Asteroid impact bichromatic ratio photometry triggering system and method

Abstract

This invention provides a dual-color ratio photometric triggering system and method for asteroid impacts, belonging to the field of deep-space asteroid exploration technology. The system includes: a first photoelectric detection module that receives incident light and outputs a first photocurrent signal; a second photoelectric detection module that receives incident light and outputs a second photocurrent signal; a signal conditioning module that conditions the first photocurrent signal and the second photocurrent signal respectively to obtain a first conditioning voltage and a second conditioning voltage; a feature parameter calculation module that calculates a ratio feature parameter based on the first conditioning voltage and the second conditioning voltage; and a trigger determination module that outputs an impact trigger signal when both the first conditioning voltage and the second conditioning voltage are greater than a preset voltage threshold and the ratio feature parameter is greater than a preset feature parameter threshold. This enables the on-board triggering system to autonomously distinguish between high-temperature impact flashes and low-temperature solar reflections on a microsecond timescale, eliminating false triggers caused by distance and brightness ambiguity.

Description

Technical Field

[0001] This invention belongs to the field of deep space asteroid exploration technology, specifically relating to an asteroid impact dual-color ratio photometric triggering system and method. Background Technology

[0002] The hypervelocity kinetic energy impact of an asteroid is accompanied by transient flashes ranging from microseconds to milliseconds, with an extremely wide dynamic range of brightness. To capture these microsecond-level transient processes, such as impact crater formation, ejecta evolution, and crack propagation, the observation payload needs to employ a space-based high-speed camera with a resolution of 10 kHz or higher. Due to the unpredictable timing of the impact and the limited onboard storage and downlink bandwidth, the high-speed camera needs to incorporate an autonomous triggering mechanism to freeze and save data frames before and after the event within a circular buffer only at the instant the impact flash occurs.

[0003] To achieve autonomous triggering, a separate hardware photometer unit is typically used to monitor changes in light intensity in the target's field of view. The core of the hardware photometer unit is a silicon photodiode, whose spectral response range is approximately 320 nanometers to 1060 nanometers. Combined with a transimpedance amplifier and a high-speed ADC (Analog-to-Digital Converter), it can convert the incident light signal into a digital voltage signal. When the signal exceeds a preset threshold, a trigger signal is generated.

[0004] Existing technologies include single-photodetector channel absolute brightness triggering, dual-photodetector channel same-band redundant triggering, and laboratory multi-band photometric diagnostics. However, all have shortcomings. Whether it's single-photodetector channel triggering or same-band dual-photodetector channel redundant triggering, the discrimination is based on absolute light intensity or its consistency, which cannot distinguish between two fundamentally different scenarios: "high light source temperature but far distance (impact flash)" and "low light source temperature but close distance (solar reflection)," i.e., the "distance-brightness ambiguity" problem. Although laboratory multicolor photometrics involves multi-band PDs (photodiodes), it has not disclosed the use of signal ratios from different bands for real-time autonomous triggering and discrimination, nor has it addressed front-end signal conditioning schemes under solar DC (direct current) conditions.

[0005] There are two categories of prior art closest to this invention: First, laboratory diagnostic multicolor impact flash photometry (Ernst et al., 2009; Tandy et al., 2020), which records the impact flash light curve using a multi-band photodiode array, and then processes and fits the flash temperature. The experimental environment is a darkroom vacuum target chamber, where there is no solar DC background, and it does not involve real-time triggering decisions or on-board signal conditioning. Second, industrial dual-color (colorimetric) thermometry, which uses the property that the ratio of the two wavelengths of radiation intensity depends only on the temperature of the light source to invert the target temperature for temperature measurement purposes, and does not involve transient event triggering or the space solar background.

[0006] Existing technologies do not have specialized triggering and judgment logic for binary classification tasks such as high-temperature impact flashes and low-temperature solar reflections. Summary of the Invention

[0007] The purpose of this invention is to provide a dual-color ratio photometric triggering system and method for asteroid impacts, which can solve the problem of false triggering risk caused by distance-brightness ambiguity.

[0008] To achieve the above objectives, the present invention provides an asteroid impact dual-color ratio photometric triggering system. The system includes: a first photoelectric detection module for receiving incident light from the target field of view and outputting a first photocurrent signal; a second photoelectric detection module for receiving incident light from the target field of view and outputting a second photocurrent signal; a signal conditioning module connected to the first and second photoelectric detection modules for performing transimpedance amplification, AC coupling high-pass filtering, low-noise voltage amplification, and analog-to-digital conversion on the first and second photocurrent signals, respectively, to obtain a first conditioning voltage and a second conditioning voltage; a feature parameter calculation module for calculating a ratio feature parameter based on the first and second conditioning voltages; and a trigger determination module for outputting an impact trigger signal when both the first and second conditioning voltages are greater than a preset voltage threshold and the ratio feature parameter is greater than a preset feature parameter threshold. This allows for the autonomous differentiation of high-temperature impact flashes from low-temperature solar reflections on a microsecond-level timescale, eliminating false triggering caused by distance and brightness ambiguity.

[0009] Accordingly, the present invention provides a method for triggering asteroid impact using a two-color ratio photometry. The method includes: receiving incident light from a target field of view and outputting a first photocurrent signal; receiving incident light from the target field of view and outputting a second photocurrent signal; performing transimpedance amplification, AC-coupled high-pass filtering, low-noise voltage amplification, and analog-to-digital conversion on the first and second photocurrent signals respectively to obtain a first conditioning voltage and a second conditioning voltage; calculating a ratio characteristic parameter based on the first and second conditioning voltages; and outputting an impact trigger signal when both the first and second conditioning voltages are greater than a preset voltage threshold and the ratio characteristic parameter is greater than a preset characteristic parameter threshold, so as to autonomously distinguish between high-temperature impact flashes and low-temperature solar reflections on a microsecond-level timescale, eliminating false triggering caused by distance and brightness ambiguity.

[0010] In scenarios where spacecraft approach asteroids at a distance of approximately 500m to conduct impact or flyby observations, how can the photometric triggering system autonomously distinguish between high-temperature impact flashes (>10000K) and low-temperature solar reflection backgrounds (approximately 6000K) to fundamentally eliminate the risk of false triggering caused by distance-brightness ambiguity, and output trigger signals with microsecond-level time accuracy?

[0011] The beneficial effects of this invention are as follows:

[0012] 1. A pioneering solution to the core problem of distance-brightness blurring:

[0013] Breaking away from the traditional framework of absolute brightness triggering, this system is the first to use the dual-band spectral ratio as the criterion for impact event triggering, eliminating the distance-brightness ambiguity problem at its physical root. The system can autonomously distinguish between true and false impact flashes and solar reflections without ground intervention or prior knowledge of the target asteroid's albedo and precise distance. This fully meets the high autonomy requirements of deep space exploration missions and fills a technological gap in the field of autonomous triggering of deep-space asteroid impacts.

[0014] 2. Strong anti-interference capability adapted to the unique environment of deep space:

[0015] To address the unique constraints of the ozone-free deep space environment and the unavoidable full-band DC background from the sun, an independent AC-coupled high-pass front-end circuit is employed to separate transient flash signals from the strong DC background. An optimized cutoff frequency of 1–10kHz (preferably 5kHz) not only fully preserves the transient characteristics of the <10μs flash rise time and approximately 100μs main pulse, but also effectively suppresses spurious signals introduced by the solar DC component and low-frequency motion of the spacecraft, achieving a DC background suppression ratio better than 60dB. Combined with a three-condition conformance logic of dual-path amplitude lower limit + ratio threshold, and simultaneous verification of signal-to-noise ratio validity and spectral shape correctness, this fundamentally reduces the probability of false triggering caused by electrical noise, electromagnetic interference, and non-impact transient events.

[0016] 3. Microsecond-level real-time trigger response:

[0017] Through a dual-channel synchronous sampling and FPGA pipeline ratio calculation architecture, a trigger signal can be output within 1–2 μs of the flash rise edge, with a trigger delay of ≤2 μs, perfectly matching the pre-trigger frame saving requirements of high-speed cameras above 10kfps. Taking the 395nm / 630nm band pair as an example, the ratio difference between high-temperature impact flash and low-temperature solar reflection reaches 3.4 times; when using the 350nm / 950nm extreme band pair, the ratio difference can reach more than 9 times, with sufficient decision margin on both sides. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 This is a block diagram of the asteroid impact dual-color ratio photometric triggering system provided by the present invention;

[0020] Figure 2This is a flowchart of the asteroid impact bicolor ratio photometric triggering method provided by the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0022] The core idea of ​​this invention is to use two photoelectric detection channels with different center wavelengths, and use the ratio of the output photocurrent of the two photoelectric detection channels (rather than the absolute photocurrent value) or the logarithm of the ratio as the trigger criterion. This ratio or the logarithm of the ratio depends only on the spectral shape (temperature) of the light source and is independent of the distance of the light source, absolute brightness and absolute responsivity of the photodiode, thereby realizing the physical layer discrimination between true impact flashes and solar reflections.

[0023] Figure 1 This is a block diagram of the asteroid impact dual-color ratio photometric triggering system provided by the present invention, as shown below. Figure 1 As shown, the system includes:

[0024] The first photoelectric detection module is used to receive the incident light in the target field of view and output the first photocurrent signal;

[0025] The second photoelectric detection module is used to receive the incident light in the target field of view and output the second photocurrent signal;

[0026] The signal conditioning module is connected to the first photodetector module and the second photodetector module, and is used to perform transimpedance amplification, AC coupling high-pass filtering, low-noise voltage amplification and analog-to-digital conversion on the first photocurrent signal and the second photocurrent signal, respectively, to obtain the first conditioning voltage and the second conditioning voltage.

[0027] The characteristic parameter calculation module is used to calculate the ratio characteristic parameter based on the first conditioning voltage and the second conditioning voltage.

[0028] The trigger determination module is used to output an impact trigger signal when both the first conditioning voltage and the second conditioning voltage are greater than a preset voltage threshold and the ratio characteristic parameter is greater than a preset characteristic parameter threshold. This allows for the autonomous differentiation between high-temperature impact flashes and low-temperature solar reflections on a microsecond timescale, eliminating false triggers caused by distance and brightness ambiguity.

[0029] In this invention, the asteroid impact dual-color ratio photometric triggering system comprises two independent parallel photoelectric detection channels—an ultraviolet channel and a visible channel—each equipped with an independent bandpass filter and photodetector, receiving incident light from the target's field of view, without requiring an optical beam splitter. Each of the two photoelectric detection channels is equipped with an independent transimpedance amplifier, an AC coupling front end, and an ADC (Analog-to-Digital Converter) (e.g., a high-speed ADC). The two ADC outputs are connected in parallel to the high-speed camera FPGA, where the ratio calculation and trigger determination are performed internally within the FPGA.

[0030] In this invention, there are two photoelectric detection channels, namely a first photoelectric detection channel (or ultraviolet channel) and a second photoelectric detection channel (or visible channel).

[0031] The first photoelectric detection module includes: a first bandpass filter for spectrally filtering incident light based on a first center wavelength to obtain a first monochromatic beam; and a first photodetector for receiving the first monochromatic beam and converting it into a first photocurrent signal, which is proportional to the incident light power. The first center wavelength can be located in the ultraviolet to visible light band, for example, in the 320nm to 450nm band.

[0032] The first photodetector module, located in the first photodetector channel, includes a first bandpass filter and a first photodetector. The first bandpass filter filters the incident light spectrally, allowing only light beams within a specified wavelength range near the first center wavelength λ1 to pass through. The first photodetector receives the first monochromatic light beam filtered by the first bandpass filter and converts it into a corresponding first photocurrent signal. The first center wavelength λ1 of the first bandpass filter is located in the ultraviolet to visible light band (preferably 320-450 nm), and the first full width at half maximum (FWHM) Δλ1 is 10-50 nm. The first photodetector is a silicon PIN photodiode, outputting a first photocurrent signal I1 proportional to the incident light power.

[0033] The second photoelectric detection module includes: a second bandpass filter for spectrally filtering the incident light based on a second center wavelength to obtain a second monochromatic beam; and a second photodetector for receiving the second monochromatic beam and converting it into a second photocurrent signal, which is proportional to the incident light power. The first center wavelength and the second center wavelength are located in different spectral regions. The second center wavelength can be located in the visible to near-infrared band, for example, in the 600nm to 1000nm band. The difference between the first center wavelength and the second center wavelength is greater than or equal to 150nm, preferably greater than or equal to 500nm.

[0034] The second photodetector module (also called the second photodetector channel) includes a second bandpass filter and a second photodetector. The second bandpass filter filters the incident light spectrally, allowing only light beams within a specified wavelength range near the second center wavelength λ2 to pass through. The second photodetector receives the second monochromatic beam filtered by the second bandpass filter and converts it into a corresponding second photocurrent signal. The second center wavelength λ2 of the second bandpass filter is located in the visible to near-infrared band (preferably 600-1,000 nm), and the second full width at half maximum (FWHM) Δλ2 is 10–50 nm. The first center wavelength λ1 and the second center wavelength λ2 are located in different spectral regions (|λ1-λ2|≥150 nm, preferably ≥500 nm), ensuring that the two photodetector channels produce significantly different response amplitudes to the same temperature change. The second photodetector is a silicon PIN photodiode, outputting a second photocurrent signal I2 that is proportional to the incident light power.

[0035] The signal conditioning module is used to condition the first photocurrent signal and the second photocurrent signal respectively. The first photodetector channel corresponding to the first photodetector module includes: a first transimpedance amplifier, used to perform linear conversion and primary amplification on the first photocurrent signal to obtain a first transimpedance amplified voltage; a first AC-coupled high-pass filter, used to filter out the DC photocurrent component generated by solar reflection from the first transimpedance amplified voltage, retaining only the transient signal to obtain a first transient AC voltage; a first low-noise voltage amplifier, used to perform controllable gain amplification on the first transient AC voltage to output a first low-noise amplified voltage; and a first analog-to-digital converter, used to perform analog-to-digital conversion on the first low-noise amplified voltage to output a first conditioning voltage.

[0036] The second photodetector channel corresponding to the second photodetector module includes: a second transimpedance amplifier, used to perform linear conversion and primary amplification of the second photocurrent signal to obtain a second transimpedance amplified voltage; a second AC-coupled high-pass filter, used to filter out the DC photocurrent component generated by solar reflection from the second transimpedance amplified voltage, retaining only the transient signal to obtain a second transient AC voltage; a second low-noise voltage amplifier, used to perform controllable gain amplification of the second transient AC voltage to output a second low-noise amplified voltage; and a second analog-to-digital converter, used to perform analog-to-digital conversion of the second low-noise amplified voltage to output a second conditioning voltage.

[0037] It should be understood that the first photoelectric detection channel includes a first bandpass filter, a first photodetector, a first transimpedance amplifier, a first AC-coupled high-pass filter, a first low-noise voltage amplifier, and a first analog-to-digital converter, and the second photoelectric detection channel includes a second bandpass filter, a second photodetector, a second transimpedance amplifier, a second AC-coupled high-pass filter, a second low-noise voltage amplifier, and a second analog-to-digital converter.

[0038] The first and second photodetector channels are each equipped with independent signal conditioning modules. Each photodetector channel includes a transimpedance amplifier (TIA), an AC-coupled high-pass filter, a low-noise voltage amplifier, and an analog-to-digital converter. The TIA receives the photocurrent signal output from the photodetector, linearly converts it into a voltage signal, and performs primary amplification. The low-noise voltage amplifier receives the transient AC voltage processed by the AC-coupled high-pass filter, performs controllable gain amplification on the transient AC voltage, and outputs a low-noise amplified voltage that meets the acquisition level range. The AC coupling is used to filter out the DC photocurrent component generated by solar reflection, retaining only the transient signal. The high-pass cutoff frequency f of the AC coupling is... c The design is within the range of 1-10kHz, preferably about 5kHz, so that: (i) the passband fully covers the rising edge (<10us) and main pulse (about 100us) of the impact flash; and (ii) it effectively suppresses low-frequency (<100Hz) background fluctuations introduced by solar reflection DC components, spacecraft attitude changes, target surface feature transitions, etc.

[0039] It should be noted that the space environment lacks an atmospheric ozone layer, and solar radiation across the entire spectrum (including ultraviolet to near-infrared) reaches the detector without attenuation. Therefore, the "solar-blind ultraviolet band" strategy relied upon by ground-based flame detectors cannot be used to suppress solar interference. The AC-coupled high-pass filter introduced in this invention is designed to solve this unique space-based problem.

[0040] The first and second photoelectric detection channels are each equipped with independent high-speed ADCs (preferably 1 MSPS, 12-16 bits), which synchronously acquire low-noise amplified voltages processed by AC-coupled high-pass filters and low-noise voltage amplifiers. The conditioning voltages (digital voltages) output from the two analog-to-digital converters are input in parallel to the high-speed camera FPGA, where a pipelined divider calculates the ratio or logarithmic value of the ratio between the two photoelectric detection channels in real time.

[0041] The trigger determination module includes: a first comparison unit, used to determine whether the first conditioning voltage is greater than a preset voltage threshold, and if the determination result is yes, then the first condition is met; a second comparison unit, used to determine whether the second conditioning voltage is greater than a preset voltage threshold, and if the determination result is yes, then the second condition is met; a third comparison unit, used to determine whether the ratio characteristic parameter is greater than a preset characteristic parameter threshold, and if the determination result is yes, then the third condition is met; and a result determination unit, used to output an impact trigger signal if the first condition, the second condition, and the third condition are all met.

[0042] When the ratio characteristic parameter is the ratio of the first conditioning voltage to the second conditioning voltage, the preset characteristic parameter threshold is the preset ratio threshold; when the ratio characteristic parameter is the logarithm of the ratio of the first conditioning voltage to the second conditioning voltage, the preset characteristic parameter threshold is the preset logarithm threshold.

[0043] This invention uses the calculation of ratios as an example for illustration.

[0044] The ratio R(t) of the first conditioning voltage V1(t) to the second conditioning voltage V2(t) is calculated as follows:

[0045] R(t) = V1(t) / V2(t);

[0046] Where t is the timestamp of ADC synchronous sampling, representing the instantaneous moment corresponding to each synchronous acquisition.

[0047] The result determination unit receives three signal streams: the first conditioning voltage V1(t), the second conditioning voltage V2(t), and the ratio R(t), and executes the following three-condition compliance logic:

[0048] First condition: V1(t)>V_min, that is, the first conditioning voltage V1(t) is greater than the preset voltage threshold V_min, ensuring that the corresponding first photoelectric detection channel (also known as the ultraviolet channel) has a usable signal-to-noise ratio;

[0049] The second condition is: V2(t) > V_min, that is, the second conditioning voltage V2(t) is greater than the preset voltage threshold V_min, to ensure that the second photoelectric detection channel is effective;

[0050] The third condition is: R(t) > R_th, which means that the ratio R(t) of the first conditioning voltage V1(t) to the second conditioning voltage V2(t) is greater than the preset ratio threshold R_th, indicating that the temperature of the light source is within the impact flash characteristic range rather than the solar reflection characteristic range.

[0051] The recommended value range for V_min is 100–500mV (i.e., the equivalent voltage at the ADC input), corresponding to approximately 10–50nA of photocurrent at the PD end (depending on the TIA gain and amplification stage), ensuring that the signal-to-noise ratio (SNR) of the two photodetector channels has an effective detection level of SNR≥10.

[0052] The result determination unit sends a valid impact trigger signal to the trigger output interface only when all three conditions are met simultaneously within the preset compliance time window. The compliance time window is preferably less than or equal to 1µs, that is, the result determination unit will send an impact trigger signal only when all three conditions are met simultaneously within N consecutive compliance time windows at a sampling rate of 1MSPS. N is an integer greater than or equal to 1.

[0053] The asteroid impact dual-color ratio photometric triggering system provided by the present invention further includes: a data storage module for storing a lookup table, wherein the lookup table stores the mapping relationship between a first center wavelength, a second center wavelength and a preset ratio threshold or a preset logarithmic threshold; wherein the trigger determination module is further used to obtain the preset ratio threshold or the preset logarithmic threshold based on the lookup table according to the first center wavelength and the second center wavelength.

[0054] The preset ratio threshold is greater than or equal to the ratio of the first conditioning voltage to the second conditioning voltage calculated at the equivalent blackbody temperature of solar reflection, and less than or equal to the ratio of the first conditioning voltage to the second conditioning voltage calculated at the equivalent blackbody temperature of the expected impact flash.

[0055] Specifically, the preset ratio threshold R_th is obtained from a lookup table. The lookup table is based on the selected band pair (λ1, λ2) and a series of discrimination temperature thresholds T_min. T_min is the lowest equivalent blackbody temperature discrimination threshold for impact flash events, serving as the temperature boundary for binary classification: transient light sources in the target's field of view are divided into high-temperature impact flashes and low-temperature solar reflections. Light sources below T_min are classified as solar reflection background interference, while those above or equal to T_min are classified as valid impact flash events. This threshold is pre-calculated by the blackbody radiation model, and R_th takes the value corresponding to T_min in the lookup table shown in Table 1. The value must satisfy the following conditions:

[0056] R(T_sun)≤R_th≤R(T_flash);

[0057] Where R(T_sun) represents the solar reflectance ratio, which is the ratio of the first conditioning voltage to the second conditioning voltage calculated at the equivalent blackbody temperature of solar reflection. R(T_flash) represents the expected impact flash ratio, which is the ratio of the first conditioning voltage to the second conditioning voltage calculated at the equivalent blackbody temperature of the expected impact flash. R_th must fall between the solar reflectance ratio and the expected impact flash ratio. T_min is typically taken as 8,000-10,000K to ensure sufficient decision margin on both sides. T_min represents the minimum equivalent blackbody temperature required for a valid impact flash. Compared to the dimensionless ratio R_th, it makes it easier for engineers to select an appropriate trigger threshold based on mission parameters (impact velocity, asteroid material, expected flash temperature, background interference intensity). For low-speed impact and weak flash scenarios, a lower T_min (e.g., 8000K) is used, corresponding to a lower R_th, to ensure trigger sensitivity. For high-speed impact and strong background interference scenarios, a higher T_min (e.g., 10000K) is used, corresponding to a higher R_th, to improve resistance to accidental triggering.

[0058] The discrimination temperature threshold T_min is the boundary temperature between the two types of events. Its value lies between the equivalent blackbody temperature T_sun (reflected by the sun) and the equivalent blackbody temperature T_flash (the expected impact flash of the mission). It is used to calculate the corresponding preset ratio threshold R_th = R(T_min) through the blackbody radiation model, ensuring that R(T_sun) ≤ R_th ≤ R(T_flash), providing sufficient decision margin for both sides. T_min is only used for the pre-designed generation of the lookup table; the system does not require temperature input during real-time operation, directly determining the event by comparing the voltage ratio with the preset threshold.

[0059] Example values ​​for the lookup table are shown in Table 1:

[0060] Table 1. Example values ​​in the lookup table

[0061]

[0062] After obtaining the preset ratio threshold through the lookup table shown in Table 1 above, the impact trigger signal that meets the judgment conditions (including the first condition, the second condition, and the third condition) is transmitted to the high-speed camera control unit, so that it performs operations such as freezing the ring buffer, marking key frames, and updating exposure parameters.

[0063] The physical principle of this invention is as follows:

[0064] The equivalent blackbody temperature T_flash of an impact flash is greater than 10,000 K, while the equivalent blackbody temperature T_sun of solar reflection is approximately 6,000 K. According to Planck's blackbody radiation law, the ratio of spectral radiance at two different wavelengths, namely the first center wavelength λ1 and the second center wavelength λ2, within the spectral response range of a silicon photodiode from 320 nm to 1,060 nm, is calculated as follows:

[0065] ;

[0066] Where B(λ1,T) and B(λ2,T) are the spectral radiances at the first central wavelength λ1 and the second central wavelength λ2 at thermodynamic temperature T, respectively; h is Planck's constant; c is the speed of light in vacuum; k is Boltzmann's constant; and exp represents the natural exponential function.

[0067] It can be seen that the ratio of the spectral radiance at the first center wavelength λ1 and the second center wavelength λ2 at two different wavelengths depends only on the thermodynamic temperature T, and is independent of the absolute distance from the source, the effective emission area, and the absolute responsivity of the photodiode (these factors are mathematically reduced and canceled out in the ratio).

[0068] Therefore, the ratio of the first conditioning voltage to the second conditioning voltage has different characteristic values ​​under high-temperature impact flash and low-temperature solar reflection. For example, for the band pair λ1=395nm, λ2=630nm, R(T_flash=15,000K)=2.09, R(T_sun=6,000K)=0.61, with a ratio difference of about 3.4 times. The ratio corresponds one-to-one with the equivalent blackbody temperature of the light source: the equivalent blackbody temperature T_sun of solar reflection is about 6000K, and the corresponding ratio is expressed as R(T_sun); the equivalent blackbody temperature T_flash of the expected impact flash is usually higher than 10000K (15,000K in this example), and the corresponding ratio is expressed as R(T_flash). For more extreme band pairs (e.g., λ1=350nm, λ2=950nm), the ratio difference can reach more than 9 times.

[0069] In this invention, "judging whether the light source is bright or not" is transformed into "judging whether the spectral shape of the light source is correct". The ratio of the first conditioning voltage to the second conditioning voltage is used as a proxy variable for temperature, enabling the triggering system to have the ability to distinguish between real and fake events at the physical layer.

[0070] As can be seen from the above detailed description of the technical solution provided by the present invention, compared with the closest prior art, the present invention has at least the following distinguishing technical features:

[0071] (a) Use the dual-band ratio as a microsecond-level real-time binary trigger criterion instead of temperature inversion: only determine whether R exceeds the threshold, and output the result within 1μs to 2μs and directly drive the high-speed camera's ring buffer to freeze.

[0072] (b) Each photoelectric detection channel is independently AC-coupled to a high-pass front end: the DC component of solar reflection is first stripped off, and then the ratio is calculated on the pure transient signal. This is a special design for the unique on-orbit conditions of no ozone layer in space and full-band solar DC background, which is fundamentally different from the solar-blind ultraviolet strategy for ground-based flame detection;

[0073] (c) All three conditions meet the judgment logic: simultaneously verify the validity of signal strength and the correctness of spectral shape; among them, the lower limit guard in the judgment of the second condition is a special failure mode for ratio judgment - to prevent the division result from diverging when the second photoelectric detection channel is close to zero level, causing false triggering;

[0074] (d) A ratio threshold lookup table based on the temperature threshold is used to satisfy R(T_sun)≤R_th≤R(T_flash), which supports on-orbit reconfiguration of the satellite bus.

[0075] The technical problem actually solved by this invention is: under the condition of full-band solar DC background and no prior distance information, enable the on-board triggering system to autonomously distinguish between high-temperature impact flashes (>10000K) and low-temperature solar reflections (about 6000K) on a μs time scale, and eliminate false triggering caused by "distance-brightness ambiguity".

[0076] Those skilled in the art cannot gain any technical inspiration from the prior art for the following reasons: (1) The problem itself is not recognized: "Distance-brightness ambiguity" only holds true in the specific scenario of "spacecraft approaching an asteroid + no prior distance + autonomous triggering". Neither laboratory diagnostics nor industrial temperature measurement faces this constraint, and there is no motivation in the prior art to solve this problem; (2) The ratio method is redefined with different functions: industrial dual-color temperature measurement teaches ratio → temperature value (measurement function), while this invention teaches ratio → event truth or false judgment (triggering function). There is no literature in the prior art that records the ratio as a real-time trigger criterion to eliminate distance-brightness ambiguity; (3) Laboratory multicolor photometry lacks the environmental prerequisite for migration: its darkroom environment does not have a solar DC background and does not require AC coupling; if it is directly moved to the on-orbit environment, it will immediately fail due to the strong solar background. The existing technology neither addresses this problem nor provides any inspiration for introducing AC coupling front end; (4) The distinguishing features are mutually dependent and synergistic: without AC coupling, the original photocurrent ratio approaches the solar ratio under strong background, and the original photocurrent ratio criterion fails; without the original photocurrent ratio criterion, AC coupling cannot distinguish between true and false events; without the second conditioning voltage lower limit guard, the original photocurrent ratio judgment has zero denominator divergence false triggering, and the three constitute an organic whole.

[0077] Regarding the quantitative support for the technical effects, for the band pair of λ1=395nm and λ2=630nm, R(T_flash=15,000K)=2.09 and R(T_sun=6,000K)=0.61, with a ratio difference of approximately 3.4 times; for the band pair of λ1=350nm and λ2=950nm, the ratio difference is approximately 9.9 times. When R_th=1.05, the impact flash exceeds the threshold by approximately 2 times, and the solar reflection is below the threshold by approximately 1.7 times, with sufficient decision margins on both sides; the three conditions are met with a delay ≤2μs, satisfying the pre-trigger frame preservation requirements of a 10kfps camera. The above effects cannot be obtained from any one or a combination of single photoelectric detection channel threshold triggering, same-band redundant triggering, laboratory multicolor photometry, or industrial dual-color thermometry.

[0078] The present invention will be described in more detail below through specific embodiments.

[0079] Example 1:

[0080] (1) Task scenario:

[0081] The spacecraft approached an S-type (silicate) asteroid at a relative speed of approximately 6 km / s, delivering a kinetic impact at a distance of approximately 500 m. The high-speed camera operated at 10 kfps (frame period 100 μs) in a circular buffer mode, with a buffer depth of 512 frames (approximately 51.2 ms). The photometric sampling rate was 1 MSPS (100 samples per frame).

[0082] (2) Optical configuration:

[0083] Two independent and parallel photoelectric detection channels, each equipped with an independent optical front end, directly receive the incident light from the target field of view without the need for beam splitters or other beam-splitting components.

[0084] First photoelectric detection channel (ultraviolet channel): The first center wavelength of the first bandpass filter is λ1=395±5nm, and the first full width at half maximum (FWHM) is Δλ1=10nm or Δλ1=20nm to obtain higher light flux, peak transmittance >85%, and Ø25mm standard installation.

[0085] Second photoelectric detection channel (visible channel): The second center wavelength of the second bandpass filter is λ2=630±5nm, the second full width at half maximum is Δλ2=10nm, and the peak transmittance is >80%.

[0086] Each bandpass filter is followed by a silicon PIN photodiode with a photosensitive area of ​​approximately 1.1 mm². 2 It has a spectral response range of 320-1,060 nm, a typical dark current of ≤10 pA, and operates under low bias.

[0087] (3) Circuit configuration:

[0088] Each photodetector channel has an independent signal link: PD → Transimpedance Amplifier (TIA, gain 10). 5 V / A) → First-order high-pass RC filter (cutoff frequency of 5kHz) → Two-stage low-noise voltage amplification → Independent ADC.

[0089] ADC: Each photodetector channel has an independent ADC, 1MSPS, 12–14bit resolution, and two digital outputs that are connected in parallel to the high-speed camera FPGA.

[0090] Preset voltage threshold V_min: corresponds to approximately 10nA photocurrent (the weakest detectable signal level with SNR>10).

[0091] Preset ratio threshold R_th: Based on an impact velocity of 6 km / s, assuming T_flash = 15,000 K, and with T_min = T_flash, R_th is set to 2.09 (corresponding to the λ1 = 395 nm, λ2 = 630 nm band pair) through a lookup table.

[0092] The time window is 1 μs (one consecutive sampling period at a sampling rate of 1 MSPS).

[0093] (4) Work process:

[0094] As the spacecraft approached its target, the camera continuously wrote to the circular buffer at 10kfps.

[0095] The solar reflected DC photocurrent is filtered out by AC coupling, and the baselines of V1(t) and V2(t) are close to zero.

[0096] At the moment of impact (t=0), the UV / visible light components of the flash reach the two PDs through the first center wavelength of 395nm and the second center wavelength of 630nm, respectively.

[0097] AC coupling can completely preserve transient flash signals: the high-pass cutoff frequency f_c is designed to be 5kHz (within the preferred range of 1–10kHz), which is much lower than the characteristic frequency of the 10μs rising edge flash signal (about 16kHz), so the rising edge of the impact flash can pass through without attenuation.

[0098] Each photodetector channel has an independent ADC that synchronously acquires the first and second conditioning voltages at 1 MSPS and sends them to the FPGA in parallel.

[0099] The FPGA pipeline divider outputs the ratio R(t) of the first conditioning voltage V1(t) to the second conditioning voltage V2(t) in real time, and updates it once every 1μs clock cycle.

[0100] Three digital comparators make parallel decisions: V1(t)>V_min, V2(t)>V_min, R(t)>R_th.

[0101] A three-input AND gate outputs a collision trigger signal when all conditions are true within one consecutive sampling period.

[0102] The impact trigger signal is transmitted to the camera control unit, which performs ring buffer freezing and keyframe saving.

[0103] (5) Technical effects:

[0104] At a distance of 500m (actual measured distance) and under the corresponding optical aperture conditions:

[0105] Impact flash (T_flash=5,000K): R_th=2.09;

[0106] Solar reflection (T_sun=6,000K): R_th=0.61;

[0107] The ratio difference is approximately 3.4 times.

[0108] Three-condition compliance delay: ≤2μs (including 1μs for ADC acquisition + 1 clock cycle for division / comparison);

[0109] AC coupling suppression ratio of DC solar background: >60dB (the DC component is theoretically completely blocked, and the residual is determined by the non-ideal characteristics of RC devices).

[0110] Figure 2 This is a flowchart of the asteroid impact two-color ratio photometric triggering method provided by the present invention, the method comprising:

[0111] Receive the incident light from the target field of view and output the first photocurrent signal;

[0112] It receives the incident light from the target field of view and outputs a second photocurrent signal;

[0113] The first photocurrent signal and the second photocurrent signal are respectively subjected to transimpedance amplification, AC coupling high-pass filtering, low-noise voltage amplification and analog-to-digital conversion to obtain the first conditioning voltage and the second conditioning voltage;

[0114] Calculate the ratio characteristic parameter based on the first conditioning voltage and the second conditioning voltage;

[0115] When both the first conditioning voltage and the second conditioning voltage are greater than the preset voltage threshold and the ratio characteristic parameter is greater than the preset characteristic parameter threshold, an impact trigger signal is output to autonomously distinguish between high-temperature impact flashes and low-temperature solar reflections on a microsecond time scale, eliminating false triggers caused by distance and brightness ambiguity.

[0116] It should be noted that the specific details and benefits of the asteroid impact dual-color ratio photometric triggering method provided by the present invention are similar to those of the asteroid impact dual-color ratio photometric triggering system provided by the present invention, and will not be repeated here.

[0117] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0118] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0119] Furthermore, various different implementations of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed in the present invention.

Claims

1. A dual-color ratio photometric triggering system for asteroid impacts, characterized in that, The system includes: The first photoelectric detection module is used to receive the incident light in the target field of view and output the first photocurrent signal; The second photoelectric detection module is used to receive the incident light in the target field of view and output the second photocurrent signal; The signal conditioning module is connected to the first photodetector module and the second photodetector module, and is used to perform transimpedance amplification, AC coupling high-pass filtering, low-noise voltage amplification and analog-to-digital conversion on the first photocurrent signal and the second photocurrent signal, respectively, to obtain the first conditioning voltage and the second conditioning voltage. The characteristic parameter calculation module is used to calculate the ratio characteristic parameter based on the first conditioning voltage and the second conditioning voltage; The trigger determination module is used to output an impact trigger signal when both the first conditioning voltage and the second conditioning voltage are greater than a preset voltage threshold and the ratio characteristic parameter is greater than a preset characteristic parameter threshold, so as to autonomously distinguish between high-temperature impact flashes and low-temperature solar reflections on a microsecond time scale and eliminate false triggering caused by distance and brightness ambiguity.

2. The asteroid impact dual-color ratio photometric triggering system according to claim 1, characterized in that, The first photoelectric detection module includes: A first bandpass filter is used to perform spectral filtering of incident light based on a first center wavelength to obtain a first monochromatic beam. A first photodetector is used to receive the first monochromatic light beam and convert the first monochromatic light beam into a first photocurrent signal, which is proportional to the incident light power.

3. The asteroid impact dual-color ratio photometric triggering system according to claim 2, characterized in that, The second photoelectric detection module includes: The second bandpass filter is used to spectrally filter the incident light based on the second center wavelength to obtain a second monochromatic beam. The second photodetector is used to receive the second monochromatic light beam and convert the second monochromatic light beam into a second photocurrent signal, which is proportional to the incident light power. The first center wavelength and the second center wavelength are located in different spectral regions.

4. The asteroid impact dual-color ratio photometric triggering system according to claim 3, characterized in that, The signal conditioning module is used to condition the first photocurrent signal and the second photocurrent signal respectively. The first photodetector channel corresponding to the first photodetector module includes: The first transimpedance amplifier is used to perform linear conversion and primary amplification on the first photocurrent signal to obtain the first transimpedance amplification voltage. The first AC-coupled high-pass filter is used to filter out the DC photocurrent component generated by solar reflection from the first transimpedance amplified voltage, retaining only the transient signal to obtain the first transient AC voltage; The first low-noise voltage amplifier is used to perform controllable gain amplification of the first transient AC voltage and output the first low-noise amplified voltage. A first analog-to-digital converter is used to convert the first low-noise amplified voltage into an analog-to-digital voltage and output a first conditioning voltage; The second photoelectric detection channel corresponding to the second photoelectric detection module includes: The second transimpedance amplifier is used to perform linear conversion and primary amplification on the second photocurrent signal to obtain the second transimpedance amplified voltage. The second AC-coupled high-pass filter is used to filter out the DC photocurrent component generated by solar reflection from the second transimpedance amplified voltage, retaining only the transient signal to obtain the second transient AC voltage. The second low-noise voltage amplifier is used to perform controllable gain amplification of the second transient AC voltage and output the second low-noise amplified voltage. The second analog-to-digital converter is used to perform analog-to-digital conversion on the second low-noise amplified voltage and output the second conditioning voltage.

5. The asteroid impact dual-color ratio photometric triggering system according to claim 4, characterized in that, The trigger determination module includes: The first comparison unit is used to determine whether the first conditioning voltage is greater than a preset voltage threshold. If the determination result is yes, then the first condition is satisfied. The second comparison unit is used to determine whether the second conditioning voltage is greater than the preset voltage threshold. If the determination result is yes, then the second condition is satisfied. The third comparison unit is used to determine whether the ratio feature parameter is greater than the preset feature parameter threshold. If the determination result is yes, then the third condition is satisfied. The result determination unit is used to output the impact trigger signal when the first condition, the second condition, and the third condition are all satisfied.

6. The asteroid impact dual-color ratio photometric triggering system according to claim 5, characterized in that, When the ratio characteristic parameter is the ratio of the first conditioning voltage to the second conditioning voltage, the preset characteristic parameter threshold is the preset ratio threshold. When the ratio characteristic parameter is the logarithm of the ratio of the first conditioning voltage to the second conditioning voltage, the preset characteristic parameter threshold is a preset logarithmic threshold.

7. The asteroid impact dual-color ratio photometric triggering system according to claim 6, characterized in that, The system also includes: The data storage module is used to store a lookup table, which stores the mapping relationship between the first center wavelength, the second center wavelength and a preset ratio threshold or a preset logarithmic threshold. The trigger determination module is further configured to obtain the preset ratio threshold or the preset logarithm threshold based on the lookup table according to the first center wavelength and the second center wavelength.

8. The asteroid impact dual-color ratio photometric triggering system according to claim 7, characterized in that, The preset ratio threshold value is greater than or equal to the ratio of the first conditioning voltage to the second conditioning voltage calculated at the equivalent blackbody temperature of solar reflection, and less than or equal to the ratio of the first conditioning voltage to the second conditioning voltage calculated at the equivalent blackbody temperature of the expected impact flash.

9. The asteroid impact dual-color ratio photometric triggering system according to claim 8, characterized in that, The first center wavelength is located in the ultraviolet to visible light band, the second center wavelength is located in the visible light to near-infrared band, the first center wavelength is located in the 320nm to 450nm band, the second center wavelength is located in the 600nm to 1000nm band, and the difference between the first center wavelength and the second center wavelength is greater than or equal to 150nm.

10. A method for triggering asteroid impact two-color ratio photometry, characterized in that, The method includes: Receive the incident light from the target field of view and output the first photocurrent signal; It receives the incident light from the target field of view and outputs a second photocurrent signal; The first photocurrent signal and the second photocurrent signal are respectively subjected to transimpedance amplification, AC coupling high-pass filtering, low-noise voltage amplification and analog-to-digital conversion to obtain the first conditioning voltage and the second conditioning voltage; Calculate the ratio characteristic parameter based on the first conditioning voltage and the second conditioning voltage; When both the first conditioning voltage and the second conditioning voltage are greater than the preset voltage threshold and the ratio characteristic parameter is greater than the preset characteristic parameter threshold, an impact trigger signal is output to autonomously distinguish between high-temperature impact flashes and low-temperature solar reflections on a microsecond time scale, eliminating false triggering caused by distance and brightness ambiguity.

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