PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM LABEL_REVISION_NOTE = "2009-07-01, T. Barnes (SBN): Updated SBN copy from EN copy for ABSTRACT_DESC, CITATION_DESC, and DATA_SET_TERSE_DESC. 2009-08-05 SBN:McLaughlin This data set spans two volumes but each original volume has a different data set catalog file, one to describe Level 2 products on the first volume and another for Level 3 products on the second volume. Therefore, combined the two different catalog files here and adjusted ABSTRACT_DESC and DATA_SET_TERSE_DESC to reflect the merge; Corrected a few typos." OBJECT = DATA_SET DATA_SET_ID = "NEAR-A-GRS-3-EDR-EROS/SURFACE-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "NEAR GRS SPECTRA EROS ON ASTEROID" DATA_SET_COLLECTION_MEMBER_FLG= "N" DATA_OBJECT_TYPE = "SPECTRUM" START_TIME = 2001-02-19T16:59:24 STOP_TIME = 2001-02-28T17:49:37 DATA_SET_RELEASE_DATE = 2001-07-15 PRODUCER_FULL_NAME = "JACOB TROMBKA" DETAILED_CATALOG_FLAG = "N" DATA_SET_TERSE_DESC = "Reduced (integrated and corrected) Level 2 and Level 3 NEAR Gamma Ray Spectrometer observations taken during the Eros Surface phase of the mission." ABSTRACT_DESC = "This data set contains reduced (integrated and corrected) science data products from observations acquired by the Near Earth Asteroid Rendezvous (NEAR) Gamma Ray Spectrometer (GRS) instrument during the Eros Surface phase." CITATION_DESC = "UNK" DATA_SET_DESC = " Introduction ============= This document provides an overview of the Near Earth Asteroid Rendezvous Gamma-Ray Spectrometer On-asteroid Level 2 and 3 data archive. This data set contains reduced (integrated and corrected) science data products from observations acquired by the Near Earth Asteroid Rendezvous (NEAR) Gamma Ray Spectrometer (GRS) instrument during the Eros Surface phase. The following sections describe this data set and its documentation delivered as part of the NEAR XGRS instrument team delivery to NASA's Planetary Data System. Data Set Information ==================== It was found that the on-surface attitude of the spacecraft did not facilitate the use of the fixed high gain antenna and the low gain antenna was used for the duration of the on-surface mission. As a result available telemetry rates did not facilitate the downlink of the full complement of instrument, engineering and ancillary information with priority being given to selected spectra. The first two days of on-surface activity were used to calibrate the detectors to account for deviations of temperature between orbital and on surface operations. Adjustments were then made to the instrument high voltage to improve the energy gain in the escape peak spectra. In this configuration, several long term integrations were collected and spectra taken for the four longest integrations along with ancillary information were used to generate the Level 2 science products on the first volume of this data set, NXERSF_2001. For the Level 3 products on the second volume, NXERSF_2002, spectra from the two longest integration times (total duration of 586320 seconds) were summed for NAI, ANTI, NAI1, and NAI2 spectra. The higher counting rate BGO spectrum was taken for a single integration (total duration of 346480 seconds) and summed. Each of set of spectra were corrected for channel rollover which occurred in several instances due to long integration times causing accumulations of counts in some channels to exceed and rollover the maximum numerical range of the 2 byte channel. Higher counting rates in the lower energies of each spectrum incurred multiple rollovers and algorithms were developed to rectify this effect. A second correction made to the on-surface spectra is the removal of differential non-linearities (DNL) contained within the spectra. The effect being high frequency spikes in channels spaced at regular intervals within the spectrum. (DNL)`s were removed using a 3rd order polynomial fit and smoothing function for a sliding boxcar of 21 channels through each raw spectrum. Level 2 Data Products --------------------- As a result three Level 2 spectra were generated for the BGO instrument and three for the NAI instrument and finally the NAI 1 and 2 escape spectra only were collected as the last spectra integrated from the surface. The resulting 17 individual Level 2 spectra are listed with ancillary information in the following table: ID MET (start) UTC (at Start) I-Time NAI ANT BGO N1 N2 ------------------------------------------------------------ 1 158012304 2001:050:17:00:48 23108 x x x x x 2 158035412 2001:050:23:25:56 237840 x x x x x 3 158273394 2001:053:17:32:18 346480 x x x x x 4 158619998 2001:057:17:49:02 169440 x x where 'x' = Available as a Level 2 DATA product. NAI = Sodium Iodide BGO = Bismuth Germanate N1 = NAI 1 Escape N2 = NAI 2 Escape Spectra only. I-Time = Integration time. The GRS On-asteroid Level 2 corrected spectra are provided as fixed-width ASCII table files. Ancillary information specific to each integration is provided as a separate ASCII table. All Level 2 tables (*.TAB files) and detached labels (*.LBL files) are ASCII files with a carriage return (ASCII 13) and a line feed character (ASCII 10) at the end of each line. This allows the files to be read by MacOS, DOS, and UNIX operating systems. A description of the content and format of the On-asteroid Level-2 record files is provided next. Format: ONSURxAz.TAB - Asteroid Surface Position (Lat, Lon) West Longitude - Starting time tags (MET) for each summed integrations - End (MET) - Energy Calibration - Instrument Attitude - 'x' denotes (N = NAI, B = BGO, A = ANTI, 1 = NAI 1, 2 = NAI 2) - 'A' denotes ancillary - 'z' denotes integration number (1,2,3,4) - 11 columns in single record ONSURxSz*.TAB - Surface Spectrum - 'x' denotes (N = NAI, B = BGO, A = ANTI, 1 = NAI 1, 2 = NAI 2) - 'S' denotes Spectrum - 'z' denotes integration number (1,2,3,4) - 2 columns, 1024 channels - Plus label (.LBL) files These Level 2 products are located in the DATA directory of the first volume of this data set, NXERSF_2001. Level 3 Data Products --------------------- The GRS On-asteroid Level 3 corrected and summed spectra are provided as fixed-width ASCII table files. Ancillary information specific to each integration is provided as a separate ASCII table. All Level 3 tables (*.TAB files) and detached labels (*.LBL files) are ASCII files with a carriage return (ASCII 13) and a line feed character (ASCII 10) at the end of each line. This allows the files to be read by MacOS, DOS, and UNIX operating systems. A description of the content and format of the two On-asteroid Level-3 record files is provided next. File 1: ONSURNAS.TAB - Starting and ending time tags (MET) for each summed integration - Asteroid Surface Position (Lat, Lon) West Longitude - Energy Calibration - Instrument Attitude ONSURNSS.TAB - 4 Spectra (NAI, ANTI, NAI1, NAI2) - Summed from 2 separate integrations (total duration = 586320 sec) File 2: ONSURBAS.TAB - Starting and ending time tags (MET) for the single BGO integration - Energy Calibration - Surface Position (Lat, Lon) West Longitude - Instrument Attitude ONSURBSS.TAB - 1 Spectrum, BGO - Summed from one separate integration (total duration = 346480 sec) These Level 3 products are located in the DATA directory of the second volume of this data set, NXERSF_2002. Coordinate System ================= All products were derived in the Asteroid Body Fixed Coordinate System Software ======== Requirement Specifications For Level-2 Parameters Required Stored or Derived by The Near Earth Asteroid Rendezvous (NEAR) Gamma-Ray Spectrometer (GRS) Ground System Media ====== CD-ROM" CONFIDENCE_LEVEL_NOTE = " Overview ======== Data in this archive have been reduced as part of mission data analysis activities of the NEAR XGRS Science Team. Data of questionable validity have been omitted from the solutions. Review ====== This archival data set was reviewed by the NEAR XGRS Team prior to submission to the Planetary Data System (PDS). It was one of several data sets included in a comprehensive review by the PDS Small Bodies Node in August 2001, prior to PDS acceptance and ingestion. Data Coverage and Quality ========================= The data included in this archive were collected from 2001-02-19 to 2001-02-28 during the Eros Surface (i.e., On-asteroid) phase of the NEAR mission. Limitations =========== None" END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = "EROS" END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_MISSION MISSION_NAME = "NEAR EARTH ASTEROID RENDEZVOUS" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = "NEAR" INSTRUMENT_ID = "GRS" END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "CHENGETAL1998" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END