The Enhanced Medium Altitude Reconnaissance and Surveillance System, or EMARSS, is an American reconnaisance aircraft project that grew out of the failed Aerial Common Sensor

Aerial Common Sensor

The Lockheed Martin Aerial Common Sensor platform was a reconnaissance aircraft airframe, for the United States Army and Navy. The aircraft would have been able to detect troop movements, intercept enemy communications and radar transmissions, and communicate with other aircraft. It would have had...

 project.

The EMARSS system will consist of a commercial derivative aircraft equipped with Electro-optic/Infrared (EO/IR) Full Motion Video (FMV) sensor, a COMINT collection system, an aerial precision Geolocation system, line-of-site (LOS) tactical and beyond line-of-site (LOS/BLOS) communications suites, two operator workstations and a self-protection suite.

Four competing teams submitted bids:

• Boeing
  Boeing
  The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
  
  
• L-3 Communications
  L-3 Communications
  L-3 Communications Holdings, Inc. is a company that supplies command and control, communications, intelligence, surveillance and reconnaissance systems and products, avionics, ocean products, training devices and services, instrumentation, space, and navigation products. Its customers include...
  
  
• Lockheed Martin
  Lockheed Martin
  Lockheed Martin is an American global aerospace, defense, security, and advanced technology company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area....
  
  
• Northrop Grumman
  Northrop Grumman
  Northrop Grumman Corporation is an American global aerospace and defense technology company formed by the 1994 purchase of Grumman by Northrop. The company was the fourth-largest defense contractor in the world as of 2010, and the largest builder of naval vessels. Northrop Grumman employs over...
  
  

The contract was awarded to The Boeing Company in November 2010.

The system is to be based on the Beechcraft King Air 350ER

Beechcraft King Air

The Beechcraft King Air family is part of a line of twin-turboprop aircraft produced by the Beech Aircraft Corporation...

 aircraft (which is already in service as the C-12); the ACS project had selected a larger aircraft, an Embraer ERJ-145.