by Scott Boardsen
The following illustrations have been created to aid in the development of the long term science plan and the polar despun platform planning. They illustrate how the oval view will change on a seasonal and on an hourly basis. Each plot illustrates the oval position at a viewpoint above the geographic pole in one hemisphere at 2 hour intervals (12 illustrations per plot). Plots were created for the first day and the 15th day of each month for both the Northern and Southern hemispheres, yielding fourty eight plots in all for the entire year.
The Holzworth and Meng model of Auroral Oval (GRL Sept 75, vol.2,no.9,pg. 377) was used to determine the oval position. The cusp was based on the cusp study of Newell and Meng (JGR,vol.93,no.a12,pg.14,549). The oval position computed in corrected geomagnetic coordinates was transformed to geographic coordinates and plotted, using IGRF coefficients for year 1995 to transform from corrected geomagnetic coordinates to geographic coordinates. The equatorward edge of the oval was computed for high geomagnetic activity (Q-index of 6), and the poleward edge of the oval was computed for low geomagnetic activity (Q-index of 0).
The darkened side of the image corresponds to the nightside of the Earth. The terminator was computed at a 0 km altitude. The blue trace is the intersection of the polar orbital plane with the Earth's surface at the indicated UT. The orbit normal used in computations has GEI components of [0.43, -0.90, 0.067]. It is assumed that the variation in the orbit normal is negligible over the course of an year. This trace also corresponds the bore sight viewing of Earth's surface by the imagers, whose degree of freedom lies in the orbital plane.
The GIF images are located here.
The postscript files can be obtained by: