Medium Data Rate (MDR) Payload

For the Milstar medium data rate (MDR) payloads that fly aboard Flights 4, 5 and 6, Northrop Grumman Space Technology supplies two types of antenna and the digital processing subsystem. MDR’s data rates—as high as 1.55 megabits per second (MBPS) —accommodate voice and data, imagery and targeting intelligence at the 1.55 mbps rate on each of 32 uplink channels.  This capability greatly increases the capacity of the Milstar system and support new missions, such as high-capacity links between Navy shore stations and ships at sea. 

The MDR payload’s Northrop Grumman-developed nulling antennas are capable, without any instruction from a ground station, of detecting and then countering enemy signal-jamming.  This revolutionary capability was developed for Milstar II, with each MDR payload carrying two nulling antennas.  The nulling antennas are well suited to Army coverage requirements, where many troops may occupy a relatively small theater of operations near the enemy.  The Army, therefore needs coverage with protection against close-in jamming. 

Six smaller Northrop Grumman-built MDR antennas produce spot beams and 1.55 mbps data rates without the nulling.  These are called distributed user coverage antennas (DUCAs) and are best matched to the dispersed, global-type requirements of the Navy, which operates ships and shore stations around the world.  Navy vessels and bases tend to be removed from the front and the threat of close-in jamming is much less likely.