National Weather Service United States Department of Commerce

Frequently Asked Questions

 

General Questions about ASOS?:

 

 

 1. How many sites are operated under the ASOS program?
 2. What are the differences between ASOS and AWOS?
 3. When was the ASOS program established?
 4. What are the primary components at a standard ASOS site?
 5. Who receives the information that is observed and transmitted from each ASOS site?
 6. How many ASOS sites are located at non-airport locations?
 7. Where can I see a schedule for planned maintenance/upgrades at a particular ASOS site?
 8. How does ASOS operation affect commercial aviation?
 9. Who maintains the historical data that has been recorded by the ASOS sites and what is that data used for?
10. What weather parameters are observed by a standard ASOS site?
11. Who is responsible for ASOS corrective repairs and maintenance?
12. Where can I get a list of all ASOS sites?
13. What plans are there for ASOS sensors?
14. Can I connect directly to an ASOS to get its data or weather observations?
15. Is it intended to continue forward with two distinct types of Surface Observing Systems?
16. Does NWS intend to transition their ASOS systems to AWOS as well, and if so, when?

 

 

NWS and FAA Transitioning 207 Sites:

 

 

17. Why is the NWS and FAA transitioning 207 ASOS sites to AWOS-C?
18. What sites will be affected under the 207 transition?
19.  When will the ASOS to AWOS -C Transition happen?
20.   Who can I contact about the ASOS to AWOS conversion to these 207 systems?

 

 

AWOS-C Questions:

 

 

21.   Will NWS techniques still be required to maintain the AQOS-C?
22.   Will the NWS logistics and depot centers and repair the AWOS-C's?
23.   As an airport manager, I need to know what is happening to my ASOS. Where can I find this information?
24.   Is the AWOS-C as good as the ASOS?
25.   Will there be any integretion issues with the change over from ASOS to AWOS-C?
26.   When will I be notified of the installation of my AWOS-C?
27.   Who determines the priority for installation of the AWOS-C's?
28.   Will the Airport Managers have any voice in the roll-out of the AWOS-C's
29.   Who will be responsible for maintaing the AWOS-C's - NWS or FAA?
30.   Will the AWOS-C data be available to the NWS when the FAA transitions the sites?
31.   What is the impact of this change to first responders, the general public, etc.?
32.   Does NWS intend to transition their ASOS systems to AWOS as well, and if so, when?
33.   Will the FAA reduce the operations and maintenance reimbursement to NWS?
34.   How will the reduction of the FAA's participation in the ASOS program impact the NWS staffing model and system support?
35.   How does the FAA level of service for existing AWOS-C systems compare to the level of service for NWS supported ASOS?
36.   When will notifications be offered?

 

 

Following Answers Are Below:

 

 

1. How many sites are operated under the ASOS program?​
Currently, there are 953 active ASOS sites.
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2. What are the differences between ASOS and AWOS?​
Both systems work to support the reporting of accurate meteorological data to the NWS and FAA for the purposes of weather forecasting and real-time data for aviation safety and are part of the . Whereas AWOS data typically includes ceiling and sky conditions, visibility, temperature, dew point, altimeter setting, and wind speed, gusts, and direction, ASOS can additionally provide type and intensity of precipitation and obstructors to visibility such as fog and haze.
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3. When was the ASOS program established?​
The initial deployment of hardware at ASOS sites began in 1991 and was completed in 2004.
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4. What are the primary components at a standard ASOS site?​
A standard ASOS site will consist of a sensor array of meteorological sensors that includes a 10 meter wind tower, one or more data collection package units (DCP) that take sensor data and package it for transmission to an acquisition control unit (ACU) where algorithms are applied and the observations are transmitted to end users. The physical sensor group typically requires an area of 75ft. by 59ft. clear of debris, ground obstructions, reflective surfaces, and light sources.
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5. Who receives the information that is observed and transmitted from each ASOS site?
There are two types of data transmissions from ASOS, Local and Long Line. Observations are initially viewed by local airport personnel on dedicated terminals and they are also sent to other systems operating at the location being serviced by the ASOS. The long line transmission goes to the National Centers for Environmental Prediction where the observations are then distributed to global networks over the Internet.
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6. How many ASOS sites are located at non-airport locations?
There are 35 ASOS sites not co-located with an aerodrome
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7. Where can I see a schedule for planned maintenance/upgrades at a particular ASOS site?
Maintenance schedules for ASOS sites are published in Engineering handbook #4 and is not available to the general public. The schedule however is based on the equipment maintenance intervals recommended by the manufacturer the most common being a quarterly preventative maintenance followed by semiannual, annual and biennial preventative maintenance regimes.
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8. How does ASOS operation affect commercial aviation?
ASOS is a critical component for aviation safety as it provides real-time local weather information directly to pilots and air traffic control. Real-time weather and altimeter information are essential for safe operation of commercial aircraft and, if the local ASOS at an airport is not functioning properly, a qualified weather observer must be present on site to provide the necessary information for any incoming flight.
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9. Who maintains the historical data that has been recorded by the ASOS sites and what is that data used for?
The National Centers for Environmental Information (NCEI) is the official climatological archive of all weather observations.
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10. What weather parameters are observed by a standard ASOS site?
ASOS sites track wind speed, direction, and gusts, temperature, dew point, altimeter setting, cloud height and type, visibility, present weather, precipitation identification and accumulation, and thunderstorm occurrence.
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11. Who is responsible for ASOS corrective repairs and maintenance?
The ASOS Operations and Monitoring Center (AOMC) provides around-the-clock operational monitoring support for the ASOS network and is the single point of contact for any operational issue i.e. missing observations, missing observational elements etc.. The AOMC is the tier-one service desk providing real-time monitoring, triage of identified issues and remote diagnostic for identifying, tracking and documenting ASOS malfunctions. The AOMC can be reached via email at aomc@noaa.gov or 1 (800) 242-8194.
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12. Where can I get a list of all ASOS sites?
Here is a link to all active ASOS sites that the NWS maintains.
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13.  What are the planned upgrades for the ASOS sensors?
The NWS has undertaken a comprehensive plan to replace most of the sensors on the ASOS sensor array by the end of 2030. The plan is already in action and the status is: Wind sensor: Vaisala Inc. is the manufacturer of the new ASOS wind sensor. It is the WMT-702 model with heated transducer tips. It is known as an Ice Free Wind Sensor (IFWS). The original contract was awarded in 2017 and is now fully executed. NWS technicians will be completing the deployment of all the new wind sensors by 30 September 2023. Temperature/Dew Point (RH) Sensor (TRH):Vaisala Inc. is the manufacturer of the new ASOS Temperature and Relative Humidity sensor. It is the HUMICAP® Humidity and Temperature Probe HMP155. The original contract was awarded in September 2021 and is still active. The NWS has completed integration testing into the ASOS and is now preparing for operational test and evaluation and full scale National Operational Implementation. Barometer Sensor: Planned for FY2024. Precipitation Accumulation Sensor: Planned for FY2024 Ceilometer: Planned for FY2024 Visibility and Present Weather: Planned for FY2025 Other sensors are in the planning development stage; this FAQ will be updated annually as the projects progress. Last update was April 28, 2023. Back to top

14. Can I connect directly to an ASOS to get its data or weather observations?
Currently this is not possible, however there are plans to make high-frequency ASOS data available through a proxy. When it is ready to debut into the production environment, it will be announced. The most recent METAR is available on the Aviation Weather site METAR page.
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15.  Is it intened to continue forward with two distinct types of Surface Observing Systems?
Currently there are several different types of surface observing systems. More information about the number of systems and their placement in the Automated Surface Weather Observing Network (ASWON) can be found Here Back to top

16.  Does NWS intend to transition their ASOS systems to AWOS as well, and if so, when?
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NWS and FAA Transitioning 207 Sites:

 

17.  Why is the NWS and FAA transitioning 207 ASOS sites to AWOS-C?
The FAA funding budgeted for this upgrade is insufficient to recondition all 570 FAA ASOS locations to the modernized processing and dissemination integrated systems. The decision to transition to the AWOS-C in lieu of ASOS 2.0 was therefore a budgetary decision by the FAA. Back to top

18. What sites will be affected under the 207 transition and what parameters were used for their selection?
See a complete list here Back to top

19.  When will the ASOS to AWOS-C Transition happen?
The schedule currently has a start date of 2025 and lasts through 2029. Back to top

20. Who can I contact about the ASOS to AWOS-C?
Mr. Steve Kim and Mr. Jerry Krantz. steve.kim@faa.gov, jerry.ctr.kranz@faa.gov. Back to top

 
 

 

AWOS-C Questions:

 

21.  Will NWS technicians still be required to maintain the AWOS-C?
Yes. Electronics technicians from the FAA will take over all operations and maintenance of those 207 ASOS to AWOS converted locations. Once the AWOS-C is commissioned, the NWS will no longer be responsible for the operations and maintenance of the AWOS sites. Back to top

22.  Will the NWS logistics and depot centers stock and repair the AWOS-C’s?
No. The FAA will be responsible for stocking consumable and repairable parts and spares for the AWOS-C sites upon conversion. Back to top

23. As an airport manager, I need to know what is happening to my ASOS. Where can I find this information?
As of 11 July 2022, the FAA is planning to convert the ASOS to an AWOS-C; the schedule will be published at a later date. An FAA representative will be in touch to coordinate the scheduled maintenance and upgrade. Back to top

24. Is the AWOS-C as good as the ASOS?
Yes, the sensors are almost identical to the ASOS. The AWOS-C has similar performance characteristics as ASOS. Back to top

25.  Will there be any integration issues with the change over from ASOS to AWOS-C?
Yes, during the coordination with the FAA in advance of the installation date. Back to top

26.  When will I be notified of the installation of the AWOS-C?
The schedule for the ASOS to AWOS transition is slated to begin in October 2025. More information will be provided by the FAA as the installation date approaches. Back to top

27.  Who determines the priority for installation of the AWOS-C’s?
The FAA will make this decision in coordination with the affected sites. Back to top

28.  Will the Airport Managers have any voice in the roll-out of the AWOS-C’s?
Yes, during the coordination with the FAA in advance of the installation date. Back to top

29. Who will be responsible for maintaining the AWOS-C's - NWS or FAA?
The FAA will be responsible for the maintenance of the FAA AWOS-C Systems. Back to top

30. Will the AWOS-C data be available to the NWS when the FAA transitions the site?
Yes, routine weather data availability will be maintained after the ASOS to AWOS-C transition. Back to top

31.  What is the impact of this change to first responders, the general public, etc.?
There should be no impact to weather observation availability for all users of the data being provided by these systems. Back to top

32.  Does NWS intend to transition their ASOS systems to AWOS as well, and if so, when?
There are no NWS plans to transition ASOS to AWOS. Back to top

33.  Will the FAA reduce the operations and maintenance reimbursement to NWS?
Yes, the exact amount has yet to be determined. Back to top

34.  How will the reduction of the FAA’s participation in the ASOS program impact the NWS staffing model and system support?
The extent to which the FAA will reduce payments to the NWS has not been determined. Weather Service HQ is working toward a solution that will be transparent to the system support model currently in place. Back to top

35.  How does the FAA level of service for existing AWOS-C systems compare to the level of service for NWS supported ASOS?
They are comparable based on each Agency’s respective maintenance policies. Back to top

36. When will notifications be offered?
The FAA will provide the necessary notifications to airport managers for the transition of their ASOS to an AWOS-C in advance of any planned activity. Back to top

 

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