Thermospheric mass density is a major source of uncertainty in spacecraft orbit prediction, particularly in low earth orbit. Since 2023, the Tianmu-1 constellation has deployed 12 satellites in sun-synchronous orbits at ~500 km altitude, each equipped with the Orbital Neutral Atmospheric Detectors (OADs) to provide in-situ measurements of thermospheric mass density and composition. In this study, density data from five Tianmu-1 satellites (TM02, TM03, TM07, TM11, and TM15) are used to construct a preliminary empirical thermospheric mass density model. The OAD measurements are firstly compared against the independent GRACE-FO accelerometer-derived density data. The results show that the calibrated Tianmu-1 densities agree well with GRACE-FO observations, with correlation coefficients exceeding XX and mean biases below XX%. The calibrated densities are then analyzed to quantify their responses to solar EUV flux and geomagnetic activity. Finally, an empirical density model is developed using the Empirical Orthogonal Function (EOF) decomposition. The EOF-based model reproduces the major spatial-temporal variability of the thermosphere and achieves a modeling accuracy of XX%, demonstrating the potential of the Tianmu-1 constellation for operational thermospheric mass density specification.

In this study, we analyze the impact of the May 2024 geomagnetic storm on the thermospheric mass density by using TianMu-1 constellation satellite (TM02, TM06, TM07, TM11, TM15) observations. These observations reveal intense large-scale traveling atmospheric disturbances (TADs) originating at high latitudes and propagating equatorward. Observations by TM02 captured the evolution of a TAD structure: An initial amplitude of similar to 3.89 x 10(-12) kg/m(3) at hundred-kilometer scale subsequently intensified to 4.78 x 10(-12) kg/m(3), with the spatial extent expanding to the thousand-kilometer level. Significant hemispheric asymmetry was observed: the absolute density was higher predominantly in the northern hemisphere (TM02, TM06, TM07, TM11), whereas the difference in the relative density consistently showed greater enhancements in the southern hemisphere across all satellites, with the maximum north-south density differences exceeding 195%-640% above 60 degrees latitude. In conjunction with SuperDARN (Super Dual Auroral Radar Network) observations, this striking hemispheric asymmetry can likely be attributed to disparities in plasma convection patterns between the two hemispheres. Furthermore, density perturbation characteristics exhibited strong local time (LT) dependence: Near noon (similar to 10.7 LT, TM02 descending), the northern hemisphere onset preceded the southern onset. Conversely, near dusk (similar to 17.6 LT, TM15 descending), the southern onset led the northern onset by approximately 3 hours. Ascending orbits (TM02, TM06, TM07, TM15) typically yielded larger global density enhancements compared with smaller southern-confined enhancements during descending orbits. Satellite TM11 showed comparable perturbations in both ascending and descending orbits. By leveraging its unique orbital architecture, the TianMu-1 constellation enables global near-simultaneous multi-LT sampling, providing a robust data foundation for both scientific research and engineering applications.

Abstract During the geomagnetic storm on 10 May 2024, neutral density measurements from 14 Tianmu, Swarm, and GRACE‐FO satellites at ∼510 km altitude, combined with total electron content (TEC) observations, enabled the first global observational comparison of large‐scale traveling atmospheric and ionospheric disturbances (LSTADs/TIDs) via snapshots and keograms. LSTADs/TIDs exhibited similar wavefronts aligned with geomagnetic latitude, spanning 90–180° in longitude, originating from auroral or cusp Joule heating regions on both day and night sides. They propagated along overlapping meridional trajectories at 450–1,100 m/s. LSTADs lag LSTIDs by ∼30 min due to the phase polarization and differing observation heights. Besides, rare instantaneous neutral density enhancements were detected at low to mid latitudes during storm onset. These findings provide near‐continuous global observational insights into storm‐time thermosphere‐ionosphere wave coupling and demonstrate a feasible approach for future global LSTADs monitoring through empirical mode decomposition adaptive filtering of multi‐satellite data.

Abstract In situ observations of thermospheric composition have long been scarce, limiting our understanding of the upper atmosphere and its response to space weather. This study focuses on the Neutral Gas Mass Spectrometer (NGMS) onboard the TM19 and TM20 satellites of China's TianMu‐1 constellation, presenting the first systematic elaboration of its core technical characteristics and novel in situ observational results of O and N 2 number densities. During the 10–12 October 2024 geomagnetic storm, the ratio of O to N 2 number densities (O/N 2 ) decreased significantly at mid‐high latitudes, owing to the stronger enhancement of N 2 compared with O. N 2 perturbations were confined to latitudes above ∼±30° in both hemispheres, whereas O perturbations exhibited a global latitudinal distribution, likely reflecting that heavy N 2 is locally enhanced by upwelling and decays equatorward via diffusion, while O is transported globally by storm‐time circulation and waves. Additionally, the O/N 2 observations from TM19 and TM20 showed high cross‐satellite response consistency with a correlation coefficient of 0.89, while the MSIS 2.0 model systematically overestimated the O/N 2 under geomagnetically quiet conditions. The NGMS onboard TianMu‐1 provides crucial data support for optimizing atmospheric models.

The Tianwen-2 mission aims at exploring the near-Earth asteroid 2016HO3 and the main belt comet 311P by means of near-distance measuring and asteroid sampling and return. As one of main payloads of the Tianwen-2 mission, the Charged and Neutral Particle Analyzer (CANPA) will measure in-situ the plasmas and neutral atmosphere around the asteroid and the comet. The CANPA instrument is highly integrated and miniaturized, and composes four independent subsystems: the thermal ion analyzer (TIA), the thermal electron analyzer (TEA), the solar wind ion analyzer (SIA) and the gas and ion analyzer (GIA). The flight model has been calibrated by using the on-ground calibration system. The results show that the TIA can measure thermal ions at the energy range of 2.79 eV-32.03 keV with an energy resolution of 8.79%. The TEA can measure thermal electrons at the energy range of 1.07 eV-20.61 keV with an energy resolution of 14.29%. Both TIA and TEA have the field-of-view of 360 degrees x 90 degrees. The SIA can measure solar wind ions at the energy-per-charge range of 5 eV-5 keV with an energy resolution of 4.23%. The GIA can measure neutral gas and ions of the comet ionosphere at the mass range of 1-350 amu and the mass resolution is about 0.17 amu@1-50 amu, 0.52 amu@51-150 amu, and 1.22 amu@151-350 amu. The CANPA instrument can fulfill the detection requirements for the asteroid and the comet.

Thermospheric mass densities are investigated to explore their responses to solar irradiance and geomagnetic activity during the period from 31 October to 7 November 2021. Utilizing data from the Global Navigation Satellite System (GNSS) payload and an ionization gauge mounted on the Orbital Neutral Atmospheric Detector (OAD) payload onboard the QQ-Satellite, thermospheric mass densities are derived through two independent means: precise orbit determination (POD) and pressure measurements. For the first time, observations of these two techniques are compared and analyzed in this study to demonstrate similarities and differences. Both techniques exhibit similar spatial–temporal variations, with clear dependences on local solar time (LT). However, the hemispheric asymmetry is almost absent in simulations from the NRLMSISE-00 and DTM94 models compared with observations. At high latitudes, density enhancements of observations and simulations are shown, characterized by periodic bulge structures. In contrast, only the OAD-derived densities exhibit wave-like disturbances that propagate from two poles to lower latitudes during geomagnetic storm periods, suggesting a connection to traveling atmospheric disturbances (TADs). Over the long term, thermospheric mass densities derived from the two means of POD and the OAD show good agreements, yet prominent discrepancies emerge during specific periods and under different space-weather conditions. We propose possible interpretations as well as suggestions for utilizing these two means. Significantly, neutral winds should be considered in both methods, particularly at high latitudes and under storm conditions.

The highly sensitive millimeter-wave telescope is an important tool for accurate measurement of Cosmic Microwave Background (CMB) radiation, and its core component is a detector array located in a cryogenic focal plane. The feasibility of utilizing thermal kinetic inductance detectors (TKIDs) for CMB observations has been demonstrated. We propose a pixel design of TKIDs for observing CMB through atmospheric windows for observations in the 90/150 GHz bands. Assuming lossless dielectric, the coupling efficiency of a single pixel is around 90 array designs for CMB observations.

The highly sensitive millimeter-wave telescope is an important tool for accurate measurement of cosmic microwave background (CMB) radiation, and its core component is a detector array located in a cryogenic focal plane. The feasibility of utilizing thermal kinetic inductance detectors (TKIDs) for CMB observations has been demonstrated. We propose a pixel design of TKIDs for observing CMB through atmospheric windows for observations in the 90/150 GHz bands. The TKIDs are designed to achieve photon noise limited sensitivity with overall noise equivalent power can be less than 20 aW/ √(Hz) . Silicon-rich silicon nitride is used as the dielectric of TKIDs, and Al is used as the inductance material. Two pairs of probes are designed on the pixel to divide the signal into two polarization directions. Orthogonal transducer and diplexer are used for signal conversion and frequency division. Assuming lossless dielectric, the coupling efficiency of a single pixel is around 90

We present a thermal kinetic inductance detector array design for CMB polarization observation at 90/150 GHz bands. A horn-coupled planar ortho-mode transducer is used for a broadband linear polarization separation. The frequency separation is done using a fast roll-off lumped-element diplexer. Thermal kinetic inductance detectors with Al is used as the detector. The array has more than 450 optical pixels with more than 1800 detectors. The array design and preliminary measurement results will be discussed.

In this article, high spatiotemporal resolution data obtained by the atmospheric density detector carried by China’s APOD satellite are used to study the hemispheric asymmetry of thermospheric density. A detailed analysis is first performed on the dual magnetic storm event that occurred near the autumnal equinox on 8 September 2017. The results show that the enhancement ratio of atmospheric density in the southern polar region (SPR) on the duskside was approximately 1.33–1.65 times that of the northern polar region (NPR), demonstrating a strong hemispheric asymmetry of thermospheric atmospheric density response during the magnetic storm. However, the asymmetry response was smaller on the dawnside, suggesting that the hemispheric density response asymmetry is related to local time (LT). The energy injection in high-latitude regions increases local atmospheric density and forms traveling atmospheric disturbances (TADs). TADs can propagate to low-latitude regions over several hours and affect the global distribution of thermospheric atmospheric density. Similarly, the geomagnetic index fitting slope of SPR relative density difference is greater than that of NPR. The SuperDARN convection pattern indicates that the plasma convection velocity of SPR is significantly greater than that of NPR, indicating that joule heating caused by neutral friction of ions in the Southern Hemisphere may be stronger. Subsequently, an analysis of annual solar activity and seasons was carried out on the thermospheric NPR, SPR atmospheric density, and their differences from December 2015 to December 2020. The results show that thermospheric atmospheric density decreases overall as the number of sunspots decreases. The differences between the NPR and SPR atmospheric densities in the thermosphere exhibits a noticeable annual periodicity. The NPR and SPR atmospheric densities appear to have different distribution characteristics in different seasons. The NPR density peak is mainly in March or April. In particular, the “double-peak” phenomenon occurred in 2017, with peaks in March and September, while the most obvious feature of SPR atmospheric density is that its minimum value occurs in the summer months of June and July. This paper reveals the annual, seasonal, and magnetic storm response characteristics of the hemispheric asymmetry of thermospheric atmospheric density, which has significant implications for the study of multilayer energy coupling of the magnetosphere–ionosphere–thermosphere.

Quadrupole mass spectrometers are widely used, and voltage scanning is their traditional working mode. By fixing the scanning voltage frequency and changing the value of the RF voltage, ions with different mass numbers can reach the detector in sequence, achieving ion selection. When analyzing high-mass molecules, several kilovolts of scanning voltage are required, which is not conducive to the miniaturization and safety of the instrument. By selecting the frequency of the scanning RF power supply and fixing the value of the RF power supply voltage, ion selection can be achieved by changing the frequency of the RF power supply, enabling miniaturized mass spectrometry analysis of high-mass molecules. In this paper, a high-speed gallium nitride driver circuit for frequency scanning mass spectrometry analysis is designed. The NCP51820 high-speed gate driver and INN650D140A gallium nitride MOS tube are selected to form a full-bridge driver, realizing a quadrupole rectangular wave RF power supply. The system has a maximum withstand voltage of 650 V and a frequency range of 400 K–4 MHz, allowing for scanning measurements of mass numbers ranging from 3 to 606 amu.

The longitudinal distribution of upper atmospheric density has been broadly studied. However, the studies mostly focused on 24 h averaged distribution. This study presents the longitudinal distribution of thermospheric density at dawn and dusk, using observations collected by the atmospheric density detector onboard the Chinese satellite APOD (Atmospheric Density Detection and Precise Orbit Determination) during low solar activity. The APOD observations show a significant relative longitudinal variation of thermospheric density with global maxima (Δρrmax) near the geomagnetic pole, especially in the winter hemisphere. The annual maximum of Δρrmax appears in the Southern Hemisphere around the June solstices and reaches 26.3% and 39.6% at dawn and dusk, respectively. The auroral heating and meridional wind might play a significant role in the longitudinal variation of thermospheric density. We further compare the APOD observations with the semi-empirical atmospheric model MSIS (Mass Spectrometer Incoherent Scatter Radar) 2.0 predictions under low solar activity conditions. The MSIS 2.0 model reproduces similar longitudinal variations to the observations, with hemispheric asymmetry. The longitudinal variation of thermospheric density from APOD should be related to the distribution of the atmospheric average molecular weight from the model. More observational data are needed to verify the results of this study further.

The response of thermosphere density to geomagnetic storms is a complicated physical process. Multi-satellite joint observations at the same altitude but different local times（LTs） are important for understanding this process; however, until now such studies have hardly been done. In this report, we analyze in detail the thermosphere mass density response at 510 km during the April23-24, 2023 geomagnetic storm using data derived from the TM-1（TianMu-1） satellite constellation and Swarm-B satellites. The observations show that there were significant LT differences in the hemispheric asymmetry of the thermosphere mass density during the geomagnetic storm. Densities observed by satellite TM02 at nearly 11.3 and 23.3 LTs were larger in the northern hemisphere than in the southern. The TM04 dayside density observations appear to be almost symmetrical with respect to the equator, though southern hemisphere densities on the nightside were higher. Swarm-B data exhibit near-symmetry between the hemispheres. In addition, the mass density ratio results show that TM04 nightside observations, TM02 data, and Swarm-B data all clearly show stronger effects in the southern hemisphere, except for TM04 on the dayside, which suggest hemispheric near-symmetry. The South-North density enhancement differences in TM02 and TM04 on dayside can reach 130%, and Swarm-B data even achieve 180% difference. From the observations of all three satellites, large-scale traveling atmospheric disturbances（TADs） first appear at high latitudes and propagate to low latitudes, thereby disturbing the atmosphere above the equator and even into the opposite hemisphere. NRLMSISE00 model simulations were also performed on this geomagnetic storm. TADs are absent in the NRLMSISE00 simulations. The satellite data suggest that NRLMSISE00 significantly underestimates the magnitude of the density response of the thermosphere during geomagnetic storms,especially at high latitudes in both hemispheres. Therefore, use of the density simulation of NRLMSISE00 may lead to large errors in satellite drag calculations and orbit predictions. We suggest that the high temporal and spatial resolution of direct density observations by the TM-1 constellation satellites can provide an autonomous and reliable basis for correction and improvement of atmospheric models.

Orbitrap mass spectrometers have been widely used in environmental component analysis . This paper presents an enhanced data acquisition system for in-situ detection of Orbitrap mass spectrometry, which enables in-suit real-time signal processing and analysis for atmospheric molecules with small mass numbers.During previous space atmospheric explorations, quadrupole mass spectrometry (QMS) was usually utilized for analyzing isotopic compositions and complicated compounds in the mixture. However, the inevitable ion scattering and drift during mass transfer, as well as the QMS attenuator loss, result in a relatively lower signal-to-noise ratio of the produced mass spectrum. In recent years, a novel mass spectrometer, called an Orbitrap mass spectrometer, has been gradually accepted and used because of its non-destructive detection ability, high mass resolution, and accuracy. Nevertheless, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is preferred over the Orbitrap mass spectrometry for ground applications, especially for detecting low-mass components (e.g. below 50 atomic mass units) due to the former’s superior resolution. As the mass number decreases, the detection system demands a higher sampling and processing rate. Additionally, in ground-based scenarios, mass spectrometry analysis software on computers is often employed to analyze the signals. Therefore, in order to achieve in-situ detection of the space atmospheric environment using the Orbitrap mass spectrometer, this paper proposes a real-time signal acquisition and processing system for mass spectrometry analysis. The system comprises of signal conditioning circuits, analog-to-digital conversion circuits, programmable logic circuits, and related software. These components perform spectrum analysis and process the signal in real-time on hardware components, allowing for high-speed acquisition and analysis of the signals produced by the Orbitrap mass spectrometer.

Orbitrap mass spectrometers have gained widespread popularity in ground-based environmental component analysis. However, their application in atmospheric exploration for space missions remains limited. Existing data acquisition solutions for Orbitrap instruments primarily rely on commercial systems and computer-based spectrum analysis. In this study, we developed a self-designed data acquisition solution specifically tailored for atmospheric molecule detection. The implementation involved directly integrating a spectrum analysis algorithm onto a field programmable gate array (FPGA), enabling miniaturization, real-time performance, and meeting the desired requirements. The system comprises signal conditioning circuits, analog-to-digital conversion (ADC) circuits, programmable logic circuits, and related software. These components facilitate real-time spectrum analysis and signal processing on hardware, enabling high-speed acquisition and analysis of signals generated by the Orbitrap. Experimental results demonstrate that the system can sample front-end analog signals at a rate of 25 MHz and differentiate signal spectra with an error margin of less than 7 kHz. This establishes the viability of the designed data acquisition system for atmospheric mass spectrometry analysis.

Chinese space station has entered its construction stage, starting a new journey of manned spaceflight. According to the operation requirements of Chinese space station, an atmospheric density multidirectional detector for the core module was independently developed to obtain density changes in spatial and temporal distribution at operating altitude. The detector could provide services of flight control management, precise positioning, and analysis for the space station and accumulate long-term autonomous detection data to provide basis for studying physical models and effects in neutral geospace environments. The atmospheric density detection for the core module of the space station was achieved by two atmospheric density multidirectional detectors that were symmetrically installed, each equipped with sensors in three directions. The basic working principle of the detector is as follows. The in-track gas inflow entered the sensor at high speed. According to the theory of molecular gas dynamics, the atmospheric density could be calculated from the pressure and temperature in the sensor. Furthermore, special techniques, e.g., nanoscale thermal cathode coating, were used to extend the working life of the detector beyond 15 years. This thesis mainly introduced the scientific objectives, payload configuration, and long-life design. In addition, preliminary results of in-situ detection were used to analyze the variations of atmospheric density on the operating orbit, showing the changes on the dayside and nightside orbits. The dayside and nightside peak-to-valley ratio during the quiet time of the space environment from September 11 to 14 and November 19 to 22, 2021, was between 2 and 3. During the strong geomagnetic storm on November 4, 2021, the measured peak atmospheric density increased to 1.966 times, whereas the peak model value increased to 1.483 times. The model of the geomagnetic storm recovery period was 6 h, while the measured data was 12 h later than model. During the geomagnetic storm event on March 13, 2022, the measured atmospheric density increased to 1.424 times, and the model value increased to 1.250 times. The global rise of atmospheric density began in the southern hemisphere and extended to the northern hemisphere, which was opposite the location of the disturbance source on November 4, 2021. According to statistics of six geomagnetic storm events in 2021 and 2022, the increase in the ratio of atmospheric density was positively related to the intensity and duration of the geomagnetic storm, and the maximum ratio could reach 96.6%. The disturbance source of atmospheric density varied its location with the injection position of energy particles, which might appear at the poles or near the equator. During the quiet time from December 11 to 31, 2021, the relative deviation between the measured value and the daily mean of the model was less than 10%. Compared to model, measured data exhibited a larger variation amplitude, wider propagation range, longer duration, more sensitive response, and smaller wave structures, which could reflect more abundant details in the change. The measured data would constitute a long-term independent database for the study of space environment physics and effects.

我国空间站已经进入建造阶段,开启了载人航天新征程.根据我国空间站试验任务需求,自主设计研制了空间站核心舱大气密度多向探测器,探测获取空间站运行高度上大气密度的时空分布变化,为空间站的飞控管理、精密定位和分析服务,并积累长期自主探测数据,为地球空间中性环境物理模式和效应研究提供基础数据.本文主要介绍了探测器的探测目标、载荷配置、长寿命设计等情况,同时使用在轨探测初步结果进行了运行轨道上大气密度的变化特性分析,呈现出日侧和夜侧轨道圈上大气密度变化, 2021年9月11～14日和11月19～22日空间环境平静期日侧和夜侧的峰谷比在2～3之间; 2021年11月4日的较强地磁暴期间实测大气密度峰值增加至1.966倍,而模式值峰值增加至1.483倍,磁暴恢复期模式为6 h,而实测数据晚12 h; 2022年3月13日的磁暴事件期间,实测大气密度增加至1.424倍,模式值增加至1.250倍,大气密度全球抬升从南半球开始,扩展到北半球,与2021年11月4日扰动源位置相反;统计了2021～2022年期间6次磁暴事件,大气密度抬升比例与磁暴强度、持续时间呈正相关; 2021年12月11～31日空间环境平静期,实测值和模式的日均值相对偏差小于10%.实测数据与模式数据相比,增变幅度大、传播范围广、持续时间长、响应更加灵敏.实测数据将为地球空间环境物理与效应研究提供长期自主数据库.

The spherical satellite is Chinese first spherical small satellite, integrating atmospheric composition, atmospheric density detection and precision orbit determination. The payload is the Orbital Atmosphere Detector, which was launched into a near-circular polar orbit with the orbit altitude of 520 km and an inclination angle of 97.4° on 14 October, 2021. The scientific objectives, operating principle and the ground calibration results of the Orbital Atmosphere Detector are presented in this paper. The preliminary in-situ observed results are analyzed and discussed. The observed mass densities are strongly correlated with F10.7 and Kp. The peak-tovalley ratio of observed mass densities during the quiet period of solar and geomagnetic activity on 3 November 2021 was 3.02; the peak of observed mass density increased from 2.8×10 -13 to 8.0×10 -13 kg/m~3 during the strong geomagnetic storm event on 4 November, 2021, an increase of 2.857 times compared to the MSIS00 model of 1.316 times. The observed data show that the increase in atmospheric density started at the South Pole and spread to the middle and low latitudes, while the MSIS00 model only shows a weak symmetrically increase between the northern and southern hemispheres during the storm. The observed results show that the observed data objectively reflect the spatial and temporal distribution of thermosphere density during the quiet period and the geomagnetic storm event, and thermosphere atmospheric model correction can be implemented based on a large amount of observed data.

The Meridian Project's sounding rocket mission uses a mass spectrometer to conduct in-situ atmospheric detection. In order to assess the influence of surface material outgassing and the attitude control jet on the spectrometer's detection, a sounding rocket platform was modeled and simulated. Using the physical field simulation software COMSOL and the Monte Carlo method, this study investigated whether the gas molecules from the two cases could enter the in-situ atmospheric mass spectrometer's sensor sampling port after colliding with the background atmosphere. The simulation results show that the influence of surface material outgassing on the in-situ atmospheric detection is very small, even under the conditions of medium solar activity and medium geomagnetic activity, while the influence of the attitude control jet on the in-situ atmospheric detection is large but can be reduced by reducing the low-altitude attitude control operation and decreasing the transmission probability. Through simulation optimization and according to engineering needs, increasing the nozzle outlet cross-sectional area, increasing the temperature of the gas used for attitude control, increasing the nozzle rotation angle, increasing the nozzle outlet angle, or increasing the nozzle center height can reduce the transmission probability. This model can simulate and analyze the influence of both surface material outgassing and attitude control jets on in-situ atmospheric detection, optimize relevant parameters, and provide new ideas for relevant work.

Atmospheric drag provides an indirect approach for evaluating atmospheric mass density, which can be derived from the Precise Orbit Determination (POD) of Low Earth Orbit (LEO) satellites. A method was developed to estimate nongravitational acceleration, which includes the drag acceleration of the thermospheric density model and empirical force acceleration in the velocity direction from the centimeter-level reduced-dynamic POD. The main research achievements include the study of atmospheric responses to geomagnetic storms, especially after the launch of the spherical Qiu Qiu (QQ)-Satellite (QQ-Satellite) with the global navigation system satellite (GNSS) receiver onboard tracking the Global Positioning System (GPS) and Beidou System (BDS) data. Using this derivation method, the high-accuracy POD atmospheric density was determined from these data, resulting in better agreement among the QQ-Satellite-derived densities and the NRLMSISE-00 model densities. In addition, the POD-derived density exhibited a more sensitive response to magnetic storms. Improved accuracy of short-term orbit predictions using derived density was one of the aims of this study. Preliminary experiments using densities derived from the QQ-Satellite showed promising and encouraging results in reducing orbit propagation errors within 24 h, especially during periods of geomagnetic activity.