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
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.
Scott Boardsen, firstname.lastname@example.org
Last updated on July 14, 1997