An Object-oriented mission control system development: A progress 
report on SCOS-II and its client projects.

Michael Jones, Andrea Baldi, Paul Howard, R. Melvin, W. O'Mullane

ESA/ESOC, Science Systems Ltd. at ESOC, Vega UK, CARA at ESOC

Abstract:
The second generation of the Spacecraft Operations System (SCOS-II) 
is ESA's new infrastructure for building Mission Control Systems. The 
development started in 1992 and at the time of writing (January 1996) 
has reached release 1.1. It is a very ambitious project, involving 
embarking several new technologies as compared with its predecessor 
system: UNIX platforms (replacing the previous VAX / VMS platforms), 
a distributed system architecture (replacing the former centralised 
one) and object-oriented development techniques, to name the main 
ones. In addition, SCOS-II aims to extend the functions supported 
generically, and the concept of "system elements" permits users to 
have views of the status of spacecraft subsystems, monitoring at 
different levels in the hierachy being possible.

Papers were presented on SCOS-II at SPACEOPS 92 and SPACEOPS 94, 
mainly concentrating on the concepts and early prototyping work. At 
this Symposium, we take a more retrospective look at the project, 
since deliveries have been made covering many basic functionalities 
and substantial work has been done on three "client" missions 
(ENVISAT, MARECS and HUYGENS).

This paper outlines the extent to which the project's aims have been 
achieved, and gives the outlook for the rest of the project (which is 
due to complete at end 1997). Particular emphasis is given to 
experience with object-oriented development techniques. It was found 
that ESA's Software Engineering Standards can be successfully applied 
to object-oriented projects. However, attention (and possibly 
tailoring) is needed in certain areas, for example:

-   mapping the major OO methods to the PSS-05-0 phases.

-   exploitation of the advantages of OO techniques, for example of 
the encapsulation and inheritance properties of OO to achieve better 
reusability and maintainability.

-   management aspects and costing.

Lessons learned from both SCOS-II and its client missions are 
described.