The perturbations of low earth orbit(LEO)satellites operating in the orbit of 300~2000 km are complicated.In particular,the atmospheric drag force and solar radiation pressure force change rapidly over a short period ...The perturbations of low earth orbit(LEO)satellites operating in the orbit of 300~2000 km are complicated.In particular,the atmospheric drag force and solar radiation pressure force change rapidly over a short period of time due to solar activities.Using spaceborne global positioning system(GPS)data of the CHAMP,GRACE and SWARM satellites from 2002 to 2020,this paper studies in depth the influence of solar activity on LEO satellites’precise orbit prediction by performing a series of orbit prediction experiments.The quality of GPS data is more susceptible to being influenced by solar activity during years when this activity is high and the changes in dynamic parameters are consistent with those of solar activity.The effects of solar activity on LEO orbit prediction accuracy are analyzed by comparing the predicted orbits with the precise ones.During years of high solar activity,the average root-mean-squares prediction errors at 10,20,and 30 minutes are 0.15,0.20,and 0.26 m,respectively,which are larger than the corresponding values in low-solar-activity years by 59%,63%,and 68%,respectively.These results demonstrate that solar activity has a great influence on the orbit prediction accuracy,especially during high-solar-activity years.We should strengthen the real-time monitoring of solar activity and geomagnetic activity,and formulate corresponding orbit prediction strategies for the active solar period.展开更多
The solar flare is a sudden eruptive solar phenomenon with significant enhancements in solar X-ray and Extreme Ultraviolet radiations,resulting in large amounts of energy being injected into the planetary atmosphere.C...The solar flare is a sudden eruptive solar phenomenon with significant enhancements in solar X-ray and Extreme Ultraviolet radiations,resulting in large amounts of energy being injected into the planetary atmosphere.Case studies have been extensively presented to analyze the effect of extremely large flares on the Martian upper atmosphere,but the general features of the Martian thermospheric response to flares are still poorly understood.In this work,we select 12 intense solar flares that occurred between 2015 and 2017 and investigate the densities and compositional variations of the dayside Martian thermosphere to these flares with the aid of the measurements made by the Mars Atmosphere and Volatile EvolutioN.The statistical studies indicate that the responses of the Martian thermosphere to flares are complicated that both the class of the flare and the wavelength of the enhanced radiation may have prominent influences on the thermal expansion of the atmosphere and the atmospheric photochemical reactions.展开更多
We present a new optical transmission spectrum of the hot Jupiter HAT-P-32Ab acquired with the Carnegie Observatories Spectrograph and Multiobject Imaging Camera(COSMIC) on the Palomar 200 inch Hale Telescope(P200).Th...We present a new optical transmission spectrum of the hot Jupiter HAT-P-32Ab acquired with the Carnegie Observatories Spectrograph and Multiobject Imaging Camera(COSMIC) on the Palomar 200 inch Hale Telescope(P200).The P200/COSMIC transmission spectrum,covering a wavelength range of 3990–9390 A,is composed of 25 spectrophotometric bins with widths ranging from 200 to 400 A and consistent with previous transit measurements obtained in the common wavelength range.We derive a combined optical transmission spectrum based on measurements from five independent instruments,which,along with the 1.1–1.7 μm spectrum acquired by the Hubble Space Telescope and two Spitzer measurements,exhibits an enhanced scattering slope blueward of a relatively flat optical continuum,a water absorption feature at 1.4 μm,and a carbon dioxide feature at 4.4 μm.We perform Bayesian spectral retrieval analyses on the 0.3–5.1 μm transmission spectrum and find that it can be well explained by a two-limb approximation of 134_(-33)^(+45)×solar metallicity,with a strongly hazy morning limb of 1134_(-194)^(+232) K and a haze-free evening limb of 1516_(-44)^(+33) K.This makes HAT-P-32Ab a promising target for James Webb Space Telescope to look for asymmetric signatures directly in the light curves.展开更多
The nearby bright M-dwarf star L 98–59 has three terrestrial-sized planets.One challenge remaining in characterizing atmospheres around such planets is that it is not known a priori whether they possess any atmospher...The nearby bright M-dwarf star L 98–59 has three terrestrial-sized planets.One challenge remaining in characterizing atmospheres around such planets is that it is not known a priori whether they possess any atmospheres.Here we report on study of the atmospheres of L 98–59 c and L 98–59 d using near-infrared spectral data from the G141 grism of Hubble Space Telescope(HST)/Wide Field Camera 3.We can reject the hypothesis of a clear atmosphere dominated by hydrogen and helium at a confidence level of ~3σ for both planets.Thus they could have a primary hydrogen-dominated atmosphere with an opaque cloud layer,or could have lost their primary hydrogen-dominated atmosphere and re-established a secondary thin atmosphere,or have no atmosphere at all.We cannot distinguish between these scenarios for the two planets using the current HST data.Future observations with the James Webb Space Telescope would be capable of confirming the existence of atmospheres around L 98–59 c and d and determining their compositions.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.12173072 and 12103077)。
文摘The perturbations of low earth orbit(LEO)satellites operating in the orbit of 300~2000 km are complicated.In particular,the atmospheric drag force and solar radiation pressure force change rapidly over a short period of time due to solar activities.Using spaceborne global positioning system(GPS)data of the CHAMP,GRACE and SWARM satellites from 2002 to 2020,this paper studies in depth the influence of solar activity on LEO satellites’precise orbit prediction by performing a series of orbit prediction experiments.The quality of GPS data is more susceptible to being influenced by solar activity during years when this activity is high and the changes in dynamic parameters are consistent with those of solar activity.The effects of solar activity on LEO orbit prediction accuracy are analyzed by comparing the predicted orbits with the precise ones.During years of high solar activity,the average root-mean-squares prediction errors at 10,20,and 30 minutes are 0.15,0.20,and 0.26 m,respectively,which are larger than the corresponding values in low-solar-activity years by 59%,63%,and 68%,respectively.These results demonstrate that solar activity has a great influence on the orbit prediction accuracy,especially during high-solar-activity years.We should strengthen the real-time monitoring of solar activity and geomagnetic activity,and formulate corresponding orbit prediction strategies for the active solar period.
基金supported by the Guangdong Basic and Applied Research Foundation through Grant 2021A1515110271。
文摘The solar flare is a sudden eruptive solar phenomenon with significant enhancements in solar X-ray and Extreme Ultraviolet radiations,resulting in large amounts of energy being injected into the planetary atmosphere.Case studies have been extensively presented to analyze the effect of extremely large flares on the Martian upper atmosphere,but the general features of the Martian thermospheric response to flares are still poorly understood.In this work,we select 12 intense solar flares that occurred between 2015 and 2017 and investigate the densities and compositional variations of the dayside Martian thermosphere to these flares with the aid of the measurements made by the Mars Atmosphere and Volatile EvolutioN.The statistical studies indicate that the responses of the Martian thermosphere to flares are complicated that both the class of the flare and the wavelength of the enhanced radiation may have prominent influences on the thermal expansion of the atmosphere and the atmospheric photochemical reactions.
基金the support by the B-type Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the National Natural Science Foundation of China(Grant Nos.42075122 and 12122308)+2 种基金Youth Innovation Promotion Association CAS(2021315)the Space debris and NEO research project(Grant Nos.KJSP2020020204 and KJSP2020020102)Civil Aerospace pre-research project(Grant No.D020304)。
文摘We present a new optical transmission spectrum of the hot Jupiter HAT-P-32Ab acquired with the Carnegie Observatories Spectrograph and Multiobject Imaging Camera(COSMIC) on the Palomar 200 inch Hale Telescope(P200).The P200/COSMIC transmission spectrum,covering a wavelength range of 3990–9390 A,is composed of 25 spectrophotometric bins with widths ranging from 200 to 400 A and consistent with previous transit measurements obtained in the common wavelength range.We derive a combined optical transmission spectrum based on measurements from five independent instruments,which,along with the 1.1–1.7 μm spectrum acquired by the Hubble Space Telescope and two Spitzer measurements,exhibits an enhanced scattering slope blueward of a relatively flat optical continuum,a water absorption feature at 1.4 μm,and a carbon dioxide feature at 4.4 μm.We perform Bayesian spectral retrieval analyses on the 0.3–5.1 μm transmission spectrum and find that it can be well explained by a two-limb approximation of 134_(-33)^(+45)×solar metallicity,with a strongly hazy morning limb of 1134_(-194)^(+232) K and a haze-free evening limb of 1516_(-44)^(+33) K.This makes HAT-P-32Ab a promising target for James Webb Space Telescope to look for asymmetric signatures directly in the light curves.
基金the financial support from the National Key R&D Program of China(2020YFC2201400)National Natural Science Foundation of China(NSFC,Grant Nos.12073092,12103097,and 12103098)+5 种基金the science research grants from the China Manned Space Project(No.CMS-CSST-2021-B09,B12)Guangzhou Basic and Applied Basic Research Program(202102080371)the Strategic Priority Program on Space Science,the Chinese Academy of Sciences(Grant No.XDA15020601)China Postdoctoral Science Foundation(No.2020M672936)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University,Hainan Provincial Natural Science Foundation of China under Grant No.122RC546the National Natural Science Foundation of China under grant Nos.12063001。
文摘The nearby bright M-dwarf star L 98–59 has three terrestrial-sized planets.One challenge remaining in characterizing atmospheres around such planets is that it is not known a priori whether they possess any atmospheres.Here we report on study of the atmospheres of L 98–59 c and L 98–59 d using near-infrared spectral data from the G141 grism of Hubble Space Telescope(HST)/Wide Field Camera 3.We can reject the hypothesis of a clear atmosphere dominated by hydrogen and helium at a confidence level of ~3σ for both planets.Thus they could have a primary hydrogen-dominated atmosphere with an opaque cloud layer,or could have lost their primary hydrogen-dominated atmosphere and re-established a secondary thin atmosphere,or have no atmosphere at all.We cannot distinguish between these scenarios for the two planets using the current HST data.Future observations with the James Webb Space Telescope would be capable of confirming the existence of atmospheres around L 98–59 c and d and determining their compositions.
