Slide 1 Second European Space Weather Week, ESA - ESTEC, 14 –18 November, 2005 The GPS Validation Project 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 GPS validation project is a monitoring service developed by the Danish Meteorological Institute and TERMA. The basic objectives for the project are the following:

Slide 2 Second European Space Weather Week, ESA - ESTEC, 14 –18 November, 2005 The content of the service Metop GPS The service monitors effects of space weather on radio occul- tations. Data from CHAMP is used. Difference in temperature is monitored. GRAS SAF will deliver RO products based on data from Metop.

Slide 3 Second European Space Weather Week, ESA - ESTEC, 14 –18 November, 2005 User needs 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 km. Each difference is shown as a function of UTC for the given occultation. 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.

Slide 4 Second European Space Weather Week, ESA - ESTEC, 14 –18 November, 2005 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

Slide 5 Second European Space Weather Week, ESA - ESTEC, 14 –18 November, 2005 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 SDAs 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 customers are satellite organisations such as EUMETSAT. However this involves making the service a co- operating part of EUMETSAT.