What is TAMDAR?
TAMDAR (Tropospheric Airborne Meteorological Data Reporting) is a new, high-resolution atmospheric observing system. The TAMDAR system comprises a patented multi-function atmospheric sensor installed on commercial scheduled aircraft, a near real time satellite data communication system, and AirDat's ground-based data processing and distribution systems. High-resolution continuous TAMDAR observations fill in the gaps in conventional atmospheric data to create more accurate weather forecasts.

Who is AirDat?
AirDat LLC is a privately held company formed in 2003 to develop the TAMDAR sensor, implement the supporting infrastructure, and create superior weather information solutions with the unique data set. AirDat also provides communication, tracking and specialized weather services to its airline partners in exchange for their carrying the TAMDAR sensors.

Can TAMDAR be installed on any aircraft?
TAMDAR has been installed on a wide range of airframe types, however twin- or multi-engined aircraft offer the broadest choice of mounting locations. The TAMDAR sensor is a lightweight (1.5 lb.), low drag (0.4 lb. @ 200 knots), low power device designed for easy installation and retrofit to any aircraft. It is a stand-alone system that does not require interaction with any critical aircraft systems; this simplifies certification and crew training requirements.

How are TAMDAR observations collected?
Observations are taken at specified pressure altitude levels (remotely programmable by AirDat) as the aircraft takes off and climbs to cruise altitude. At cruise, observations are switched to a time-based protocol (also remotely programmable) and then switched back to pressure-based levels as the aircraft descends to land. As they are made, observations are transmitted to AirDat's data center and are typically available for model assimilation or analysis within a minute of the time of observation.

AirDat employs a two-way satellite communication system to downlink TAMDAR data and uplink sensor commands. The data center receives, processes, archives and distributes TAMDAR atmospheric data in effectively real time and can provide other data link, modeling, and analysis solutions as well as network services to weather information customers and aircraft operators.

What atmospheric variables are measured by TAMDAR?
Atmospheric measurements performed by the TAMDAR sensor include:

		Humidity
		Pressure
		Temperature
		Winds aloft
		Icing
		Turbulence
		Location,time, and altitude from built-in GPS

Are TAMDAR measurements consistent with current meteorological standards?
The TAMDAR sensor was designed to requirements defined by NASA, NOAA/FSL, and the World Meteorological Organization (WMO). The data output format meets the unique needs of TAMDAR, while maintaining compatibility with US ACARS and international AMDAR standards. Independently reviewed flight tests have confirmed the accuracy of the TAMDAR observations.

How frequently are TAMDAR measurements taken?
TAMDAR observations are based on pressure, rather than time, intervals during the ascent and descent phases. Time defaults are provided for portions of the flight when the aircraft is not significantly ascending or descending. All intervals and defaults are remotely adjustable from the data center.

When operating under typical high-resolution settings, ascent and descent observations are made at 10 hPa (300 feet) pressure intervals up to 200 hPa (6000 feet) above ground level. Observations more than 200 hPa (6000 feet) above ground level are made at 25 hPa intervals. If an observation has not been made below 20,000 feet (465 hPa) for three minutes, then an observation is triggered by time default; if an observation has not been made above 20,000 feet (465 hPa) for seven minutes, then an observation is triggered by time default.