This document contains the C&DH software requirements. Comments on this document should be addressed to:
| Mike Blau Building 5, Room N18 GSFC, Mail Code 743.3 (301) 286-7880 blau@sunland.gsfc.nasa.gov |
or |
Joel Chiralo Building 5, Room N18 GSFC, Mail Code 743.3 (301) 286-2931 chiralo@sunland.gsfc.nasa.gov |
|---|
FIGURES
The purpose of this document is to specify the functional and performance requirements for the Command and Data Handling (C&DH) flight software for the Wide - Field Infrared Explorer (WIRE) mission.
WIRE was selected for flight by NASA in 1995 as part of its Small Explorer ( SMEX ) program. WIRE will contain the Spacecraft Computer System (SCS) which was developed as part of the Submillimeter Wave Astronomy Satellite ( SWAS ). Like SWAS, WIRE incorporates standardized space-to-ground communications. Data transmitted to the ground and commands received from the ground are formatted into "packets" within "frames" in accordance with the Consultative Committee for Space Data Systems (CCSDS) and Goddard Space Flight Center (GSFC) standards.
This document is divided into four sections. The first two sections provide an introduction to the WIRE project and a brief discussion of scope, background and objectives of this document followed by an overview of the hardware and operational characteristics which affect the flight software system. The third section discusses the relevant external interfaces and the data flow in both directions of the interface. Section four presents the flight software functional and performance requirements.
Each functional requirement has been assigned a number to be used for traceability and testability during testing and validation of the flight software. Acceptance tests will verify that the flight software implementation satisfies all stated functional requirements. Successful completion of the formal acceptance tests will qualify the software as "operationally ready" for spacecraft Integration and Test (I&T).
The requirements have been grouped according to functional area. The numbering scheme chosen is hierarchical in nature. Each functional section has been assigned a range of numbers that have the format "nnn". Subrequirements within a functional area have the format "nnn.n" where the number to the right of the period is assigned in ascending order based on the number of subrequirements needed to further specify the requirement. Top level requirements throughout this document have been underlined for readability.
The required capabilities of the flight software are defined within this section. The C&DH system control functions, including mode transitions and error detection and response, are provided within the System Management section. Command Management, Telemetry Management, Payload Management, Health and Safety Management, Software Management, and Performance requirements are specified in the succeeding subsections.
FIGURE: C&DH SOFTWARE REQUIREMENTS STRUCTURE DIAGRAM
The flight software requirements are organized into seven functional groups as shown in the above figure. The requirements allocated to C&DH are as follows:
System Management -- contains specifications for the operating system functions, the I/O scheduling, spacecraft time keeping services, and message routing functions;
Command Management -- contains specifications for receiving and executing commands from the ground as well as on-board stored commands.
Telemetry Management -- contains specifications for the output of telemetry to the ground and to the solid state recorder, and the interface to the launch vehicle.
Payload Management -- contains specifications for transferring commands to and receiving telemetry from the instrument.
Health and Safety Management -- contains specifications for the bootstrap functions, collection and reporting of software status, identification and recovery from SEUs and a set of anomalies to ensure fail-safe operations.
Software Management -- contains specifications for memory loads and dumps and the monitoring of memory locations.
Performance -- contains specifications for critical resource utilization and system timings.
When there are functional requirements on the flight software to support an external interface, those functional processing requirements are defined within this section. Refer to appendix A for the ICDs describing the specific interface characteristics.
The allocation of requirement numbers is as follows:
Detailed Requirements:
Associated Links:
WIRE Home Page|||
|||WIRE Mission Requirements|||
|||WIRE System Requirements
Authors: Mike Blau (Code 743.3) (blau@sunland.gsfc.nasa.gov),
Joel Chiralo (the Hammers Company) (chiralo@sunland.gsfc.nasa.gov)
Curator: Tim
Singletary (tsingle@sunland.gsfc.nasa.gov)
Revision: February 15, 1996
Revision History