New Measurement of the Vertical Atmospheric Density Profile From Occultations of the Crab Nebula With X‐Ray Astronomy Satellites Suzaku and Hitomi

We present new measurements of the vertical density profile Earth's atmosphere at altitudes between 70 and 200 km, based on Earth occultations Crab Nebula observed with X-ray Imaging Spectrometer onboard Suzaku Hard Imager Hitomi. spectral variation due to atmospheric absorption is used derive tangential column densities absorbing species, i.e., N O including atoms molecules, along line sight. The are then inverted obtain number density. data from 219 occultation scans low latitudes in both hemispheres September 15, 2005 March 26, 2016 analyzed generate a single, highly-averaged (in space time) profile. good agreement NRLMSISE-00 model, except for altitude range 70-110 where measured about 50% smaller than model. Such deviation consistent recent measurement SABER aboard TIMED satellite (Cheng et al. 2020). Given that model was constructed some time ago, decline could be radiative cooling/contracting upper as result greenhouse warming troposphere. However, we cannot rule out possibility NRL simply imperfect this region. also future prospects upcoming Japan-US astronomy satellite, XRISM, which will allow us measure composition unprecedented resolution dE ~ 5 eV 0.3-12 keV.