Aviation Surface Weather Observation Network (ASWON) is a service portfolio with the following primary and backup weather observation systems that we deploy throughout the National Airspace System (NAS):

• Automated Weather Observing System (AWOS)
• Automated Surface Observing System (ASOS)*
• Surface Weather System (SWS)
• Stand Alone Weather Sensors (SAWS)
• Digital Altimeter Setting Indicator (DASI)

* The National Oceanic and Atmospheric Administration National Weather Service (NWS) maintains ASOS through an interagency agreement.

AWOS-C and ASOS provide required surface weather observations. These systems generate weather observations containing the following:

• Wind speed, direction and gust information
• Temperature
• Dew point
• Altimeter setting
• Cloud height and amount
• Visibility
• Present weather
• Precipitation accumulation
• Thunderstorm occurrence

SWS, SAWS and DASI provide a second source of required weather parameters at towered/staffed airports in the NAS.

Description of ASWON Portfolio

The ASWON portfolio includes several surface sensors that measure weather parameters on the surface and report conditions to air traffic facilities and pilots. The data collected is important to pilots and dispatchers as they prepare and file flight plans and vital for weather forecasting.

AWOS-C and ASOS, which are the primary automated surface observing systems, provide around-the-clock weather observations at airports throughout the NAS. These primary systems construct weather observations using a suite of meteorological sensors typically located at an airfield. The weather observation is broadcast to pilots in the airport vicinity using a Very High Frequency radio transmitter or an Automatic Terminal Information Service and provided by dial-up telephone service.

Leased telecommunication services send the Meteorological Terminal Aviation Routine Weather Report's weather observation to users through the national weather data network. NWS uses the observation data to prepare forecast and warning products. Each primary system consists of a sensor group located on the airfield, a platform for data collection (usually collocated with the sensor group) and a centralized data processor which receives data from the data collection platform and processes it using weather algorithms.

As secondary systems, SWS, SAWS and DASI, are used for backup or enhancement of the primary system weather elements (for example, barometric pressure, wind and temperature/dew point) and for operational support of air traffic control. SWS and SAWS support primary systems by providing data on wind speed and direction, gust, dew point and relative humidity. DASI measures the atmospheric pressure and provides data in a digital format at Tower and Terminal Radar Approach Control controller positions. Controllers send the altimeter setting value to aircraft pilots for their use in local settings of the aircraft altimeter. 

ASWON Sustainment 2 (ASWON S2)

ASWON is a part of the Weather Sensors Portfolio, which consolidates, prioritizes and manages sustainment activities for the weather sensors programs.

ASWON S2 address obsolescence of hardware components no longer manufactured or supported by the vendor coupled with insufficient inventory of sub-systems and parts.  

Current Goals

ASWON S2 provides technology updates or replacements (based on form, fit or function) for the ASOS, AWOS-C, SWS, SAWS and DASI which are required to sustain operational capabilities provided by this network. The program is currently:

• Replacing obsolescent weather sensors, processors and software
• Increasing hardware commonality among systems 
• Providing Operation and Maintenance cost savings by reducing the number of surface weather system types in the NAS 

Systems Being Sustained

• Two Primary surface weather observing systems - AWOS-C and ASOS
• Two Backup systems - SWS and DASI
• SAWS will be converted to SWS
• Replace 206 ASOS with AWOS-C