News Archive History:

Update: Jan 8, 2024

Data errors at the first operational test site required the rollback of the HMP-155E Temp/Dew sensor to the legacy 1088/DTS1 sensors at Annapolis, MD (NAK). This was successfully completed Thursday, December 14, 2023. NAK was fully operational with the legacy sensors as of the 1754 UTC METAR.

Resumption of the Temp/Dew Operational Test will be announced in the near future.

Update: November 20,2023

The NWS announced the commencement of the Air and Dew Point Temperature sensor replacement Operational Test and Evaluation in this public statement. The ASOS Program is now in an Operational Test and Evaluation posture, the following schedule is provided for information.

The first three sites are being installed in between FAA mandated maintenance moratoriums due to the Thanksgiving and Christmas Holidays that will provide the opportunity for the NWS to monitor these three sites through the month of December 2023. The schedule picks back up in January.

The dates provided are target dates with no guarantees of successful installation. Additional information will be provided as it becomes available.

Temperature and Dew Point Sensor Upgrade

September 20, 2023

Procurements for the new Ta/Td (TRH) sensor system are now complete; the components of the system are:

1. Vaisala HMP-155E dual probe Temperature and Relative Humidity sensor with warmed RH probe to prevent condensation with the additional temperature probe. The HMP-155 can measure temperatures as low as -80C (-112F) and as high as +60C (140F). The full specifications can be found here. The full HMP-155 Users Guide is available here.

2. RM Young Solar Radiation Shields will be employed with HMP-155 specific mounting interfaces. The Ta probe will be in the Compact Aspirated Radiation Shield, Model 43502 while the RH Probe will be mounted into the Multi-Plate Radiation Shield, Model 41005-5. 

3. Campbell Scientific will provide the Electronics enclosure and mounting hardware for the replacement system. The HMP-155 and RM Young Radiation Shields will be interfacing with the Legacy ASOS through an electronics enclosure supplying power and processing data into the Data Collection Package. This power supply will be mounted using ASOS standard flange adaptors to existing pedestals and additional mounting hardware to secure the radiation shields in accordance with the Federal Standard for Siting Meteorological Sensors at Airports.

The ASOS Program Office is preparing for Operational Test and Evaluation OT&E) of the new Temp/Dew system beginning in October 2023 for a period of about four months ending in January 2024. Pending successful operational test, operational implementation will follow throughout 2024 and into 2025 at approximately 953 ASOS sites. Once OT&E sites receive and install their new Temp/Dew systems and testing begins, we will announce the sites to the public.