- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
The Ice, Cloud, and Land Elevation Satellite – 2 mission: A global geolocated photon product derived from the Advanced Topographic Laser Altimeter System
摘要： The Ice, Cloud, and land Elevation Satellite – 2 (ICESat-2) observatory was launched on 15 September 2018 to measure ice sheet and glacier elevation change, sea ice freeboard, and enable the determination of the heights of Earth's forests. ICESat-2's laser altimeter, the Advanced Topographic Laser Altimeter System (ATLAS) uses green (532 nm) laser light and single-photon sensitive detection to measure time of flight and subsequently surface height along each of its six beams. In this paper, we describe the major components of ATLAS, including the transmitter, the receiver and the components of the timing system. We present the major components of the ICESat-2 observatory, including the Global Positioning System, star trackers and inertial measurement unit. The ICESat-2 Level 1B data product (ATL02) provides the precise photon round-trip time of flight, among other data. The ICESat-2 Level 2A data product (ATL03) combines the photon times of flight with the observatory position and attitude to determine the geodetic location (i.e. the latitude, longitude and height) of the ground bounce point of photons detected by ATLAS. The ATL03 data product is used by higher-level (Level 3A) surface-specific data products to determine glacier and ice sheet height, sea ice freeboard, vegetation canopy height, ocean surface topography, and inland water body height.
关键词： Laser altimeter,Ice sheets,Altimetry,ICESat-2,Sea ice,Photon counting,Remote sensing,Cryosphere
更新于2025-09-16 10:30:52
-
[IEEE IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Yokohama, Japan (2019.7.28-2019.8.2)] IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - The Comparison of Denoising Methods for Photon Counting Laser Altimeter Data
摘要： The space-borne earth observation LiDAR satellite Ice, Cloud and Land Elevation Satellite-2 (ICESat-2) equipped with photon counting LiDAR system was launched on September 15, 2018. Significantly different from waveform laser altimeter carried on ICESat, the multiple beams photon counting laser altimeter can better measure Earth’ surface and directly provide the location of the scattering event. Due to the high sensitivity, the photon detector responds photons come from the solar background and the atmospheric scattering, which causes plenty of noise. It is necessary to study an effective method to identify signal photons from noise. This paper aims to study serval typical noise filtering methods and discuss their characteristics. The experiments are conducted on both ice sheet and vegetation data sets. The results are presented and some suggestions for choosing which denoising method to face in different environmental conditions are given.
关键词： ICESat-2,laser altimeter,noise filtering,MABEL,photon-counting
更新于2025-09-16 10:30:52
-
Deep-Space Optical Communication Link Engineering: Sensitivity Analysis
摘要： Science and exploration missions are continuously enlarging the science volume generated onboard the spacecraft, limited typically by the capabilities of the communication link. Although the rather unexploited Ka-band allocation around 32 GHz provides some relief in this respect [1], particularly if used with large size high gain antennas, optical communications bear the promise of delivering higher data rates in the mid-term [2]. For setting the scene for the optical communications technology, it is always interesting to understand where the limits are of current RF-based deep-space systems. Toward this, [3] is extrapolating the performance of Payload Data Transmitters from the current state-of-the-art to the 2023 technology time frame (see Table 1). Coming now to the technology which is the scope of this paper, for deep-space optical communications, the space agencies in Consultative Committee for Space Data Systems (CCSDS) recently concluded on a standard for high photon efficiency (HPE). The standard comprises a specification on the coding and synchronization layer [4] and one on the physical layer [5]. After specifying the standard, space agencies are now focused on planning in orbit demonstrations (IOD), although the waveform of [4] was already demonstrated to laser a frame of in the extent lunar large the Authors’ current addresses: N. K. Lyras, School of Electrical and Computer Engineering, National Technical University of Athens, Athens 15780, Greece. A. D. Panagopoulos, School of Electrical and Computer Engineering, National Technical University of Athens, Athens 15780, Greece, E-mail: (thpanag@ece.ntua.gr). P.-D. Arapoglou, European Space Agency/ESTEC, Noordwijk 2200, The Netherlands. Manuscript received January 15, 2019, revised July 5, 2019, and ready for publication September 24, 2019. Review handled by Prof. Mauro De Sanctis. 0885-8985/19/$26.00 (cid:1) 2019 IEEE communication demonstration [6]. From the European Space Agency point of view, a deep-space optical communication system IOD opportunity could be the space safety program, space weather mission to the Sun–Earth Lagrange point L5 [7]. In this paper, a tool is presented for aiding such IOD missions fully relying on the CCSDS HPE. The main elements that must be taken into account in a deep-space link budget analysis are summarized in Figure 1. The main assumptions of the work involve an optical downlink operating under cloud-free line of sight (CFLOS) conditions [8], [9] between an optical terminal onboard a deep-space spacecraft and an optical ground station. A Poisson is representative of deep-space optical channel model links. Due to the power limited nature of these links intensity modulation (IM) and direct detection (DD) with photon-counting detectors the transmitter and receiver architecture, respectively. Under these conditions, the pulse position modulation (PPM) signaling [11] and a serially concatenated pulse position modulation (SCPPM) [12] are capacity achieving. [10] are considered for Apart from performing a sensitivity analysis of various hypothetical deep-space missions, the paper presents a practical methodology that allows the link designer to select the main signaling parameters (modulation order, code rate, slot width), without resorting to lengthy coded bit error rate (BER) evaluations that otherwise need to be run for a large parameter set. This allows faster link budget calculations, e.g., for performing trade-off studies.
关键词： sensitivity analysis,deep-space optical communication,CCSDS HPE,link budget,photon-counting detectors
更新于2025-09-16 10:30:52
-
Monomeric cohesin state revealed by live‐cell single‐molecule spectroscopy
摘要： The cohesin complex plays an important role in the maintenance of genome stability. Cohesin is composed of four core subunits and a set of regulatory subunits that interact with the core subunits. Less is known about cohesin dynamics in live cells and on the contribution of individual subunits to the overall complex. Understanding the tethering mechanism of cohesin is still a challenge, especially because the proposed mechanisms are still not conclusive. Models proposed to describe tethering depend on either the monomeric cohesin ring or a cohesin dimer. Here, we investigate the role of cohesin dynamics and stoichiometry in live yeast cells at single-molecule resolution. We explore the effect of regulatory subunit deletion on cohesin mobility and found that depletion of different regulatory subunits has opposing effects. Finally, we show that cohesin exists mostly as a canonical monomer throughout the cell cycle, and its monomeric form is independent of its regulatory factors. Our results demonstrate that single-molecule tools have the potential to provide new insights into the cohesin mechanism of action in live cells.
关键词： cohesin,photon counting histogram,chromosome,fluorescence correlation spectroscopy,SMC complexes
更新于2025-09-16 10:30:52
-
Free-Space Optical Communications with Detector Arrays: A Mathematical Analysis
摘要： Photon counting detector arrays are commonly used for free-space optical communications in deep space. Such detector arrays—by virtue of their size—help in the collection of the optical signal even when there is some misalignment between the transmitter and receiver systems. In this paper, we argue that, for the common Gaussian beam pro?le, a detector array receiver is more useful for minimizing the probability of error than a single detector receiver of the same dimensions. Furthermore, the improvement in the error probability is more pronounced for low signal-to-noise ratio conditions, and the probability of error decreases monotonically as a function of the number of detectors in the array. However, communication with detector arrays results in a larger computational and hardware complexity at the receiver.
关键词： Free-space optical communications,photon counting detector arrays,error probability,Gaussian beam
更新于2025-09-16 10:30:52
-
[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - Laser Induced Cavitation Bubble Dynamics from Twin Breakdown Sites
摘要： This paper presents a readout integrated circuit called UFXC32k, designed for hybrid pixel semiconductor detectors used in X-ray imaging applications. The UFXC32k integrated circuit, designed in a CMOS 130 nm process, contains about 50 million transistors in the area of 9.64 mm × 20.15 mm. The core of the IC is a matrix of 128 × 256 square-shaped pixels of 75 μm pitch. Each pixel contains a charge sensitive ampli?er, a shaper, two discriminators, and two 14-bit ripple counters. The analog front-end electronics allow processing of sensor signals of both polarities (holes and electrons). The UFXC32k chip is bump-bonded to a pixel silicon sensor and is fully characterized using X-ray radiation. The measured equivalent noise charge for the standard settings is equal to 123 e? rms (for the peaking time of 40 ns) and each pixel dissipates 26 μW. Thanks to the use of trim blocks working in each pixel independently, an effective off- set spread calculated to the input is only 9 e? rms with a gain spread of 2%. The maximum count rate per pixel depends mainly on effective CSA feedback resistance. Dead time in the front end can be set as low as 85 ns. In the continuous readout mode, a user can select the number of bits read out from each pixel to optimize the UFXC32k frame rate, e.g., for a readout of 2 bits/pixel with 200 MHz clock, the frame rate is equal to 23 kHz.
关键词： X-ray imaging,pixel detectors,Matching,single photon counting
更新于2025-09-16 10:30:52
-
Iterative Pointing Angle Calibration Method for the Spaceborne Photon-Counting Laser Altimeter Based on Small-Range Terrain Matching
摘要： The satellite, Ice, Cloud and Land Elevation Satellite-2 (ICESat-2) has been equipped with a new type of spaceborne laser altimeter, which has the benefits of having small footprints and a high repetition rate, and it can produce dense footprints on the ground. Focusing on the pointing angle calibration of this new spaceborne laser altimeter, this paper proposes a fast pointing angle calibration method using only a small range of terrain surveyed by airborne lidar. Based on the matching criterion of least elevation difference, an iterative pointing angle calibration method was proposed. In the experiment, the simulated photon-counting laser altimeter data and the Ice, Cloud and Land Elevation Satellite-2 data were used to verify the algorithm. The results show that when 1 km and 2.5 km lengths of track were used, the pointing angle error after calibration could be reduced to about 0.3 arc-seconds and less than 0.1 arc-seconds, respectively. Meanwhile, compared with the traditional pyramid search method, the proposed iterative pointing angle calibration method does not require well-designed parameters, which are important in the pyramid search method to balance calculation time and calibration result, and the iterative pointing angle calibration method could significantly reduce the calibration time to only about one-fifth of that of the pyramid search method.
关键词： ICESat-2,photon-counting,pointing angle calibration,spaceborne laser altimeter,terrain matching
更新于2025-09-12 10:27:22
-
Photon-Counting Underwater Wireless Optical Communication by Recovering Clock and Data From Discrete Single Photon Pulses
摘要： To realize a long-distance underwater communication by using low-cost light emitting diode (LED) and single photon avalanche diode (SPAD), we proposed a method for recovering clock and data directly from discrete random pulse sequences output by SPAD. On this basis, a new communication model is established, taking into account not only ?uctuations in photon ?ux and quantum ef?ciency of photon detection in a time-slot, but also the phase difference of the recovered clock caused by it. A photon-counting underwater optical wireless communication (UOWC) system was built. The effects of the system setting parameters such as the number of gating signals, synchronous character length and baud rate on the average bit error rate (BER) were veri?ed by experiments. The experimental results show that under condition of only average 10 photons in one time-slot, photon-counting UOWC with a BER of 3.51 × 10?4 and a baud rate of 1 Mbps can be achieved.
关键词： clock synchronization,Underwater optical wireless communication (UOWC),photon-counting,data recovery
更新于2025-09-11 14:15:04
-
[IEEE 2019 7th International Conference on Information, Communication and Networks (ICICN) - Macao, Macao (2019.4.24-2019.4.26)] 2019 7th International Conference on Information, Communication and Networks (ICICN) - A Photon Counting Underwater NOMA Wireless Optical Communication System
摘要： In recent years, Underwater wireless optical communication (UWOC) has become one of hot spots of human exploration of the unknown deep-sea space. In this paper, a shot noise limited interleaver iterative non-orthogonal multiple access (NOMA) UWOC system with photon counting is proposed. The characteristics of underwater receiver wireless optical channel are studied. In addition to single receiver scheme, a diversity receiving scheme is also considered. According to the result of simulation, the proposed multi-user system can perform well in very low receiving signal energy, which achieves the bit error rate (BER) performance of 2*10e-5 at 40 photon number per bit for 4-user scenario with 1/10 repetition coding rate. Moreover, this system also has the rapid convergence and good receiving diversity property.
关键词： underwater optical wireless communication,NOMA,photon counting
更新于2025-09-11 14:15:04
-
Total image constrained diffusion tensor for spectral computed tomography reconstruction
摘要： Photon counting detector (PCD)-based spectral computed tomography (CT) is a promising imaging technique that enables high energy resolution imaging with narrow energy bins. However, the image quality is degraded because the number of photons in each energy bin is less than the number of photons in the full spectrum. To reconstruct high quality spectral CT images with narrow energy bins, we developed a total image constrained diffusion tensor (TICDT) for statistical iterative reconstruction (SIR) based on a penalized weighted least-squares (PWLS) principle, which is called “PWLS-TICDT.” Specifically, TICDT uses supplementary information from a high-quality total image as a structural prior for SIR, so that the narrow energy bin image can be enhanced, while some primary features are preserved. We also developed an alternating minimization algorithm to solve the associated objective function. We conducted qualitative and quantitative studies to validate and evaluate the PWLS-TICDT method using digital phantoms and preclinical data. Results from both numerical simulation and real PCD data studies show that the proposed PWLS-TICDT method achieves noticeable gains over competing methods in terms of suppressing noise, detecting low contrast objects, and preserving resolution. More importantly, the multi-energy images reconstructed by PWLS-TICDT method can generate more accurate basis material decomposition results than the other methods.
关键词： Photon counting detector,Image reconstruction,Diffusion tensor,Spectral CT
更新于2025-09-10 09:29:36