MISSION PLAN - PDS Small Bodies Node

Several imaging calibration activities will be performed on approach to the comet and
after comet flyby. These activities are required to ensure proper performance from the
camera and interpretability of the images acquired during encounter. Table 6.2-2
summarizes the required calibration activities during the encounter phase.
Table 6.2-2 Encounter Imaging Calibrations
Time
(days) Image Description
no. of
images
bits /
pixel
no. of
filters Comments
E-60 Mini cal sequence 7 16 7 windowed about center (100x100?)
Mirror pointing, align &
sensitivity cal
20 16 1
(nav)
pattern matched, windowed
(10x10), nominal attitude, tight
deadband
E ±30
1 Standard solar analog
1 Flux standard (star
TBD)
28 /ea 16 7 /ea 4 exp / 7 filters, windowed (15x15),
yaw turn, mirror, tight deadband
Zero exposure 3 16 1 windowed (20x20), determine
camera bias (~400 DN).
E-30, ±15 Photocal w/ lamp ‘on’ 21 16, 8 7 3 exposures / image, windowed
6.2.3 CIDA and DFMI Encounter Experiments
At E-5 hours, communications will be continuous and CIDA and DFMI data included in
the telemetry to Earth. It is after this time, that most, if not all, dust related activity is
expected to occur. This configuration will continue through to approximately E-3
minutes at which time the telemetry link is interrupted if the roll maneuver is required.
Data from CIDA events will be compressed and stored on board. Any free memory left
from the encounter period will be used for imaging after the primary encounter period.
6.2.4 Delivery Accuracy and Science Implications
If navigation targeting is perfect, Wild-2 will be located at z=150 km, y=0 km and x=0
km in the spacecraft fixed coordinate system at the closest approach to the comet. Table
6.2-3, however, shows the potential delivery error after the E-18 h and E-6 h TCMs.
Remember that the E-6 h TCM will be performed only in the event of an anomaly.
However, the knowledge improvement will be used to initialize the nucleus tracking
algorithm and to update the start of the encounter sequence block, if necessary, thus
keeping the navigation delivery in line with the spacecraft and sequencing capabilities.
Table 6.2-3 Encounter Delivery Accuracy (1-sigma)
TCM Cross-track (km) Time-of-Flight (sec)
E-18 h 10 29
E-6 h 7 29
77