As of November 2012[update], the launch was tentatively scheduled by NASA for 6 April 2014, with docking to the station occurring two days later on 8 April 2014. It is set to return to earth 8 May 2014.
NASA has contracted for the CRS-4 mission and therefore determines the primary payload. Among other NASA cargo, The ISS-RapidScat will be launched as an external payload to be attached on the end of the station's Columbus laboratory.
The CRS-4 mission will also carry two satellites that will be deployed from the ISS. One is Arkyd-3, a 3U CubeSat technology demonstrator from Planetary Resources, and the other is SPINSAT, a 56 cm diameter sphere built by the Naval Research Lab to study atmospheric density. SPINSAT is also a technology demonstrator for electric solid propellant (ESP) thrusters from Digital Solid State Propulsion.