aptin - creates APT AVHRR datasets from APT telemetry data.

aptin - Creates APT AVHRR datasets from APT telemetry data.

SYNOPSIS

aptin  [ parameter=value ... ]  [ inputfile outputfile ]

Parameters are: satellite, timetag, pass_date, start_time, scan_rate.

DESCRIPTION

aptin creates APT AVHRR (Advanced Very High Resolution Radiometer) sensor datasets from APT telemetry data. APT AVHRR is generated from HRPT AVHRR. APT AVHRR is averaged to reduce transmission rate, and subsampled to correct for earth curvature. Also, APT AVHRR data is 8-bit data obtained from an analog signal, whereas HRPT AVHRR is 10-bit data.

aptin uses satellite, pass_date, and start_time to create the earth transform for the output dataset.

The scan_rate is the rate at which the APT analog data stream was sampled to produce the input data. The ideal APT scan_rate is 4160 bytes/second, matching the transmission rate, but rates between 3200 and 6400 are allowed.

scan_rate has an effect on the number of APT video samples per line. If the scan_rate is 4160, the number of APT video samples per line is 909. However, if the scan_rate is 4096, the number of APT video samples per line is 909 * (4096/4160) = 895 (approximately).

aptin does not automatically generate names like other telemetry ingesters, such as avin. The setname function can be used to change the name of the dataset output by aptin to reflect the date, time, and satellite.

An output dataset produced by aptin contains two variables, named ls and ts. Normally, ts is infrared data from AVHRR channel 4, and ls is visible data from AVHRR channel 2. However, for night passes, ls may be infrared data from AVHRR channel 3.

PARAMETERS

satellite: This is the name of the NOAA satellite from which the input raw APT data was obtained, e.g., noaa-11. There is no default.

timetag: This is a [y/n] parameter, indicating whether pass_date and start_time are appended to the front of the raw datafile, or if they need to be specified. The default is no.

pass_date: This is the start date of the input raw APT data. The default pass_date is today. See formats for valid date formats.

start_time: This is the start time (GMT) of the input raw APT data. There is no default start_time. See formats for valid time formats.

scan_rate: This is the scan rate of the process sampling the APT analog data stream. scan_rate is measured in bytes/second. The ideal scan_rate for APT is 4160, but rates between 3200 and 6400 are allowed. The default scan_rate is 4096.

EXAMPLES

Ingest APT data sampled at a rate of 4096 bytes per second.

[902] % aptin /worker/apt/thu22_00.noa XTHU
satellite      : char( 11) ? noaa-11
timetag        : char(  3) ? [no]
pass_date      : char( 15) ? [92/10/17] 92 10 15
start_time     : char( 15) ? 22 00 00
scan_rate      : int       ? [4096]
/worker/apt/thu22_00.noa: Offset to video data = 27
/worker/apt/thu22_00.noa: Number of records found = 1288
[903] %

FILES

$SATDATA/satellite/sensor, orbdata

NOTES

The accuracy of the output dataset's earth transform depends heavily on the accuracy of the start_time given to aptin.

Last Update: $Date: 2000/11/20 18:59:49 $