios.

[0064] In some embodiments, for example:

[0065] The standard spectrum data is defined as SpecD, the header information that meets the level 0 definition is HeadI, and the observation time period simulated by the simulation data to be generated is [t i , t i +T], the total observation time length T is set to 30min, the time interval between two adjacent sets of simulation data is ΔT is set to 1s, the total number of data sets generated is L = Ceil (T / ΔT), the intensity of simulated cosmic ray interference is T burst The simulated local oscillator frequency f is 20K. LO is 460GHz, the frequency interval between two adjacent channels is Δf, which is 73.2421875kHz, and the coupling coefficient simulated in the sunny area is η l Set to 0.94, the coupling coefficient in the shaded area is η d Set to 0.95, the number of spectrum data channels generated by simulation is N c is set to 16384, which is consistent with the total number of HSTDM channels. According to the HSTDM observation mode, in the simulated observation period [t i , t i +T] to set single-point observation and OTF observation simulation scenarios.

[0066] like Figure 2 As shown, setting a single-point observation scenario specifically refers to determining the basic observation operations in the HSTDM single-point observation mode: the time lengths for the ON-point observation integration, the OFF-point observation integration, and the internal load calibration to be performed in sequence, forming a basic observation sequence Pseq = {t ON , t BLK , t OFF}, ensuring that the total execution time of the basic sequence is no greater than the relevant time τ of the HSTDM, that is, TPseq =t ON +t BLK +t OFF ≦τ, usually t ON =t OFF , t BLK The maneuvering time of the telescope from the ON point to the OFF point is determined; then the number of cycles of the basic sequence is calculated based on the total observation time length T as NP = floor (T / T Pseq ), thereby constructing a periodic observation sequence {Pseq1, Pseq2, …, Pseq NP}, the rounded and truncated part is filled with the internal observation operation of the observation sequence Pseq;

[0067] like Figure 3 As shown, setting the OTF observation simulation scenario specifically refers to determining the basic observation operations according to the OTF observation mode: ON point scanning observation integration, OFF point observation integration, and internal load calibration are performed in sequence for a certain length of time, forming a basic observation sequence OTFseq = {t ONS , t BLK , t OFF}, ensuring that the total execution time of the basic sequence is no greater than the relevant time τ of the HSTDM, that is, T OTFseq =t ONS +t BLK +t OFF ≦τ, where N ON Refers to the number of scanning sample points corresponding to each OFF point. This value is determined by the OTF observation scene setting parameters. BLK The maneuvering time of the telescope from the ON point to the OFF point is determined; the correlation time τ of HSTDM is determined by performing Allan variance analysis on the output data of each channel, and in the present invention, the value is 180s.

[0068] S2: Two technical solutions are designed for the simulation of instrument effects on observed spectrum data: one based on ground measurement and the other based on the Ornstein-Uhlenbeck model. One of them can be selected through configuration in actual use.

[0069] S3: Obtain the standard spectrum data SpecD with the specified name from the public astronomical database. The amplitude value dimension is Kelvin and the data length is N. s ; if N s <N c , then use the standard interpolation algorithm to interpolate SpecD to obtain a length of N c Spectrum data SpecDI; if N s >N c, then use the standard sampling algorithm to extract SpecD to obtain a length of N c Spectrum data SpecDI; if N s =N c , SpecD is used as the spectrum data SpecDI; during the interpolation or sampling process, ensure that the frequency axis corresponding to the SpecDI channel number is consistent with the frequency axis of the observation data generated by the simulation.

[0070] S4: Ground truth based methods include:

[0071] 1. When the HSTDM working temperature is T c , the raw spectrum data of HSTDM output is measured under the condition that the local frequency oscillator output is enabled and there is no external RF signal, and the data set Raws = {Rawd 1， Rawd2, …Rawd N}, Raw i is the ith spectrum output, and its amplitude value is the count of the spectrum analyzer output, dimensionless; the number of spectrum data channels output each time is N c , the time interval of the output spectrum data is set to ΔT to ensure that the total number of groups N ≥ L;

[0072] 2. Select L groups from the N groups of data in the Raws dataset and sort them in order of output time. The observation period for simulation is [t i , t i +T]; SRaws, a base spectrum dataset containing instrument effects;

[0073] 3. Obtain the length N through step S3 c Spectrum data SpecDI;

[0074] 4. N in SpecDI c The median Da is calculated from the amplitude values ​​of the outputs of the channels m , and output Da for each channel in SpecDI i Make a judgment, if Da i <Da m Then set the channel amplitude value to Da m , no operation is performed in other cases, and the length after processing is N c Standard spectrum data SpecDIP;

[0075] 5. Get HSTDM at temperature T cold The original spectrum data set output under cold load Rcold = {Rcold 1， Rcold2,…Rcold N}, calculate the average value Acold of N groups of spectrum data, at temperature Thot The original spectrum data set output under thermal load Rhot = {Rhot1, Rhot2, ... Rhot N}, and calculate the average value Ahot of N groups of spectrum data.

[0076] 6. For each set of data SRaw in the dataset SRaws containing L sets of data in step 2 i By formula: Obtain the spectrum data set Sds including instrument effect after cold and hot load conversion = {Sd 1， Sd2,…Sd L}, the amplitude dimension of the spectrum data is Kelvin;

[0077] 7. Add spectrum data SpecDIP to each set of data in the Sds data set, that is, Sd i =SpecDIP+Sd i , thus the simulated observation time period is [t i , t i +T] contains the instrument effect spectrum data set SPd = {Sd 1， Sd2,…Sd L}.

[0078] S5: The steps of the instrument effect simulation method based on the Ornstein-Uhlenbeck model include:

[0079] 1. Through step S3, obtain a length of N c Spectrum data SpecDI;

[0080] 2. Data Dat for each channel i of SpecDI i Perform iterative updates: Dat i [0] = SpecDI[i], n∈{1, 2, ..., L}, so the simulated observation period can be obtained as [t i , t i +T]; where ε is the noise of normal distribution, i.e., ε~M(0,1), θ, μ, σ are all configurable parameters, θ represents the mean reversion parameter, μ represents the long-term stable mean, and σ represents the variance fluctuation;

[0081] 3. For all N c Each channel generates a series of channel outputs according to the method in step 2, and the simulated observation time period [t i , t i +T] contains the instrument effect spectrum data set SPd = {Dat i, Dat2, ..., Dat L}.

[0082] S6. The space environment effects include cosmic ray interference simulation, cosmic microwave background radiation simulation, and Doppler frequency shift simulation; Figure 4 As shown, the method for simulating the effects of the cosmic space environment includes:

[0083] 1. In the integer set {1, 2, ..., N c} randomly select a number n r As the spectrum channel number corresponding to the frequency band of simulated cosmic ray interference;

[0084] 2. For each set of spectrum data in the instrument effect spectrum data set SPd obtained in step S4 or S5, the channel number is n. r The corresponding amplitude value superposition intensity is T burst interference;

[0085] 3. For each set of spectrum data in step 2, all channels are superimposed with the cosmic microwave background radiation intensity T cmb， Get the simulated spectrum data set SPdc after superimposing cosmic ray interference and microwave background radiation;

[0086] 4. Based on the simulated orbit information and the simulated observation time period [t i , t i +T], calculate the relative position information of the telescope, the sun and the earth, and the telescope's running speed information vel, thereby updating the header information HeadI of each group of SPdc observation data, and judging the observation time period [t i , t i +T] is the SPdc observation data in the sunny area or the shaded area. If it is in the shaded area, the amplitude value of each channel in each group of observation data under SPdc is multiplied by the coupling coefficient η d If it is in the sunny area, then the amplitude value of each channel of each group of observation data under SPdc is multiplied by the coupling coefficient η l , thus obtaining the observed spectrum data set SPdcc;

[0087] 5. According to the telescope velocity vel corresponding to each set of data obtained in step 4, calculate its Doppler frequency offset fdop and convert it to the offset channel number ΔN, and translate each set of spectrum data in SPdcc according to ΔN, thereby obtaining the spectrum data set SPdccd after the cosmic effect;

[0088] 6. Similar to step 4 in step S4, set SPdccd = {Spccd1, Spccd2, ..., Spccd L}Each group of spectrum data Spccd iThrough the hot and cold calibration formula: Get the simulated dimensionless HSTDM raw spectrum data set {Cspcd1, Cspcd2...Cspcd L}.

[0089] S7. Figure 5 As shown, the observation data stream generation method includes:

[0090] 1. According to S1 in the simulated observation period [t i , t i +T], set the single-point observation and OTF observation simulation scenarios, and construct the observation sequences Seqs = {seq1, seq2, ... seq L}, including ON point integration, OFF point integration, internal load calibration, waiting and telescope rotation, a total of 5 basic observation types; among them, single point observation general scenes such as Figure 2 As shown, its basic observation operations include: ON point observation integration, OFF point observation integration and internal load calibration. They are executed in sequence for a specific time length, thus forming a basic observation sequence Pseq = {t ON ,t BLK ,t OFF One observation contains multiple cycles of this basic observation sequence. It should be noted that the total execution time of the basic sequence should not exceed the relevant time τ of HSTDM, that is, T Pseq =t ON +t BLK +t OFF ≦τ, usually t ON =t OFF , t BLK The maneuvering time of the telescope from the ON point to the OFF point is determined, and then the number of cycles of the basic sequence is calculated based on the total observation time length T as NP = floor (T / T Pseq ), thereby constructing a periodic observation sequence {Pseq1, Pseq2,…, Pseq NP}, the rounded and truncated parts are filled with the internal observation operations of the observation sequence Pseq. The OTF observation simulation scenario is as follows Figure 3 As shown in FIG. 1 , the basic observation operations include: ON point scanning observation integration, OFF point observation integration, and internal load calibration. The length of time they are executed in sequence constitutes the basic observation sequence OTFseq = {t ONS ,t BLK ,t OFF One observation contains multiple cycles of this basic observation sequence. It should be noted that the total execution time of the basic sequence should not exceed the relevant time τ of HSTDM, that is, T OTFseq =t ONS+t BLK +t OFF ≦τ, where N ON Refers to the number of scanning sample points corresponding to each OFF point. This value is determined by the OTF observation scene setting parameters. BLK Determined by the maneuvering time of the telescope from the ON point to the OFF point.

[0091] 2. The spectrum data set SPdccd obtained in S6 is compared with the observation sequence Seqs to re-evaluate and calculate the spectrum data. The method is as follows:

[0092] a. Update header information HeadI i Observation type information;

[0093] b. If the current observation action Seq i For ON point integration, the corresponding spectrum data Cspcd is retained i ;

[0094] c. If the current observation action Seq i If the integration is OFF, then start from step 3 in step S4 and set N in SpecDI c The channel amplitude value is greater than the median Da m are replaced by Da m , and then execute from step 4 in S4 to the end of S6 to recalculate the i-th group of data Cspcd i ;

[0095] d. If the current observation action Seq i For internal load calibration, at temperature T load The original spectrum data set Rlds output under load = {Rlds 1， Rlds2,…Rlds N} and set any spectrum data as the i-th group of data Cspcd i ;

[0096] e. If the current observation action Seq i If the telescope is in waiting state or rotating, the spectrum data has no practical meaning. i Set to empty.

[0097] Preferably, in step S6, it is determined in step 4 that during the observation time period [t i , t i +T], the method to determine whether each group of SPdc observation data is in the sunny area or the shaded area is:

[0098] 1. Get the time of current observation data and use CSST orbit parameters to calculate the position of the telescope and the sun at the current time;

[0099] 2. Calculate the angle β between the vector connecting the telescope and the center of the earth and the vector connecting the sun and the center of the earth. If β is less than 70 degrees, the telescope corresponding to the observation data of the current group is in the sunlit area. If β is greater than 110 degrees, the current telescope is in the shaded area.

[0100] Preferably, in step S6, in step 5, the Doppler frequency shift f is calculated. dop The method is:

[0101] 1. Project the satellite velocity vector vel to the direction of the observed target source to obtain the radial velocity value V of the satellite velocity relative to the target source in the geocentric coordinate system r1， The unit is km / s;

[0102] 2. Calculate the galactic longitude l and galactic latitude b of the observed target source by the formula: V r2 =V r1 +9cos(l)cos(b)+12sin(l)cos(b)+7sin(b)Calculate V r1 Radial velocity V in LSR (Local Standard of Rest) coordinate system r2 , unit is km / s.

[0103] 3. Through the Doppler frequency shift formula: Calculate the frequency offset f dop , where c is the speed of light, which is 299792.458 km / s, and f LO Represents the simulated HSTDM local oscillator frequency.

[0104] The method of converting to the offset channel number ΔN is through the formula It is obtained that ΔN>0 means that the channel number is shifted to the right by |ΔN| units, and ΔN<0 means that the channel number is shifted to the left by |ΔN| units.

[0105] The present invention is based on the actual needs of CSST HSTDM observation data calibration and processing, adopts a modular design concept to construct an overall framework of observation data simulation, and provides a modular observation data simulation generation method, including HSTDM instrument effect simulation methods based on real test archives and simulation models, as well as an observation data stream generation method based on HSTDM observation mode scenarios, which provides technical support for the simulation generation of observation data for space terahertz telescopes.

[0106] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for simulating and generating observation data for a space terahertz telescope, characterized in that: It includes instrument effect simulation of observed spectrum data, simulation of cosmic space environment effect of observed spectrum data and generation of observation data stream; the HSTDM instrument effect simulation and cosmic space environment effect simulation are incorporated into a unified effect simulation framework, and the HSTDM level 0 simulation observation data stream is obtained by combining the CSST HSTDM single-point observation mode, On-The-Fly observation mode and the HSTDM standard level 0 data format.

2. The method for simulating and generating observation data for a space terahertz telescope according to claim 1, characterized in that: In the unified effect simulation framework, the standard spectrum data is defined as SpecD, the head information that meets the level 0 definition is HeadI, and the observation time period simulated by the simulation data to be generated is [t i , t i +T], the total observation time length is T, the time interval between two adjacent sets of simulation data is ΔT, the total number of data sets generated is L = Ceil (T / ΔT), and the intensity of simulated cosmic ray interference is T burst , in Kelvin, the simulated local oscillator frequency f LO , the frequency interval between two adjacent channels is Δf, and the coupling coefficient simulated in the sunny area is η l , the coupling coefficient in the shaded area is η d , the number of spectrum data channels generated by simulation is N c , and according to the HSTDM observation mode, in the simulated observation period [t i , t i +T] to set single-point observation and OTF observation simulation scenarios.

3. The method for simulating and generating observation data for a space terahertz telescope according to claim 2, characterized in that: Obtain the standard spectrum data SpecD with the specified name from the public astronomical database. The amplitude value dimension is Kelvin and the data length is N. s ; if N s <N c , then use the standard interpolation algorithm to interpolate SpecD to obtain a length of N c Spectrum data SpecDI; if N s >N c , then use the standard sampling algorithm to extract SpecD to obtain a length of N c Spectrum data SpecDI; if N s =N c , SpecD is used as the spectrum data SpecDI; during the interpolation or sampling process, ensure that the frequency axis corresponding to the SpecDI channel number is consistent with the frequency axis of the observation data generated by the simulation.

4. The method for simulating and generating observation data for a space terahertz telescope according to any one of claims 1 to 3, characterized in that: The instrument effect simulation of the observed spectrum data adopts at least one of a ground measurement method and an Ornstein-Uhlenbeck model method.

5. The method for simulating and generating observation data for a space terahertz telescope according to claim 4, characterized in that: The ground-based measurement method includes: The operating temperature of HSTDM is T c , the raw spectrum data of HSTDM output is measured under the condition that the local frequency oscillator output is enabled and there is no external RF signal, and the data set Raws = {Rawd 1， Rawd2, …Rawd N }, Raw i is the ith spectrum output, and its amplitude value is the count of the spectrum analyzer output, dimensionless; the number of spectrum data channels output each time is N c , the time interval of the output spectrum data is set to ΔT to ensure that the total number of groups N ≥ L; Select L groups from the N groups of data in the Raws dataset and sort them in the order of output time, and use the observation period [t i , t i +T]; SRaws, a base spectrum dataset containing instrument effects; Get the length N c Spectrum data SpecDI; For SpecDI c The median Da is calculated from the amplitude values ​​of the outputs of the channels m , and output Da for each channel in SpecDI i Make a judgment, if Da i <Da m Then set the channel amplitude value to Da m , no operation is performed in other cases, and the length after processing is N c Standard spectrum data SpecDIP; Get HSTDM at temperature T cold The original spectrum data set output under cold load Rcold = {Rcold1, Rcold2, ... Rcold N }, calculate the average value Acold of N groups of spectrum data, at temperature T hot The original spectrum data set output under thermal load Rhot = {Rhot1, Rhot2, ... Rhot N }, calculate and obtain the average value Ahot of N groups of spectrum data; For each set of data SRaw in the dataset SRaws containing L sets of data i By formula: Obtain the spectrum data set Sds including instrument effect after cold and hot load conversion = {Sd1, Sd2, ... Sd L }, the amplitude dimension of the spectrum data is Kelvin; Add spectrum data SpecDIP to each set of data in the spectrum data set Sds, that is, Sd i =SpecDIP+Sd i , thus the simulated observation time period is [t i , t i +T] contains the instrument effect spectrum data set SPd = {Sd1, Sd2, ... Sd L }.

6. The method for simulating and generating observation data for a space terahertz telescope according to claim 4, characterized in that: The Ornstein-Uhlenbeck model-based method includes: Get the length N c Spectrum data SpecDI; The data Dat for each channel i of SpecDI i Perform iterative updates: Dat i [0] = SpecDI[i], n∈{1, 2, ..., L}, and the simulated observation period is [t i , t i +T]; where ε is the noise of normal distribution, ε~N(0,1), θ, μ, σ are all configurable parameters, θ represents the mean regression parameter, μ represents the long-term stable mean, and σ represents the variance fluctuation; For all N c Each channel generates a series of channel outputs according to the above method, and the simulated observation time period [t i , t i +T] contains the instrument effect spectrum data set SPd = {Dat i , Dat2, ..., Dat L }.

7. The method for simulating and generating observation data for a space terahertz telescope according to claim 5 or 6, characterized in that: The cosmic space environment effect simulation of the observed spectrum data includes: In the set of integers {1, 2, ..., N c } randomly select a number n r As the spectrum channel number corresponding to the frequency band of simulated cosmic ray interference; For each set of spectrum data in the instrument effect spectrum data set SPd, the channel number is n r The corresponding amplitude value superposition intensity is T burst interference; For each set of spectrum data, all channels are superimposed with the cosmic microwave background radiation intensity T cmb , obtain the simulated spectrum data set SPdc after superimposing cosmic ray interference and microwave background radiation; According to the simulated orbit information and the simulated observation time period [t i , t i +T], calculate the relative position information of the telescope, the sun and the earth, and the telescope's running speed information vel, and update SPd accordingly c The header information HeadI of each group of observation data is used to determine the i , t i +T] is the SPdc observation data in the sunny area or the shaded area. If it is in the shaded area, the amplitude value of each channel in each group of observation data under SPdc is multiplied by the coupling coefficient η d If it is in the sunny area, then the amplitude value of each channel of each group of observation data under SPdc is multiplied by the coupling coefficient η1, so as to obtain the observation spectrum data set SPdcc; According to the telescope velocity vel corresponding to each set of data obtained, calculate its Doppler frequency offset f dop , and convert it to the offset channel number ΔN, and translate each set of spectrum data in SPdcc according to ΔN, thereby obtaining the spectrum data set SPdccd after the cosmic effect; According to the above method, SPdccd={Spccd1, Spccd2, ..., Spccd L }Each group of spectrum data Spccd i Through the hot and cold calibration formula: Get the simulated dimensionless HSTDM raw spectrum data set {Cspcd1, Cspcd2...Cspcd L }.

8. The method for simulating and generating observation data for a space terahertz telescope according to claim 7, characterized in that: Determine the observation period [t i , t i +T] is in the sunlit area or the shaded area. The method is as follows: obtain the time of the current observation data, use the CSST orbit parameters to calculate the telescope position and the sun position at the current time; calculate the angle β between the vector connecting the telescope and the center of the earth and the vector connecting the sun and the center of the earth. If β is less than 70 degrees, the telescope corresponding to the current group of observation data is in the sunlit area. If β is greater than 110 degrees, the current telescope is in the shaded area.

9. The method for simulating and generating observation data for a space terahertz telescope according to claim 7, characterized in that: Calculate the Doppler frequency shift f dop The method is: Project the satellite velocity vector vel to the direction of the observed target source to obtain the radial velocity value V of the satellite velocity relative to the target source in the geocentric coordinate system r1 , the unit is km / s; Calculate the galactic longitude 1 and galactic latitude b of the observed target source using the formula: V r2 =V r1 +9cos(l)cos(b)+12sin(l)cos(b)+7sin(b)Calculate V r1 Radial velocity V in LSR (Local Standard of Rest) coordinate system r2 , unit is km / s; Through the Doppler shift formula: Calculate the frequency offset f dop , where c is the speed of light, which is 299792.458 km / s, and f LO represents the simulated HSTDM local oscillator frequency; The channel number ΔN converted to offset is calculated by the formula It is obtained that ΔN>0 means that the channel number is shifted to the right by |ΔN| units, and ΔN<0 means that the channel number is shifted to the left by |ΔN| units.

10. The method for simulating and generating observation data for a space terahertz telescope according to claim 5, characterized in that: The generation of the observation data stream includes: According to the observation period [t i , t i +T], set the single-point observation and OTF observation simulation scenarios, and construct the observation sequences Seqs = {seq1, seq2, ... seq L }, including five basic observation types: ON point integration, OFF point integration, internal load calibration, waiting, and telescope rotation. The methods are as follows: For the single-point observation scenario, the three basic observations of ON point integration, OFF point integration, and internal load calibration are first combined to form the basic observation time series Pseq = {t ON , t BLK , t OFF }, ensuring that the total execution time of the basic sequence is no greater than the relevant time τ of the HSTDM, that is, T Pseq =t ON +t BLK +t OFF ≦τ, take t ON =t OFF , t BLK The maneuvering time of the telescope from the ON point to the OFF point is determined; then the number of cycles of the basic sequence is calculated based on the total observation time length T as NP = floor (T / T Pseq ), thereby constructing a periodic observation sequence {Pseq1, Pseq2, …, Pseq NP }, the rounded and truncated part is filled with the basic observation types in the observation sequence Pseq. For the OTF observation simulation scenario, the three basic observation types of ON point scanning observation integration, OFF point observation integration, and internal load calibration are first used to form the basic observation sequence OTFseq = {t ONS , t BLK , t OFF }, ensuring that the total execution time of the basic sequence is no greater than the relevant time τ of the HSTDM, that is, T OTFseq =t ONS +t BLK +t OFF ≦τ, where N ON Refers to the number of scanning sample points corresponding to each OFF point. This value is determined by the OTF observation scene setting parameters. BLK The maneuvering time of the telescope from the ON point to the OFF point is determined, and the correlation time τ of the HSTDM is determined by performing Allan variance analysis on the output data of each channel; The spectrum data set SPdccd is compared with the observation sequence Seqs to re-evaluate and calculate the spectrum data. The method is as follows: Update header information HeadI i Observation type information; If the current observation action Seq i For ON point integration, the corresponding spectrum data Cspcd is retained i ; If the current observation action Seq i For OFF point integration, by setting N in SpecDI c The channel amplitude value is greater than the median Da m are replaced by Da m , recalculate the i-th group of data Cspcd i ; If the current observation action Seq i For internal load calibration, at temperature T load The original spectrum data set Rlds output under load = {Rlds 1， Rlds2,…Rlds N } and set any spectrum data as the i-th group of data Cspcd i ; If the current observation action Seq i If the telescope is in waiting state or rotating, the spectrum data has no practical meaning. i Set to empty.

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