2009: Heid=30sec, AKUR=15sec, ISAF=30sec
The rest is 30 sec data.
Here you can find 30 sec data made from 1 sec data (automatically using geo++ GNSMART).
This automatic 30 sec data was implemented at the end of 2013.
If you will not find 30 sec data from 2013, you can get 30sec data using GNWEB application http://atlas.lmi.is/geopp_gnweb/gnweb.html