EXPLANATION OF SNAPSHOTS

The purpose of these plots is to show where the imagers on POLAR will be pointed at the Earth's surface within the next few weeks. Snapshots illustrates the the view of the Earth from Polar, with the VIS, UVI, and PIXIE field of views indicated. A snapshot of the Earth is generated at each slew manuever, followed by a snapshot halfway in time between the adjacent slew manuevers. Therefore, the snapshots alternate between times at slew manuevers and times halfway between slew manuevers. Twelve snapshots are given per plot, so one day requires 4 to 6 plots.

• The snapshot of the Earth at a slew manuever shows the fov of VIS, UVI and PIXIE just before the slew manuever (dashed lines ) and just after the slew manuever (solid lines). The snapshot of the Earth halfway in time between adjacent slew manuevers shows the fovs of the imagers at that time.
• Only the portions of the fovs that intersect the Earth's surface at an altitude of 120 km, spherical Earth approximation 1RE ==6378.14 km, are indicated. The UVI fov is circular, with a 4 degree halfwidth, and is shown in blue, the VIS fov is rectangular, +/-10 X +/-10 degrees, and is shown in red , and the PIXIE fov is rectangular, +/-20 X +/- 20 degrees, and is shown in yellow.
• NOTE:During the summer season the fov of VIS is that of the earth camera, and during the winter season the fov of VIS is that of the visable camera's.
• The blue asterisk is the center of the fov of UVI, the red rectangle is the center of the fov of VIS, and the yellow rectangle is the center of the fov of PIXIE.
• The vertical solid blue line is the intersection of the Polar orbital plane with the Earth's surface. The vertical dashed blue line is the intersection of the spin plane (platform plane) with the Earth's surface.
• For L>5 on the perigee pass the magnetic footprint is indicated on the Earth's surface by a red cross.
• The auroral ovals are shaded in orange and are determined from the Holzworth-Meng auroral oval model. The equatorward boundary of the auroral oval is determined by using a Qindex of 6 (high auroral activity), while the poleward boundary is determined by using a Qindex of 0 (low auroral activity).
• The average cusp location as determined by Newell et.al. [JGR,1991] is indicated by a black box that lies within the oval.
• The dawn-dusk terminator is located at 0 km altitude, determined by a spherical Earth approximation and neglecting the angular width of the Sun.
• In the lower left hand corner of each snapshot the time label in hr:min, and the polar radius in RE, and just above the time label the angle between the boresight and nadir direction are given.

Last updated on July 14, 1997