The NWS ASOS was deployed in the early 1990's with chilled mirror dew point sensors manufactured by Technical Services Laboratory. At the time of deployment, ASOS had a design goal for periodic maintenance to be conducted at intervals exceeding 90 days minimum. As the number of deployed ASOS's increased through the mid 1990's, it became apparent that the sensors required more frequent mirror cleanings than anticipated, resulting in higher maintenance costs. In an effort to reduce maintenance costs, and increase sensor availability, an initiative was generated by the ASOS Product Improvement Program to identify a replacement technology for the chilled mirror dew point sensor. A solicitation was issued in August 1998, commercial-off-the-shelf sensors from competing contractors were tested in the spring of 1999, and the successful contractor was awarded a development contract for pre-production sensors in February 2000. Sensor development was completed in early 2001, and pre-production sensors from the chosen manufacturer were delivered for qualification testing. This paper will report on the results of the pre-production sensor test.