ROS is a brand-new Amateur Radio digital spread spectrum mode.
The first contact with ROS took place on February 18, 2010, at 20:56 UTC from Vitoria in Spain to the University of Twente in the Netherlands covering a distance of 1265 Km on 7.065 MHz. The first Ham Radio Operator to receive was EA2LE.
The HF frequencies currently used for ROS are USB 3.600, 7.053, 14.101, 28.300 MHz
To use ROS you just need your HF radio, a PC and a basic PC sound card interface, see link below.
The software for ROS is free and can be found at http://rosmodem.wordpress.com/ along with the Introduction to ROS Spread Spectrum and a user guide