On July 4, 2005 at 05:44:34 UTC the Impactor spacecraft (s/c) impacted comet 9P/Tempel 1 with a relative speed of more than 10 km/s. The Flyby s/c captured the impact event, using both the medium resolution imager and the high resolution imager, and tracked the impact site for the entire observing period following impact. The objective of the Impactor s/c was to impact in an illuminated area viewable from the Flyby s/c and telemeter high-resolution context images of the impact site prior to impact. The Flyby s/c had two primary objectives: (1) capture the impact event in order to observe the ejecta plume expansion dynamics and (2) track the impact site for at least 800 s to observe the crater formation and capture high-resolution images of the fully developed crater. All of these objectives were met by estimating the trajectory of each spacecraft relative to 9P/Tempel I using the autonomous navigation system, precise attitude information from the attitude determination and control subsystem, and allowing each spacecraft to independently select the same impact site. This paper describes the challenges of targeting and tracking comet 9P/Tempel 1. (c) 2007 Wiley Periodicals, Inc.

On July 4, 2005 at 05:44:34.2 UTC the Impactor Spacecraft (s/c) impacted comet Tempel 1 with a relative speed of 10.3 km/s capturing high-resolution images of the surface of the nucleus just seconds before impact. Meanwhile, the Flyby s/c captured the impact event using both the Medium Resolution Imager (MRI) and the High Resolution Imager (HRI) and tracked the nucleus for the entire 800 sec period between impact and shield attitude transition. The objective of the Impactor s/c was to impact in an illuminated area viewable from the Flyby s/c and capture high-resolution context images of the impact site. This was accomplished by using autonomous navigation (AutoNav) algorithms and precise attitude information from the attitude determination and control subsystem (ADCS). The Flyby s/c had two primary objectives: 1) capture the impact event with the highest temporal resolution possible in order to observe the ejecta plume expansion dynamics; and 2) track the impact site for at least 800 sec to observe the crater formation and capture the highest resolution images possible of the fully developed crater. These two objectives were met by estimating the Flyby s/c trajectory relative to Tempel I using the same AutoNav algorithms along with precise attitude information from ADCS and independently selecting the best impact site. This paper describes the AutoNav system, what happened during the encounter with Tempel I and what could have happened.

We have installed a large-format CCD camera on the 0.6-meter telescope at JPL's Table Mountain Observatory and used it to obtain high-accuracy astrometric observations of asteroids and other solar system targets of interest. The detector contains 4096x 4096 15-mu m pixels and produces a field of view 21'.9 square at a resolution of 0 ".321/pixel. The field is wide enough to obtain sufficient reference stars from the ACT Catalog, and the oversampled images can produce centroids to a precision of 10-30 milliarcseconds. We describe the calibration and reduction procedures, including routine use of the overlapping field technique, that are necessary in order to obtain an accurate mapping of distortions in the focal plane. Our observations have enabled a successful flyby of 253 Mathilde, predicted ground tracks for several asteroid occultations, and will support onboard autonomous navigation for the Deep Space One mission.

The first flight of NASA's New Millennium Program, Deep Space 1, will include a new navigational technology: an autonomous optical navigation system. The DSI Navigation system will be the first use of autonomous navigation in deep space. The task for this system is to 1) perform interplanetary cruise orbit determination, using images of distant asteroids, 2) control and maintain the orbit of the spacecraft using the ion propulsion system (another technology never before applied to deep space) and conventional thrusters, 3) perform approach orbit determination and control using images of the science targets, 4) perform late knowledge updates of target position during close fast flybys in order to facilitate a high degree of quality data return from 2 targets: asteroid McAuliffe and comet West-Kohoutek-Ikemura. Additionally, an encounter with Mars will probably be performed with possibly a close flyby of one of the Martian moons, Phobos or Deimos. Several functional components are necessary to accomplish these tasks. These include picture planning and image processing, dynamical modeling and integration, planetary ephemeris and star catalog handling, orbit determination data filtering and estimation, maneuver estimation, spacecraft ephemeris updates and maintenance, and general interaction with the other onboard autonomous systems. These systems are described, as is the means of their operation onboard. Finally, performance statistics from trial runs of the system are given.

G. W. Null, W. M. Owen, Jr., and S. P. SynnottNavigation SystemsSectionDeep-space telecommunications systems will eventually operate at visible ornear-infrared reg/ons to provide increased information return from interplanetaryspacecraft. This would require an onboard laser transponder in place of (or in ad-dition to) the usuM microwave transponder, as well as a network of ground-basedand/or space-based optical observing stations. This article examines the expectednavigation requirements for future missions, as well as possible ground-based opticalobserving systems to meet these requirements. Special emphasis is given to opticalastrometric (angular) measurements of stars, solar system target bodies, and (whenavailable) laser-bearing spacecraft, since these observations can potentially providethe locations of both spacecraft and target bodies. The role of astrometry in thenavigation system and the development options for astrometric observing systemsare also discussed.

Interplanetary spacecraft navigation requires accurate a priori knowledge of target positions. A concept is presented for attaining improved target ephemeris accuracy using two future Earth-orbiting optical observatories, the European Space Agency (ESA) Hipparcos observatory and the Nasa Hubble Space Telescope (HST). Assuming nominal observatory performance, the Hipparcos data reduction will provide an accurate global star catalog, and HST will provide a capability for accurate angular measurements of stars and solar system bodies. The target location concept employs HST to observe solar system bodies relative to Hipparcos catalog stars and to determine the orientation (frame tie) of these stars to compact extragalactic radio sources. The target location process is described, the major error sources discussed, the potential target ephemeris error predicted, and mission applications identified. Preliminary results indicate that ephemeris accuracy comparable to the errors in individual Hipparcos catalog stars may be possible with a more extensive HST observing program. Possible future ground and spacebased replacements for Hipparcos and HST astrometric capabilities are also discussed.

Planetary approach orbit determination target errors using Mariner IV Doppler tracking data

Statistical formulas, doppler residuals, and equations of condition are used to obtain certain physical constant data from the radio tracking of mariner ii