The different optical paths followed by the signals coming from a constellation of GNSS (Global Navigation satellite systems; GPS, Galileo, etc) satellites are governed by variations on the moist air refractivity. The difference between the refracted (atmosphere) and the ideal straight line (vacuum) optical paths are equivalent to delays in the time of reception by ground antennas. This delay can be modeled to retrieve the actual PWV conditions at the Observatories.
The IAC has setup two PWV monitors based on this technique at both Observatories. The monitors use the public data released by two geodetic antennas belonging to the Spanish Instituto Geográfico Nacional (IGN).
Characterization of the Canary Island Observatories
The IAC has long been aware of the importance of promoting initiatives for the characterization and protection of the Canarian Observatories (Roque de los Muchachos -ORM- on La Palma and Teide -OT- on Tenerife). For this reason, the Sky Quality Team was created and then a technical office for sky protection (OTPC) to ensure that the Law protectingCasianaMuñoz Tuñón