Stephen P. Synnott

Publications (8)31.2 Total impact

• Article: The challenges of deep impact autonomous navigation.

  Daniel G. Kubitschek, Nickolaos Mastrodemos, Robert A. Werner, Stephen P. Synnott, Shyam Bhaskaran, Joseph E. Riedel, Brian M. Kennedy, George W. Null, Andrew T. Vaughan
  J. Field Robotics. 01/2007; 24:339-354.
• Source

  Available from: nasa.gov

  Article: Autonomous target tracking of small bodies during flybys

  Shyam Bhaskaran, Joseph E. Riedel, Stephen P. Synnott
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  ABSTRACT: Spacecraft flybys of small solar system bodies provide important science return in the form of images of the target body taken around closest approach. In order to maximize the number of images taken of the target, an autonomous closed-loop tracking system has been developed to maintain lock on the target during the flyby. The system uses images to estimate the spacecrafts target-relative position and attitude, which is then used to point the camera. The system has been successfully used three times: the Deep Space 1 flyby of comet Borrelly and the STARDUST flybys of asteroid Annefrank and comet Wild 2. This paper describes in detail the tracking algorithms and flight results. Copyright (copyright) 2004 by the California Institute of Technology.
  02/2005;
• Article: An approach for targeting landers and penetrators using orbital optical navigation

  Tseng-Chan Wang, Thomas C. Duxbury, Stephen P. Synnott, Kathleen Edwards
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  ABSTRACT: Onboard orbital optical navigation data is analyzed with the purpose of generating topographic maps for selecting a landing site. It is suggested that a near-real time orbit-determination process be used for solving a large set of parameters including the spacecraft orbit and primary-body gravity field, the rotational properties of the planetary body, the coordinates of surface features, and the camera-pointing and orientation angles of each picture. A batch-sequential formulation of the standard least-squares problem is employed, along with backward smoothing and a square-root formation filter. An experiment in which over 100 images of Phobos are processed to estimate about 2000 parameters is presented, with emphasis on coordinate systems, transforming points on the reference surface to images in the picture, parameter estimation, and cartographic accuracy.
  02/1990;
• Article: C-smithing of Voyager 2 non-imaging instrument pointing information at Uranus

  Tseng-Chan Wang, Charles H. Acton, Ian M. Underwood, Stephen P. Synnott
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  ABSTRACT: The development of a family of techniques, collectively called C-smithing, for improving spacecraft nonimaging instrument pointing knowledge is discussed. C-smithing studies using data from the Voyager 2 Uranus Encounter show that significant improvements in pointing knowledge for nonimaging instruments can be achieved with these techniques. This improved pointing information can be used to regenerate instrument viewing geometry parameters for the encounter, which can then be made available to science investigators.
  02/1988;
• Article: Planetary geodesy

  Bruce G. Bills, Stephen P. Synnott
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  ABSTRACT: New geodetic data obtained during the years of 1983-1986 on terrestrial planets are presented. New or improved data on rotation, topography, and gravity are reported for Venus (from Pioneer Venus Orbiter observations), Jupiter (Pioneer 10 and 11 and Voyager 1 and 2 data) and its satellites, Saturn (from Voyager data) and its satellites, Uranus (from Voyager 2) and its satellites, and Neptune and Pluto (from various indirect observations). There was relatively little new to report on moon and Mars. The physical significance of the information is discussed.
  07/1987;
• Article: Discovery of a new jupiter satellite.

  D C Jewitt, G E Danielson, S P Synnott
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  ABSTRACT: During detailed analysis of Voyager 2 pictures of the Jupiter ring, a starlike object was identified in the plane of the ring. The same object was subsequently found on a higher-resolution frame and proved to be a satellite of Jupiter. This satellite has a circular orbit whose radius is 1.8 Jupiter radii, a period of 7 hours and 8 minutes, and a diameter of less than 40 kilometers. It is located at the outer edge of the Jupiter ring.
  Science 12/1979; 206(4421):951. · 31.20 Impact Factor
• Source

  Available from: pdssbn.astro.umd.edu

  Chapter: Autonomous Navigation for the Deep Impact Mission Encounter with Comet Tempel 1

  Nikos Mastrodemos, Daniel G. Kubitschek, Stephen P. Synnott
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  ABSTRACT: The engineering goal of the Deep Impact mission is to impact comet Tempel 1 on July 4, 2005, with a 370 kg active Impactor spacecraft (s/c). The impact velocity will be just over 10 km/s and is expected to excavate a crater approximately 20m deep and 100m wide. The Impactor s/c will be delivered to the vicinity of Tempel 1 by the Flyby s/c, which is also the key observing platform for the event. Following Impactor release, the Flyby will change course to pass the nucleus at an altitude of 500 km and at the same time slow down in order to allow approximately 800 s of observation of the impact event, ejecta plume expansion, and crater formation. Deep Impact will use the autonomous optical navigation (AutoNav) software system to guide the Impactor s/c to intercept the nucleus of Tempel 1 at a location that is illuminated and viewable from the Flyby. The Flyby s/c uses identical software to determine its comet-relative trajectory and provide the attitude determination and control system (ADCS) with the relative position information necessary to point the High Resolution Imager (HRI) and Medium Resolution Imager (MRI) instruments at the impact site during the encounter. This paper describes the Impactor s/c autonomous targeting design and the Flyby s/c autonomous tracking design, including image processing and navigation (trajectory estimation and maneuver computation). We also discuss the analysis that led to the current design, the expected system performance as compared to the key mission requirements and the sensitivity to various s/c subsystems and Tempel 1 environmental factors.
  01/1970: pages 95-121;
• Source

  Available from: nasa.gov

  Article: Deep Impact Autonomous Navigation: the trials of targeting the unknown

  Daniel G Kubitschek, Nickolaos Mastrodemos, Robert Werner, Brian Kennedy, Stephen P Synnott, George Null, Shyam Bhaskaran, Joseph E Riedel, Andrew T Vaughan, Robert A Werner, Brian M Kennedy, George W Null
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  ABSTRACT: 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 a cometary 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 1 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 1 and what could have happened.