Page 218 - Intro to Space Sciences Spacecraft Applications

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Spacecraft Design
mission and payload, a number of different concepts may be formulated
that can achieve the mission objectives, and these concepts will be
expanded to determine the feasibility of conducting the mission. This con-
cept development will include ground system and operations as well as
launch vehicle and spacecraft descriptions, but the level of detail is usual-
ly in the form of estimates based on contemporary systems and technolo-
gies. After the concept is formulated, a rough order ofmagnitude (ROM)
cost for the mission is attained using heritage cost models and known
costs for subsystems and services. Exceptions to this are unique, one-of-
a-kind designs or pioneering first efforts.
The results of this phase are reviewed at a “local” level-within a tech-
nical center, military or industrial laboratory, university, or similar orga-
nization-to determine if the concept warrants further consideration out-
side the group. For example, within NASA, if the concept looks
promising, an announcement ofopportunity (AO) may be issued which is
the first step in defining and selecting the instruments/experiments that
will fly on the mission if it is fully developed and launched. If concept
study results prove to be promising, the evolving program moves on to the
next step in Phase A, a more detailed mission evaluation.

Mission Analysis Phase (Phase A). The purpose of the mission analysis
phase is to translate the broad mission concepts and objectives into a fea-
sible preliminary system design. This is a refinement and expansion of the
conceptual study phase made with the intention of providing a concise,
clear overview of the proposed system. Implementation planning is done
in cooperation with discipline engineering groups (attitude control,
power, thermal, and other spacecraft subsystems areas defined in the pre-
ceding chapter), payload specialists (e.g., remote sensors and communi-
cations transponders), and ground and launch services organizations.
Financial analysts utilize parametric cost models to derive top-level
resource estimates for the overall mission and its component elements.
Key activities during this phase are system and subsystem trade studies,
analyses of performance requirements, identification of advanced technol-
ogyAong lead items, risk assessments, and end-to-end system life-cycle
costs as a trade parameter. In addition, considerable attention is given to
schedule options and selection and evaluation of operational concepts.
Specific tasks to support this phase may include technical feasibility
and risk assessments associated with cost estimate modeling. Special
attention is given to interface identification, definition, and analysis