The global characteristics and trends of the tropopause physical parameters,height and temperature,obtained from the GPS/CHAMP radio occultation(RO) data in the period from Jul.2001 to Oct.2008,were modeled and analyzed in this work.The global distribution and variation of these parameters with latitude were estimated and analyzed using the Empirical Orthogonal Function(EOF),which was introduced to reveal the possible relationship between the tropopause variations and global climate change.The tropopause height and temperature varied with latitude.The results obtained by using the Empirical Orthogonal Function analysis suggested a recent rise in tropopause height and decrease in tropopause temperature;and also partly supported the argument that the global rise in the tropopause is consistent with global climate change.These results also revealed that the tropopause height increased mainly in the Polar regions,particularly in the South Polar region,as well as the regions where human activity is relatively significant,and decreased in the areas that are sparsely populated or have less human activity,such as the tropic region and south hemisphere.This paper also confirms that the GPS/LEO RO data are more reliable and can be effectively used to analyze the tropopause physical parameters.
Previous analyses showed a clear asymmetry in the topography,geological material distribution,and crustal thickness between the nearside and farside of the Moon. Lunar detecting data,such as topography and gravity,have made it possible to interpret this hemisphere dichotomy. The high-resolution lunar topographic model CLTM-s01 has revealed that there still exist four unknown features,namely,quasi-impact basin Sternfeld-Lewis (20°S,232°E),confirmed impact basin Fitzgerald-Jackson (25°N,191°E),crater Wugang (13°N,189°E) and volcanic deposited highland Yutu (14°N,308°E). Furthermore,we analyzed and identified about eleven large-scale impact basins that have been proposed since 1994,and classified them according to their circular characteristics.
The lunar Apennines,located in the southeast of Mare Imbrium,is the largest range on the Moon. The gravity anomalies on profiles across the mountains reveal evidence of a great fault zone characteristic. The deep crustal structures of lunar Apennines are analyzed on the basis of topographic data from Chang'E-1 satellite and gravity data from Lunar Prospector. The inverted crust-mantle models indicate the presence of a lithosphere fault beneath the mountains. Inverted results of gravity and the hypothe-sis of lunar thermal evolution suggest that the lunar lithosphere might be broken ～3.85 Ga ago due to a certain dynamic lateral movement and compression of lunar lithosphere. This event is associated with the history of magma filling and lithosphere deformation in the mountain zone and adjacent area. Moreover,the formation and evolution of Imbrium basin impose this effect on the process.
In the Chinese lunar exploration project,the Chang'E-1 (CE-1) satellite was jointly monitored by the United S-band range and Doppler and the VLBI technique. A real-time reduction of the tracking data is realized to deduce the time series of the instantaneous state vectors (ISV) (position and velocity vec-tors) of the CE-1 satellite,and is applied to the orbital monitoring of pivotal arcs. This paper introduces this real-time data reduction method and its application to the orbital monitoring of pivotal arcs of the CE-1 satellite in order to serve as a source of criticism and reference.
The same-beam VLBI observations of Rstar and Vstar,which were two small satellites of Japanese lunar mission,SELENE,were successfully performed by using Shanghai and Urumqi 25-m telescopes. When the separation angle between Rstar and Vstar was less than 0.1 deg,the differential phase delay of the X-band signals between Rstar and Vstar on Shanghai-Urumqi baseline was obtained with a very small error of 0.15 mm rms,which was reduced by 1-2 order compared with the former VLBI results. When the separation angle was less than 0.56 deg,the differential phase delay of the S-band signals was also obtained with a very small error of several mm rms. The orbit determination for Rstar and Vstar was performed,and the accuracy was improved to a level of several meters by using VLBI and Doppler data. The high-accuracy same-beam differential VLBI technique is very useful in orbit determination for a spacecraft,and will be used in orbit determination for Mars missions of China Yinghuo-1 and Russia Phobos-grunt.
The Mars Advanced Radar for Subsurface and Ionosphere Sounding(MARSIS) onboard the Mars Express(MEX) spacecraft started to collect data of the Martian topside ionosphere from May,2005.By now a large amount of ionograms has been obtained.It is important to extract vertical ionospheric information effectively from the ionograms for further study.In this paper a new method,Object Tracking Method(OTM),is proposed to automatically extract the ionospheric electron density profiles by computer.This method is based on three algorithms,namely the Hough transform,region growing segmentation algorithm and moving objects detection method from video sequences.In processing ionosphere echoes are treated as moving objects.The identification ratio of OTM for the MARSIS ionograms is estimated to be around 90%.
Like other optical astrometric techniques,the Photographic Zenith Tube(PZT) has played a key role in the past observations of the Earth rotation,and it also has a potential to be applied to several other observations by taking advantage of automatic observations with self compensation of tilt of the tube.We here propose In-situ Lunar Orientation Measurement(ILOM) to study lunar rotational dynamics by direct observations of the lunar rotation from the lunar surface by using a small telescope like PZT with an accuracy of 1 milli-seconds of arc(1 mas) in the post-SELENE mission.Our second application is to obtain local gravity field on the Earth by combining deflection of the vertical measured by PZT and the position measured by Global Positioning System(GPS) or Global Navigation Satellite System(GNSS).The accuracy required for this purpose is not as strict as ILOM.We have already developed a Bread Board Model(BBM) of the telescope for ILOM and made some experiments in order to know the performance of the driving mechanism under a similar condition to the lunar environment showing high vacuum,large temperature change and dusty condition.We have also shown that it is possible to correct the effects of uniform temperature change upon the optical system by using a simple model with an accuracy of better than 1 mas.This model has the potential to attain the accuracy of 1 mas,based on the results of the experiments and the simulations.
Using eight years of time-variant gravity measurements from the GRACE gravity satellite mission, we estimate monthly terrestrial water storage variations in the North China Plain between August 2002 and August 2010. We find that during this period, the water storage is not constant but accelerate at a rate of -1.1 cm/yr over time. The study confirms that the relatively long-term trend of water storage in the North China Plain (by 13-point moving average) is consistent well with that by linear fitting. Two hydrological models, CPC and GLDAS, are adopted in calculating surface water variations, with results indicating that they agree with those of GRACE. Furthermore, rates of -0.6 cm/yr for surface water variations and -0.5 cm/yr for groundwater variations are found in the North China Plain during the study period. Decrease of rainfall and the groundwater over-exploitation are possibly the main causes for groundwater depletion in the North China Plain. The results will be helpful for better understanding climatic changes and provide reference for the management of water resources and the establishment of policies on preventing and alleviating natural hazards.
