Proposed Priority Science Operations Topic
SPOT No. 8: Topic 'Observations of Comet Hale-Bopp'
Goal: To utilize the imagers on the Polar spacecraft to observe Comet
Hale-Bopp during its closest approach to the Sun. We have a unique
opportunity to observe Comet Hale-Bopp over a broad range of wavelengths
from the visible to near ultraviolet to far ultraviolet to soft x-rays.
It is extremely fortuitous that Comet Hale-Bopp crosses the orbital plane
of the Polar spacecraft on approximately April 2, 1997. This is within a
few days of its closest approach to the Earth (March 22-23, 1997) and
within a day of its perihelion (April 1, 1997). As a consequence, Polar
spacecraft attitude re-orientations will not be required.
For the period (Year/Day of Year) 97/086 to 97/092, the Polar
platform should be pointed to allow observations of Comet Hale-Bopp for 1
hour of each orbit. These 1 hour observation periods should occur near
apogee to eliminate the need for platform slews during the observation
period and allow sufficient time to acquire images that can be summed to
obtain maximum sensitivity. The ephemeris
of Comet Hale-Bopp is available.
POLAR DATA REQUIRED
VIS will be operated to obtain a complete set of images in 11 different
wavelengths during each observation period. UVI and PIXIE should be
operated in the mode that is most appropriate to achieve the maximum
POLAR De-Spun PLATFORM OPERATIONS
A test run to verify pointing and camera operations will occur on 97/084.
Observation of Comet Hale-Bopp will begin on 97/086 and continue through
97/092. The following table contains the current plan for Comet Hale-Bopp
observations with the imaging instruments on the Polar spacecraft where
long - the angle between the comet(sun) direction and nadir direction
projected into the platform plane
lat - the angle between the comet(sun) direction and the anti-spin axis
vector. NOTE: in this coordinate system UVI has a 'lat' offset of
angle sun-comet - is the angle between the comet and the sun from the Polar
POLAR apogee Comet Sun ANGLE Centered on
time long lat long lat Sun-Comet Apogee time
yydddhhmm (deg.) (deg.) (deg.) (deg.) (deg.) (minutes) Comments
970840151 134.0 12.4 88.3 20.0 44.4 60 Test Run
970860642 133.6 8.6 89.4 18.0 43.9 60 Begin Comet
970870018 133.5 7.3 89.8 17.4 43.7 60 Observations
970871757 133.2 6.1 90.0 16.7 43.5 60
970881133 133.1 4.8 90.4 16.1 43.3 60
970890509 133.0 3.6 90.9 15.4 43.1 30 Short run*
970892245 133.0 2.3 91.3 14.8 42.9 30 Short run*
970901624 132.7 1.1 91.5 14.1 42.7 60
970911000 132.6 -0.1 91.9 13.4 42.5 60
970920336 132.5 -1.3 92.4 12.8 42.3 30 Short run*
970922112 132.4 -2.5 92.7 12.1 42.1 60 End Comet
* Short runs (30 minutes as opposed to 60 minutes) are due to overall
mission science constraints.
A plot of the comet latitude vs.
DOY is available.
Investigator: John B. Sigwarth
The University of Iowa
Department of Physics and Astronomy
Iowa City IA 52242-1479