Low-frequency Channel Research Articles

Assessments of Cloud Liquid Water and Total Precipitable Water Derived from FY-3E MWTS-III and NOAA-20 ATMS

Cloud liquid water (CLW) and total precipitable water (TPW) are two important parameters for weather and climate applications. Typically, microwave temperature sounding instruments onboard satellites are designed with two low-frequency channels at 23.8 and 31.4 GHz and can be used for retrieving CLW and TPW over global oceans. Since MWTS-III polarization at above two frequencies is uncertain, we must first determine their polarization involved in retrieval algorithms. Through radiative transfer simulation, we found that uses of the quasi-horizontal polarization for MWTS-III can produce smaller biases between observations and simulations and the scan-angle dependence of the biases is also in a general frown pattern, which is similar to ATMS pitch-maneuver observations. After the characterization of MWTS-III polarization, CLW and TPW are derived from Microwave Temperature Sounder (MWTS-III) and are compared with those from ATMS. It is found that CLW and TPW derived from two instruments exhibit a high consistency in terms of their spatial distributions and magnitudes.

Estimation of Water Saturation in Shale Formation Using In Situ Multifrequency Dielectric Permittivity

Estimating water saturation via conventional logging tool such as resistivity cannot provide an accurate solution in a formation with low conductivity water and tight porosity. As an alternative, we employed a dielectric permittivity, which makes it easy to differentiate the water from the other fluids in pore structures. A multichannel frequency dielectric logging tool is used for measuring in situ permittivity. To simulate a dielectric permittivity, we used two analytic models: Lichtenecker-Rother (LR) and Stroud-Milton-De (SMD) models. The key goal of this research is to propose a workflow to evaluate an equivalent Archie’s parameter which can generate the same dielectric logging tool responses with core measurement results using a given analytic models. According to the results of the LR model curve-fitting, the estimated Archie’s parameter shows inversely proportional relationship with clay volumes. The estimated Archie’s parameter from the SMD model is sensitive to the lower frequency channels of the multifrequency dielectric logging tool. Nevertheless, utilizing the response of the dielectric logging tool in the frequency range, where interfacial polarization effect does not exist, can provide an alternative to estimate water saturation in shale formations with relatively less conductive waters.

Cross Validation of TEMPEST-D and RainCube Observations Over Precipitation Systems

This paper presents cross-validation of nearly simultaneous observations between the Temporal Experiment for Storms and Tropical Systems<b>&#x00A0;-</b>Demonstration<b>&#x00A0;(</b>TEMPEST-D) and RainCube (Radar in a CubeSat) satellite microwave sensors over precipitation systems. RainCube senses the atmosphere using a Ka-band nadir-pointing radar, and TEMPEST-D senses using multi-frequency millimeter-wave radiometers. Nine precipitation systems were used in this cross-validation study. Occurring over nearly a two-year period, these storms were scattered over many regions of the world from the Tropics to the mid-latitudes. A shift correction algorithm was developed to remove the uncertainty between the two sensors&#x0027; observations due to the time difference and the storm motion between the two instrument overpasses. Correlation coefficients were calculated between self-normalized, inverted RainCube cumulative reflectivity and self-normalized TEMPEST-D brightness temperatures. As expected, these correlation coefficients are consistently higher for the four TEMPEST-D high-frequency channels than for the single low-frequency channel. The shift correction algorithm improved the average correlation coefficient by 19&#x0025; for the four high-frequency channels and by 58&#x0025; for the single low-frequency channel. The average correlation coefficient after shift correction is 0.76 for TEMPEST-D&#x0027;s four high-frequency channels and 0.54 for the single low-frequency channel. The comparisons demonstrated high consistency between the TEMPEST-D and RainCube observations, even though the two microwave sensors&#x0027; fundamental physics is different; one is passive, and the other is active.

Optimization strategy of power control for C+L+S band transmission using a simulated annealing algorithm.

To increase the transmission capacity, ultra-wideband wavelength-division multiplexing (UWB WDM) has been exploited to enlarge the spectral range. However, inter-channel stimulated Raman scattering (ISRS) results in power transition from high-frequency channels to low-frequency channels in wideband scenarios, which degrades the Q-factor of signals. Hence, we modify the optimization method of power control by applying the simulated annealing (SA) algorithm to search for the optimal power slopes and offsets of three bands to construct an optimum distribution of launch powers over channels. High transmission capacity can be reached by carrying 384 channels (96+96+192) in the C+L+S band with the consideration of dynamic Raman gain and channel-dependent parameters. We show that compared to using brute-force searching (BFS), a comparable and even higher transmission capacity can be achieved by the SA algorithm. Meanwhile, the searching speed of the SA algorithm is much faster. Also, different optimizing strategies can be selected to balance the trade-off between capacity and spectral flatness. This method can be used for designing arbitrary optical fiber UWB WDM systems before practical testing.

Observations of high-frequency acoustic attenuation due to bubble entrainment at estuarine fronts

Frontal boundary features with strong gradients in water properties and velocity are common features in coastal environments where fresh discharge meets ambient ocean waters. Convergence at these fronts results in two features that support the entrainment of bubbles. First, horizontal velocity gradients causes surface waves to steepen and break at these boundaries. Second, localized downwelling can further entrain and transport these bubbles. In experiments using broadband echosounders (45–420 kHz) at the Connecticut River ebb plume front and James River tidal intrusion front, bubble entrainment was observed to cause frequency-dependent excess attenuation. Seabed backscattering near fronts is used as a baseline, whereas a decrease in observed backscattering from the seabed under bubble plumes was attributed to excess attenuation due to bubble concentrations. Despite observing significant (>10 dB in some cases) excess attenuation in lower-frequency channels, we hypothesize that these fronts are unlikely to significantly affect propagation in the horizontal at these frequencies and that factors, such as refraction and three-dimension structure, are more operationally significant. [This work was funded by ONR.]

Effective modes of operation of radio-bombing devices for covert information gathering in the field of noise interference

The information security of modern society is in constant counteraction and constant improvement of technical means used for unauthorized information pickup, and technical means that prevent it. The paper analyzes examples of methods of applying noise interference to counteract the unauthorized pickup. The possibility of unauthorized pickup by passive radio devices using noise interferences is shown and analyzed using noise interferences, which are used to suppress the eavesdropping devices. The transfer of picked up information is possible both by radio wave and low-frequency channels using metal structures or water pipes. As a model of noise interference, a random narrow-band signal with a Gaussian distribution was used. The electrical model of the device was simulated by a transmission line with a high-frequency diode at its end. The idealized exponential dependence of the diode current on the voltage was used. The reflected wave spectra are obtained for different ratios of the transmission line resistance, the differential resistance of diode, and the external offset voltage at the diode. The modes and features of analog and digital information transmission by the radio tab device using energy of radio noises are analyzed. In the radio tab device, the information is transmitted by reflected wave, the spectrum of which is distorted at a nonlinear element placed at the end of transmission line. An analysis of the device operation was carried out along the full possible frequency range associated with the spectrum of the incident noise interference. The optimal elements parameters for the passive electrical circuit are calculated: the resistance of the transmission line, the differential resistance of the diode, the offset voltage, and the modulation mode, depending on the frequency range in which the leak is possible.

The Passive microwave Empirical cold Surface Classification Algorithm (PESCA): application to GMI and ATMS

AbstractThis paper describes a new Passive microwave Empirical cold Surface Classification Algorithm (PESCA) developed for snow cover detection and characterization by using passive microwave satellite measurements. The main goal of PESCA is to support the retrieval of falling snow, as several studies have highlighted the influence of snow cover radiative properties on the falling snow passive microwave signature. The developed methodology is based on the exploitation of the lower frequency channels (&lt; 90 GHz), common to most microwave radiometers. The methodology applied to the conically scanning GMI and the cross-track scanning ATMS is described in this paper. PESCA is based on a decision tree developed using an empirical method and verified using the AutoSnow product built from satellite measurements. The algorithm performance appears to be robust for both sensors in dry conditions (TPW &lt; 10 mm), and for mean surface elevation &lt; 2500 m, independently of the cloud cover. The algorithm shows very good performance for cold temperatures (2 m temperature below 270 K) with a rapid decrease of the detection capabilities between 270 K and 280 K, where 280 K is assumed as the maximum temperature limit for PESCA [overall detection statistics: POD=0.98(0.92), FAR=0.01(0.08), HSS=0.72(0.69) for ATMS(GMI)]. Some inconsistencies found between the snow categories identified with the two radiometers are related to their different viewing geometry, spatial resolution, and temporal sampling. The spectral signatures of the different snow classes appear to be different also at high frequency (&gt;90GHz), indicating potential impact for snowfall retrieval. This method can be applied to other conically and cross track scanning radiometers including the future operational EPS-SG mission microwave radiometers.

Retrieval of Oceanic Total Precipitable Water Vapor and Cloud Liquid Water from Fengyun-3D Microwave Sounding Instruments

Fengyun-3D (FY-3D) satellite is the latest polar-orbiting meteorological satellite launched by China and carries 10 instruments onboard. Its microwave temperature sounder (MWTS) and microwave humidity sounder (MWHS) can acquire a total of 28 channels of brightness temperatures, providing rich information for profiling atmospheric temperature and moisture. However, due to a lack of two important frequencies at 23.8 and 31.4 GHz, it is difficult to retrieve the total precipitable water vapor (TPW) and cloud liquid water path (CLW) from FY-3D microwave sounder data as commonly done for other microwave sounding instruments. Using the channel similarity between Suomi National Polar-orbiting Partnership (NPP) advanced technology microwave sounder (ATMS) and FY-3D microwave sounding instruments, a machine learning (ML) technique is used to generate the two missing low-frequency channels of MWTS and MWHS. Then, a new dataset named as combined microwave sounder (CMWS) is obtained, which has the same channel setting as ATMS but the spatial resolution is consistent with MWTS. A statistical inversion method is adopted to retrieve TPW and CLW over oceans from the FY-3D CMWS. The intercomparison between different satellites shows that the inversion products of FY-3D CMWS and Suomi NPP ATMS have good consistency in magnitude and distribution. The correlation coefficients of retrieved TPW and CLW between CMWS and ATMS can reach 0.95 and 0.85, respectively.

First steps towards an all-sky assimilation framework for tropical cyclone event over Bay of Bengal region: Evaluation and assessment of GMI radiances

The present study designs a data assimilation framework for all-sky GMI radiances in the Weather Research Forecast (WRF) model for the prediction of tropical cyclone events over the Bay of Bengal (BOB) region. Experiments are performed using the RTTOV-SCATT radiative transfer model for three cyclone events (Hudhud (2014), Vardah (2016), and Kyant (2016)) for 19 V, 23 V, 37 V, 89 V, 166 V, 183±3, and 183±7 V channels. Results show that observed and simulated brightness temperatures (Tb) agree well for low-frequency channels (<89 GHz). However, significant discrepancies do exist when simulating low Tb at high frequency channels. Therefore, a set of 26 simulations is considered using snow particle shapes from single scattering property databases. A new methodology is devised in order to compare the 26 simulations with observations; taking into account the uncertainties on hydrometeor radiative properties. Results reveal that model simulations are characterized by an underestimation of occurrences within several Tb ranges (~200–300 K). The probability distribution function (PDF) of normalized observed-minus first guess is close to a Gaussian shape after applying a dedicated model of observation errors. The potential to integrate the GMI sensor data within a WRF data assimilation system is thus demonstrated.

Daily Rainfall Estimate by Emissivity Temporal Variation from 10 Satellites

AbstractRainfall retrieval algorithms for passive microwave radiometers often exploit the brightness temperature depression due to ice scattering at high-frequency channels (≥85 GHz) over land. This study presents an alternate method to estimate the daily rainfall amount using the emissivity temporal variation (i.e., Δe) under rain-free conditions at low-frequency channels (19, 24, and 37 GHz). Emissivity is derived from 10 passive microwave radiometers, including the Global Precipitation Measurement (GPM) Microwave Imager (GMI), the Advanced Microwave Scanning Radiometer 2 (AMSR2), three Special Sensor Microwave Imager/Sounders (SSMIS), the Advanced Technology Microwave Sounder (ATMS), and four Advanced Microwave Sounding Units-A (AMSU-A). Four different satellite combination schemes are used to derive the Δe for daily rainfall estimates. They are all 10 satellites, 5 imagers, 6 satellites with very different equator crossing times, and GMI only. Results show that Δe from all 10 satellites has the best performance with a correlation of 0.60 and RMSE of 6.52 mm, compared with the Integrated Multisatellite Retrievals for GPM (IMERG) Final run product. The 6-satellites scheme has comparable performance with the all-10-satellites scheme. The 5-imagers scheme performs noticeably worse with a correlation of 0.49 and RMSE of 7.28 mm, while the GMI-only scheme performs the worst with a correlation of 0.25 and RMSE of 11.36 mm. The inferior performance from the 5-imagers and GMI-only schemes can be explained by the much longer revisit time, which cannot accurately capture the emissivity temporal variation.

A Mixed Valence CoIICoIII2 Field-Supported Single Molecule Magnet: Solvent-Dependent Structural Variation.

One-pot reaction of the Schiff base N,N’-ethylene bis(salicylaldimine) (H2L), CoCl2.6H2O, and [Ph2SnCl2] in acetone produces the mixed valence CoIICoIII2 compound [CoIICoIII2(μ-L)2(Ph)2(μ-Cl)2]·(CH3)2CO·H2O (1). Our recent study already revealed that the same reaction mixtures in methanol or ethanol produced a heterometallic SnIVCoIII (2) or monometallic CoIII complex (3), respectively. Comparison of these organometallic systems shows that the 2,1-intermetallic Ph shift occurs in any of those solvents, but their relevant structural features (mononuclear, dinuclear-heterometallic, and trinuclear mixed valence) are solvent dependent. Geometrical structural rotation is also discussed among the related organometallic CoIICoIII2 systems. The AC magnetic susceptibility measurements indicate that 1 is a single molecule magnet (SMM), exhibiting a field-induced slow magnetic relaxation with two modes. The relaxation time for the low-frequency channel is as slow as τ~0.6 s at T = 2.0 K and BDC = 1.0 T.

Mindfulness and De-automatization: Effect of Mindfulness-Based Interventions on Emotional Facial Expressions Processing

Past research has suggested that mindfulness training reduces automaticity while processing socio-emotional stimuli. The present study aimed to analyze how mindfulness practice may reduce the use of prior knowledge during the recognition of emotional facial expressions. Based on a predictive brain model, we hypothesized that mindfulness practice would reduce the top-down processing of low spatial frequency information. This experiment compared the performance of a mindfulness group (n = 32) and a waitlist control group (n = 30) in an emotional Stroop task before and after an 8-week training course. The emotional Stroop task comprised two emotional facial expressions (joy or anger) topped with a congruent or incongruent word, and was primed by facial expressions filtered in two spatial frequency bands: high spatial frequency (HSF) or low spatial frequency (LSF). Having measured the reaction time, the results showed a significant interaction between group (mindfulness vs. control) and session (before vs. after training; p = 0.04; R2 = 0.001), irrespective of spatial frequency channels. Breaking down the interaction showed that mindfulness-trained participants responded significantly faster than the controls to any type of information. The interaction Group by Session by Priming was not significant. These results are in line with research underlining the effects of mindfulness-based interventions on global attentional control. More precisely, the global reduced reaction time did not support lower top-down predictive coding abilities specifically driven by low spatial frequency channels, but indicated a better general sensitivity to the perceptual environment.

Spatial Hearing by Bilateral Cochlear Implant Users With Temporal Fine-Structure Processing.

Several studies have demonstrated the advantages of the bilateral vs. unilateral cochlear implantation in listeners with bilateral severe to profound hearing loss. However, it remains unclear to what extent bilaterally implanted listeners have access to binaural cues, e.g., accurate processing of interaural timing differences (ITDs) for low-frequency sounds (<1.5 kHz) and interaural level differences (ILDs) for high frequencies (>3 kHz). We tested 25 adult listeners, bilaterally implanted with MED-EL cochlear implant (CI) devices, with and without fine-structure (FS) temporal processing as encoding strategy in the low-frequency channels. In order to assess whether the ability to process binaural cues was affected by fine-structure processing, we performed psychophysical ILD and ITD sensitivity measurements and free-field sound localization experiments. We compared the results of the bilaterally implanted listeners with different numbers of FS channels. All CI listeners demonstrated good sensitivity to ILDs, but relatively poor to ITD cues. Although there was a large variability in performance, some bilateral CI users showed remarkably good localization skills. The FS coding strategy for bilateral CI hearing did not improve fine-structure ITD processing for spatial hearing on a group level. However, some CI listeners were able to exploit weakly informative temporal cues to improve their low-frequency spatial perception.

A physical algorithm for precipitable water vapour retrieval over land using passive microwave observations

ABSTRACT Precipitable water vapour (PWV) plays an important role in weather prediction, hydrological cycles and climate change. In this study, a physics-based algorithm was proposed to retrieve PWV over land using satellite passive microwave observations near 165.50 GHz and 183.31 GHz, which have higher spatial resolution and lower sensitivity to land surface emissivity than low-frequency channels. The algorithm uses a perturbation formulation of simplified radiative transfer equation to derive PWV and at-surface brightness temperature (BT) in 165.50 GHz simultaneously. It directly derives the at-surface BT instead of land surface temperature, so the algorithm needs no prior information of surface emissivity. Sensitivity analysis and retrieval experiments from simulated data were carried out for Advanced Technology Microwave Sounder (ATMS) onboard the National Polar-orbiting Operational Environmental Satellite System (NPOESS) Preparatory Project (NPP) satellite. The results showed that the algorithm using ATMS channels 17, 18 and 19 measurements can significantly reduce the PWV retrieval errors caused by surface emissivity uncertainty. The coefficient of determination (R 2), root-mean-square error (RMSE), and bias of the retrieved PWV from ATMS data by the proposed algorithm and SuomiNet Global Positioning System (GPS) PWV were 0.90, 0.43 cm and −0.02 cm, respectively. In addition, the Visible Infrared Imaging Radiometer Suite (VIIRS) cloud products were used to evaluate the effects of cloud on the PWV retrievals. The results showed that the presence of cloud does not decrease the accuracy of the PWV retrievals.

Retrieval of Sea Surface Temperature From HY-2A Scanning Microwave Radiometer

The scanning microwave radiometer (RM) onboard the Haiyang-2A (HY-2A) satellite has low-frequency channels with the capability of observing sea surface temperature (SST) from space. To improve the accuracy of the HY-2A RM SST data, the intercalibration of RM brightness temperature (BT) and SST retrieval were carried out. Based on the simulated BTs using the microwave radiative transfer model (RTM), the double-difference approach was applied to perform the intercalibration of RM BTs for the 10.7, 18.7, 23.8, and 37.0 GHz channels, with the Global Precipitation Measurement (GPM) Microwave Imager (GMI) as the reference. The RM 6.6-GHz BTs were corrected with the RTM modeled BT on account of a lack of the similar channel in GMI. The comparison of RM original BTs with GMI and modeled BTs showed large biases and the strong dependence on latitude. We obtained latitude-dependent coefficients using robust linear regression for RM BT correction and applied recalibrated RM BTs for the SST retrieval. The validation of the RM retrieved SST showed the bias of −0.12 °C and the robust standard deviation (RSD) of 1.10 °C compared with buoy SST in the region between 70°S and 70°N. In the tropical and subtropical regions, the bias was −0.12 °C and the RSD was 0.93 °C. In addition, the relationships between the SST difference and the sea surface and atmospheric parameters were investigated. Both statistics of validation results and error analysis indicated significant improvement of RM SST accuracy.

Evaluation of V05 Precipitation Estimates from GPM Constellation Radiometers Using KuPR as the Reference

AbstractThis study assesses the level-2 precipitation estimates from 10 radiometers relative to Global Precipitation Measurement (GPM) Ku-band precipitation radar (KuPR) in two parts. First, nine sensors—four imagers [Advanced Microwave Scanning Radiometer 2 (AMSR2) and three Special Sensor Microwave Imager/Sounders (SSMISs)] and five sounders [Advanced Technology Microwave Sounder (ATMS) and four Microwave Humidity Sounders (MHSs)]—are evaluated over the 65°S–65°N region. Over ocean, imagers outperform sounders, primarily due to the usage of low-frequency channels. Furthermore, AMSR2 is clearly superior to SSMISs, likely due to the finer footprint size. Over land all sensors perform similarly except the noticeably worse performance from ATMS and SSMIS-F17. Second, we include the Sondeur Atmospherique du Profil d’Humidite Intertropicale par Radiometrie (SAPHIR) into the evaluation process, contrasting it against other sensors in the SAPHIR latitudes (30°S–30°N). SAPHIR has a slightly worse detection capability than other sounders over ocean but comparable detection performance to MHSs over land. The intensity estimates from SAPHIR show a larger normalized root-mean-square-error over both land and ocean, likely because only 183.3-GHz channels are available. Currently, imagers are preferred to sounders when level-2 estimates are incorporated into level-3 products. Our results suggest a sensor-specific priority order. Over ocean, this study indicates a priority order of AMSR2, SSMISs, MHSs and ATMS, and SAPHIR. Over land, SSMIS-F17, ATMS and SAPHIR should be given a lower priority than the other sensors.

Sea Ice and Atmospheric Parameter Retrieval From Satellite Microwave Radiometers: Synergy of AMSR2 and SMOS Compared With the CIMR Candidate Mission

AbstractResearch on improving the prediction skill of climate models requires refining the quality of observational data used for initializing and tuning the models. This is especially true in the polar regions where uncertainties about the interactions between sea ice, ocean, and atmosphere are driving ongoing monitoring efforts. The Copernicus Imaging Microwave Radiometer (CIMR) is an European Space Agency (ESA) candidate mission which promises to offer high resolution, low uncertainty observation capabilities at the 1.4, 6.9, 10.65, 18.7, and 36.5 GHz frequencies. To assess the potential impact of CIMR for sea ice parameter retrieval, a comparison is made between retrievals based on present AMSR2 observations and a retrieval using future CIMR equivalent observations over a data set of validated sea ice concentration (SIC) values. An optimal estimation retrieval method (OEM) is used which can use input from different channel combinations to retrieve seven geophysical parameters (sea ice concentration, multi‐year ice fraction, ice surface temperature, columnar water vapor, liquid water path, over ocean wind speed, and sea surface temperature). An advantage of CIMR over existing radiometers is that it would provide higher spatial resolution observations at the lower frequency channels (6.9, 10.65, and 18.7 GHz) which are less sensitive to atmospheric influence. This enables the passive microwave based retrieval of SIC and other surface parameters with higher resolution and lower uncertainty than is currently possible. An information content analysis expands the comparison between AMSR2 and CIMR to all retrievable surface and atmospheric parameters. This analysis quantifies the contributions to the observed signal and highlights the differences between different input channel combinations. The higher resolution of the low frequency CIMR channels allow for unprecedented detail to be achieved in Arctic passive microwave sea ice retrievals. The presence of 1.4 GHz channels on board CIMR opens up the possibility for thin sea ice thickness (SIT) retrieval. A combination of collocated AMSR2 and SMOS observations is used to simulate a full CIMR suite of measurements, and the OEM is modified to include SIT as a retrieval parameter. The output from different retrieval configurations is compared with an operational SIT product. The CIMR instrument can provide increased accuracy for SIC retrieval at very high resolutions with a combination of the 18.7 and 36.5 GHz channels while also maintaining sensitivity for atmospheric water vapor retrieval. In combination with the 1.4 GHz channels, SIT can be added as an eighth retrieval parameter with performance on par with existing operational products.

Time–Frequency Attribute Analysis of Channel 1 Data of Lunar Penetrating Radar

The Lunar Penetrating Radar (LPR) carried by the Chang’E-3 (CE-3) and Chang’E-4 (CE-4) mission plays a very important role in lunar exploration. The dual-frequency radar on the rover (DFR) provides a meaningful opportunity to detect the underground structure of the CE-3 landing site. The low-frequency channel (channel 1) maps the underground structure to a depth of several hundred meters, while the high-frequency channel (channel 2) can observe the stratigraphic structure of gravel near the surface. As the low-frequency radar image is troubled by unknown noise, time–frequency analysis of a single trace is applied. Then, a method named complete ensemble empirical mode decomposition (CEEMD) is conducted to decompose the channel 1 data, and the Hilbert transform gives us the chance for further data analysis. Finally, combined with regional geology, previous studies, and channel 2 data, a usability analysis of LPR channel 1 data provides a reference for the availability of the CE-4 LPR data.

Cosmology with recombination spectrum

Precision measurement of the cosmological recombination spectrum can provide an entire new window to look at the early universe. We aim to quantify the information hidden in the cosmological recombination spectrum and for this purpose we have developed a new code following the algorithm proposed in [1,2]. Our code is closely based on the COSMOSPEC [3] code. We find, using Fisher information matrix and assuming that the foregrounds can be subtracted by using higher or lower frequency channels and spatial information, that going beyond the detection will need an experiment with sensitivity 25× better compared to the proposed experiment PIXIE. Such an experiment will be able to measure the cosmological parameters with a precision that is competitive with the CMB anisotropy experiments. The best constrainted parameter is baryon energy density, Ωb, which can be nailed down with incredible precision in principle. We also show that the shape of the hydrogen lines is connected to the speed of the hydrogen recombination, with the peaks of the recombination lines coinciding with the peak of the recombination rate. In general, the shape of the lines encodes information about the rate of recombination as a function of redshift.

The Mars rover subsurface penetrating radar onboard China's Mars 2020 mission

China's Mars probe, named Tianwen-1, including an orbiter and a landing rover, will be launched during the July-August 2020 Mars launch windows. Selected to be among the rover payloads is a Subsurface Penetrating Radar module (RoSPR). The main scientific objective of the RoSPR is to characterize the thickness and sub-layer distribution of the Martian soil. The RoSPR consists of two channels. The low frequency channel of the RoSPR will penetrate the Martian soil to depths of 10 to 100 m with a resolution of a few meters. The higher frequency channel will penetrate to a depth of 3 to 10 m with a resolution of a few centimeters. This paper describes the design of the instrument and some results of field experiments.