ESA title
Enabling & Support


6749 views 12 likes
ESA / Enabling & Support / Operations / Ground Systems Engineering

Short description: Space Link Extension API


The ESA SLE API Package implements the SLE C++ Application Program Interface for the CCSDS Space Link Extension (SLE) Transfer Services, which are independent of any specific technology used for communication between a SLE Service User and a SLE Service Provider and therefore facilitate the cross-support between space agencies.

The API is intended for use by application programs implementing SLE Services.

The ESA SLE API Package (single package for both SLE API user and provider) supports the following SLE transfer services:

  •  The Return All Frames (RAF)
  •  The Return Channel Frames (RCF)
  •  The Return Operational Control Field (ROCF)
  •  The Forward Command Link Transmission Unit (CLTU)
  •  The Forward Space Packet (FSP)


The ESA SLE API Package provides the following extensions to the SLE API required for integration of the package into existing ESA applications:

  •  An additional layer that allows applications to retrieve SLE Protocol Data Units from the API instead of providing an interface that is called by the API
  •  A wrapper providing an interface for the C Language

The ESA SLE API Package implements the following main features:

  • Mapping of the SLE protocol to TCP/IP (via fully implementing the ISP1 standard), including association establishment and release
  • Access control and authentication
  • Handling of state machine for the SLE transfer services as recommended by CCSDS
  • Handling of transfer buffers and flow control for Return services

The API software package is portable; it currently supports Solaris 8, Linux (SLES 11) 32 and 64 bits and Windows 2003. 

Related Links