According to Jane’s ‘Land-Based Air Defence’ Velos (with quote “12 Skyguard fire-control systems, 20 quadruple RIM-7M missile launchers, 280 missiles, 44 GDF-003 guns and four Giraffe radar systems”) was quote “delivered from 1984.”
Velos seems to be used by HAF rather than the Hellenic Army – as far as I can tell. I think it might be used to protect Greece’s main airbases.
Some photos of Velos and other Greek air defence systems:
http://greekmilitary.net/airdefence.htm