Page 219 - Intro to Space Sciences Spacecraft Applications

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Introduction to Space Sciences and Spacecraft Applications
including spacecrafdground data communications interfaces, satellite
tracking system interfaces, and payloadspacecraft bus interfaces. The
definition and evaluation of alternative strategies for the execution and
management of the mission is also an important consideration.
The typical satellite Phase A study has a duration of approximately nine
months to two years. Study costs are usually one to two percent of total
mission costs.

Definition Phase (Phase B). The purpose of this phase is the refinement
of the mission and system architecture and the system design created dur-
ing the mission analysis phase. It is designed to convert the conceptual
system design, which may still include some open trade-off and develop-
ment options, into a final design and baseline for entering the execution
phase. Functional, operational, and performance requirements are refined.
Established interface requirements and specifications are allocated down
to the subsystem or major component level. Firm cost estimates and
schedules are prepared to assure a smooth transition to the subsequent
execution phase C/D. Once a detailed baseline configuration that satisfies
all the mission and program requirements has been established, the defin-
ition phase design, cost, and schedule are submitted to the program spon-
sor for approval.
Key activities during this phase are revalidation of mission require-
ments and system operational concepts. This phase also marks the con-
version of mission requirements to much more specific project require-
ments. Final risk assessments are made along with more narrowly drawn
system and subsystem studies and trades. Schedules and life-cycle costs
are finalized to support the budget acquisition process.
This phase covers the full range of technical, management, resource,
facility, and procurement assumptions. Phase B results in the full docu-
mentation of the entire proposed flight and ground support system. Alter-
nate designs are analyzed in detail to allow the choice of one optimum
flight and ground system approach considering technical performance,
cost, risks, and schedules. The baseline design is totally defined as well as
all major interfaces and system, subsystem, and component specifications.
Specific tasks conducted during this phase include telemetry assess-
ments, analysis of payload hardware, launch vehicle interface analyses,
and in-depth evaluation and categorization of the expected space environ-
ment. Components and subsystems are evaluated, as are production plans,
facility requirements, and contingency workaround or offset plans.