Data Set Information
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| DATA_SET_NAME |
MCDONALD OBSERVATORY IMAGES OF COMET 19P/BORRELLY
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| DATA_SET_ID |
EAR-C-IGI-3-EDR-BORRELLY-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview------------------This data set contains images of comet Borrelly, obtained by TonyFarnham at the McDonald Observatory on five different observing runsduring the comet's 2001 apparition: 21-23 Sep 2001 12 Nov 2001 04-07 Dec 2001 07-08 Feb 2002 17-18 May 2002 The images from Sept 21 and 22 bracket the Deep Space 1 spacecraftencounter. The December data were obtained at the 2.1-m Otto Struve telescope andthe data from the other four runs were obtained at the 2.7-m HarlanJ. Smith telescope. In both cases, the Imaging Grism Instrument(IGI), a 5:1 focal reducer and a TeK 1024x1024 CCD were used. On the2.7-m telescope, this configuration produces a 7 arcmin vignettedfield of view with 0.57 arcsec pixels. On the 2.1-m the field of viewis 6 arcmin, with 0.48 arcsec pixels. For most of the observing runs, both a Harris V and a Mould R filterwere used for imaging. On 7 Dec 2001 and 17 May 2002, only R imageswere obtained. An extensive discussion of the data can be found in Farnham, T.L. &A.L. Cochran, 'A McDonald Observatory Study of Comet 19P/Borrelly:Placing the Deep Space 1 Observations into a Broader Context' Icarus,160, 398-418, 2002 [FARNHAM&COCHRAN2002]. Processing----------------The data were processed in a standard manner. The bias was removed ina two-step process: In the first step, the overscan region was used toremove the bulk of the bias level, and in the second step, a masterbias frame (created by averaging many bias frames) was used to removethe residual for each individual pixel. Flat fielding was done usingtwilight sky flats that were medianed together to remove any stars. Note that the data from May 2002 (UT020517 and UT020518 files) wasobtained during twilight, and much of the structure (dust specks onthe filter, etc) in the images did not completely flat field out. Calibration--------------On nights that were photometric, Landolt standard stars were observedat several different airmasses to provide a measurement of theatmospheric extinction and a means of obtaining an absolute fluxcalibration. (Landolt, A., UBVRI Photometric Standard Stars in theMagnitude Range 11.5-16.0 Around the Celestial Equator.Astron. J. 104, 340-371, 1992) [LANDOLT1992] The standard star observations were used to compute the extinctioncoefficient (in mag/airmass) and to determine the instrumental zeropoint offset (in mag) for each filter. These were then applied to theimages, using the following relation, to convert to observed fluxes: F : F_0 * P/t * 10^(-0.4*(25.0 - X*E - DM)) where F is the calibrated flux for each pixel (erg/sec/cm^2/Angstrom),F_0 is the flux for a 0 mag star (erg/sec/cm^2/Angstrom), P/t is thecount level per second for each pixel, X is the airmass, E is theextinction coefficient (mag/airmass) and DM is the instrumental zeropoint offset (mag). The values used for the calibration are givenbelow. Flux of zero magnitude star (erg/sec/cm^2/Angstrom) Filter F_0 ------ --------- V 3.526e-9 R 1.702e-9 Extinction coefficients and zero point offsets Date E_V DM_V E_R DM_R ----------- ----- ----- ----- ----- Sep 23 2001 0.161 1.189 0.117 1.549 Nov 12 2001 0.128 1.138 0.106 1.141 Dec 4 2001 0.291 1.310 0.211 1.751 Dec 5 2001 0.178 1.131 0.142 1.562 Feb 7 2001 0.115 1.334 0.073 1.347 Feb 8 2001 0.138 1.282 0.101 1.245 Data---------The data consist of images from the different observing runs. Theimages are contained in three directories. The first (basic) containsthe bias subtracted, flat fielded images of comet Borrelly from all ofthe observing runs. The second, (standards) contains the images ofthe standard star fields that are used to compute the extinctioncoefficients and instrumental zero point offsets. The third(calibrated) contains the images from photometric nights calibrated toobserved flux values.
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| DATA_SET_RELEASE_DATE |
2003-01-01T00:00:00.000Z
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| START_TIME |
2001-09-21T11:14:33.000Z
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| STOP_TIME |
2002-05-18T05:04:47.000Z
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| MISSION_NAME |
DEEP SPACE 1
SUPPORT ARCHIVES
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| MISSION_START_DATE |
1998-10-24T12:00:00.000Z
2004-03-22T12:00:00.000Z
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| MISSION_STOP_DATE |
2001-12-18T12:00:00.000Z
N/A (ongoing)
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| TARGET_NAME |
19P/BORRELLY 1 (1904 Y2)
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| TARGET_TYPE |
COMET
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| INSTRUMENT_HOST_ID |
MCD21
MCD27M
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| INSTRUMENT_NAME |
IMAGING GRISM INSTRUMENT
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| INSTRUMENT_ID |
IGI
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| INSTRUMENT_TYPE |
CAMERA
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| NODE_NAME |
Small Bodies
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| ARCHIVE_STATUS |
ARCHIVED
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| CONFIDENCE_LEVEL_NOTE |
Review : This data was peer reviewed on May 29, 2003.
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| CITATION_DESCRIPTION |
Farnham, T.L., MCDONALD OBSERVATORY IMAGES OF COMET 19P/BORRELLY EAR-C-IGI-3-EDR-BORRELLY-V1.0, NASA Planetary Data System, 2004.
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| ABSTRACT_TEXT |
Images of comet 19P/Borrelly obtained at the McDonald Observatory with the Imaging Grism Instrument on five observing runs during the 2001 apparition
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| PRODUCER_FULL_NAME |
TONY L. FARNHAM
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| SEARCH/ACCESS DATA |
SBN Comet Website
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