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Special Intelligence Submarine Satellite Information Exchange Subsystem (SI SSIXS)

SSIXS is designed to complement terrestrial VLF and Medium Frequency/High Frequency (MF/ HF) communication links between shore-based submarine Broadcast Control Authorities (BCAs) and submarines. In addition to the General Service (GENSER) SSIXS subsystems, an additional SSIXS capability dedicated to Special Intelligence (SI) communications and designated SI SSIXS, has been installed at all five BCAs. SI SSIXS is functionally similar to GENSER SSIXS. The SI SSIXS capability provides privacy among subscribers through the use of unique ID numbers.

The Tactical Data Information Exchange Subsystem (TADIXS) is designed to support the exchange of over-the-horizon targeting (OTH-T) information between shore and Fleet-based computer systems (collectively referred to as tactical data processors [TDPs]) for Navy cruise missile operations. The submarine version of TADIXS hosts the special-interest and general-service SSIXS subscriber program, the FLT SECURE voice, and TACBUOY programs.

The subsystem provides the submarine commander with the capability to receive messages transmitted via the satellite at scheduled intervals ("Group Broadcasts"). Between Group Broadcasts, submarines may transmit messages to the BCA, including a request for messages held in queue. The shore terminal responds to these transmissions with acknowledgments for the individual messages just received and transmits all messages held that are addressed to the queuing submarine. The availability of the two modes of operation, Group Broadcast and Query/Response, permits the choice of whether to be active or passive at the discretion of the submarine commander. One 25-kHz wideband channel on each of the four FLTSATCOM satellites is allotted to SSDCS.

A single SSIXS network may have up to 120 submarine subscribers. A single network may be established on more than one satellite (e.g. when the operating area under the cognizance of a BCA extends beyond the footprint of a single satellite), or two BCAs may share a single satellite channel by offsetting the time of their respective Group Broadcast transmissions.

The SSIXS baseband equipment installed at the BCA locations ashore perform a dual function. It accepts messages for delivery to submarines via either satellite or VLF paths, and receives messages from submarines via the satellite path for onward delivery. It also provides the shore SSIXS operator with the capability to compose and control the VLF VERDIN broadcasts by an interface with the Integrated Submarine Automated Broadcast Processing System (ISABPS).

The SSIXS subscriber terminals afloat perform the complementary operations necessary to permit reception of Group Broadcasts or conduct a Query/ Response episode.

At the BCA, messages addressed to submarines (that have been received from AUTODIN, NAVCOMPARS, or locally over-the-counter in the Message Center) are entered into the SSIXS shore terminal by using the operator console keyboard, the high-speed paper tape reader, or the Submarine Message Automated Routing Terminal (SMART). Aboard the submarine, the message traffic is input via the teletypewriter or tape reader equipment. SSN submarines that have the Data Link Control System (DLCS) installed have an additional input/output capability via the Sensor Interface Unit (SIU) for over-the-horizon targeting (OTH-T) messages. (OTH-T messages are segregated in SSIXS by the presence of a unique two-character (OH) message indicator code in the SSIXS message format.)

Ashore, the SSIXS subsystem shares access to the same satellite RF terminal equipment at the NCTAMS as the other UHF SATCOM subsystems, with the exception of COMSUBGRU SEVEN, Yokosuka Japan, which is equipped with dedicated AN/WSC-3 transceivers. Since each BCA is located some distance away from the NCTAMS, line modems and land lines are required for interconnection. The submarine UHF RF terminal is the single-channel, half-duplex AN/WSC-3. SSIXS transmissions are at the 4800 bps rate. The capability to operate SSIXS in a DAMA net has been successfully demonstrated and will be employed in the future.

Each subscriber to a SSIXS network is assigned a unique identification number which is used in all transmissions to or from the subscriber. The identification numbers are stored within the shore station and subscriber processors. The application of these numbers takes many forms.

At the shore stations, the subscriber identification number, when combined with broadcasts, will determine the number of times message traffic is transmitted to a subscriber. In the event a subscriber chooses to make a transmission to the shore station, this identification number will be included in the transmission. If the number is not included, the shore station will not acknowledge the transmission. The identification number is used at subscriber terminals to screen broadcast transmissions for message traffic directed to the subscriber. The remaining data in the transmission are discarded. In the link-control protocol employed by SSIXS, the broadcast of message traffic does not require an acknowledgment by the receiving subscribers. When a transmission is made by a subscriber to the shore station, the shore station transmits an acknowledgment of the subscriber transmission. The acknowledgment occurs at the beginning of the transmission and is not an integral part of an individual data block transfer.

In 1996, The ASD (C3I) approved the "Integrated Broadcast Service (IBS) Plan" which provides for the integration of the Tactical Information Broadcast Service (TIBS), the Tactical Related Applications (TRAP) Data Dissemination System (TDDS), the Tactical Reconnaissance Intelligence eXchange System (TRIXS), TADIXS-B, and the BINOCULAR efforts into a standardized protocols with compatible hardware and software. This effort was directed by the 1996 House Intelligence Bill.


SSIXS subscriber terminals are installed in SSBN and SSN type submarines.


The shore terminal installations are:

  • Submarine Group 7 Yokosuka, Japan
  • Submarine Group 8 Agnano, Italy
  • Submarine Group 10 Kings Bay, Georgia
  • SUBPAC Pearl Harbor, Hawaii
  • SUBLANT Norfolk, Virginia

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Page last modified: 28-07-2011 00:51:12 ZULU