gmsin - creates VISSR datasets from GMS telemetry data.

gmsin - Creates VISSR datasets from GMS telemetry data.

SYNOPSIS

gmsin  [ parameter=value ... ]  [ outputfile ... ]
gmsin  [ parameter=value ... ]  [ directory ]

Parameters are: on_pass_disk, pass_number, tape_device, first_file, num_files, calibrate, temp_units, byte_output, base_temp, temp_step, vis_delta, ir_delta, use_master, master_file, start_spin, num_spins, start_percent, width_percent, sixbit, fix_missing, ir_rad_table .

DESCRIPTION

gmsin creates TeraScan CDF datasets from raw GMS VISSR telemetry data. The dataset contains two dimensional image data from visible and infrared sensors, and an ascii information block detailing sensor scheduling (MANAM Block).

The raw data can be read from the pass disk or from tape. Raw data on tape must be in TeraScan Archive Format (TAF).

GMS (Geostationary Meteorological Satellite) is a weather satellite in an Earth-fixed orbit over the equator which (re)transmits environmental data. Its imaging sensor is called the VISSR (Visible and Infrared Spin Scan Radiometer). The telemetry containing VISSR imagery is called Stretched VISSR (S-VISSR) telemetry. The TeraScan gmsin command extracts the VISSR image data and the Manual Amendment Block (MANAM) from the S-VISSR telemetry.

GMS begins a north-south scan of the Earth every half hour (hereafter referred to as a pass). Details of scheduling are provided in the telemetry stream in the MANAM block. This information is stored in each gmsin created VISSR dataset. An example below shows how to extract the scheduling information.

At the satellite sub point, the visible (0.5-0.75um) data have a resolution of 1.25 km and the infrared (10.5-12.5um) data have a resolution of 5.0 km. This gives approximately 10000 visible and 2500 infrared lines and samples for each full Earth scan. Options are provided for subsampling the image data.

The overall spatial subset of data to be extracted can be specified in one of two ways:

1) the smallest rectangular area required to cover a region defined by a master dataset (see master).

2) a rectangular area of a specified size, determined by a start spin number, number of spins (i.e. lines), and two parameters determining the width.

There are no input TeraScan datasets. The sources for input telemetry data are described above. Output is either to a user supplied directory or a user-supplied list of dataset names. If a directory name is entered, output names will be generated and the files will reside in the specified directory. Names will automatically be generated that look like g#.yyddd.hhmm, where # is the GMS satellite number, yyddd is the year and julian date, and time.

Output datasets may optionally be calibrated. The visible data is calibrated from raw count values (0-63) into percent albedo. The infrared data is calibrated from raw count values (0-255) into degrees temperature. The calibration is taken from tables (C.7 and C.8) provided in "The GMS User's Guide" 2nd Ed., Meteorlogical Satellite Center, Tokyo, Japan. March, 1989. Output datasets when calibrated may be 1 or 2-byte data depending on the setting of byte_output.

PARAMETERS

on_pass_disk

Answer yes if the passes are on disk and no if the passes are on tape.
Valid responses are [yes or no]. The default is no.

pass_number

If on_pass_disk=yes, gmsin prompts for pass_number. This is the number of the pass on pass disk to process. You can list passes on disk with the command lspass.
The range of valid responses depends on the disk configuration. The default is the most recent pass.

tape_device

If on_pass_disk=no, gmsin prompts for tape_device. This takes the device address of the input tape device. Tape device names are machine specific.
This must be a valid UNIX tape device address.

first_file

This is the number of the pass on tape where processing is to begin. gmsin only prompts for this parameter if the answer to on_pass_on_disk was no (i.e. pass is on tape).
This number is relative to the current position on the tape. For example, if the tape is positioned at the beginning of the tape, first_file=2 will process the second pass on the tape. If the tape is positioned at the third pass on the tape, first_file=1 will process the third pass, and first_file=2 will process the fourth pass.
Valid range [>=1]. The default is 1.

num_files

This is the number of consecutive pass(es) to process when the passes are archived on tape and the output dataset is a directory.
Valid range is [>=1]. The default is 1.

calibrate

This specifies whether the output datasets should be calibrated as described above.
Valid responses are [yes or no]. The default is yes.

temp_units

OPTIONAL. This determines the temperature units for calibrated IR data. Valid responses are [celsius, kelvin, fahrenheit]. The default is kelvin.

byte_output

If calibrate=yes then this specifies that the output dataset is to consist of 1-byte unsigned values rather than 2-byte values. For the visible channel, the effective range of the output data is 0-76.2 percent albedo at steps of .3%. The effective range of the calibrated infrared data is determined by the base_temp and temp_step parameters described below.
Valid responses are [yes or no]. The default is yes.

base_temp, temp_step

OPTIONAL. If calibrate=yes and byte_output=yes, these two parameters are used to convert temperature output to 8-bit values as follows:
      8-bit value = nearest int( ( temp - base)/step )
temp_step must be in the range [.1, 2.]. There are no restrictions on base_temp. The default values for base_temp and temp_step depend on temp_units. For Kelvin or Celsius, the default temp_step is .5. For Fahrenheit, the default temp_step is 1. The default values for temp_base are -85, 188.15, and -120 for Celsius, Kelvin, and Fahrenheit respectively.

vis_delta

This specifies the rate of visible channel subsampling. If vis_delta=4 every fourth sample of every fourth line will be used. If vis_delta=1, all samples and lines will be retained. Specifying vis_delta=0 indicates that the visible data should not be extracted/stored in the dataset. A subsampling of 4 gives the same visible resolution as full resolution infrared data.
Valid responses are [0,1,2,4,8]. The default is 4.

ir_delta

This specifies the rate of infrared channel subsampling. If vis_delta=4 every fourth sample of every fourth line will be used. If vis_delta=1, all samples and lines will be retained. Specifying vis_delta=0 indicates that the visible data should not be extracted/stored in the dataset.
Valid responses are [0,1,2]. The default is 1.

use_master

Answer yes if the data is to be selected from the intersection of a master dataset (number 1 in the description above, also see master). Answer no if subsets are to be specified by start spin and width (number 2 in description above).
Valid responses are [yes or no]. The default is yes.

master_file

If use_master=yes, this is the name of the master dataset used to specify a region for data extraction (see master).
Valid responses are any TeraScan dataset that contains an Earth transform. The default is Master.

start_spin

If use_master=no, this is the spin (i.e. line) number to start saving data. This number is relative to the infrared resolution (spin numbers).
Valid responses are [1..2500]. The default is 1.

num_spins

If use_master=no, this is the number of spins (i.e. lines) to retrieve. This number is relative to the infrared resolution (spin numbers) and in terms of unsampled spins. Thus if num_spins=500 and delta_vis=2 then the actual number of visible lines will be 250.
Valid responses are [1..2500]. The default is 2500.

start_percent

If use_master=no, this is the percentage of the image to skip in the scan direction (i.e left to right) before saving data. Thus if start_percent=50, the retrieved image will begin halfway into the scan lines, i.e. at middle of the Earth, and consist of data to the right (east) of this starting point.
Valid responses are [0..<100]. The default is 0.

width_percent

If use_master=no, this is the percentage of the image to retrieve beyond the start_percent. Thus if start_percent=50 and width_percent=50 then the right half of the image will be retrieved.
Valid responses are [>0..100]. The default is 100.

fix_missing

OPTIONAL. This parameter controls whether or not gaps of one or two missing lines are automatically fixed. Valid responses are yes and no. The default response is yes.
The fix rule is as follows; here 'b' means missing data, and numbers mean good data
           input                        output

      b b b b b b b b              b b b b b b b b
      b b b b b b b b              1 1 1 1 1 1 1 1
      1 1 1 1 1 1 1 1              1 1 1 1 1 1 1 1
      b b b b b b b b              1 2 1 2 1 2 1 2
      2 2 2 2 2 2 2 2              2 2 2 2 2 2 2 2
      b b b b b b b b              2 2 2 2 2 2 2 2
      b b b b b b b b              b b b b b b b b
This works well with IR resolution data, but not very good with full resolution visible data, since the minimum gap is usually 4 visible lines.

sixbit

OPTIONAL. This parameter indicates whether the receiving system preserves 6-bit visible data words (yes); or converts them into 8-bit words. Valid responses are yes and no. The default response yes should be used for; data captured with TeraScan system.
ir_rad_table: OPTIONAL. ir_rad_table=yes enables generation of the corresponding radiation lookup tables for IR channel data.; These will be generated only if calibrate=no was specified , otherwise this parameter will be ignored. Radiation lookup; table variable-names are identified by their suffix "_radlut" .; The default is ir_rad_table=no.