SMAD

6 The Space Mission Analysis and Design Process 1.1
1.2 The Space Mission Life Cycle 7
A major technological change in future space missions will be increased use of
onboard computers. Space system developers have been very slow to use computers
because of the conservative approach to spacecraft design, long lead times in spacecraft
production, and very real difficulties associated with running a computer reliably
in space.· The shift to increased onboard processing is moving spacecraft toward more
autonomy and increased complexity in terms of the tasks they undertake. Whether this
change drives space costs up or down depends upon the government and industry's
approach to autonomy and software development for space. Spacecraft may follow the
example of ground systems, carrying either low-cost commercial systems or vastly
more expensive but more capable special purpose systems.
We anticipate continuing emphasis on low-cost spacecraft. Small spacecraft will
increase for future space missions. These could be either individual, single-pmpose,
small satellites or large constellations of smaI1 satellites used for communications,
space-based radar, or tactical applications. Again, the community appears to be dividing
into those who can build smaI1, low-cost spacecraft and those who continue to
build large, expensive systems. Creating LightSats represents a new ethic and a new
way of doing business in space. If the space business is to grow and prosper as commercial
aviation has, we must find a way to reduce the costs of using space. Lowering
cost is the real challenge for space mission analysis and design, as well as the govemment
and industrial groups which have created and used this process.
Fmally, the mission' concept and associated space mission architecture largely
determine the cost, complexity, and efficiency of the overall system, This is compounded
greatly when you begin to consider integrating the operational aspects of
many different missions. For example, today within DoD, we have communication,
navigation, signal intelligence, reconnaissance, and weather systems; each with their
own mission concept and architecture. The upcoming challenge is to find ways for
these systems to operate together to meet user needs.
The fundamental question is ''Who are the customers, and what products or services
do they require?" In trying to answer this we find ourselves dealing with informationrelated
issues: What information is required, Where, and in what form? Most
customers don't care about the existence of communications, navigation, or weather
satellites. They need specific information and are not interested in what systems
provide it Today's challenge is to blend the capabilities and information available
from multiple systems to meet customer needs. Military people often express this as
tasking, processing, interpretation, and dissemination, whereas commercial people
often express the same issues as customer requests processing, formatting, and
delivery.
Figure 1-3 is divided along somewhat arbitrary, functional boundaries. We need to,
find ways to dissolve theSe artificial boundaries and create cost-effective solutions to
our customer's information needs. For example, instead of trying to integrate the
separate systems discussed above, we might consider having multimission payloads
and spacecraft that have the ability to gather intelligence information, weather, and
provide navigation using one payload-multimission payloads.
An alternative to creating multimission payloads is to divide the architecture
differently by placing all sensors on one space asset, processing capability on another
• Space computers are far more susceptible than ground computers to single-evenl upsets caused
by the bigh-radiation environment or randomly occurring cosmic rays. To protect against this
damage, we must design computers specifically for use in space, as described in Chap. 16.
and using existing or proposed communications links to move the information around.
A third alternative might be to use a series of low-cost LightSats each doing a separate
function, but in such a way that the end results can be easily and directly integrated by
the user's equipment on the grpund.
These examples provide a slightly different perspective which is difficult for many
organizations, both industrial and government, to adopt because we think and organize
functionally-launch, spacecraft, operations, and so on. Being able to functionally
decompose our missions and divide them into workable pieces has been one of the
reasons, for our success. On the other hand, if we think only functionally it may cause
significant problems. We must also think horizontally and create systems that can be
integrated with other space and ground systems to create capabilities that are greater
than the sum of their parts. As always, our goal is to meet the total user needs at
minimum cost and risk.
1.2 The Space Mission Life Cycle
Table 1-2 illustrates the life cycle of a space mission, which typically progresses
through four phases:,
• Concept exploration, the initial study phase, which results in a broad definition
of the space mission and its components.
• Detailed development, the formal design phase, which reswts in a detailed
definition of the system components and, in larger programs, development of
test hardware or software.
• Production and deployment, the construction of the ground and flight hardware
and software and launch of the first full constellation of satellites.
• Operations and support, the day-ta-day operation of the space system, its
maintenance and support, and finally its deorbit or recovery at the end of the
mission life.
These phases may be divided and named differently depending on whether the
sponso1'-the group which provides and controls the program budget-is DoD,
NASA, one of the many international organizations, or a commercial enterprise. The
time required to progress from initial concept to deorbiting or death of the space asset
appears to be independent of the sponsor. Large, complex space missions typically
require 10 to 15 years to develop and operate from 5 to 15 years, whereas small,
relatively simple missions require as few as 12 to 18 months to develop and operate
for 6 months to several years.
Procurement and operating policies and procedures vary with the sponsoring
organization, but the key players are the same: the space mission operator, end user or
customer, and developer. Commercial space missions are customer driven. The main
difference between users and customers is that customers usua1ly pay for a service,
whereas users receive services that others pay for. Operators control and maintain the
space and ground assets, and are typically applied engineering organizations. End
users receive and use the products and capability of the space mission. They include
astronomers and physicists for science missions, meteorologists for weather missions.
you and me for communication and navigation missions, geologists and agronomists
for Earth resources missions, and the war fighter for offensive and defensive military