Environmental Engineering Reference
In-Depth Information
data to point Triana's imaging instrument at the earth. The FSW for the
Epic SI used to image the earth could have been used to process the sci-
ence data in order to derive the earth centroid. The centroid data would then
be communicated to the spacecraft platform FSW for use in improving the
accuracy of the spacecraft's pointing toward the earth center, or a region
offset from the center. This basic autonomy capability will, however, fly on
the Solar Dynamics Observatory (SDO) (scheduled for launch in late 2009).
SDO's guide telescopes (providing precision-pointing support to its science
instruments) will supply data to SDO's FSW, which will then compute a Sun
centroid to support direct autonomous pointing of SDO's science instruments
at the Sun without realtime ground-processing of science data.
Fifth, an experiment in spacecraft formation flying was performed in 2001
using the EO-1 (launched in 2000) mission and the existing Landsat-7 mis-
sion. Landsat-7 was a passive participant, simply executing its normal science
mission. EO-1, equipped with a global positioning system (GPS) receiver to
measure the EO-1 orbital coordinates in realtime and an orbit propagator sup-
plying predictive Landsat-7 orbital coordinates, maintained approximately a
1 min separation between its orbit and the Landsat-7 orbit. This experiment
successfully demonstrated an important capability that can be used by future
earth science constellation missions to synchronize science data taken at dif-
ferent local times and to use images gathered by the “lead” spacecraft over the
target to optimize science instrument configuration on the trailing spacecraft,
or establish for the trailing spacecraft that the target is “socked-in” so that
advance preparations for viewing the next target can begin.
3.2.5 Flight Autonomy Capabilities of the Future
Future GSFC missions are expected to advance current onboard capabilities
significantly in the areas of planning and scheduling and FDC. JWST (and
several other missions currently under development) have proposed the use of
onboard event-driven scheduling to exploit the benign thermal environment of
tion would enable the spacecraft to move through its observation schedule on
an as-ready basis, rather than pausing to hit absolute time points dictated by
traditional fixed-time scheduling approaches. On the other hand, if anomalous
conditions occurred that precluded observing the desired target (for example,
guide stars not being acquired), the OPE function would simply move on to
the next target on the list without further loss of observing time. So the use of
the OPE function should produce some gains in overall observing eciency.
Further, by taking advantage of realtime knowledge onboard concerning the
spacecraft's angular momentum, the OPE function could intelligently plan
when to perform necessary angular momentum dumps with minimal impact
to science observations.
Other major enhancements in FSW capabilities are likely to be driven by
the needs of the interferometry missions proposed to study star formation,
