How to Interface


There are eight primary science ports on the MARS node.  In general, a Principal Investigator (PI) will be assigned one science port.  Each port provides 48 VDC, 375 VDC, a 10/100Base-T TCP/IP Ethernet connection, and a pulse per second (PPS) precision timing signal.  The port interface is detailed below.



The science port connector is a 12-pin, wet mateable, 45 degree, flying ROV style connector from Ocean Design, Inc. (ODI). ODI does not provide a part number for the connector. ODI will work with MARS PIs to develop a complete cable assembly.

Front view
Side view





Longer lengths will require smaller, more flexible cable types. The choice of cables and connectors that the ROV must handle are critical to the success of your deployment. We will be happy to work with you to properly specify these elements.

Molded cable
Molded cable
Oil-filled cabled





Important: It is critical for PIs to work with MARS Operations and Maintenance staff to ensure that their cable assemblies are suitable for successful deployments.

Cable assembly must use the pinout described on this page.


The pin assignments for the science port:

Pin No.Description
51 PPS+
61 PPS-
9375 VDC+
10375 VDC-
1148 VDC+
1248 VDC-


Electrical specifications:

  • 48 VDC:
    • Continuous power:
      100 W maximum.
    • Peak power:
      Additional power can be provided to meet short term needs.  Please discuss your power requirements with MARS O&M staff.
    • Inrush current:
      10A absolute maximum; 3 millisecond max. duration.
  • 375 VDC:
    • Continuous power:
      500 W maximum.
    • Peak power:
      Significantly more power can be provided at 375 VDC to meet short term needs.  Please discuss your power requirements with MARS O&M staff.
    • Inrush current:
      15A absolute maximum, 3 millisecond max duration.

Note: Please monitor your equipment’s inrush current.  We have observed many commercial power supplies that draw as much as 50A on power up, regardless of steady state current requirements.

  • 1 PPS
    • The 1 PPS is driven by this circuit:

Click image for specification

Specification for 4N37 optocoupler.

A typical receive circuit is shown below:


Suggested user interface circuit

Ethernet Communication

The communication channel for all MARS science ports is a standard 10/100Base-T Ethernet port using TCP/IP protocol.  Each MARS science port is assigned a Class C subnet which can provide up to 245 individual IP addresses to a single science port (11 are reserved for internal MARS functions).  MARS O&M staff will work with PIs to assign appropriate IP addresses.