The GPS Validation Project The GPS validation project is a monitoring service developed by the Danish Meteorological Institute and TERMA. The basic objectives for the project are the following: • Identify and describe Space Weather conditions which can adversely affect the quality and reliability of atmospheric profiling data acquired through GPS occultation measurements. • Define characteristics indicative of poor GPS data quality resulting from adverse space weather effects. • Devise algorithms to validate GPS data products in an operating near-real-time end-to-end chain for processing of GPS data from telemetry to application
The content of the service GRAS SAF will deliver RO products based on data from Metop. Metop GPS The service monitors effects of space weather on radio occul-tations. Data from CHAMP is used. Difference in temperature is monitored.
User needs Defined to monitor and identify the occurrence of space weather effect on GPS radio occultation measurements. The difference between the retrieved temperature profile and ECMWF is selected as a suited measure to use for this identification. • The temperature difference with respect to ECMWF in each height interval must reflect the same local time and each difference are obtained as an average difference in the given interval. • Local time difference between occultations shall be less than 1 hour. • An average difference wrt. ECMWF is derived for each height interval. • Height intervals are defined as 10-15, 15-20, 20-25, and 25-30 km. • Each difference is shown as a function of UTC for the given occultation.
User satisfaction • The primary user of GPS validation is the GRAS SAF project, delivering atmosphere profiles in NRT to (NWP) centers. • The algorithms to identify and validate effects of space weather on radio occultations is the primary goal. • The cost of an operational service at the current level (web page, no guarantee for NRT) is approx. 0.5 my/yr. • With additional products such as electron density the service has a potential to be supported as a EUMETSAT activity
Prospects for improvements • This service is designed to monitor the effects of space weather on atmosphere profiles derived from radio occultation measurements (currently based only on GPS). • The radio occultation data can also be used to directly derive profiles of electron density. Monitoring of the ionosphere is a potential for improvement. • Collaboration with other SDA’s such as: Scintillation Quickmaps, SPECTRE, and SWIPPA. • The data sources will increase next year with both Metop setting and rising occultations and the COSMIC constellation of six satellites. • The potential customersare satellite organisations such as EUMETSAT. However this involves making the service a co-operating part of EUMETSAT.