Measuring atmospheric density with X-ray occultation sounding

摘要

Astronomical X-ray sources provide opportunities for global remote sensing of the Earth’s atmosphere. We present a novel technique, complementary to other methods, that involves atmospheric occultation of celestial X-ray sources to measure the neutral density of the upper mesosphere and lower thermosphere in the 70- to 150-km region. These are the first such measurements in the 2- to 45-keV (～0.28–6.0 ?) passband, and the technique permits both dayside and nightside soundings. Measurements were made using the Unconventional Stellar Aspect (USA) experiment aboard the Advanced Research and Global Observation Satellite (ARGOS) and the Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) satellite. The data are time-tagged, energy-resolved photon extinction curves which provide sufficient information to determine the altitude profile of the neutral atmosphere. An ensemble of observations of the Crab Nebula and Cygnus X-2 were used to develop a “proof of concept” of this new technique, and results are presented for each source.