Requirements Engineering

Overview

In spaceflight software development, requirements engineering forms the critical foundation that prevents costly mission failures. A single ambiguous requirement can cascade into software defects that manifest millions of kilometers from Earth, where patches are impossible and failures are catastrophic.

FSW Engineering specializes in developing rigorous, traceable requirements that bridge the gap between high-level mission objectives and implementable software specifications. Our approach ensures every requirement is testable, unambiguous, and directly traceable to mission success criteria.

What We Deliver

01

Software Requirements Specifications (SRS)

Comprehensive documents detailing functional and non-functional requirements, conforming to IEEE 29148 and mission-specific standards.

02

Requirements Traceability Matrices

Guidance on establishing bidirectional traceability from mission objectives through design, implementation, and verification artifacts.

03

Interface Requirements Documents

Detailed specifications for all software interfaces including command and data handling, telemetry, and inter-subsystem communications.

04

Verification and Validation Planning Guidance

Consulting on test approach strategies and mapping requirements to appropriate verification methods.

Our Process

Requirements Elicitation

Conduct stakeholder interviews, mission concept reviews, and technical analysis to extract complete requirements from mission objectives and constraints.

Requirements Analysis

Decompose high-level requirements, resolve conflicts, identify gaps, and ensure completeness and consistency across all requirements.

Requirements Specification

Document requirements using precise language, establish measurable acceptance criteria, and structure requirements for traceability.

Requirements Validation

Conduct formal reviews, validate testability, verify completeness against mission objectives, and obtain stakeholder sign-off.

Requirements Examples

Structured Natural Language Requirement

SCOPE: In eclipse mode
CONSTRAINT: when PayloadDeckTemperature < 8 degrees Celsius
SUBJECT: ATCS
SHALL: shall
TIMING: always
RESPONSE: HeaterCommand = ON

                            "In eclipse mode, when PayloadDeckTemperature < 8 degrees Celsius, ATCS shall always satisfy HeaterCommand = ON."
                        

An Example Formal Specification (SPARK/Ada Contract)

-- Mission parameters loaded from configuration table
procedure Update_Thermal_Control
(Mode : in Operation_Mode;
Temperature : in Sensor_Reading;
Heater_Cmd : out Heater_Command)
with Pre =>
Temperature.Valid and
Temperature.Value in MIN_SENSOR_TEMP .. MAX_SENSOR_TEMP,
Post =>
(if Mode = Eclipse and Temperature.Value < HEATER_SETPOINT
then Heater_Cmd = ON)
and then
(if Mode = Eclipse and Temperature.Value >= HEATER_SETPOINT
then Heater_Cmd = OFF);

Conformance and Compliance

The aerospace industry operates under stringent government regulation subject to multiple compliance regimes. Functional safety standards including MISRA for software reliability, DO-178C for airborne systems, NASA NPR 7150.2 for software engineering, ISO 26262 for automotive-grade safety systems, and applicable FDA CFR requirements for medical devices establish the framework for safety-critical software development. Conformance and compliance with applicable IEEE and MIL standards are accomplished through carefully planned, systematic approaches. FSW Engineering provides expert consulting on compliance planning and execution strategies, recognizing that achieving certification requires coordinated effort across engineering, quality assurance, and program management disciplines.

Technical Expertise

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Flight Software Modes and States: Requirements for nominal operations, safe modes, contingency responses, and state transition logic

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Command and Data Handling: Flight computer and avionics requirements, Protocol specifications, timing constraints, and telemetry requirements for spacecraft communications

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Fault Detection and Isolation: Requirements for anomaly detection, diagnostic logic, and autonomous recovery procedures

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Safety-Critical Systems: Requirements engineering for systems requiring formal verification and DO-178C Level A certification