OBJECT = DATA_SET DATA_SET_ID = "GO-J-NIMS-4-ADR-SL9IMPACT-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "GO NIMS Tabular Data from the SL9 Impact with Jupiter v1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" START_TIME = 1994-07-14T08:09:03Z STOP_TIME = 1994-07-21T05:04:36Z DATA_SET_RELEASE_DATE = 1996-01-19 DATA_OBJECT_TYPE = TABLE PRODUCER_FULL_NAME = "Dr. Robert W. Carlson" DETAILED_CATALOG_FLAG = "N" DATA_SET_DESC = " *************************************************************************** SBN Note: added information about this data can be found in the DOCUMENT directory in the Galileo subdirectory which outlines the processing steps. *************************************************************************** Data Set Overview ================= The Near Infrared Mapping Spectrometer (NIMS) on the Galileo spacecraft took unique data of Comet Shoemaker-Levy/9's impact with Jupiter. A preliminary analysis of this data is presented in this submission to the Planetary Data System (PDS). It consists of nine small tables with detached labels and documentation. Background ========== The Galileo spacecraft, enroute to Jupiter, was situated 240 million kilometers from Jupiter with a spacecraft-Jupiter-Sun phase angle of 51 degrees during the collision of Comet Shoemaker-Levy/9 with the planet. This geometry allowed a direct view of the impacts, which occurred on the nightside of Jupiter, not viewable from the Earth, and provided an opportunity to investigate the early temporal evolution of the impact events. Much of the radiation occurs in the infrared region, and time-resolved infrared spectral observations, obtained over a broad wavelength range, are ideal for studying these phenomena. The Galileo Near Infrared Mapping Spectrometer (NIMS) instrument (CARLSONETAL1992, see REF.CAT) observed the C, F, G, and R events, simultaneously with the Photopolarimeter (PPR) and Ultraviolet Spectrometer (UVS) instruments. Only data for the G and R events were telemetered to Earth. In order to ensure successful observations of the impacts, given uncertainties in the absolute spacecraft pointing, a 'checkerboard' scan pattern was used, covering Jupiter and the immediate vicinity. One dimension of scanning was provided by the NIMS mapping capability, giving a 10 mrad column of 20 pixels. Each pixel is acquired in 1/63 sec and is 0.5 mrad by 0.5 mrad in size (Jupiter's diameter as seen from Galileo was 0.6 mrad). The spacecraft scan platform provided the second dimension, scanning back and forth by 3 mrad at 0.92 mrad/sec and a period of 10 2/3 sec. Jupiter was in the field-of-view for only a fraction of each scan, giving a net time resolution of 5 1/3 seconds. The instrument was operated in the 'Fixed Map' mode in which, for each spatial pixel, 17 spectral bands are simultaneously monitored. The wavelength setting was chosen to include continuum bands, where the atmospheric gases are transparent, and bands with differing absorption strengths so as to perform vertical sounding of the fireball in the atmosphere. It also included a band for possible H3+ emissions. For short wavelengths, the intense reflected sunlight signal precludes ready identification of fireball emission while Jovian thermal emission obscures the fireball signature in the 5 micron region. Between these limits, in the 1.8 to 4.4 micron region, the reflected sunlight signal is weak and little atmospheric thermal emission occurs. Consequently, we employ this region for our preliminary analysis. The corresponding wavelengths and atmospheric absorption properties are listed in the table below. The spectral resolution for each wavelength channel is 0.025 microns. \t Wavelengths and Jovian Atmospheric Absorption Properties Det. No. Wavelength Wavenumber Absorber, Emitter (microns) (cm-1) ======== ========== ========== ========================== 6 1.84 5430 Continuum 7 2.12 4710 Molecular hydrogen, pressure induced 8 2.40 4160 Methane (stratosphere) 9 2.69 3720 Continuum 10 2.97 3370 Ammonia (troposphere) 11 3.25 3075 Methane (stratosphere) 12 3.53 2830 Methane (stratosphere), H3+ 13 3.82 2620 Methane (stratosphere) 14 4.10 2440 Continuum 15 4.38 2280 Phosphine (troposphere) \t Some of the above has been abstracted from CARLSONETAL1995A. Another useful reference is CARLSONETAL1995B. In addition, a comprehensive paper on the G fireball is being submitted to Icarus, and an analysis of the G and R splash spectra is currently underway. Tables in the Dataset The data provided here for the G and R events are of three types: calibration data, raw and averaged data numbers, and processed data, giving source intensities in physical units. \t CAL_DATA.TAB: A file of calibration data and related information useful for interpretation. JREF_DNS.TAB: Reference spectra for the undisturbed full disc Jupiter, in data numbers (DNs). JREF_GAM.TAB: Reference spectra for Jupiter's morning hemisphere, just prior to the G fireball event, in DNs. JREF_RAM.TAB: Reference spectra for Jupiter's morning hemisphere, just prior to the R fireball event, in DNs. G_DATA.TAB: Raw DNs versus time for pixels containing the G impact site. R_DATA.TAB: Raw DNs versus time for pixels containing the R impact site. SI_G_1.TAB: Source intensities versus time for the G event using chi squared minimization for the fireball period, which finds the fraction (eta) of reflected light to subtract to obtain the best fit of a blackbody spectrum. A regression fit of eta to detector 1 was developed from the fireball period and applied to the pre- and post-fireball periods. SI_G_2.TAB: Same as above, but the regression algorithm found in the chi squared minimization was used for all data, including the fireball period. This is to test the sensitivity of the results to the analysis procedure. SI_R_2.TAB: Same as above, but for the R event. \t Details of the structure and contents of these tables may be found in the detached label accompanying each table and in the AAREADME.TXT file. Processing ========== The raw NIMS data received from the spacecraft were collected on EDRs by the Image Processing System (MIPS) at the Jet Propulsion Laboratory (JPL) and are archived on PDS CD-ROM volume GO_1004. The tables in the submitted dataset were generated by Dr. Robert W. Carlson of JPL, Principal Investigator of the NIMS experiment on the Galileo Orbiter. The detached PDS labels were prepared by Bob Mehlman of the NIMS team and UCLA, who also edited the documentation supplied by Dr. Carlson into PDS format. Data structure ============== The table files follow PDS structure and labelling conventions. A detached PDS label accompanies each file, and describes its structure and contents using ASCII keyword=value statements. Ancillary Data ============== Calibration files derived from ground and flight calibration of the NIMS instrument were used in generating the CAL_DATA.TAB file in this dataset, but are not included with it. These calibration files are continually being improved. The most recent calibration files are available with the Integrated Software for Imaging Spectrometers (ISIS) system. Software ======== The nine tables in this dataset are small and in ASCII character format. They are therefore printable and accessible with ordinary editing software. They are also easily ingested by most database systems. Media/Format ============ This dataset is an electronic submission to PDS but may be included on a future CD-ROM volume of NIMS data from the Jupiter Tour. Formats are based on standards for table objects established by PDS." CONFIDENCE_LEVEL_NOTE = "UNK" END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = JUPITER END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = GO INSTRUMENT_ID = NIMS END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "CARLSONETAL1992" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "CARLSONETAL1995A" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "CARLSONETAL1995B" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END