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ASDL Format
Aircraft-Satellite Data Link

The Aircraft-Satellite Data Link (ASDL) is a method of transmitting data in real-time from research and reconnaissance aircraft via a satellite uplink to land stations, so that it might be ingested into computer models in a timely manner. The data is sent every 30 seconds, one minute, or two minutes as set by the onboard operator. The data are in ASCII format and consist of a two line header which identifies the aircraft, mission, storm, and date of the transmission. There follows a block of flight information, where each line is one observation. Each line displays the time of the observation, the aircraft location, the air pressure, height of the aircraft, the extrapolated surface pressure, the temperature, dew point, wind direction and speed, 10 second average wind speed, SFMR derived wind speed, and quality control flags.

The following is taken from Appendix G of the National Hurricane Operations Plan.

Example ASDL transmission

01234567890123456789012345678901234567890123456789012345678901234567890
-----------------------------------------------------------------------
URNT15 KNHC 281426
AF302 1712A KATRINA HDOB 41 20050928
142030 2608N 08756W 7093 03047 9333 +192 +134 133083 089 080 999 00
142100 2609N 08755W 7091 03054 9330 +166 +146 133106 115 103 999 00
142130 2610N 08754W 7058 03040 9295 +134 +134 135121 124 111 999 00
142200 2611N 08753W 7037 03060 9291 +124 +124 138129 136 122 999 00
.
.
.
142230 2612N 08752W 7010 03057 9282 +102 +102 141153 166 148 999 00
142300 2612N 08751W 7042 03010 9293 +088 +083 133159 164 147 999 00
142330 2613N 08750W 6999 03064 9279 +088 +088 138158 161 144 999 00
142400 2614N 08749W 7005 03046 9281 +080 +080 138155 158 142 999 00
142430 2614N 08748W 6998 03048 9278 +078 +078 138151 153 137 999 00
142500 2615N 08747W 7002 03048 9279 +084 +084 140146 148 133 999 00
$$

ASDL header explanation

01234567890123456789012345678901234567890123456789012345678901234567890
-----------------------------------------------------------------------
IIIIIIIIIIIIIIIIIIIIIIIIIIIIII HDOB NN YYYYMMDD
AF302 1712A KATRINA            HDOB 41 20050928 <  example

III...III:
Mission identifier, starting with the aircraft ID, followed by
the mission number and storm ATCF code, and then the storm name.

HDOB:
High Density OBservation

NN:
Observation number (01-99), assigned sequentially for each
message during the flight. This sequencing is independent of the
numbering of other types of messages (RECCO, DROP, VORTEX, etc.),
which have their own numbering sequence.

YYYYMMDD:
Year, month, and day of the first data line of the message.

ASDL data explanation

01234567890123456789012345678901234567890123456789012345678901234567890
-----------------------------------------------------------------------
hhmmss LLLLH NNNNNW PPPP GGGGG XXXX sTTT sddd wwwSSS MMM KKK ppp FF
142230 2612N 08752W 7010 03057 9282 +102 +102 141153 166 148 999 00 < example


hhmmss : Observation time, in hours, minutes and seconds (UTC). The observation
         time is the midpoint of the 30-s averaging interval used for the
         record's meteorological data.

LLLLH  : The latitude of the aircraft at the observation time in degrees (LL)
         and minutes (LL). The hemisphere (H) is given as either N or S.

NNNNNH : The longitude of the aircraft at the observation time, in degrees
         (NNN) and minutes (NN). The hemisphere (H) is given as either E or W.

PPPP   : Aircraft static air pressure, in tenths of mb with decimal omitted,
         at the observation time. If pressure is equal to or greater than 1000
         mb the leading 1 is dropped.

GGGGG0 : Aircraft geopotential height, in meters, at the observation time.

XXXX   : Extrapolated surface pressure or D-value (30-s average). Encoded as
         extrapolated surface pressure if aircraft static pressure is 550.0 mb
         or greater (i.e., flight altitudes at or below 550 mb). Format for
         extrapolated surface pressure is the same as for static pressure. For
         flight altitudes higher than 550 mb, XXXX is encoded as the D-value,
         in meters. Negative D-values are encoded by adding 5000 to the
         D-value.

s      : Sign of the temperature or dew point (+ or -).

sTTT   : The air temperature in degrees and tenths Celsius, decimal omitted
         (30-s average).

sddd   : The dew point temperature, in degrees and tenths Celsius, decimal
         omitted (30-s average).

www    : Wind direction in degrees (30-s average). North winds are coded as
         000. 999 indicates missing value.

SSS    : Wind speed, in kt (30-s average). 999 indicates missing value.

MMM    : Peak 10-second average wind speed occurring within the encoding
         interval, in kt. 999 indicates missing value.
KKK    : Peak 10-second average surface wind speed occurring within the
         encoding interval from the Stepped Frequency Microwave Radiometer
         (SFMR), in kt. 999 indicates missing value.

ppp    : SFMR-derived rain rate, in mm/hr, evaluated over the 10-s interval
         chosen for KKK . 999 indicates missing value.

FF     : Quality control flags.

	First column indicates status of positional variables as follows:
		0 	All parameters of nominal accuracy
		1 	Lat/lon questionable\
		2 	Geopotential altitude or static pressure questionable
		3 	Both lat/lon and GA/PS questionable

	Second column indicates status of meteorological variables as follows:
		0 	All parameters of nominal accuracy
		1 	T or TD questionable
		2 	Flight-level winds questionable
		3 	SFMR parameter(s) questionable
		4 	T/TD and FL winds questionable
		5 	T/TD and SFMR questionable
		6 	FL winds and SFMR questionable
		9 	T/TD, FL winds, and SFMR questionable
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