PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM SPACECRAFT_NAME = "INFRARED ASTRONOMICAL SATELLITE" INSTRUMENT_NAME = "IRAS FOCAL PLANE ARRAY" OBJECT = TEXT NOTE = "Definitions of PDS keywords used in the data labels, listed in alphabetical order." PUBLICATION_DATE = 2003-10-30 /* Peer Review Date */ END_OBJECT = TEXT END PDS Keyword Definitions ======================= NAME = AXIS_ORDER_TYPE DESCRIPTION = The AXIS_ORDER_TYPE element is used to identify the storage order for elements of a multidimensional ARRAY object. The default storage order for an ARRAY object presumes the rightmost or last index of a sequence varies the fastest. This is the ordering used in the C programming language and is equivilant to ROW_MAJOR storage order for COLUMN elements within tables. Specifying an AXIS_ORDER_TYPE of FIRST_INDEX_FASTEST may be used for ARRAYs that must be labelled and referenced in the reverse, and is the ordering used in the Fortran programming language. NAME = B1950_DECLINATION UNIT_ID = DEGREE MINIMUM = -90.000000 MAXIMUM = 90.000000 DESCRIPTION = The B1950_declination element provides the declination of the target using the B1950 coordinate frame rather than the J2000 frame. IRAS used the B9150 coordinate frame. For an IRAS Tempel 1 image, B1950_DECLINATION refers to the declination assigned to the pixel at the center of the image. NAME = B1950_RIGHT_ASCENSION UNIT_ID = DEGREE MINIMUM = 0.000000 MAXIMUM = 360.000000 DESCRIPTION = The B1950_right_ascension element provides the right ascension of the target object using the B1950 coordinate frame rather than the J2000 frame. IRAS used the B9150 coordinate frame. For an IRAS Tempel 1 image, B1950_RIGHT_ASCENSION refers to the declination assigned to the pixel at the center of the image. NAME = BYTES DESCRIPTION = The bytes element indicates the number of bytes allocated for a particular data representation. NAME = DATA_SET_ID DESCRIPTION = The data_set_id element is a unique alphanumeric identifier for a set of data. The data_set_id is an abbreviation of the data_set_name. For the IRAS Additional Observation and Survey Scan data for comet 9P/Tempel 1, the convention for constructing data_set_id is IRAS-C-FPA-x-yyy-DI-TEMPEL1-DI-V1.0, where C = Target is a comet FPA = Instrument is the focal plane array x = Processing level equals 5 for derived data or 6 for ancillary data such as calibration files yyy = Data set type equals RDR for the Additional Observation and Survey Scan radiance and image maps. DI = Deep Impact mission that initiated this archive TEMPEL1 = specific target V1.0 = Version 1.0 of the data set NAME = EXPOSURE_DURATION UNIT_ID = SECOND DESCRIPTION = For IRAS, the exposure_duration element provides the actual time observing the target. For Additional Observations, it does not include time used to make fine attitiude updates on reference stars at the beginning and at the end of the target observation. NAME = FILE_RECORDS DESCRIPTION = The file_records element indicates the number of physical file records, including both label records and data records. NAME = HEADER_TYPE DESCRIPTION = The header_type element identifies a specific type of header data structure. For example: FITS. Note: In the PDS, header_type is used to indicate non-PDS headers. NAME = INTERCHANGE_FORMAT DESCRIPTION = The interchange_format element represents the manner in which data items are stored. NAME = INSTRUMENT_HOST_NAME DESCRIPTION = The instrument_host_name element provides the full name of the host on which an instrument is based. NAME = INSTRUMENT_NAME DESCRIPTION = The instrument_name element provides the full name of an instrument. NAME = LINE_DISPLAY_DIRECTION DESCRIPTION = The line_display_direction element is the preferred orientation of lines within an image for viewing on a display device. The default value is down, meaning lines are viewed top to bottom on the display. See also SAMPLE_DISPLAY_DIRECTION. NAME = LINE_SAMPLES DESCRIPTION = The line_samples element indicates the total number of data instances along the horizontal axis of an image. NAME = LINES DESCRIPTION = The lines element indicates the total number of data instances along the vertical axis of an image. NAME = MAP_PROJECTION_TYPE DESCRIPTION = The map_projection_type element identifies the type of projection characteristic of a given map. The IRAS Additional Observation images in this data set use a Plate Carree projection for right ascension and declination. NAME = MAXIMUM DESCRIPTION = The maximum element indicates the largest value occurring in a given instance of the data object. NAME = MEAN_OBSERVATION_TIME DESCRIPTION = The MEAN_OBSERVATION_TIME is the average date and time associated with an observation that itself consists of recording multiple events (photon arrival times, for example). It is distinct from OBSERVATION_TIME, which is the midpoint of the observation period, in that it is calculated by taking the arithmetic average of all event times associated with the single observation. For IRAS Additional Observation (AO) images, this is the observing time spent on the target. The rest of the time was used to make fine attitude updates on reference stars at the begining and at the end of an AO. See also EXPOSURE_DURATION. For Survey Scan (SS) images, this is the mean of NAME = MINIMUM DESCRIPTION = The minimum element indicates the largest value occurring in a given instance of the data object. NAME = OBSERVATION_INCLINATION MINIMUM = 0.000000 MAXIMUM = 360.000000 DESCRIPTION = the inclination of an observation with respect to a non-standard coordinate system. For IRAS: The IRAS satellite has a natural, non-standard, coordinate system defined by solar_elongation and inclination_observation. Solar_elongation is the angle between the line of site and the Sun. Inclination_observation is the angle between the ecliptic plane and the plane containing the Earth, Sun, and the observation direction (that is, the azimuth angle about the Earth-Sun axis). The value is zero when IRAS looks at the ecliptic plane in the direction opposite to the motion of the Earth around the Sun. The value increases clockwise around the Earth-Sun axis when facing the Sun, and opposite from the direction of the motion of the satellite in its polar orbit about the Earth. Inclination_observation is related to iras_clock_angle by the relation: inclination_observation = 90 - iras_clock_angle. Solar_elongation and inclination_observation are related to geocentric ecliptic latitude (beta) and longitude (lambda) and the longitude of the Sun (lamda Sun) through the relations: sin(inclination_observation) = sin(beta)/sin(solar_elongation) cos(solar_elongation) = cos(beta)*cos(lamda - lamda Sun). PDS defines iras_clock_angle as the satellite viewing angle projected onto the plane perpedicular to the Sun- line, measured from ecliptic North, clockwise as viewed from the Sun. This is the same direction as the IRAS orbital motion. NAME = PHASE_ANGLE UNIT_ID = DEGREE MINIMUM = 0.000000 MAXIMUM = 180.000000 DESCRIPTION = The phase_angle element provides a measure of the relationship between the instrument viewing position and incident illumination by solar light. Phase_angle is measured at the target; it is the angle between a vector to the illumination source and a vector to the instrument. If illumination is from behind the instrument, phase_angle will be small. NAME = PROCESSING_HISTORY_TEXT DESCRIPTION = The processing_history_text element provides an entry for each processing step and program used in generating a particular data file. NAME = PRODUCT_CREATION_TIME DESCRIPTION = The product_creation_time element defines the UTC system format time when a product was created. Formation rule: YYYY-MM-DDThh:mm:ss[.fff]. NAME = PRODUCT_ID DESCRIPTION = The product_id data element represents a permanent, unique identifier assigned to a data product by its producer. NAME = PRODUCT_NAME DESCRIPTION = The PRODUCT_NAME element provides the full name of a product. It is related to product_id and provides a brief, descriptive title for a particular data product. NAME = RECORD_BYTES DESCRIPTION = The record_bytes element indicates the number of bytes in a physical file record, including record terminators and separators. NAME = RECORD_TYPE DESCRIPTION = The record_type element indicates the record format of a file. NAME = RECORDS DESCRIPTION = The records data element identifies the number of physical records in a file or other data object. NAME = SAMPLE_BITS DESCRIPTION = The sample_bits element indicates the stored number of bits, or units of binary information, contained in a line_sample value. NAME = SAMPLE_DISPLAY_DIRECTION DESCRIPTION = The SAMPLE_DISPLAY_DIRECTION element is the preferred orientation of samples within a line for viewing on a display device. The default is right, meaning samples are viewed from left to right on the display. See also line_display_direction. NAME = SAMPLING_PARAMETER_NAME DESCRIPTION = The sampling_parameter_name element provides the name of the parameter which determines the sampling interval for an image. NAME = SAMPLING_PARAMETER_INTERVAL DESCRIPTION = The sampling_parameter_interval element identifies the spacing of points at which data are sampled and at which a value for an instrument or dataset parameter is available. See also sampling_parameter_unit. NAME = SAMPLING_PARAMETER_UNIT DESCRIPTION = The sampling_parameter_unit element specifies the unit of measure of associated data sampling parameters. For IRAS Tempel 1 images, the unit is degree/pixel. See also sampling_parameter_interval. NAME = SAMPLE_TYPE DESCRIPTION = The sample_type element indicates the data storage representation of sample value. NAME = SOLAR_ELONGATION UNIT_ID = DEGREE DESCRIPTION = The angle between the line of sight of observation and the direction of the Sun. For IRAS, solar_elongation is the line of sight of observation is the boresight of the telescope as measured by the satellite sun sensor. NAME = SPACECRAFT_CLOCK_START_COUNT UNIT_ID = SECOND DESCRIPTION = The spacecraft_clock_start_count element provides the value of the spacecraft clock at the beginning of a time period of interest. For an IRAS Tempel 1 Additional Observation, spacecraft_clock_start_count is the value of the spacecraft clock at the start of the entire observation (see also observation_duration). For an IRAS Tempel 1 Survey Scan, spacecraft_clock_start_count is the value of spacecraft clock at the start of the earliest scan in the set of scans used to make an image mosaic. NAME = SPACECRAFT_CLOCK_STOP_COUNT UNIT_ID = SECOND DESCRIPTION = The spacecraft_clock_stop_count element provides the value of the spacecraft clock at the end of a time period of interest. For an IRAS Tempel 1 Additional Observation, spacecraft_clock_start_count is the value of the spacecraft clock at the end of the entire observation (see also observation_duration). For an IRAS Tempel 1 Survey Scan, spacecraft_clock_start_count is the value of spacecraft clock at the end of the latest scan in the set of scans used to make an image mosaic. NAME = START_TIME DESCRIPTION = The start_time element provides the UTC date and time of the beginning of observation in UTC system format. The IRAS Tempel 1 data, start_time is the spacecraft_clock_start_count converted to UTC date and time. Formation rule: YYYY-MM-DDThh:mm:ss[.fff] NAME = STOP_TIME DESCRIPTION = The stop_time element provides the UTC date and time of the end of observation in UTC system format. The IRAS Tempel 1 data, stop_time is the spacecraft_clock_stop_count converted to UTC date and time. Formation rule: YYYY-MM-DDThh:mm:ss[.fff] NAME = TARGET_GEOCENTRIC_DISTANCE UNIT_ID = AU DESCRIPTION = The target_geocentric_distance element provides the distance from the center of the earth to the target. NAME = TARGET_HELIOCENTRIC_DISTANCE UNIT_ID = AU DESCRIPTION = The target_heliocentric_distance element provides the distance from the center of the sun to the target body. NAME = TARGET_NAME DESCRIPTION = The target_name element identifies a target. NAME = UNIT DESCRIPTION = The unit element provides the full name or standard abbreviation of a unit of measurement in which a value is expressed. NAME = WAVELENGTH DESCRIPTION = The wavelength element identifies the mean wavelength to which an instrument detector/filter combination is sensitive. For IRAS Tempel 1 data, wavelength have values of 12, 25, 60, 100 micron.