NOAA KLM User's Guide Section 9.7.3

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9.7.3 Historical Instrument File

9.7.3.1 Overview

The Historical Instrument File (HIF) contains the data necessary to characterize the instrument performance and albedo correction over time. Included are interrange ratio statistics, diffuser degradations (unsmoothed at each discrete instrument wavelength), preliminary irradiances (i.e. before application of albedo correction factors), electronic calibration data, wavelength calibration data, and current and next day projections of interrange ratios and albedo correction factors.

9.7.3.2 Contents

Each Historical Instrument File contains a daily HIF directory and eight groups of information for each day's HIF arranged in the following order:

1. Daily HIF Directory
2. OOPS Standard Headers
3. Instrument Calibration and Albedo Correction Data
4. Interrange Ratio Statistics
5. Electronic Calibration Data
6. Wavelength Calibration Data
7. Diffuser Degradation Data
8. Preliminary Irradiance Data
9. Albedo Correction Data

The arrangement of the data segments generally reflects the processing sequence of the Generate Historical Instrument File program.

Figure 9.7.3.2-1 provides a physical overview of a monthly archival HIF tape. Table 9.7.3.2-1 provides a detailed description of the arrangement of records within each Daily Historical Instrument File. Details regarding contents and record layout of each record type listed in Table 9.7.3.2-1 be found at the end of this section, in the 1b Data Set description (Section 9.7.1.4), and, for individual data items, in the Data Dictionary (Section 9.7.5).

The daily HIF directory record contains information pertaining to that day's data. All record numbers are relative record numbers within the day's data file.

OOPS Standard Header records for the following data sets occur on the Daily Historical Instrument File in the following order:

1. Daily Historical Instrument File

2. Daily 1b Data Set

3. Instrument Calibration and Albedo Correction Data Set

The first set of standard headers are generated by the Generate Historical Instrument File Program and pertain to the entire data set. The second and third sets are copies of the OOPS Standard Header records from those data sets read by the Generate Historical Instrument File program.

If a Daily Historical Instrument File is reprocessed, the set of current OOPS Standard Header records will be followed by the earlier OOPS Standard Header records. In the event of multiple reprocessing, the most current reprocessed header records will follow the current header records.

The Instrument Calibration and Albedo correction Data segment is a copy of the Instrument Calibration and Albedo Correction Data Set less OOPS Standard Headers after the interrange ratios and albedo correction factors are updated to next day projections by the Generate Historical Instrument File program. The directory is updated to reflect record numbers on the Daily Historical Instrument File.

The Interrange Ratio Data contains three record types arranged in the following order:

1. Instrument Characterization Header Records

2. Offset Data Record

3. Interrange Ratio Statistical record

The Instrument Characterization Header records identify the SBUV/2 orbits selected for zero offset interrange ratio computation. The Offset Data Record contains a flag which indicates whether offsets were computed from nighttime discrete mode earth view, default values were used, previous day's offsets were used or offsets as computed from non-illuminated mercury lamp view were used in computing interrange ratios. The offsets used are included. The Interrange Ratio Statistics Record include averages, standard deviations, minima, maxima, and number of samples of interrange ratios between gain ranges for each discrete wavelength. Also included are the minimum and maximum signal levels for acceptance in the interrange ratio computations and a source indicator similar to that described for the Offset Data Record.

The Electronic Calibration Data includes an Instrument Characterization Header record corresponding to the orbit selected for electronic calibration from the Daily 1b Data Set followed by discrete 1b data records for every other scan in the selected orbit. ECAL data are in samples 13, 14, 15 and 16.

The Wavelength Calibration Data includes the Instrument Characterization Header record corresponding to the orbit selected for wavelength calibration from the Daily 1b Data Set. This header record is followed by data records containing wavelengths of mercury line peaks.

The Diffuser Degradation Data segment contains Instrument Characterization Header records which identify the orbits selected for the diffuser degradation calculation from the Daily 1b Data Set. These header records are followed by a data record containing the wavelength and wavelength windows for mercury lines selected for diffuser degradation computation and the unsmoothed diffuser degradation at the mercury lines. A source indicator similar to that described for the Offset Data record is included.

The Preliminary Irradiance segment contains the Instrument Characterization Header records followed by discrete data records containing adjusted irradiances for solar view discrete mode data from the Daily 1b Data Set. The irradiance values have been adjusted for goniometric calibration and sun-earth distance and calibrated with prelaunch coefficients. A statistical record (averages, standard deviations, minima, maxima and number of samples) precedes the data records. A source indicator for albedo corrections is included in this statistical record.

The Albedo Correction data portion contains Instrument Characterization Header records followed by a data record. The data record includes smoothed diffuser degradations and albedo correction factors computed for the current day at the discrete monochromator and Cloud Cover Radiometer wavelengths.

9.7.3.3 Data Organization

Each Historical Instrument file consists of an IBM 3480 tape cartridge containing a calendar month of data. An OOPS Standard Header Record pair for the monthly product describes the data contained on the tape. This is followed by a series of Daily HIF data Sets, one for each day of the month. Each day's HIF is contained within one file.

The HIF has a logical record length of 720 bytes and a physical block size of 25,920 bytes.

9.7.3.4 Record Layouts

The following pages describe the layout of each record type unique to the Historical Instrument File. Other record types are described in Sections 9.7.4 ( OOPS Standard Header Record) and 9.7.1.4 (1b Data Records). Individual data items are described in the Data Dictionary (Section 9.7.5).

Table 9.7.3.4-1 contains a list of each record type found in the Historical Instrument File.