Page 220 - Intro to Space Sciences Spacecraft Applications

Spacecraft Design
207
This phase has a duration of from one to two years. The costs associat-
ed with this study are usually four to eight percent of total mission costs.

many
In
DesigdDevelopment Phase (Phase 0). instances, these phas-
es are combined into a single phase, since by now the commitment to
build the system may already have been made. The purpose of the
designldevelopment phase is the implementation of the Phase B Plan. The
final design, production development, and fabrication of hardware and
software needed to translate the mission into a reality begins. The phase
often includes launch, deployment, and postlaunch on-station system
checkouts and follow-on operations. Depending on the scope of the
deployed system (Le., multiple satellite weather or navigation system
developments versus one-of-a-kind single satellite programs) this phase
can have an extremely variable duration, lasting from two years to more
than a decade. The costs associated with this phase can also vary consid-
erably-from tens of millions of dollars for SMALLSAT or LIGHTSAT
missions to billions of dollars for defense or planetary exploration satel-
lite programs.
Key activity categories during this phase are linked to the scheduled
sequence of events, with each item listed below applicable to all the mis-
sion elements (space and ground systems and subsystems; payload ele-
ments including spacecraft/payload/ground system interfaces and links):
1. Design and development.
2. Fabrication.
3. Assembly.
4. Integration.
5. Test and evaluation (ambient and space environment exposures).
6. Transfer to the launch site followed by mating and prelaunch checkout.
7. Launch and launch sequence monitoring.
8. On-orbit checkout.
9. Postlaunch operations, which can include retrieval and on-orbit
change or repair.

Perhaps the most important milestones in the Phase C/D process, shown
in Figure 9-2, are the preliminary design review and the critical design
review (PDR and CDR). These signify the release of the design for final
production review (in the PDR), and the essential freeze of the design for
fabrication and assembly (in the CDR).