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ISIS 2 Documentation


Isis ISIS Appendix G - ISL Spectral Header Structure

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The following describes the data columns contained in the header
of each spectrum stored in an Instrument Spectral Library.  A
description of this header structure is written to the label of an
Instrument Spectral Library file in the SPECTRAL_HEADER_DEFINITION
GROUP of keywords within the object description for the QUBE
object that contains the library spectra.  (See example ISL label
in Appendix F.)

The data columns listed below include the required and optional
columns defined by the S_INIT_HREC routine.  Columns denoted with
an asterisk (*) are required in the spectral header.  All others
are optional.  Note that each of the data columns described below
contains a scalar data value rather than an array of values.
However, an application could define additional optional columns
that contain arrays of values as well as scalar values.


                                                 Byte
Column Name            Type      Size     Description
-------------------    --------- ----     --------------------------------
*SPECTRUM_TYPE_ID      INTEGER      4     Specifies type of stored primary
                                          spectrum and secondary data
                                          arrays.  Note that primary
                                          spectra type codes are
                                          restricted to positive values
                                          whereas secondary data array
                                          type codes are restricted to 
                                          negative values.
                                           -6 - count of valid pixels in
                                                 averaged group
                                           -5 - maximum of averaged group
                                           -4 - minimum of averaged group
                                           -3 - standard deviation of
                                                 averaged group
                                           -2 - uncertainty
                                           -1 - imaginary part of any
                                                 complex type defined by
                                                 its primary ID

                                            0 - empty slot - reserved for
                                                 system usage

                                            1 - real part of complex index
                                                 of refraction
                                            2 - radiance
                                            3 - reflectance
                                            4 - reflectance*solar spectrum
                                            5 - transmission
                                            6 - transmission*solar
                                                 spectrum
                                            7 - absorption
                                            8 - absorption coefficient
                                            9 - emissivity
                                            10 - instrument noise spectrum
                                            11 - unclassifiable

MATERIAL_STATE_ID     INTEGER       4     Specifies the state of the
                                          observed medium
                                            0 - unknown
                                            1 - gas
                                            2 - liquid
                                            3 - solid, polished
                                            4 - solid, rough
                                            5 - solid, particulate
                                            6 - natural surface 
                                                 (remote sensed)
                                            7 - suspended droplets (clouds)

MATERIAL_PRESSURE      REAL         4     Specifies the [surface] pressure 
                                          of a gas in PASCALS
                                                                 
MATERIAL_TEMPERATURE   REAL         4     Specifies the sample temperature
                                           in KELVIN

MATERIAL_PATH_LENGTH   REAL         4     Specifies the path length in a
                                          fluid or the particle size of a 
                                          particulate solid in METERS.
                                          For rough or polished solids,
                                          this is the mean crystal size
                                          if known.

*SPECTRUM_NAME         CHARACTER   40     The name of the spectrum.  Unique
                                          for all primary spectra within
                                          the library file.

SOURCE_TYPE_ID         INTEGER      4     Code that helps identify where
                                          the spectrum originated 
                                           1 - laboratory
                                           2 - Flight instrument, e.g.,  via
                                               "cv" or "cubespec" or other
                                               such applications
                                           3 - theory
                                           4 - others (?)

SOURCE_NAME            CHARACTER   48     Name of the source where the
                                          spectrum originated. Dependent
                                          upon SOURCE_TYPE_ID as to what is
                                          stored in this column.  For
                                          SOURCE_TYPE_ID=1, 3 and 4,
                                          SOURCE_NAME will contain the name
                                          of the person who generated the
                                          spectrum. For SOURCE_TYPE_ID=2,
                                          the name of the file from which
                                          the spectrum was generated can be
                                          found here.

SOURCE_INDEX_1         INTEGER      4     Based on the value of
                                          SOURCE_TYPE_ID, this column gives
                                          further information about the
                                          spectrum source.  For
                                          SOURCE_TYPE_ID=1, the spectrum
                                          is from a library generated from
                                          laboratory observations and this
                                          column contains the library
                                          number. For SOURCE_TYPE_ID=2,
                                          source is from applications such
                                          as "cv"/"cubespec" and this column
                                          will contain the SAMPLE number
                                          from a file where the spectrum
                                          was obtained.  (This will usually
                                          be the CENTER of the averaged
                                          area.)  For SOURCE_TYPE_ID=3,
                                          this column can be used to refer
                                          to the run number, for example.

SOURCE_INDEX_2         INTEGER      4     A second column of information
                                          about the spectrum source. For
                                          SOURCE_TYPE_ID=1, this column
                                          specifies the location or index
                                          of the spectrum from the library.
                                          For SOURCE_TYPE_ID=2, this column
                                          specifies LINE number from a file
                                          where the spectrum was obtained.
                                          (This will usually be the CENTER
                                          of the averaged area.)
                                          For SOURCE_TYPE_ID=3, this column
                                          can be used for the curve number.

SOURCE_REGION_WIDTH    INTEGER      4     For SOURCE_TYPE_ID=1 and 3, this 
                                          column is undefined.  For 
                                          SOURCE_TYPE_ID=2, this column
                                          specifies the width of the box 
                                          size in SAMPLEs used in "cv"
                                          or "cubespec" to generate the
                                          spectrum.

SOURCE_REGION_HEIGHT   INTEGER      4     For SOURCE_TYPE_ID=1 and 3, this
                                          column is undefined.  For
                                          SOURCE_TYPE_ID=2, this column 
                                          specifies the height of the box
                                          size in LINEs used in "cv" or
                                          "cubespec" to generate the spectrum.

AVERAGED_SPECTRUM_COUNT INTEGER      4    This specifies the total number
                                          of observed or original spectra
                                          averaged to result in this
                                          spectrum.

CHEMICAL_DESCRIPTION   CHARACTER   60     ASCII representation of chemical
                                          composition formula of the
                                          material.
                                          (Also available for comment.)

INCIDENCE_ANGLE        REAL         4     Angle in DEGREES at the observed
                                          point between a vector to the
                                          sun and a vector normal to the
                                          surface.

EMISSION_ANGLE         REAL         4     Angle in DEGREES at the observed
                                          point between a vector to the
                                          observer and a vector normal to
                                          the surface.

PHASE_ANGLE            REAL         4     Angle in DEGREES at the observed
                                          point between a vector to the sun
                                          and a vector to the observer.
                                         
*DATE_TIME             CHARACTER   20     Data and time the spectrum or 
                                          entry was generated.  It has the
                                          ISO form "YYYY-MM-DDTHH:MM:SS",
                                          the ISIS standard.

MEAN                   REAL         4     Computed mean of the spectrum

STANDARD_DEVIATION     REAL         4     Computed standard deviation of
                                          the spectrum

*PARENT_SPECTRUM_INDEX INTEGER      4     Is the index of a spectrum
                                          contained in this library to
                                          which this spectrum is related or
                                          linked. A value 0 specifies
                                          this is a primary or root
                                          spectrum in a chain of related
                                          data arrays.

*CHILD_SPECTRUM_INDEX  INTEGER      4     Is the index of a spectrum
                                          contained in this library that is
                                          'chained' to this spectrum and
                                          related to the primary or root
                                          spectrum in some way.  A value 
                                          of 0 specifies that this is the
                                          last spectrum in the chain.
                                          This and the previous column
                                          creates what is known as a
                                          double-linked list of primary
                                          spectrum and related secondary
                                          data arrays.

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Last updated: Oct 24 2003