PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT INTERCHANGE_FORMAT = ASCII PUBLICATION_DATE = 2002-07-01 NOTE = "AAREADME.TXT File for data set: NEAR-A-GRS-3-EDR-EROS/ORBIT-V1.0" END_OBJECT = TEXT END NEAR Mission GAMMA-RAY SPECTROMETER Level-2 Data Set ======================================================================== 1. Introduction ____________ This document provides an overview of the Near Earth Asteroid Rendezvous Gamma-Ray Level 2 data archives. This volume contains science data products from observations acquired by the Near Earth Asteroid Rendezvous (NEAR) Gamma-ray Spectrometer (GRS) instrument. The GRS Level 2 data products in this archive include daily time series of spectra collected by the instrument along with selected spacecraft engineering and instrument configuration and orbital ephemerides. Supporting documentation is included for the specifics of how these data were generated. 2. Documentation _____________ This document provides an overview of the Near Earth Asteroid Rendezvous Gamma-Ray Level 2 document archive. These documents describe the design, development, implementation, calibration and operations of the NEAR GRS instrument. The directory contains references for 2 documents that could not be included in this archive due to copyright concerns and are cited in the REFERENCES.CAT file. Additional documentation is found in the DOCUMENTATION directory, including a document describing the GRS instrument calibrations. 3. Observation Log _______________ This document provides an overview of the Near Earth Asteroid Rendezvous Gamma-Ray Level 2 Observation Log archive. These documents describe the systems that were used to command and control the spacecraft during times when XGRS was controlling attitude, as well as commands that were used to configure the instrumentation during the orbital encounter. 4. Volume Set Information ______________________ Calibrated Level 2 Products The Level 2 data product comprises the time series of the GRS instrument'sscience data in physical units. At each integration time the instrument Data Processing Unit (DPU) samples instrument spectra accumulated during the integration period as well as instrument and engineering configurationinformation. Ground processing activities at the University of Arizona produce Derived Engineering and Spatial Ephemerides information. The Level-2 data are then combined into integral products within a relational database and exported as an integral Level-2 product. Each GRS record is comprised of the following logical data units: Spectra: 5, (1024 Channel) Spectra (NAI, BGO, ANTI, NAI1, NAI2, BGO1, BGO2) NAI = Sodium Iodide: Asteroid Pointing BGO = Bismuth Germanate: Asteroid Pointing ANTI= Anti-Coincidence: Asteroid Pointing NAI1= Sod. Iod 1 Escape: Asteroid Pointing NAI2= Sod. Iod 2 Escape: Asteroid Pointing 2, (21 Channel) Spectra BGO1= Bis. Germ. 1 Escpe:Asteroid Pointing BGO2= Bis. Germ. 2 Escpe:Asteroid Pointing Instrument HouseKeeping: Instrument Rates and activity Engineering Housekeeping: Engineering Configurations Derived Engineering: Ground derived data products Spatial Orbital Ephemerides 4. CD-ROM Format _____________ The CD-ROM has been formatted so that a variety of computer systems (e.g.,PC, Macintosh, and Sun) may access the data. Specifically, it is formatted according to the ISO-9660 level 1 Interchange Standard. For further information, refer to the ISO-9660 Standard Document: RF# ISO 9660- 1988, April 15, 1988. This CD-ROM does not contain any Extended Attribute Records (XAR). Thus, VAX/VMS users may have some problems accessing files on this volume. 5. File Formats ____________ The GRS Level 2 integral data are BINARY files the describe the integrated composition of spectral, orbital ephemerides, instrument configuration and derived products for each GRS integration period. Descriptions of each integral file comes with a detached PDS header label. A header label file describes attributes specific to each integration. Each header references a common label file for each integral file. An observation log file is included also an ASCII table described by its corresponding detached label. All text files (*.TXT files) and detached labels (*.LBL files) on this volume,are stream format 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 the MacOS, DOS, and UNIX operating systems. An example format of each Level-2 BINARY record file is: Example: g2000011.dat where g = Gamma-ray Spectrometer 2000 = Year 011 = Day Number .dat = file extension For the complete description of the GRS Level-2 Products see: "The Near Earth Asteroid Rendezvous, Gamma-ray Spectrometer, Level-2 Requirements Specification": May 25, 2001 in the DOCUMENT section. For the PDS submission Level-2 Integral products have been exported on a daily basis. Each day's GRS data collection will be stored in a daily directory comprised of variable number`s of integral records. The directory format is listed below in the directory elaboration. 6. Volume Contents _______________ Files on this volume are organized into a series of subdirectories below the top-level directory. The following table shows the structure and content of these directories. In the table, directory names are enclosed in square brackets ([]). FILE CONTENTS Top-level directory | |- AAREADME.TXT The file you are reading. | |- [DATA] | |- DATAINFO.TXT Description of files in the DATA directory. | | | |- [200001] Jan 2000 Month Reference Dir | | |- G2000011.* Daily Spectra Set,G=GRS,200X=yr,NNN=daynumber | | |- ..... All days in Jan. 2000 | | | |- [200002] Feb 2000 Month Reference Dir | | |- G2000032.* Daily Spectra Set,G=GRS,200X=yr,NNN=daynumber | | .......... All months 2000 to Feb 2001 | |- [200102] Feb 2000 Month Reference Dir | | |- G2001043 Daily Spectra Set,G=GRS,200X=yr,NNN=daynumber | | |- ....... Up to Feb 11, 2001 Coverage Stops | | | |- [DOCUMENT] GRS Documentation file. | |- DOCINFO.TXT Description of files DOCUMENT directory. |- |- GRS_REQS_7_2.DOC NEAR-GRS L-2 Requirement Specs (MS Word) |- |- GRS_REQS_7_2.LBL Label file for GRS L-2 Reqs Doc versions |- |- GRS_REQS_7_2.TXT Reduced form, NEAR GRS Reqs specs. (ASCII) |- |- GRS_REQS_7_2.JPG Reqs. saved as multi-page Jpeg file. |- |- GRS_REQS_7_2.TIF Reqs. saved as multi-page TIF file. |- |- GRS_REQS_7_2_* | |- Individual Pages NEAR GRS L-2 Reqs Spec. | |- Saved as 1 page per TIF file, * = Page # | |- Also included label file each TIF image | | | |- [OBSERVATION_LOG] | | |- OBSLOGINFO.TXT Description of OBS LOG Dir | | |- XGRS_COMMAND_DESC* Obs log, config parms | | |- XGRS_INST_USER_GUIDE4* Command, CAS generation instr. | | |- XGRS_OBSLOG* Actual XGRS command log | | | | |- [INSTRUMENT] | | |- XGRS_DEFINITIONS.TXT XGRS Inst. Definitions | |- [CATALOG] | |- CATINFO.TXT Catalog directory information | |- INSTHOST.TXT Instrument design information | |- MISSION.CAT NEAR Mission related information and refs | |- PERSON.CAT Personnel associated with this submission | |- REF.CAT References to other publications | |- GRSL2DS.CAT Description of this GRS dataset | |- GRSINST.CAT Instrument related Information | 7. Whom To Contact For Information _______________________________ For questions concerning this data set collection: Planetary Data System (PDS) Small Bodies Node (SBN) Astronomy Department University of Maryland College Park, MD 20742 NEAR/XGRS Science Team Code 691, Astrochemistry Branch NASA / Goddard Space Flight Center Greenbelt, MD 20771 WWW Site: http://leptpm.gsfc.nasa.gov/near.html Electronic mail addresses: jack.trombka@gsfc.nasa.gov, tim.mcclanahan@gsfc.nasa.gov 8. Cognizant Persons _________________ NEAR/XGRS data were provided by Jacob Trombka, NEAR XGRS Team Leader: Jacob Trombka Building 2, Rm# 165 Code 691, Astrochemistry Branch NASA/Goddard Space Flight Center Greenbelt, MD 20771. jack.trombka@gsfc.nasa.gov 301-286-5941 This volume was designed and produced by: Tim McClanahan Building 2, # 166 Code 691, Astrochemistry Branch NASA/ Goddard Space Flight Center Greenbelt, MD 2077