The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the g...The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of Bei Dou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites,including two Inclined Geosynchronous Orbit satellites(IGSO) and three MEO satellites, was established between 2015 and2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link(ISL) based on Ka-band signals with time-division multiple addresses(TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto-noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space,time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional Bei Dou satellite navigation system(BDS-2). At last, the performances of positioning, navigation and timing(PNT) of the future Bei Dou global system(BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.展开更多
基金supported by National Key R&D Program of China (Grant Nos. 2016YFB0501700, 2016YFB0501701)National Natural Science Foundation of China (Grant No. 41374019)
文摘The first two Medium Earth Orbit(MEO) satellites of the third generation of Bei Dou satellite navigation System(BDS-3) were successfully launched on November 5, 2017. This historical launch starts the new era of the global navigation satellite system of Bei Dou. Before the first two satellites of BDS-3, a demonstration system for BDS-3 with five satellites,including two Inclined Geosynchronous Orbit satellites(IGSO) and three MEO satellites, was established between 2015 and2016 for testing the new payloads, new designed signals and new techniques. In the demonstration system, the new S frequency signal and satellite hydrogen clock as well as inter-satellite link(ISL) based on Ka-band signals with time-division multiple addresses(TDMA) were tested. This paper mainly analyzes the performances of the demonstration system, including the signalto-noise ratios, pseudorange errors and the multipath errors of the civilian signals of BDS-3. The qualities of signals in space,time synchronization and timing precision were tested as well. Most of the performances were compared with those of the regional Bei Dou satellite navigation system(BDS-2). At last, the performances of positioning, navigation and timing(PNT) of the future Bei Dou global system(BDS-3) were evaluated based on the signal quality of the present demonstration satellite system.
文摘针对烟粉虱Bemisia tabaci(Gennadius)、温室白粉虱Trialeurodes vaporariorum(Westwood)、黑刺粉虱Aleurocanthus spiniferus(Quaintance)、桑粉虱Pealius mori(Takahashi)、禾粉虱Aleurocybotus indicus David etSubramaniam等粉虱害虫在我国暴发危害的现状,公益性行业科研专项"粉虱类害虫可持续治理技术研究与集成示范"项目组在华南、华东、华北、华中和西南等地区开展了粉虱类害虫的调查、监测、预警以及综合防控技术研究集成与示范。结果表明,烟粉虱在我国的发生区域超过20个省份,温室白粉虱在华北和西南地区,黑刺粉虱在华南、华东和西南地区也分布较广,桑粉虱在我国南方桑植区危害严重,禾粉虱在福建省闽东稻区发生为害逐年严重。利用mt COI DNA测序、SCAR技术和CAPS等技术对B和Q型烟粉虱的鉴定结果显示,Q型烟粉虱在我国的分布范围正在不断扩大。通过Maxent预测模型和GIS技术,预测了烟粉虱在我国的适生区、自然越冬北线和不同地区的发生世代数量。对烟粉虱的抗药性监测结果表明,阿维菌素和烯啶虫胺是目前华北地区防治烟粉虱较为理想的药剂,而对联苯菊酯、噻虫嗪、啶虫脒和吡虫啉等药剂均产生了不同程度的抗药性。研究了苘麻诱集、黄板诱杀、天敌昆虫和病原微生物对粉虱类害虫的控制作用,并在华南、华东、华北、华中和西南等地区建立了12个示范基地,分别在不同地区开展了粉虱类害虫的综合防治技术的示范和推广,累计印刷技术宣传手册12.4万份,培训各类农民和基层农技人员5.43万人次,累计示范面积4.3千公顷次,技术辐射超过4万公顷次,取得了显著的经济、社会和生态效益。
