PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 2004-09-01 S.McLaughlin Created 2005-02-07 S.McLaughlin Resolved liens " RECORD_TYPE = "STREAM" OBJECT = INSTRUMENT_HOST INSTRUMENT_HOST_ID = "DII" OBJECT = INSTRUMENT_HOST_INFORMATION INSTRUMENT_HOST_NAME = "DEEP IMPACT IMPACTOR SPACECRAFT" INSTRUMENT_HOST_TYPE = "SPACECRAFT" INSTRUMENT_HOST_DESC = " This description was provided by Dr. Michael A'Hearn, the principal investigator for the Deep Impact mission. The Deep Impact Impactor vehicle is a complete spacecraft with a CCD-based camera and telescope called the Impactor Targeting Sensor (ITS) for both scientific imaging and auto-navigation, a complete attitude control subsystem using hemispherical resonator gyros, a star tracker, and a complete, hydrazine-based propulsion system. Electrical power is supplied by an internal battery since the expected operating lifetime is very short (24 hours). The Impactor is mechanically and electrically attached to the Flyby spacecraft and both launch together and fly together until one day before the impact event. On July 3, 2005, the impactor is released and pushed away from the Flyby at a distance of 864,000 km distant from comet Tempel 1. The auto-navigation system takes control and maneuvers the Impactor to ensure an impact on an illuminated portion of the cometary nucleus. On July 4, 2005, the impactor hits the nucleus at a relative speed of 10.2 km/s. The 360-kg Impactor releases 19 gigajoules of kinetic energy to excavate a crater on the surface of the nucleus. About half of the mass of the Impactor is copper, a noble metal, which minimizes chemical reactions that could lead to species that contaminate the spectrum with bright lines. About half this copper is in a spherical cap at the 'front' of the impactor. This cap is made of chamfered discs that are internally hollowed much like a lightweight telescope mirror to reduce the density by a factor two or so from the bulk density of copper. Data taken by the ITS are white-light images and are used by the onboard software for auto-navigation and transmitted to the Flyby over an S-band link at 60 kilobits per seconds (kbps). Attitude control and minor trajectory corrections are performed using a small hydrazine propulsion subsystem. In the last minute before impact, long after the last trajectory maneuver, the project expects the optics to be destroyed by dust impacts, either by sandblasting by small particles or by the impact of a large particle that cracks the primary mirror of the ITS telescope. If the optics survive, the last image will have a resolution of 20-cm per pixel. System Requirement Specifications for the Impactor are: Image Data Volume : Approximately 17 megabytes Pointing Accuracy : 2 milliradian 3-sigma Pointing Knowledge : 150 microradian, 3 axes, 3-sigma Targeting Accuracy : 300 m 3-sigma with respect to the center of brightness of the nucleus Telecom Band : S-Band Data Rate to Flyby : 64 kbps Command Rate : 16 kbps Energy Storage : 2.8 kilowatt-hr for 24 hr mission Propulsion : 25 m/s delta-velocity For further descriptions of the impactor spacecraft, the anticipated flight data, and the cratering experiment, see A'Hearn, et al. (2005) [AHEARNETAL2005], Blume (2005) [BLUME2005], Hampton, et al. (2005) [HAMPTONETAL2005], Klaasen, et al. (2005) [KLAASENETAL2005], Richardson, et al. (2005) [RICHARDSONETAL2005], and Schultz and Ernst (2005) [SCHULTZ&ERNST2005]. " END_OBJECT = INSTRUMENT_HOST_INFORMATION OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "AHEARNETAL2005" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "BLUME2005" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "HAMPTONETAL2005" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "KLAASENETAL2005" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "RICHARDSONETAL2005" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO OBJECT = INSTRUMENT_HOST_REFERENCE_INFO REFERENCE_KEY_ID = "SCHULTZ&ERNST2005" END_OBJECT = INSTRUMENT_HOST_REFERENCE_INFO END_OBJECT = INSTRUMENT_HOST END