超低轨道热层大气密度原位探测

In-situ measurement of atmospheric density in very low Earth orbits

超低轨道(VLEO)由于其轨道较低,在该轨道运行的航天器在对地观测、科学研究方面具有独特优势,但对该轨道的大气密度变化特性认知不足。在阐述国内外超低轨道大气密度原位探测发展历史及现状的基础上,总结了现有超低轨道大气密度原位探测技术,对中国超低轨道大气密度原位结果进行了初步分析和讨论。结果表明:在2020年10月空间环境平静期,250 km和350 km高度大气密度相差一个量级;升降轨期间,超低轨道大气密度每千米分别下降0.025×10^(-12) kg/m^(3)和0.041×10^(-12) kg/m^(3),均小于模式值的0.5倍;北纬40°时,处于午夜的升轨段(约250 km)大气密度是处于正午的降轨段(约420 km)大气密度的11.2倍,高度的影响大于地方时的影响;不同纬度下,实测日均值和模式日均值的比值从高纬的0.49降为低纬的0.39,模式值偏大。在超低轨道上,实测值总体上比模式值小,可为大气物理研究和应用研究提供基础数据。

Very low Earth orbit(VLEO)has unique advantages in Earth observation and scientific re-search due to their low orbital altitude;however,the knowledge of the atmospheric density variation in these orbits is insufficient.A preliminary analysis and discussion of the in-situ results of atmospheric density in VLEOs in China is carried out,based on the description of the history and current status of in-situ exploration of VLEO atmospheric density,and on the summary of the existing in-situ detection techniques of atmospheric density.The results show one order of magnitude difference in atmospheric density between 250 km and 350 km altitudes during the quiet period of the space environment in October 2020.During the orbit ascent and descent,the atmospheric density of VLEOs decreases by 0.025×10^(-12) kg/m^(3) and 0.041×10^(-12) kg/m^(3) per kilometer,respectively,each 0.5 times less than that of the NRLMSISE00 model.At 40°N,the atmos-pheric density in the ascending section at midnight(~250 km)is 11.2 times higher than that in the descending section at noon(~420 km),and the effect of altitude is greater than that at local time.At different latitudes,the daily mean ratio of the observed values to the model values decreases from 0.49 at high latitudes to 0.39 at low latitudes,with the NRLMSISE00 model values being larger.At the VLEO,the observed values are generally smaller than the NRLMSISE00 model values,which can provide basic data for atmospheric physical studies and applied research.