Environmental Engineering Reference
In-Depth Information
Simple constellations are groups of identical spacecraft that coordinate
their data collection. As in formation flying, merging the data collected by
the constellation enables a more complete view of the science. Advanced con-
stellations are able to collaborate during planning phases of the mission, which
allows them to allocate tasks to the most suitable spacecraft.
Complex constellations are heterogeneous mixes of different spacecraft.
They share the characteristics of simple constellations, but differences in
spacecraft sensors allow collections in either multiple spectra (e.g., infrared
(IR) and ultraviolet (UV)), or different disciplines (e.g., earth radiation and
atmospheric composition). These differences make the resulting data fusion
more dicult but allow richer, augmented sets of science data. Further, in
such a configuration, older preexisting spacecraft may be used in new ways
not planned by the original designers of the spacecraft.
This section will now use the cooperation models previously developed to
highlight issues related to the development of virtual platforms.
7.5.1 Virtual Platforms Under Current Environment
For virtual platforms to be effective, mission control must be able to select
appropriate spacecraft for data collection and then task them. The current
mission management organization, being designed for single platforms, does
not scale well when managing multiple platforms. Figure
7.13
shows the mis-
sion management structure for a two-spacecraft virtual platform using current
management techniques. Since the science planning group sets the goals for
the whole virtual platform, the group is shared among all the vehicles of the
virtual platform. The group also has the responsibility for fusing the data
returning from all spacecraft.
Each vehicle has its own mission planning group. This group is responsible
for converting the science plan into a mission plan appropriate for the specific
vehicle. This is necessary because each spacecraft will have a different role. It
might be possible to share human planners if the cooperating spacecraft were
similar and the planning demands were modest.
The sequence generation and monitoring are very specific to each vehi-
cle, because each vehicle has a specific role to play and sequence generation
is focused upon platform-specific issues like the battery charge or damaged
instruments. It is, therefore, unlikely that the human operators in these roles
could easily be shared.
Given the current mission management structure, virtual platforms would
make serious demands on NASA. Assume, for example, that the platforms
being used have a four member science team and require three mission plan-
ners and one command sequence operator. Managing one spacecraft would,
therefore, need the efforts of eight team members. Figure
7.13
represents a
two-spacecraft virtual platform, which requires twelve team members. The
components of Fig.
7.13
that are shaded are those that must be replicated to
add additional spacecraft to the virtual platform. Therefore, a ten-spacecraft
