A future constellation of at least four geomagnetic satellites(designated Macao Scientific Satellite-1(MSS-1)and Macao Scientific Satellite-2(MSS-2))was recently proposed,to continue high-quality geomagnetic observations in the post-Swarm period,focusing especially on collecting data that will provide a global,three-dimensional survey of the geomagnetic field.In this paper,we present a simulation of two years of orbits(2020.01.01-2022.01.01)of two satellites(tentatively denoted as MSS-2)that are constellated in elliptical(200×5,300 km)low-perigee orbits.By comparing error variances of Gauss coefficients,we investigate the sensitivity of lithospheric magnetic field modelling to data collected from various satellite orbits,including a near circular reference orbit of 300×350km,and elliptical orbit of 180×5,300 km,220×5,300 km,200×3,000 km and 200×1,500 km.We find that in two years the two MSS-2 satellites can collect 35,000 observations at altitude below 250 km,data that will be useful in advancing the quality of lithospheric magnetic field modelling;this number of observations reflects the fact that only 4.5%of the flight time of these satellites will be below250 km(just 6.4%of their flight time below 300 km).By combining observations from the MSS-2 satellites’elliptical orbits of 200×5,300km with observations from a circular reference orbit,the variance of the geomagnetic model can be reduced by a factor of 285 at spherical harmonic degree n=200 and by a factor of 1,300 at n=250.The planned lower perigee of their orbits allows the new satellites to collect data at unprecedentedly lower altitudes,thus dramatically improving the spatial resolution of satellite-derived lithospheric field models,(up to 80%at n=150).In addition,lowering the apogee increases the time interval during which the satellites fly at near-Earth altitudes,thus improving the model predictions at all spherical harmonic degrees(around 52%-62%at n=150).The upper limit of the expected improvement to the field model at the orbital apogee is
For the final stage of a launch vehicle which cannot start multiple times,the main constraint of a highly eccentric orbit launch mission is the argument of perigee,which is conditioned by the range.This paper studies the payload capacity at different launch sites for a highly eccentric orbit(e.g.GTO)and gives a method to improve the payload capacity with an argument of perigee constraint by increasing the sliding time before the final ignition and simultaneously adjusting the launch azimuth and yaw at the final stage.An example of launching to GTO orbit on a rocket from Hainan is given,which proves that the method has strong engineering value.
目的:评价Perigee系统治疗女性前盆腔器官脱垂的安全性及临床疗效。方法 :对24例盆腔器官脱垂定量系统(pelvic organ prolapse-quantitation,POP-Q)诊断为Ⅱ度或以上的前盆腔器官脱垂患者行Perigee前盆底重建术,采用主观评价[盆底功能障碍影响问卷简版(PFIQ-7)、性生活质量问卷]和客观评价(POP-Q)对围手术期及术后近期各项指标的变化及并发症发生情况进行分析。结果:24例患者的平均手术时间(70.83±15.30)min,术中平均出血(80.92±40.39)ml,术后中位随访时间为4个月。以POP-Q评分作为客观疗效评价指标,治愈率为100%;PFIQ-7评分较术前有显著改善;术后1例有性生活,性生活质量无明显下降。术后发生网片暴露1例(4.2%);新发压力性尿失禁2例(8.4%);会阴部、臀部疼痛4例(16.7%);新发阴道后壁脱垂3例(12.6%);无严重并发症发生。结论:Perigee系统是治疗前盆腔脏器脱垂的安全、微创术式,近期疗效肯定,中远期疗效待进一步随访。
