January 16, 2012

Interface control file - E-5

Describe all the product's interfaces in its environement

A. Scope

The Interface Control File lists and describes all the interfaces between the product and the next higher level.

It is initiated no later than phase B and provides a means of identifying the potential problems connected with the satellite-customer before development begins.

In this way, it makes it possible to negotiate these interfaces very early in the process.

During the C/D phase, it provides a descriptive status of the interfaces before delivery to the satellite-customer.

The Interface Control File is an essential document. It is the product's passport.

The Interface Control File is based on the CNES Standards Reference (RNC) document "RNC-CNES-E-HB-10-509 Contenu type du Dossier de Contrôle des Interfaces (DCI)".

B. Fundamentals

The Interface Control File is prepared by the Product Manager using the specifications of the next higher level.

It is frozen and formally approved by both parties at the end of phase B. It is then configuration managed.

The Interface Control File describes the product's interfaces in the following areas:

  • mechanical interfaces,
  • thermal interfaces,
  • electrical interfaces,
  • TM / TC interfaces,
  • software interfaces,
  • EMC constraints,
  • cleanliness constraints,
  • test interfaces.


C. Typical content

The following content is provided for information. The Interface Control File can adopt a different timetable and breakdown according to the requirements of the next higher level.

1. Scope

This section provides a precise identification and description of the interfaces managed by the Interface Control File.

The procedures for approval (By whom? When?), modification and management (issues, revisions, distribution, etc.) shall be defined in it, with reference to the Documentation Management Plan and the configuration (see M 9).

2. Presentation of the product

This is a detailed description of the product, which is similar to the information given in the "General Description" of the Definition File.

The following shall be included:

  • the scientific objectives,
  • the description of the cooperation and task sharing,
  • the main performance figures of the instrument,
  • the description of the main subassemblies.


3. Operating modes

All the operating modes shall be described here, along with their specific characteristics.

4. Mechanical interfaces

4.1 Coordinate systems

This paragraph gives the coordinate system (X, Y, Z) of the product with respect to the reference axes of the next higher assembly (satellite, launcher, probe, etc.).

4.2 Description of the mechanical concept

The mechanical concept and the various mechanical subassemblies are described and illustrated by diagrams.

4.3 Dimensions

For each pair of components being interfaced, a dimensional drawing (mechanical interface drawing) shows the following, if necessary:

  • the overall dimensions (with tolerances),
  • the surface rawness and treatments,
  • the geometrical interface of the deployable systems,
  • the reference axes, system,
  • the mounting points: position, distance between centres, diameters, tolerances,
  • flatness,
  • position of the centre of gravity (with tolerances),
  • assembly specifications (tightening torques, washers, type of lock, heat seals, etc.),
  • connectors (type, identification, position),
  • surface rawness,
  • location of the marking label.


The other internal characteristics (e.g. the internal dimensions) shall not be included on this drawing.

4.4 Weight

This paragraph is a table that states, for each subassembly:

  • the maximum weight (or estimated weight with tolerance),
  • the exact limits (e.g. without fixing screws, with thermal blanket).


4.5 Positioning and alignment constraints

These are the constraints to be complied with for each subassembly:

  • Positioning constraints

    These define the position of one subassembly with respect to another;

  • Alignment constraints

    These concern:

    • the absolute and/or relative alignment precision of one element with respect to another (e.g. instrument / satellite; optical bench / scanning system; etc.);
    • the required measurement precision for these alignments.


5. Thermal interfaces

These are, for each subassembly of the product:

  • The limit temperatures
    • for in-flight or ground storage (element not energised),
    • on energisation,
    • during operation.
  • The thermal dissipation figures

    These are provided as a function of the operating modes ("on", "off", "stand-by", etc.).

  • The characteristics of the thermal monitoring functions
    • limit temperatures,
    • type of temperature monitoring,
    • power required for the heating lines.
  • The thermal characteristics
    • conduction at the interface (with the carrier vehicle, for example),
    • surfaces and surface conditions,
    • radiation: surfaces, coefficient of absorptivity and emissivity,
    • heat storage capacity (J / kg / °K),
    • impedance of the heaters.


6. Electrical interfaces

6.1 Block diagram

This shall state all the electrical interfaces, including redundancies:

  • electric power supply: type of power supply (regulated, non-regulated, heating), number of lines for each type;
  • telemetry (TM): type of TM (analog, digital, etc.), number of TM functions of each type;
  • telecommand (TC): type of TC (relay, digital, etc.), number of TC functions of each type;
  • pyrotechnic lines: type and number of "pyro" lines;
  • insulation;
  • other interfaces: clock, other instruments, etc.


6.2 Wiring diagram

This is a general wiring diagram which includes the names of the cables, the connectors, the equipment, etc.

6.3 List of connectors

The following shall be stated for each connector:

  • the location (e.g. equipment A) ;
  • the name of the connector ;
  • the type (name of manufacturer + complete part number) ;
  • the general function (e.g. TM, power supply, etc.) ;
  • the polarisation ;
  • the exact limit of the respective supplies (e.g. base + protection cover + saver) ;
  • the principle of the shielding connection points.


6.4 Connector wiring sheets

The following shall be stated for each connector and each pin:

  • the reference of the signal carried (identical on each side of the interface),
  • the type of signal (analog, digital, power, RF, pyro, etc.),
  • the signal shape (period, cyclic ratio, maximum value, minimum value),
  • a graphical representation for complex signals (ramp, modulation, etc.),
  • the category (transmitter or receiver),
  • the pin reference on the connector,
  • the electrical diagram of the interface circuit.


6.5 Electrical grounding circuit

A diagram shall show the connection or insulation arrangement for the mechanical grounding, the primary and secondary 0 Volt references, the shielding, etc.

The maximum contact resistance values shall be defined.

6.6 Power consumption

For each operating mode and each power line, the average power consumption and the peak power, associated with the starting current, shall be provided.

6.7 Interfaces with pyrotechnic initiators

Define, for each initiator:

  • the nominal firing current and duration (or provide the graphs for I = f(Duration) for several temperatures),
  • the minimum firing current and duration,
  • the non-firing safety current,
  • the repeated test current value,
  • the total resistance of the initiator and internal wiring of the product concerned by the Interface Control File,
  • the insulation resistance between the filament and the case of the initiator.


6.8 Other electrical interfaces

This paragraph defines all the other electrical interfaces (on-board clock, other instruments, etc.).

7. Telemetry / Telecommand interfaces

A table shall provide the following, for each item of telemetry / telecommand:

  • the name of the information processed,
  • its acronym or identifier,
  • the type of TM / TC,
  • the address (if applicable),
  • the flow-rate,
  • the sampling rate (analog channels),
  • the structure of digital TM / TC (content of the various words),
  • the characteristic of the signal (high level, low level, rise time, synchro, etc.).


8. Fluid interfaces

This chapter concerns all fluids between two components (hydraulic and ancillary fluids). For each interfaced component, the following are specified:

  • the type of fluid,
  • the reference of the mechanical interface to which it is attached,
  • the pressure,
  • the flow-rate,
  • the fluid cleanliness constraints.


9. Software interfaces

Details shall be given concerning the various elements interfacing with the software:

  • Command
  • Monitoring
  • Scientific data management
  • Archiving
  • Processing
  • Storage
  • Initialisation


10. Stability and pointing constraints

The following shall be stated for each operating mode:

  • the target,
  • the pointing precision,
  • the pointing stability,
  • the required stability period.


11. Ground and in-flight cleanliness constraints

Information concerning the cleanliness constraints during the various life phases of the products in flight or on the ground.

12. Electromagnetic environment constraints

12.1 Design constraints

These are the specific adaptations of the product in response to the general EMC specifications of the project:

  • grounding,
  • insulation,
  • wiring


12.2 EMC characteristics

The EMC characteristics of the product are as follows:

  • radiated disturbance,
  • conducted disturbance,
  • radiated susceptibility,
  • conducted susceptibility.


12.3 Special constraints

These consist of special precautions due to the specificities of the product:

  • . protection against electrostatic discharges,
  • use of dangerous materials,
  • ...


13. Materials used

Expiry limit date, outgassing, etc.

14. Power profiles and volume of information

Indication of the following on timing charts:

  • power profiles,
  • volume of data to be transmitted for each type of telemetry,
  • fluid budget (if applicable),


15. Test interfaces

These are the specific interfaces connected with the test equipment

  • MGSE interfaces: mechanical test fixtures, etc.;
  • EGSE interfaces: interfaces with the satellite simulator, "health" testing equipment;
  • OGSE interfaces: reference cubes, etc.


Refer to the interface example in appendices 1 and 2

16. Operating cycle diagrams

Indication, for the various flight phases, of the defined observation cycles, their duration, their periodicity, the operational constraints on other components, etc.

D. Appendix

1. Typical example of interfaces



2. Interface management responsibilities




RisksIncompatibility with carrier vehicle
Interface Verification File (DCI)


Activities / documentation

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