As part of Deep Impact's Flight System, the flyby spacecraft
is one of two vessels carrying the three science Instruments.
Ball Aerospace & Technologies Corp. is designing the spacecraft specifically for the Deep
The flyby spacecraft features a high throughput RAD750 CPU with 1553 data bus-based avionics
architecture, and a high stability pointing control system. Spacecraft optical navigation and
conventional ground-based navigation will facilitate maneuvering the flyby spacecraft as close as
possible to the collision course with comet Tempel 1. When the impactor is released from its union
with the flyby spacecraft, the flyby spacecraft will slow itself down and align itself to observe the
impact, ejecta, crater development, and crater interior as it passes within 500 km of Tempel 1. It will
also receive data from the impactor and transfer it to the Deep Space Network ground receivers.
The flyby spacecraft carries two of the three primary instruments, the
High Resolution Instrument (HRI) and the
Medium Resolution Instrument (MRI), for imaging,
infrared spectroscopy, and optical navigation.
Spacecraft is approx. 3.2m (126") long, 1.7m (68") wide, and 2.3m (92") high.
About the size of a Ford Explorer, the flyby spacecraft is three-axis stabilized and uses a
fixed solar array and a small NiH2 battery for its power system. The structure is
aluminum and aluminum honeycomb construction. Blankets, surface radiators, finishes, and heaters
passively control the temperature. The propulsion system employs a simple blowdown hydrazine
design that provides 190 m/s of delta V. The flyby spacecraft mass is 650 kg.
During the encounter phase, a high gain antenna transmits near-real-time images of the impact back
to Earth. The flyby spacecraft uses X-band to communicate to Earth and S-band to communicate with
the impactor after separation.
Debris shielding is a key part of the flyby S/C design. As the spacecraft passes through the inner
coma of the comet it is in danger of being hit by small particles that could damage the control, imaging
and communication systems. To minimize this potential damage the spacecraft is rotated before it
passes through the inner coma allowing debris shielding to provide complete protection to the
flyby spacecraft and instrument elements.
||92 W average during engagement
||370 kg impactor, 90 kg instruments
|Payload Total Data Volume:
|Payload Data Downlinked:
(inst. boresight orientation)
||65 microradian 3 axes 3-sigma
|Telecom Band to Earth:
||125 bps/175 Kbps
(exclusive of Reed-Solomon encoding)
|Telecom Band to Impactor:
|Data Rate to Impactor:
||64 Kbps @ max range (8,700 km)
||190 m/s divert;
5000 N-s RCS total impulse