ISIS Appendix G - ISL Spectral Header Structure
Isis 2 Documentation
ISIS Appendix G - ISL Spectral Header Structure
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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