Observations of Comet Hale-Bopp

with the Imagers on the Polar spacecraft

Topic Description

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 April 1, 1997. This is on the day of its perihelion (April 1, 1997) and within a 10 days of its closest approach to the Earth (March 22, 1997). As a consequence, Polar spacecraft attitude re-orientations will not be required. Examples of up-to-date images of Comet Hale-Bopp obtained with ground-based telescopes are available at the Comet Hale-Bopp Home Page or at the Comet Hale-Bopp Home Page mirrored site both maintained at JPL.

Epoch/Orbit CHARACTERISTICS

For the period (Year/Day of Year) 97/086 to 97/092 (March 27, 1997 to April 2, 1997), 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. A pictorial diagram of the orbits of Comet Hale-Bopp and the Earth is available courtesy of Eric Frappa from the Planetarium de Saint-Etienne, France.

POLAR DATA REQUIRED

The Visible Imaging System (VIS) will be operated to obtain a complete set of images in 11 different wavelengths during each observation period. The UltraViolet Imager (UVI) and the Polar Ionosphere X-ray Imaging Experiment (PIXIE) should be operated in the mode that is most appropriate to achieve the maximum science return.

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 -1.46 degrees.

angle sun-comet - is the angle between the comet and the sun from the Polar spacecraft viewpoint. 

						    Length of     
		  				    Observation
 POLAR apogee   Comet           Sun        ANGLE    Centered on
 time (UT)   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	       240	Observations
 970871757   133.2    6.1   90.0   16.7    43.5	       243
 970881133   133.1    4.8   90.4   16.1    43.3		60
 970890509   133.0    3.6   90.9   15.4    43.1		60
 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	       180
 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
								Observations

	       POLAR apogee    Begin	       End
		 time (UT)  Obs. Time(UT) Obs. Time(UT)
     Date	 yydddhhmm  yy/ddd hh:mm  yy/ddd hh:mm	Comments
	
March 25, 1997	 970840151  97/084 01:21  97/084 02:21	Test Run
	
March 27, 1997	 970860642  97/086 06:12  97/086 07:12	Begin Comet Hale-Bopp
March 28, 1997	 970870018  97/086 22:18  97/087 02:18  Obs.
March 28, 1997	 970871757  97/087 15:57  97/087 20:00
March 29, 1997	 970881133  97/088 11:03  97/088 12:03
March 30, 1997	 970890509  97/089 04:54  97/089 05:54
March 30, 1997	 970892245  97/089 22:30  97/089 23:00	Short run*
March 31, 1997	 970901624  97/090 14:54  97/090 17:54
 April 1, 1997	 970911000  97/091 09:30  97/091 10:30
 April 2, 1997	 970920336  97/092 03:21  97/092 03:51	Short run*
 April 2, 1997	 970922112  97/092 20:42  97/092 21:42  End Comet Hale-Bopp Obs.

* 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
319-335-1867

Last Modified: Friday, 20-Sep-2024 02:32:34 CDT