Geocoronal imaging with Dynamics Explorer

The ultraviolet photometer of the University of Iowa spin-scan auroral imaging instrumentation on board the Dynamics Explorer-1 satellite has returned numerous images of the geocorona from altitudes of 570 km to 23,300 km. The geocoronal emissions viewed arise from the resonant scattering of solar lyman-alpha radiation by the neutral hydrogen atoms which make up the Earth's tenuous exosphere. The geocoronal observations from 1981 through 1984 are compared to a spherically symmetric isothermal Chamberlain model of the exospheric density distribution. Model parameters are varied to obtain an acceptable fit. The radiative transfer equation is solved numerically for this multiple-scattering problem. Stellar intensities are monitored for inflight-calibration of the DE-1 instrument. The solar Ly alpha flux is estimated through concurrent measurements made by the SME satellite, supplemented by published values of ground observable solar indices.