Experimentation with the Advanced Communications Technology Satellite (ACTS) in support of the Force Projection Army Doctrine

This paper describes the Army's involvement with the NASA ACTS satellite program. The Army's ACTS experiments are described, some preliminary results obtained from laboratory measurements, and the potential of the ACTS technology to influence future Army satellite communications is discussed. Preliminary results indicate that some implementations of data transfer protocols will not support efficient data transfer over T1 satellite links. The Army ACTS program exemplifies the leveraging of both civil and defense funds to benefit both military and the commercial interests. Goals of the Armv ACTS T1 VSAT Program The history of satellite communications is tliat of extraordinary growth and development of new technology. The United States Army has been a leader in the development and uses of satellite technology to support the defense of the United States and its allies. The United States Army Space Command (USARSPACE), in cooperation with NASA. is continuing this tradition of technology leadership through its innovative use of the newly available ACTS technology . Specifically the United States Army interest lies in the capabilities and potential of salellite communications at medium data rates, 4.8 1 5 4 kbls. For example, the benefit of medium data rate data links is illustrated by the time it takes to exhange an image file of 512 x 512 pixels with a color depth of 8 bitslpixel; the file size is 262 kB. At 2.4 kbls and 90 percent efficiency the transfer time is a little more than 16 minutes, but at 1.536 MBIs and 90 percent efficiency the transfer time is less than two seconds. The new Army Force Projection Warfighting Doctrine requires communications range extension for beyond the line-of-sight; Desert ShieldIStorm validated the need for additional satellite communications. The Army's ACTS program responds to these needs as part of USARSPACE's innovative Army Space Exploitation Demonstration Program. USARSPACE plans to use the ACTS system to demonstrate the potential of commercial satellite systems that use on-board signal processing. In particular, USARSPACE's interest lies in the potential of very small aperture terminals (VSATs) and emerging commercial satellite services in support of tactical units to augment military satellite communications. In addition, the Army will investigate the potential of demand assigned multiple access (DAMA) for range extension for the Army's mobile subscriber equipment (MSE). The Army ACTS program consists of three phases: technical, conceptual, and operational. The purpose of the technical phase is to validate a paper design's ability to provide connectivity by implementing this design in actual hardware. The technical goals include: interfacing MSE with commercial telephone equipment; proving the reliability of commercial-off-the-shelf (COTS) routers and channel service units (CSUs) in tactical operations; demonsuating the efficacy of COTS video teleconferencing equipment in tactical oprations; and demonstrating both the connectivity to a fiber optic node of the multidimensional application gigabit internetwork consortium (MAGIC), the Army information network (AIN), the defense data network (DDN), the defense simulation internet (DSI), and the Army tactical command and control system (ATCCS) and the reliability of these interconnections. The conceptual phase consists of using ACTS for new applications of Army satellite communications and proving the efficacy of the ACTS technology for