近地空间环境的GNSS无线电掩星探测技术

从GPS/MET计划开始,基于GNSS的无线电掩星技术已成为一种强大的近地空间环境探测手段.截至到目前,已经有20多颗发射的低轨道卫星带GPS掩星接收机,其中COSMIC是首个专门用于掩星探测的卫星星座.这些掩星数据被广泛应用于气象预报、气候与全球变化研究、及空间天气监测和电离层研究.由于COSMIC的成功,相关合作单位目前正积极推动COSMIC-2计划,该计划将总共有12颗卫星,于2016年与2019年各发射6颗.COSMIC-2将携带一个高级的GNSS掩星接收机,它将接受GPS与GLONASS信号,并具备接受其他可获得信号源的能力(如中国北斗定位信号),其每日观测的掩星数量将是COSMIC的4~6倍.同时COSMIC-2还将携带两个空间天气载荷,加强空间天气的监测能力.本文以COSMIC与COSMIC-2计划为主线,对掩星的发展历史、技术要点进行了简单介绍,并简要综述了COSMIC取得的部分科学成果,同时对未来包括技术发展和众多的掩星观测进行了展望.

GNSS radio occultation technique for near-Earth space environment detection

Since the GPS/MET mission, Global Navigation Satellite System (GNSS) based radio occultation (RO) technique has been a powerful technique to detect the near Earth's space environment. Up to date, there has been more than 20 launched low Earth orbit satellites equipped with GPS RO receiver, with COSMIC was the first constellation dedicated for RO. These RO data are widely used in numerical weather prediction, climate and global change, and space weather monitoring and ionospheric research. With the success of COSMIC, the corresponding partners are moving forward with a follow-on RO mission, named COSMIC-2, which will ultimately place 12 satellites in orbit with two launches approximately in 2016 and 2019, respectively. Each COSMIC-2 satellite will carry an advanced GNSS RO receiver that will track both GPS and GLONASS signals, with capability for eventually tracking other GNSS signals from such as the Chinese BeiDou and European Galileo system, as well as two secondary space weather payloads to enhance space weather monitoring. COSMIC-2 will provide 4~6 times the number of atmospheric and ionospheric observations that were tracked with COSMIC. In this article we will focus on COSMIC/COSMIC-2, discuss the history of RO and some key technique issue,and review some scientific achievements. In addition, we will look into the future of RO technique including technique improvement and multiple RO missions of opportunity.