古生代旋回地层学与天文地质年代表

古生代是显生宙距今最为久远且持续时间最长的"代",发生了多次重大构造、气候和生命演化事件。高精度年代地层格架对于深入理解古生代地球演化历史极为关键。通过识别地层中由地球轨道力引起的米兰科维奇沉积旋回并开展调谐研究,可建立连续的、分辨率达0.02~0.4Ma天文年代标尺,并用于校正国际地质年代表。目前,国际地质年代表的中、新生代部分已基本完成天文年代的校正,但古生代部分尚未开展相关工作。近年来,人们在古生代地层中获得了可靠的、受高精度放射性绝对年龄约束的米兰科维奇旋回证据,并尝试建立天文年代标尺,表明建立古生代天文地质年代表具有良好的远景,是未来旋回地层学研究的前沿。本文简要介绍了旋回地层学的基本理论,系统总结了古生代旋回地层学研究成果及重要进展,并对未来研究提出展望。

气候环境变化的湖泊沉积学响应

湖泊沉积可作为气候和环境变化的信息库，它能提供时间分辨率高达百年至十年的气候变化信息。湖泊沉积能灵敏地反映与地球轨道力变化相关的气候效应，以及在此背景上叠加的非线性气候事件。湖泊沉积与其中的古生物组合、元素同位素组成是古气候环境的重要替代指标，为检验大气动力学气候模型和进一步改进模型。

On simulation of precise orbit determination of HY-2 with centimeter precision based on satellite-borne GPS technique

The HY-2 satellite carrying a satellite-borne GPS receiver is the first Chinese radar altimeter satellite, whose radial orbit determination precision must reach the centimeter level. Now HY-2 is in the test phase so that the observations are not openly released. In order to study the precise orbit determination precision and procedure for HY-2 based on the satellite- borne GPS technique, the satellite-borne GPS data are simulated in this paper. The HY-2 satellite-borne GPS antenna can receive at least seven GPS satellites each epoch, which can validate the GPS receiver and antenna design. What＇s more, the precise orbit determination processing flow is given and precise orbit determination experiments are conducted using the HY-2-borne GPS data with both the reduced-dynamic method and the kinematic geometry method. With the 1 and 3 mm phase data random errors, the radial orbit determination precision can achieve the centimeter level using these two methods and the kinematic orbit accuracy is slightly lower than that of the reduced-dynamic orbit. The earth gravity field model is an important factor which seriously affects the precise orbit determination of altimeter satellites. The reduced-dynamic orbit determination experiments are made with different earth gravity field models, such as EIGEN2, EGM96, TEG4, and GEMT3. Using a large number of high precision satellite-bome GPS data, the HY-2 precise orbit determination can reach the centimeter level with commonly used earth gravity field models up to above 50 degrees and orders.

Earth Gravity Field Recovered from CHAMP Science Orbit and Accelerometer Data

The earth gravity field model CDS01S of degree and order 36 has been recovered from the post processed Science Orbits and on-board accelerometer data of GFZ’s CHAMP satellite. The model resolves the geoid with an accuracy of better than 4 cm at a resolution of 700 km half-wavelength. By using the degree difference variances of geopotential coefficients to compare the model CDS01S with EIGEN3P, EIGEN1S and EGM96, the result indicates that the coefficients of CDS01S are most close to those of EIGEN3P. The result of the comparison between the accuracies of geopotential coefficients in the above models, indicates that the accuracy of coefficients in CDS01S is higher than that in EGM96.The geoid undulations of CDS01S and GGM01C up to 30 degrees are calculated and the standard deviation is 4.7 cm between them.

Reducing Influence of Gravity Model Error in Precise Orbit Determination of Low Earth Orbit Satellites

Based on the orbit integration and orbit fitting method, the influence of the characters of the gravity model, with different precisions, on the movement of low Earth orbit satellites was studied. The way and the effect of absorbing the influence of gravity model error on CHAMP and GRACE satellite orbits, using linear and periodical empirical acceleration models and the so-called "pseudo-stochastic pulses" model, were also analyzed.

Capabilities and Performance of S-band Semi-active Multi-static Small SAR Constellation for the Equatorial Region

The attractiveness of flying several SAR （synthetic aperture radar） satellites in a semi-active configuration has been proposed by several studies. The closest implementation of such a mission scenario is exemplified by the current Terra SAR-X and Tandem-X mission, where both spacecraft are identical monostatic platforms capable of operating in various modes. The bistatic operation mode of the Tandem-X mission is a basic form of the semi-active multi-static operation mode where one satellite serves as a transmitter while the other records the scattered signals simultaneously. The use of a typical monostatic SAR spacecraft operating in-tandem with several receiver only spacecraft is a semi-active mode of operation. This paper examines the capabilities of implementing a constellation of S-band spaceborne SAR platform for alongtrack interferometry over the equatorial region for velocity measurement with particular focus on ship detection. The orbit for the mission is an inclined circular low Earth orbit, which ensures high revisit time, quick coverage and high data throughput. The pendulum configuration is adopted to maintain the relative distance between successive SAR platforms. The conditions and constraints necessary to achieve the orbit geometry required to conduct alongtrack interferometry are defined. The alongtrack separation between platforms necessary to measure specified ship velocity is also discussed. Finally an error budget estimate of the measure radial velocity is provided.

GOCE kinematic orbit adjustment for EGM validation and accelerometer calibration

The main principle and mathematical model of GOCE kinematic orbit adjustment for Earth gravity field model （EGM） validation and accelerometer calibration are presented. Based on 60 days GOCE kinematic orbits with 1-2 cm accuracy and accelerometer data from 2009-11-02 to 2009-12-31, the RMS-of-fit （ROF） of them using EGM2008, EIGEN-SC, ITG- GRACE2010S and GOCO01S up to 120, 150 and 180 degree and order （d/o） are evaluated and compared. The scale factors and biases of GOCE accelerometer data are calibrated and the energy balance method （EBM） is performed to test the accuracy of accelerometer calibration. The results show that GOCE orbits are also sensitive to EGM from 120 to 150 d/o. The ROFs of EGMs with 150 and 180 d/o are obviously better than those of EGMs with 120 d/o. The ROFs of GOCO01S and ITG-GRACE2010S are almost the same up to 120 and 150 d/o, which are about 3.3 cm and 1.8 cm, respectively. They are far better than those of EGM2008 and EIGEN-SC with the same d/o. The ROF of GOCO01S with 180 d/o is about 1.6 em, which is the best one among those EGMs. The accelerometer calibration accuracies （ACAs） of ITG-GRACE2010S and GOCO01S are obviously higher that those of EGM2008 and EIGEN-SC. The ACA of GOCO01S with 180 d/o is far higher than that of EGMs with 120 d/o, and a little higher than that of ITG-GRACE2010S with 150 d/o. I t is suggested that the newest released EGM such as GOCO01S or GOCO02S till at least 150 d/o should be chosen in GOCE precise orbit determination （POD） and accelerometer calibration.

前寒武纪旋回地层学研究的进展与挑战

前寒武纪占据地质历史绝大部分时期,在大气成分、古气候、生命和超大陆聚散等方面表现出不同时间尺度的变化和演化。近年来人们在全球范围内前寒武纪地层中识别出大量可靠的米兰科维奇旋回记录。借助各类沉积旋回分析,有望建立地球早期演化高分辨率年代框架,获取行星轨道相互作用资料并重建天体动力史。本文在简要回顾旋回地层学理论方法的基础上,通过前寒武纪旋回地层学研究的主要范例,分析了原始气候替代性指标、重建天体动力模型、复杂气候模型和古地理不确定性等前寒武纪旋回地层学研究的关键问题和主要挑战,尝试性地提出了这些问题的解决思路。

Energetic electron flux distribution model in the inner and middle magnetosphere

Based on the magnetospheric kinetic theory, a model is developed to specify the flux of energetic electrons in the inner and middle magnetosphere. Under the assumption of adiabatic motion and isotropic particle distribution maintained by pitch-angle scattering, the model calculates the electron flux by following bounce-averaged electric field, gradient, and curvature drift in the time dependent electric and magnetic field, meanwhile it counts the electron loss caused by pitch angle scattering. Using the model, the clectron flux distribution during a magnetic storm was calculated and compared with the observation data from the geosynchronous orbit. It is shown that the model can successfully reproduce most of the major electron flux enhancements observed at the geosynchronous orbit and generally tracks the satellite data well. The rms errors of the modeled logarithm of flux are between 0.5-1.0.